Technical E Class W210

Technical E Class W210

Sprinter Fuel Rail Pressure Regulator Problems – Poor Starting


The Mercedes CDI series of diesel engines have an electronically controlled fuel pressure regulator mounted on the end of the fuel distribution rail. This controls, as the name suggests, the fuel rail pressure. It relies on the seal made between a single small O-ring which is backed by a split fibre backing ring.  What happens over time is that the O-ring wears and often fails allowing pressurised fuel to bypass the valve and ebb away the required running pressure that the injectors need.  Often the problem becomes more noticeable once the engine is warm and poor starting results.

Usual symptoms for this can be laboured starting when warm and occasional non starting, if the fuel rail cannot maintain the required minimum of approximately 300 bar at crank to allow the injectors to fire.  If it is possible to monitor rail pressure using Live-Data, you may see the rail pressure dancing between 266 and 550 bar. Instability of pressure when holding a steady throttle will be the clue as to a problem with the fuel pressure control.  If you do not have access to a compatible code reader thankfully the repair is simple and not costly so easy and cheap to eliminate as a cause of poor warm/hot starting. (Under £10)

Sprinter fuel pressure regulator fault 1

Remove the upper section of the inlet manifold to allow access to the rear of the fuel rail, just under and against the bulkhead/firewall.  Identify the electrical connector and remove it, select a 1/4 drive socket wrench and appropriate small reverse torx socket and short extension.  Remove the two opposing pins on the regulator flange (left and right as fitted).  Pull out the fuel pressure regulator from the end of the fuel rail.

Sprinter fuel pressure regulator fault 2

Keeping the device clean, remove both the green O-ring and fibre backing ring from the tip of the regulator and replace with new components.  Refit the regulator assembly to the rail.  It makes it easier if you have the left hand threaded pin in place in the regulator flange mounting hole, before offering it into place. (left hand in fitting position, if standing at front of engine)  Once the two pins are re-fitted the electrical connector can be attached and the intake manifold upper half rebuilt.

Sprinter fuel pressure regulator fault 3

Back of the fuel rail where the regulator mounts (normally hidden from view)

It is important to note that a failing fuel injector can also deprive the fuel rail of its operating pressure. If you suspect that this is the case, perhaps after changing the regulator O-ring to find there is no difference to the fault then you must carry out or entrust a garage to do a diagnostic ‘leak-off test’ to prove the injector system is sound.  WARNING a failing fuel injector that is passing unmetered  amounts of fuel can soon damage the engine catastrophically, either through piston overheat or engine seizure and any suspected problems must be investigated promptly!  See this interesting and descriptive forum post regarding leak-off testing.

Sprinter fuel pressure regulator fault 4

Fuel rail pressure regulator seal kit part number

Sprinter Low Boost – Limp Home on Full Throttle

One of the 2004 long wheel base Mercedes Sprinters developed a problem where everything was fine under moderate throttle openings but once full power was called for, the van would register a fault and lock into limp home. Recycling the ignition cleared the fault, until the next wide open throttle and call for high power.

A great deal of work had been done on this particular van over a short period and most of the regular problematic contenders covered elsewhere on this subject had been dealt with. We knew we had good fuel delivery, good fuel pressure, sound boost and good induction hose-work. New sensors had been fitted on both low and high pressure points on the system and the only fault recorded was low boost.

Faulty Sprinter turbo boost actuator

We had previously seen another fleet operators Sprinter register low boost and discovered that the intake air filter was completely choked with muck and grime, this was not the case with this van.

Examining for mechanical issues became a primary focus as all the electrical systems were sound and cross-referring their readings on ‘live data’ proved their adequate function. In driving the vehicle with the code reader connected, we were able to see that maximum turbo boost was never achieved at full power, but was seen approaching moderate peaks at more modest and lazy throttle openings.

Often the van would perform fine unladen and fail consistently when loaded, slipping into limp home as soon as the driver tried to make good progress.

I removed the airbox and checked the vacuum pipework from the brake servo to the boost control valve and everything was in good order. I removed the supply pipe to the turbo actuator and double checked this for problems such as nicks, cuts and splits – nothing.

The lever arm to the turbo was free and this was confirmed by removing the circlip from the eye of the actuator arm and manually operating it to prove there was nothing wrong within.

Faulty turbo boost actuator Mercedes Sprinter

My next test was to push the actuator rod back into the actuator and be certain the movement was unhindered and smooth. The next test was to block the vacuum pipe opening with a finger, allowing air to be expelled while I pushed the rod inward. Closing the gap with moderate finger pressure should be enough to hold vacuum inside the diaphragm, making a ‘popping’ sound as the rod springs back to its extended position when you release your finger. I noticed the fitted actuator was not doing as it should in that respect as it was not ‘popping back’ to an extended position. Indeed, careful observation proved that the rod was moving very slowly to a fully extended position with a finger blocking the port, indicating a failure of the internal diaphragm – probably a slight leak or pin-hole.

This would under normal circumstances been difficult to spot as it had not failed completely. The actuator still pulled the turbo lever to a fully down position once the engine was started. However the small leak meant that the on-off pulse control of the actuator, given by the Pulse Width Modulation (PWM) of the vacuum control valve, was not as it should have been – resulting in under-boost on high power call situations.

The replacement of the actuator although fairly straight forward in mechanical terms, is a bit of a fiddle to accomplish, as one of the mounting bolts is a good finger-stretch into the confines of the turbo and takes some jiggling to get the pin back into position and tighten it.

There are three 10mm bolts into the exhaust side of the turbo scroll casting. These hold the actuator support bracket and also clamp the spool cartridge face against the turbo scroll casting flange making a gas tight seal.

Once these three bolts are removed and the circlip removed from the rod/lever, the actuator can be removed for inspection. Access to the area is best achieved by removing the complete air box, the turbo intake hose and brake servo vacuum pipe. Once these components have been removed, additional removing the vertical heat plate/shield that separates the air box from the turbo assembly is essential to obtain free access to the three actuator fixing bolts – especially as one is a real swine to get to!

Faulty turbo boost actuator Mercedes Sprinter 2

It is important to set the actuator arm/rod length of the replacement part to the same dimension as the original. This is critical in that it effects how the vanes are positioned within the turbo for any given actuator setting. Simply measure the new rod length to the old one and make adjustments using the 10mm lock-nut and thumbwheel provided on the actuator rod. Lock the setting once you have it and ensure the hole in the rod eye is positioned in the correct plane to accept the lever bar of the turbo once reinstalled.

Rebuild is the reverse of disassembly from this point. Once fully built, check your work and clear any remaining fault codes and then road test the vehicle. Once again boost should be available through the complete power range and it should react smoothly to engine loading, just as it did prior to the fault occurring.

Other Mercedes Sprinter turbo fault/boost related posts:

Please be sure to use the comprehensive site search facility to find what you are looking for (Just enter your search term in the search box on the top right and click search) – There are many informative Mercedes posts on this this site, just waiting to be viewed!

Mercedes SL (R129) Rear View Mirror Fix

I am not sure if it as a result of the awful condition of UK roads or the sudden hot spell we have had recently, but the rear view mirror started to rattle in a very metallic annoying way.  To be honest the way the mirror vibrates due to the inevitable convertible ‘scuttle-shake’ could be the long term underlying cause.  Anyway it was time to get it fixed!

Mercedes SL (R129) Mirror Repair 1

Having experience of the W210 E class and W202 C rear view mirror removal due in the most part to failure of filament indicator lamps, the SL (R129) presented little problem in ‘de-camping’ it from its sprung die-cast shoe above the windscreen.  The best way I have found to accomplish this is to slide two fingers up between the screen and the flat front part of the mirror support, cup your hand around the remainder of the mirror and lever it down in an arc from the screen, imagine that it is pivoting on the trim edge furthest into the passenger compartment.  Do not try a straight pull down, or using, as some people recommend:  ‘putty knife or spatula’  This is not necessary at all and you are very likely to cause trim damage using any tools at all!   The number one thing to be aware of is that the mirror has an electrical connector on a very short lead behind the section that unlatches.  You must control the unlatching of the mirror, as you may accidently over-pull and damage the wiring or connector (That is why the lever-down technique is good as you can quickly adjust the forces applied as it releases)

Mercedes SL (R129) Mirror Repair 2

Once the mirror is unlatched and the electrical connector disconnected the whole assembly can be taken the workbench or kitchen table!

First using a firm straight pull-outward, remove the dipping adjustment control knob and place it to one side.  Start by carefully prying the add-on light pod from its four peg positions. It will with care detach from the bottom of the mirror. (it is pegged into the rear cover and bezel)  Once this module is free, the rear cover levers out from the bottom, unhooking from two internal retainer hooks inside the top edge of the rear cover/bezel (one of these hooks was broken on my mirror too).  The complete back cover should now release from the bezel, allowing you to gain full access to the internals of the mirror.

Having now done this off the car – I realise that maybe the mirror back cover could be actually be removed in situ.  By unclipping the add-on pod at the bottom and hinging the cover out at the back, disengaging it from the bezel.  You could probably get access to refit a mirror holding spring without actually removing the mirror (maybe!) – Not really sure why you would want to struggle with this on the car, but I thought I would just mention it as it all adds to the DIY detail!

Mercedes SL (R129) Mirror Repair 3

As you can see the mirror glass and bezel is held onto the adjustment gimbal by a black plastic panel. On each side there is a flat spring metal clip that applies captivating pressure to the black plastic panel by trapping each end of the flat spring to the upper and lower edges of the bezel.  There are locators in the moulded plastic to facilitate this.

Mercedes SL (R129) Mirror Repair 4

These are the pair of springs that fall out – or worse, break the the retaining moulded section they latch into, so they no longer hold the mirror in place.  The springs then fall down and jangle in the bottom of the mirror housing, accompanying the rattling mirror glass.  There has been several owner forum write ups on this job, delving as far as refitting the springs, but in every case if there has been mention of the plastic breaking – then a replacement part has had to be sourced.  Matching your trim colour can be difficult with second hand parts and the later mirrors fitted the C class W202, S Class and their derivatives of the era, had an integrated one-piece pod for the alarm/locking indicators so were incompatible.  Much better I think to repair what you have to better than original if possible, than pay out a fortune for the exact replacement part.

Mercedes SL (R129) Mirror Repair 5

Just touching on how other ‘how-to’ write ups may mention bending the springs to apply more pressure to the mirror backing or even using foam pads to build out the gap between the back plate and increasing spring holding pressure – It is my view that by doing any of the above you run the risk of breaking the fragile moulded ears that locate the springs to the front bezel.  As long as the pressure applied is sufficient to hold the mirror to the backing plate then nothing more is needed – more than needed pressure on the plastic = more chance of stress and future breakage due to the harsh environment and extreme temperatures it is subjected to in the windscreen of your vehicle.

Mercedes SL (R129) Mirror Repair 6

I wonder if my mirror had maybe in the past had similar repairs or that over time (20 years) the plastic was no longer up to holding the pressure applied by the springs and eventually breaking off the moulded ears – who knows.

If as in the case of my mirror, the lower retainer ears for the springs were completely broken, the spring location point can be repaired quite easily with the use of a small drill, a length of 1.5mm solid copper wire (electrical mains cable) and some simple tools.

First take both springs to a bench vice and drill two 1.5mm clearance holes in one edge of the small upturn of the flat retainer spring.  Hold the spring in place and drill two matching holes in the lower part of the mirror bezel. Be sure that the holes you drill lie behind the small square holes that locate the add-on indicator light pod. As long as they remain behind this hole line, the repair will not be seen as it is fully covered once the pod is re-attached.

Mercedes SL (R129) Mirror Repair 7

Using snipe nose pliers, bend the copper wire to make an elongated ‘U’ shape staple with as tighter radius ‘square’ bends as possible.  Insert this through the bezel and locate the drilled end of the flat spring onto the copper wire legs. Position the flat spring as close to its original position as possible using the remaining upper locators for reference, then bend over the copper wire at 90 degrees to secure the spring.  Trim the wire to a length that just extends past the edges of the spring.  Repeat this for the other spring if necessary.

Now slide in the black plastic mirror support plate under the flat springs and position it correctly on the mirror back.  Fold down the springs, locating the middle ridge with the raised edge on the plate moulding.  Using a screwdriver, with the mirror and bezel on a stable flat surface, push the springs top edge down to latch under the remaining locators.  Once these top edges are snapped into position the mirror can be rebuilt.

Mercedes SL (R129) Mirror Repair 8

Hook the rear cover into the two retaining hooks and close the cover. Clip the add-on indicator light pod into the bezel to hold the complete case assembly in place.  Check around the bezel edge, ensuring that everything is located correctly.  If you have damaged or broken tabs that are used to hold the case together, use a spot of clear silicone on the mating edges of the case and tape it together until fully set.  Refit the mirror dipping knob, clean / wipe over the mirror and case in preparation for installation.

Mercedes SL (R129) Mirror Repair 9

If you feel the need, apply a light smear of grease to each of the two sprung loaded ‘pips’ that engage with the snap-in shoe mount on the car, connect the electrical plug and push back the newly repaired mirror into place.


Purchasing a used Mercedes Sprinter diesel engine.


For whatever reason you may be looking to purchase a used replacement engine, there are quite a lot of pitfalls that you may fall foul of if unaware. I hope to highlight some of the things to look for and be aware of when searching for that ‘mechanical bargain’ in the small ads or breakers yard.  Indeed this guide could be used to assist you if you were about to purchase a used van and needed to know/check a few things out indicating the condition of the engine before you buy.

Probably the most obvious thing is, ‘can you hear the engine start and run’?  Without doubt this is the best way to buy a used engine. Quite often engines may be removed from a scrap vehicle and sold on this basis.  They will frequently be strapped to a pallet or resting on an old tyre waiting for sale and although there is little you can do about that, there is a few things you can check to be more positive about your potential purchase – especially as you will not be able to hear it run!  Don’t forget to take along your torch on any reccy’ as you will need this for most of your checks.

If you do get chance to inspect an engine while it is still in the vehicle, make a mental note of the mileage and ask questions of the seller – even before you lift the hood/bonnet or turn the key. It goes without saying the reason for the sale should be credible, if the rest of the van looks good, one would ask why the engine was being sold – is it stolen and being parted-out?  Just be aware.

Sprinter used engine inspection

Always better to hear a used engine running if possible

If the registration plate is still there make a note of this too, along with any vin number.  The purpose of this is to have all the information to hand if you need to later double check if the engine is compatible with your vehicle, these are the details that a dealer or independent will need to cross check the parts on his system to confirm compatibility with your own vehicle if you are in any way uncertain.

Have a quick look at the engine in situ, dip the oil and look into the coolant expansion tank – it is that the vehicle was front ended, the radiator will likley be broken and there will be nothing to look for in here, but have a look anyway.  It should be clean inside with no frothy oily mess and should not be coated with thick brown rusty sludge.

As with any other vehicle purchase if you can, you will want to hear it run from cold. It should start without hesitation and soon settle into an even idle.  Try and gauge if it is as quiet as your own engine was when it was working properly.  If there is no coolant, you will not be able to run it for long so quickly pull of the breather hose from the oil separator or turbo intake pipe and look for smoke and pressure here, if either is excessive walk away.  This is an indication of worn bores and/or piston rings and really not what you want to be buying into.  You can look for fumes and blow-by pressure at the dipstick tube also, but this is not always as conclusive as what can be seen at the breather pipe.

Can you here the turbo spool up?  If you are in doubt remove the air cleaner cover or intake hose to the turbo body and dab the throttle.  You should hear a healthy howl if everything is working correctly.  Glance back to rear of the vehicle as you rev the engine and make sure you can still see the sky!

Below is a checklist to help you assess your potential ‘running’ or ‘palletised’ engine purchase, some items in this list may/may not apply:

Coolant Expansion Tank (Front right hand side slam panel area)

Should be clean inside, no brown sludge, no oily mayonnaise. With the engine cold and running, carefully remove the filler cap and place your hand over the coolant reserve neck, get an assistant to blip the throttle, there should be no pressure to lift your palm off the lip.  Have a quick glance inside – no bubbles is good.  Problems here could indicate a potential head gasket issue.

Oil Separator (Top of engine behind oil filler cap)

While it is normal for a high miles engine to be a little ‘wet’ with oil around this area, any white smoke or fumes beyond the ‘barely visible’ from the vent pipe that runs to the turbo inlet could signify worn bores and/or piston rings.  Pull the pipe from either end and observe to be sure. Do not be too concerned by traces of oil here and also if the pipe is gummed with a little mayonnaise as in many cases this is normal.

Check the crank case pressure - inspect the oil separator pipework

Check for excess crank case pressure – inspect the oil separator pipework

Water vapour, moisture and condensation escape from the crank case and exit here to the turbo inlet.  The device that is present on the lower pipe is not a sensor it is a small heater! This actually stops moisture and crank case water vapour freezing in the vent pipe in colder climates, blocking it.

Oil Dip-Stick

Pull this and check the oil level, there is not much to be told from the black oil that will be on the end but caution must be observed if there is any water droplets, froth or whitish deposits on the stick. As with the coolant tank inspection any issue here could mean that the head gasket may be suspected as leaking.  Any obvious quantity of water in here could also mean that the oil cooler fixed to the side of the oil filter housing is passing pressurised water into the engine – not good. There should be little or no pressure, or smoking from the open dip stick tube.

Oil Filler Cap

Pretty much the same visual inspection applies as above. Do not remove the oil filler cap with the engine running – you will have an ‘oil-shower’, as the duplex timing chain runs directly beneath the cap.  If there is a lot of oil around the filler cap it is not unusual for the cap-lip to be slightly split, allowing oil to pass out onto the rocker cover and run down the left of the engine finding its way onto and into the alternator!

mercedes filler cap

If there is oil around the filler look for a split plastic filler cap on the lip – Simple fix

Leaks – Visual Inspection

Start from underneath with your torch, you will not need to jack the vehicle, just slide under and look under the front bumper.  Places with oil staining and dripping will be very easy to spot. While most oil leaks can be fixed, there are some cost implications to be considered depending on what and where the leak is.  A leak around the crank pulley for example will mean it will have to be removed and a new seal fitted, often if this has been leaking for a while the harmonic  damper pulley (if fitted) may have suffered deterioration due to the oil. (See Harmonic Damper Pulley in the check list)  Oil may be leaking from the rocker cover, do not assume this will be a simple fix, if it is going to be a problem all the injectors have to be extracted to remove the cover and replace this gasket, doing so can sometimes open a whole can of worms (Injector removal and so on). Lots of oil around the turbo body is not a good sign, it should be reasonably dry and in most cases the iron casting should remain red rusty.  Look beneath the turbo and seek out where the turbo oil return pipe enters on the sump line.  This could be oily, contaminating the surrounding area, indicating the oil return pipe seal requires replacement.  (two gallons a min. circulate through here!) The turbo/manifold has to be removed to replace this commonly failing seal.

O ring seals are simple to replace to cure oil leaks on the Sprinter HP Diesel and Vac pump bodies

O ring seals are simple to replace to cure oil leaks on the HP Diesel and Vac pump bodies

Oil leaking from the area behind the vac pump (or diesel HP pump for that matter) and running down the face of the engine block are usually a simple fix. In each case this is a large diameter ‘O ring’ that seals against the block and is simple to rectify.  Any diesel leaks should be investigated carefully and if found to be from the high pressure diesel pump (triangular shaped pump block on the front of the engine) head casting seams could indicate new seals or pump are required – not a cheap fix for a replacement pump. (It is worth noting to make sure the viscous fan central hex bolt is free and not seized before any engine installation, as this could hamper future diesel pump work)

Look also at the joint between the gearbox bell housing and the rear of the engine, any serious black engine oil presence here could indicate a crankshaft rear seal that is weeping.  Not a huge job to do when the engine is out but best avoided if at all possible, certainly another tick or cross when you are debating your offer price.

Water leaks should be easy to spot, especially if antifreeze is present in the system.  It will leave tell-tale staining in the form of a coloured salty scale.  Look at the water pump behind and up from the crank pulley there is a tiny hole in the pump casting nose, any staining or wetness here could mean the pump seal is failing and will be due for unit replacement.  Obviously hoses are an easy fix if leaking and should be all checked before putting the engine into service in your own vehicle.  Importantly include the small bypass hose at the rear of the block RHS above the starter motor area, this is a nightmare to replace once the engine is in situ due to poor access.

Noted leaks from any diesel related item or component must be investigated as these could be costly to rectify. (See Injectors Injector Cover in the checklist)

Harmonic Damper Pulley – Crank Pulley

While not a major issue to rectify if found to be suspect, it is worth checking the harmonic damper/crankshaft pulley that lives at the bottom front of the engine – it drives all the belts and is the main pulley from the motor crankshaft.  This is made in two mating parts, bonded together with a rubber metalastic material that is designed to absorb crankshaft borne detonation pulses, reducing noise and vibration of the running engine.

Sprinter engine inspection guide

Pulley and idlers are worth a look

What happens over time is the rubber sandwich deteriorates (often through oil contamination) and the two pieces begin to part company.  When things have got quite bad, the pulley begins to make a ‘clacking’ sound as it rotates (usually people tend to think its a far greater internal engine problem, as it can get very loud indeed) It is actually the pulley edge catching on the crankcase as it revolves. Its presence can sometimes occur only under load as the pulley flexes it can be hard to spot.  Look at the pulley with your torch and identify the rubber seam circumference, if it looks tired and cracked then budget to replace this before you refit the engine as failure can result in expensive engine damage. In itself not a full diagnosis, but you can also try to gently pry bar the edge of the pulley away from the block to get an indication of any detrimental flexing that may be present.

Injector Cover – Injectors

This is probably the most important check that you will do and will be the most awkward, both from the point of view of asking the seller if you can take a few parts off to inspect it and also from the point of view it will take you about 20 mins to complete.  What I would do is leave this as the final ‘deal breaker’.  If you are happy with what you see, agree with the vendor a price on the proviso the injector inspection proves satisfactory and explain that without this inspection you are not interested, whatsoever – This is actually very true, as if overlooked and bought blind, the engine could land you with a bill approaching and exceeding what you have just paid for the complete engine!  Of course if the injector cover is not fitted or missing further inspection is easy and far less of an issue for all.

Sprinter used engine inspection

This looks a great clean engine…

Having agreed your ‘investigation’, you will need four tools. A flat blade screwdriver, reverse torx socket wrench or a 10mm/8mm ring spanner and a 5mm hexagon key. Undo the turbo inlet hose from the inlet manifold and tuck it out of the way.  Undo the 8x torx pins holding the top of the inlet manifold to its lower section, remove the single pin at the front near the fuel filter and the rear fixing pin behind the plastic manifold, on the top left looking in, just sneaking under the bulkhead. (This one is often not fitted/missing as it is a PITA to get at – again a measure of lesser quality servicing maybe!) Lift off the upper inlet manifold section. This will reveal the 6x injector cover hex cap-screw fixings.  Once these are removed, lift up-and-off the injector cover.  If it makes a ‘crispy crunchy’ noise as you begin to lift it away, you could almost refit it at this point and just walk away!  Once you have the cover removed all should look fairly clean and oil free under there.  Be aware the oil separator may have deposited a little oil around the adjacent area but the overall appearance should be clean and dry. Any black carbonous coal like substance and you will have some work to do.  This condition signifies the injector seals have failed on one or more injectors and will need to be replaced, as combustion gasses are blowing-by the injector seats/seals and depositing carbon waste on the engine surface.  The common name given in the trade to this condition is: ‘Black-Death’.


Mmmmm maybe its worth less than I first thought! A bad case of Black-Death… It should look like the first image at the top of this post.

The presence of any Black-Death around the injectors will and should drastically effect your offer price downward. This job is known to be very difficult to price, as issues encountered along the way could range from injectors that cannot be removed, stripped hold down clamp bolts and deep cut sealing seats in the head pockets due to passing exhaust gasses. Each extra issue encountered, over and above normal labour cost, will soon double or treble the overall cost of repair and caution should be heeded when making your offer.  Be sure to make your bid based on a worst case scenario.  There is plenty to read on this subject both here on Gen-In and on the web, just Google it and learn what you need to know.

If the vendor does not understand the issue you have uncovered, then simply look elsewhere, at least safe in the knowledge your decision was made wisely and with due diligence.  Overlooking to check here can cost you dearly! Look at the engine above that otherwise looked a very good buy indeed.  You have been warned.

Sound and Vision

Satisfy yourself that the engine sounds good (if you get chance to run it) and that there is no knocking or tapping noises over and above the normal engine song.  Any metallic ‘Brrrrap’ possibly from a little end heard under a throttle blip, or heavy knocking noticed under load or overrun, then leave well alone and look else where.

Place your hand over the exhaust at idle and feel the regular pulses from the exhaust, if irregular there is a chance you have a slight misfire at idle and this may need work in the future.  Poke your fingers up the exhaust pipe and wipe around, hopefully this is dry sooty-black.  If its ‘sticky’ or ‘oily’ this is probably an indication of water or oil passing through the exhaust and in my view  would be best avoided.  Look at the emitted gasses from the exhaust – all but for a slight whiff of black soot, visible on a sharp jab of the throttle is good.

Sprinter turbo blown

You don’t want oily smoke like this… Blown turbo in this case.

Any white smoke, as severely shown above indicates oil presence – worn engine or turbo.  White smoke that ‘magically disappears’ or dissipates quickly is likely water from a suspect head gasket.  Listen to the auxiliary belt as the engine idles, is it flapping around? Look at how it runs over the pulleys, is it straight or canted over? If not running true or overly noisy this could signify worn idlers or failing belt tension device. Check to see all the pulleys on the drive belt route are true and not wobbling, indicating worn bearings that will soon need replacement.

Sprinter serpentine belt

Check belts for flapping, running true especially round the harmonic damper/ crank pulley – this could indicate de-lamination

When you turn off the engine it should stop without fuss, any clicking or snapping, cracking noise could indicate that the ‘sprag-clutch’ on the alternator pulley is failing.  Turn the serpentine auxiliary belt over with your fingers, if its cracked or worn it is usually a good indication the van has not been regularly serviced as this would have been changed under the maintenance regime.

Sprinter Serpentine belt - worn

As a rule of thumb an auxiliary belt in this condition is an indicator of poor servicing.

Similarly the age and appearance of the fuel filter canister often gives away the lack of recent servicing.  Overall you should be happy that the engine appears to reflect its mileage – remember you are not buying new and its unlikely that it is going to be perfect. It is mainly all about minimising your risk and getting the best deal you can without spending a fortune on rectifying a catalogue of unknown problems even before you get to grafting the replacement engine to your own transport.

Turn It Over Beethoven…

It goes without saying if you are buying a ‘static engine’ out of the vehicle, do make sure it turns over by rotating the flywheel, a simple thing to do but often forgotten in the heat of the moment – who knows how long the unit has been standing?

Mercedes sprinter used engine buying

Turn the engine over a couple of rotations to make sure its all free

Electrical Loom – Model Year to 2006

If the engine has had its loom cut – often the scrap dealer considers just the engine to be of value and not the ancillaries – be prepared to negotiate your price down a little as its a time consuming job to swap your existing loom over to the replacement engine.  I had a replacement engine come in that was ‘loom-cut’ about the point where it passes across the left hand engine mount.  On this occasion I chose to cut our own existing loom section and solder/heat-shrink the individual wires to the ‘new’ engine to make up a serviceable loom. There were sixty wires or more to deal with, although time consuming it is possible, noting a few important provisos I discovered along the way when carrying out this task.

-1 Wire thickness is important when choosing your colour match – there are often pairs of wires sharing the same colour code and tracers only decernable from each other by their relative thickness. Make sure you get this correct,

-2 The ‘Twisted Thicker’ pairs of cables are injector cables and share the same colours as other conductors.  Make sure you keep the twisted pairs together when joining.

-3 There are two identical ‘Black with Yellow Tracer’ wires in the loom bundle at this point. One goes to the starter motor solenoid, the other to Glow Plug No.2  Make sure you meter these wires out and ensure you have continuity to the correct points.  The Starter cable goes back to the grey ECU connector and the other glow plug supply should route to the glow plug module loom connector.  Just make doubly sure these two Black/Yellow wires that are of identical gauge are joined and routed to the correct point or the vehicle will not have a start signal to the starter.  If after the rebuild you suspect this may have been overlooked as the starter does not spin, its an easy check to test continuity between the starter solenoid cable ring tag to the glow plug module supply. If it bells out then you will have to split the loom and swap over the two black with yellow tracer cables – a good reason to double check this in the first instance!

-4 If your purchased engine has its loom in place you should at least give the ECU connector plugs a once-over, as if its been standing outside for any length of time moisture may have begun to work its evil on the fine connections to the brain of the vehicle.  If these look good thats great, but worthwhile treating them to a squirt of switch cleaner and moisture repellant before locking them home in the ECU.

And just before you hand over your cash…

Hopefully the above has given you a little insider knowledge to be able to assess wether the used engine you are considering is worth what the seller is asking and that you factor in any remedial work into your repair budget before ‘splashing the cash’.  There are undoubtably some bargains to be had out there, equally there are also rogues who know the full nature of the faults/condition of their engines, looking for a fast return.

Always try and get a written warranty of some sort for the engine where possible, at least one that covers it running without issue when fitted.  If you are buying from a local source maybe ‘in the trade’ and they are reputable, it is worth an extra few dollars/pounds over a private sale to have the security of even a one month warranty – It is worth remembering too that although your extra labour costs would be lost in any claim, removing and returning the faulty engine – often its better to secure the return (at least a large proportion) of your hard earned than not.

I am sure the opportunity to purchase from a private buyer will crop up and the normal ‘caveat emptor’ rules apply but with careful inspection and honest pricing, taking into consideration any faults noted, there are bargains to had from genuine people.  Just remember, minimise your risk as much as possible by using care and vigilance – knowledge is power!

Obviously this has not covered every single check-point or eventuality, but it at least prepares you for what you may find on your mission! I hope that it has at least helped you out a little.

Mercedes CDI Injector leak – Honda washer/seal alternative

You may have read previously either here or on the web about the use of the Honda Accord 2.2 Diesel injector seals in applications for Mercedes CDI diesels.  Sprinter, Vito, E320, C220, C 320 etc.  Here is an instance that really benefited from the use of the alternative sealing washer.

Honda Injector Seal

Honda Accord 2.2 Diesel Injector Seal

I had one of the courier fleets T1N 4 metre Sprinters in for repair due to a chuffing injector.  Unlike most common ‘Black Death’ related failures this one had just decided to spray diesel everywhere under the bonnet without any prior warning or over-time buildup of coke around the injector. Previously the other 3 injector seals in this engine had been replaced with Honda types and this single remaining one (No.2 Cylinder) was an original Mercedes OEM seal installed at the same time as the others, simply because I had no more Honda parts available.

On removal of the injector (slacken injector hold down clamp bolt and run engine to normal operating temperature – this often unseats the injector allowing relatively trouble free removal) It was discovered the seat was scored and pitted. The seat was recut then lightly faced with a hand reamer / face cutter tool then checked with a mirror and torch.  I knew this seat was good last time I replaced the seal so there had been a problem with blow by gasses cutting the seating face.

Laser injector seat cutter tool

Laser 4597 Diesel Injector Seat Cutter Set

So now all seals have been replaced with Honda parts and the van is once more good-to-go!   This engine, along with the van itself has covered over 500,000 hard courier miles and although the piston rings/bores are now nearing end of life (increased crank case pressure) it still sounds sweet and runs like a train.  Also interesting testament to chipped and tuned engines and their longevity, this one was performance chipped from new and at half a million miles running its hard to say that it has in any way been detrimental to its life span – an interesting point of note.

I have photographed the Honda part (injector seal) above in its original packet for ease of identification and obtaining the part should you wish to use the alternative copper sealing washer.  They look slightly thicker and are definitely made from a softer more malleable material than the OEM Mercedes units – My own view is that this ‘softness’ assists in sealing to irregular hand cut/cleaned seal faces and seats better than the harder MB equivalent washers.


Mercedes Sprinter engine 500,000 miles and still going strong…