W210 E320 CDI Major Fuel Leak

[Ashley]

I have had starting issue that has got progressively worse for 6 months and a constant smell of diesel from the engine. I had all the fuel return pipes replaced a year ago. Overnight the fuel seems to drain back to the tank as it taking 1 and half ignition cycles to start from being parked overnight facing uphill.

The car finally broke down on the motorway after losing an extra gallon of fuel in 20 miles and failed to start again. Fuel seems to be the coming from the front of the engine and is coating the radiator and drive belt. When attempting to start the engine it is acting like it is starved of fuel and the drive belt is not turning the pump on the lower left of the engine due to the diesel covered belt (I assume this to be the coolant pump).

Question's

1) what is the top 'pump' type device that is driven by the drive belt that has fuel lines coming from it and is this know to develop leaks. This area seems to be the source of the leak but it's not at the junctions with the fuel lines.

2) Are there are any other know leak points at the front of the engine?

 

[ronka30]

I have had starting issue that has got progressively worse for 6 months and a constant smell of diesel from the engine. I had all the fuel return pipes replaced a year ago. Overnight the fuel seems to drain back to the tank as it taking 1 and half ignition cycles to start from being parked overnight facing uphill.

The car finally broke down on the motorway after losing an extra gallon of fuel in 20 miles and failed to start again. Fuel seems to be the coming from the front of the engine and is coating the radiator and drive belt. When attempting to start the engine it is acting like it is starved of fuel and the drive belt is not turning the pump on the lower left of the engine due to the diesel covered belt (I assume this to be the coolant pump).

Question's

1) what is the top 'pump' type device that is driven by the drive belt that has fuel lines coming from it and is this know to develop leaks. This area seems to be the source of the leak but it's not at the junctions with the fuel lines.

2) Are there are any other know leak points at the front of the engine?

your pump have leaks, you needed replaced all o-ring into pump and can be replaced fuel pipe (low side)

 

[BlackC55]

I suspect either the pump or the pipes are leaking

 

[macy]

Hi
just had the same problem with my 220 CDI (leaking pipes). Decided to replace the pipes £51.70 for the pipes from MB.

 

[cikko]

Can I ask for some advice on this thread please?

I have a 320 cdi and it's dripping fuel onto the drivebelt from around the pump area. I have tried to see what has o-ring seals and can't detect without removing stuff - which I don't want to do until I have the parts really.. also if i introduce air into fuel pipes, is it likely to cause hassles? I had an Isuzu that would destroy the pump if it got any air in there at all.


I have been to MB and they very nicely gave me a print out of the associated parts - blown up microfische type diamgram with reference numbers... anyone familiar with these diamgrams? I suspect I'm going to need #35 and #41?? It shows a washer of some kind #47.

Does this make any sense to anyone? The diagram has Major assy: M- Engine/ Group 07 - fuel inj/ Subgroup 120 - filter, lines & thermostat.

As I have a low reading temp gauge - I probably need a new thermostat and having read other owners' comments - the fuel lines will be brittle. Are these the same fuel lines I'm giscussing above?

Any help would be MUCH appreciated.

Stu

 

[cikko]

If, perhaps this request for help is too iffy... can anyone show me where to find the relevant information to diagnose/complete this work myself?

Stu

 

[kenny1000]

Hello mate, just had the same problem and sorted it myself, look at my post under engine, injector leak and if you have any questions come back and I will try and help

 

[cikko]

As no-one else other than Kenny had any advice.... I'll proffer mine for anyone lese who may be new here and having diesel leaks on the pump area.

I had fuel dripping down from the vacuum pump area and onto the drivebelt. FYI if you need it - the vac pump is the mainly circular device on the end of the camshaft with the rediculous pipe that goes over the engine covers to the brake master cyclinder. To see it you really need to get the two covers off.

Having read other posts on here I was worried about moving the pipes as they would probably be "brittle" and break easily. The cost is ££££ and I was worried. I should not have been worried at all...... worth reading on:

Removing the 2 clips that hold teh rad fan cowling in place, I was able to lift it up a few inches to gain sight of the task ahead.

To describe the job in hand:

Remove the 2 fuel lines evident on the (facing the engine) l/hand underside of the fuel pump (to the right of teh vac pump on the end of the engine) & replace the rubber o rings.

The above 2 fuel lines are held in place by what could be described as an escutcheon plate held in the centre by one torx bolt. Due to limited access, I also removed the turbo feedback pipe and the airbox feed pipe.

Once the escutcheon plate was removed, the 2 fuel lines were really tight and as i had read here - probably brittle. So I tried wiggling with long straight and cranked pliers. This was VERY limited as the access is terrible.

I tried everything and my advice is : wrap some wire around the back of the elbow of the connector that fits into the pump. Pull that with pliers and wiggle the connector left and right with your long nose pliers. This breaks the seal and out pops the connector.

Incidentally - I didn't expect quite as much fuel to drip and had not allowed for this. I would remove bottom covers and collect as much spilt diesel as possible at source.

Next - remove old o-rings. They have gone hard and have been flattened to resemble road tyres in shape - round but flattened and not typically o-ring shaped. I had to split the old ones off the coupling.

I bought 6 "green fuel o-rings" from Mercedes at 77pence each. Yes - that's right, 77p each!!!

2 were used in this location of the pump. I greased up the new o-rings and slipped them into place ensuring they were not twisted or rolled over. I had to force them into place as the rubber o-ring made contact with the pump body. The pliers were useful here.

Escutcheon plate back on and now the other end of these 2 pipes... these were decidely easier and were not leaking but I had 4 spare o-rings!!!

The location here is the 2 fuel lines on the top right hand sideof the fuel pump. One goes to the filter housing and one to other side of the pump (already done) and T'd-off to the common rail.

Pushing IN the white clips forces the shoulders of the clip off the housing/body and therefore no longer having a mechanical grip on the pump body. A wiggle later and the connector was out. The old seal broken out and new one slipped on - both pipes done.

I have 2 spare o-rings and a cleaned up engine that now only uses diesel as a fuel rather than a lube for everything in the vacinity of a v-belt spinning it around the engine bay.

What I should have done is replaced the drive belt (it had been soaked several times in diesel and it is obvioulsy not beneficial. I have since had the belt disintegrate on me by shredding and on the motorway it cut through the feedpipe for the washer bottle :shock - so it's wise to get a new one on there after you have test run for no diesel leak.

Sorry for lengthy/overly descriptive message - I just wanted those of you who are "handy" to have the confidence to go ahead and just do this job. The fuel lines are not as brittle as fear depicts and the hassle is worth the saving on labour rates! collect the leaked diesel and use it as an anti corrosion coating on the W210 :laugh

Good luck

 

[Ashley]

How rude of me not replying to this sooner.

The problem turned out to be a leak with the High Pressure pump. It got worse and worse, where I was losing a cup of Deisel overnight and then failed catastrophically on the M4 causing a big smokey trail of Diesel to be left behind me until the engine cut and it sat there hemoraging Deisel on the M4 and then the AA lorry back to my local Merc Indi.

£700 later the problem was solved with a shiny new pump. EEEEEK!

 

[mrhoef]

I have the same problem with the leaking fuel; it seems to come from the HP pump; it appears to have 3 cylinder heads and one is leaking. Is the fuel pump servicable at all or is it new pump?

 

[panason1c]

I have the same problem with the leaking fuel; it seems to come from the HP pump; it appears to have 3 cylinder heads and one is leaking. Is the fuel pump servicable at all or is it new pump?

The pump is servicable with a new 0 ring kit available from a Bosch dealer but fitting new 0 rings didnt stop my pump from leaking from one of the heads and i eventually bought a new (recon) pump from ecp. (exchange item)

 

[Vlad]

As stated these pumps can be repaired with a new seal kit, but they can also suffer from hairline cracks to the metal casing which can't be repaired.

These pumps are also used by other manufacturers in their diesel engines, notably Hyundai.

 

[mrhoef]

I was worried about the pump heads but thought better to exchange all low pressure seals first to make sure. It looks like it has worked (so far)
Cikko has given a detailed description of the task. I would only want to add: if you smell any fuel in the front area of this engine (3.2l 6cyl straight) Get at least 6 new O-rings from Mercedes, because if one leaks surely more are leaking as well. The old/original black material is not fuel resistant and gives in after a while. The green ones are the right ones.
To replace all low pressure seals you will have to remove engine covers, bottom covers, radiator and aircon fans. The radiator when older is a hellish job to get out AND to get back. Very difficult to do on your own, you really need some extra hands doing this job.
The radiator has got a drain at the passenger side bottom; sadly mine was broken and had to drain by removing the bottom hose.
Seals to be replaced: 2 in the shut off valve just before HP pump; 1 overflow from HP pump, these 3 are most difficult to reach and the radiator has to come out to exchange these.
The other three are at the top pump (prime) and the fuel filter. Fidly but possible to exchange without getting radiator out.
The clips on the connectors are very brittle; some body said they are made of recycled yoghurt pots and I think he is damn right. Have a good look first before you break them. The shifting clip has to move toward the pipe in order to release the little hooks that click around the rim of the static bit. Then you stil need a lot of force and a lot of wriggling to get the connector out of the hole. Bend nose pliers are best for this job.
When the job is done, you will find the self priming is not impressive unless you have got a battery that cranks forever. If you suck (with any device) on the top connection of the top pump you will get fuel into the top pump and then it will fuel the HP pump enough for engine run