seemingly unfixable sprinter cdi fuelling fault..

ogri

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firstly, hello all, this is my first post.
secondly, i have the most irritating problem with me 311 cdi, and im hoping beyond all hope somebody here can help, absolutely all ideas and advice very gratefully received.

im a self employed builder living in peterborough, and me van is crucial to me 6 days of the week, every week of the year, as such i bought merc.
my last sprinter, a slow but ultra reliable 208 lwb done me for ten years and 300k, the only problem it ever had was a blown head gasket at 240k, a fantastic van.
early this year i bit the bullet, sold the old faithfull and bought a '52 plate 311 cdi, one owner with 102k on the clock and fsh, and it ran faultlessly for 12000 miles until i booked it in for a full service.
a couple of days after the service, it failed to start from hot, though would when it was cold, and ran perfectly once started.
a mechanic mate suggested a the crank position sensor could be breaking down when hot, so i bought and fitted that, no good.
so, back to the garage that serviced it, they thought the new fuel filter could be faulty, fitted another and problem solved.
two days later does it again, they fit yet another filter, sorted.
a daylater its ****** doing it again and im working up north in newcastle, so into a garage there, they concurr its a fuel fault, and fit another fuel filter and a new one way valve(the little black plastic one that sits on the filter).
once again problem solved, except two days later it does it again.
this time i go to see me mechanic mate, he takes the fuel feed pipe off when its hot, and its dry, so the fuel is obviously draining back down to the tank.
he fits one of those bellow type hand pump thingys with a one way valve in line between the filter and the incoming fuel line, we pump it to prime the filter and the van starts ok but still wont start when hot without me having to pump it every time.
so last week book it into the main merc place where im working in newcastle (bell trucks) and ask them to please sort it whatever it costs (ulp!)
pick it up later that day and hallelujah, its fixed apparently.
they have replaced the fuel line from thefilter to the high pressure pump, an apparent weakness as they get old.
the pipe becomes brittle, the joint leaks, air gets in and the fuel runs back to the tank.
this makes perfect sense to me, as it explains why all the titting around people have done to try and fix it results in a temporary fix, as disturbing the joint probably allows it to seal properly just for a short while.
it runs great and the problem has finally gone.
except one week and 500 miles later i drive to a job in luton this morning, stop at the builders yard, and it wont start....
pump the bellows and its empty, fuel is draining back again..crap
phone bell trucks, they say "nip it in", i say "im 250 ****** miles away" and the bloke suggests it could be an injector gone, 300 quid to replace which is ok if that is the problem, but i dont understand how the messing about always resulted in a temporary fix if it is the injector.
anyway, come 6 pm and the van started straight away having been left for 7 hours and drove faultlessly the 60 miles home, though would not start on me drive 5 minutes after i got home when i tried it hot.
as i said, any ideas very gratefully recieved, i just dont know what to do next, am back up in newcastle in three weeks, but though i know it will start in the morning when its cold hate driving it when it aint right, and cant even turn it off when im fuelling up because it wont start.
the last fix (the fuel line replacement) lasted much longer tha the others, could this be a clue? buggered if i know..
thanks blokes
paul
 
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BlackC55

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Lack of fuel pressure is the key.

I would suspect a injector leaking off or air in the fuel system. They also suffer from chaffing wiring looms on the bulkhead.
 

dieselman

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Lack of fuel pressure is the key.

I would suspect a injector leaking off or air in the fuel system.
Could an injector cause fuel to drain right back through the pump and stop solenoid?

One query is why does it start from cold as it must have drained back when hot thus would have no fuel in it anyway.

It needs the feed pipes checking for air bubbles and the injector leak-off rate checking.
 

derek burns

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my 311 cdi started 3 weeks ago been siting for 4 months then would not startdose eny body know whats up
 

EOBD

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Firstly I AM NOT well known with these..
But isnt there a low preasure fuel pump in tank? May have issue pushing fuel to filter.
But sorry this is more of a guess..

And another completely wild guess, might go something like this..
If the fueltank had its vent blocked, all the time engine is running, it will
create "vacuum" in tank, and when you switch of, this vacuum pulls fuel
back to tank.. how about that for a wild guess :shock:
 

izo11

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did you ever resolve this problem. because am having the same problem with my 2001 311 model. the sprinter wont start when hot. it takes time to start when cold but runs fine once started. did a leak back test and one injector was leaking and I changed but am still stack there. the rail pressure does not go beyond 144 bars when cranking. it goes to 0bars when not cranking. a mech fro m local MB dealer is suggesting a failed rail pressure sensor could this be the problem or its the ECU? I have also replaced all the O.rings on the transparent fuel lines.
 

Alex Crow

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have you checked the o-rings on the pressure regulator at the back of the rail?
 

Steve@Avantgarde

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I too would go with high leak off on an injector or the rail pressure o rings as Alex has just mentioned. Find a Merc Indie with Star diagnosis and a leak off test kit and Im sure you will get it fixed.

311 sprinters are known for knackering injectors especially after 100k! Have done 2 in the last week!
 

PED

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ped

just fixed one of these x reg cdi
van would not start
turned out to be the two small o rings on the sensor at the rear of the fuel pressure rail
a quick test see if you can start it on easy start takes two people one turning the key one spraying you cant do it on your own
if it starts and runs turn it off and try again
if it wont stat then its more than likely these o rings
remove the top of inlet manifold to gain access to the sensor at rear of pressure rail
remove sensor two small female torques check the small o rings for splits
parts from merc
you would not think sutch a small o ring could give so much trouble
 

Alex Crow

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............turned out to be the two small o rings on the sensor at the rear of the fuel pressure rail.............

that is what i mean, but it is an actuator, not a sensor.
 

marxtringer

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dont rule out the pressure regulator itself, after changing the o rings to no avail i found that mine was stuck slightly open letting rail pressure back down the return line
 

izo11

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hard to start engine

Thanks all for your suggestions. I have replaced the O-rings on the CR fuel pressure regulator and all the injectors but still the engine will not start when hot unless I use easy start. also If anyone has suggestions on this one. there is a soft whining sound coming from the engine when the key is in the start position that is when all dash lights come on and then off. if the key is left in that position for a about 6 sec another symbol comes on the dash just above the position where the car mileage is located and the sound goes off. the symbol is similar to the low oil level symbol but small and adjacent to it is a clock symbol. what does this mean and could these be related to the hard starting problem? Also when the transparent fuel line from the filter to the pre-delivery pump is unplugged from the filter fuel flows to the pump and the line is left empty does this suggest that the pre-delivery pump is faulty or something else? this is no usual as previously the line would remain full when changing the filter and filling the filter with fuel.
 

izo11

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hard to start engine

Thanks all for your suggestions. have taken long to reply coz I could not get the rail pressure reg. O-rings locally. I finally got them from London and replaced but the problem persists. the star diagnosis showed an error with glow plug. one plug was not getting any current but that is sorted and still the problem persists. the van will not start when hot but will start when cold in the morning. though it starts then cuts starts then cuts until it picks at some point. I have done the leak off test even tried to direct the fuel from all the injectors to one container but all I get is just a few drops of diesel. The rail seems not to hold any fuel because when I open the supply pipes without cranking no fuel comes out as expected. I understand that the rail should hold fuel at about 5 bars when resting.

Question is
1. why does the van start on easy start but cannot rev beyond 3000. it cuts out and the EDC light comes on but it will start again on easy start.
2. there is a whining sound that comes from engine momentarily and then two lights comes on the instrument panel between the tachometer and the speedometer then the sound goes off. Its an oil level symbol on the right and a clock on the left. what do these symbols mean? can these cause a hard start
3. my pump wall leaking awhile back and I sealed it with a copper washer. simply removed one of the bolts where it was leaking put a copper washer in and tightened the bolt back and its sealed. can that cause the problem.
4 Finally, I got the service kit ( a bunch of O-rings and and gaskets) for the high pressure pump but I am afraid to open the pump as the manual prohibits opening the pump. does anyone know how to go about it? its the bosch CP1 K type with a shut off valve attached to it. any photos or schematic image or the opened pump will be appreciated.
 

Steve@Avantgarde

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If it starts and runs with easy start but cuts out on acceleration I would say you have an injector(s) with high leak off or worn nozzle(s). The cdi system needs to keep above 200bar fuel pressure to maintain running, if it drops below this the engine will stop as the ECU thinks there is a diesel leak!

Have you had a injector leak off test done yet or a quantity correction value check done on star? Like I advised around post 3 of this thread?

It seems you are guessing at this by ordering seals etc but not actually doing any solid diagnosis or trying to diagnose it using incorrect methods which is not helping.

If you open up the diesel system at any point and try and crank it and you dont see fuel running through then dont be surprised. If the fuel system detects any rail pressure drop it will cut the fuel supply to the engine. A CDI system is nothing like an in line mechanical pump system where fuel delivery is pumped regardless.

If you open up injector pipes, fuel lines, filters or anything else on CDI and try to crank it you will see nothing as the ECU will not allow fuel to be delivered as the fuel pressure sensor will see pressure has dropped below spec value. I hope that is clear enough for you to understand and that it helps you move forward.
 

izo11

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hard to start engine

Thanks Steve for the reply.

1. The engine starts with easy start but runs on its own once started. it revs to about 3000 revs when not being driven but when am driving and I try rev beyond 3000 it cuts and the EDC light comes on. Then I have to start it with easy start. in fact I do drive the car but I have to maintain revs at below 2500. I have done over 30km like this to get it to the mechanics.

2. We did a star diagnoses (rail pressure was not getting beyond 114bars) and a leak off test and one of the injectors was leaking and I have replaced it.

3. My main problem now is. The car starting on its own when cold but not when hot and not revving beyond 3000 when driving.
 

umblecumbuz

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If you open up injector pipes, fuel lines, filters or anything else on CDI and try to crank it you will see nothing as the ECU will not allow fuel to be delivered as the fuel pressure sensor will see pressure has dropped below spec value.

Thank you Steve. That's one of those useful bits of info that I will store away, ready for the inevitable 'MB rainy day.'

Presumably this holds good for all cdi series models?
 

izo11

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sprinter van 311/ 2001/ 611 DELA
hard to start engine

Thanks all for your support especially steve. I finaly found the engine problem. It was the high pressure pump. the seals and O-ring were compltely worn out. infact the O-rings were C-shaped due to wear. I simply replaced the seals and the engine starts and runs fine. My only worry is that the O-rings I used might not last long because the original O-rings were purplish (or blue) but the seal kit I got had black seals.
 

Steve@Avantgarde

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Thanks all for your support especially steve. I finaly found the engine problem. It was the high pressure pump. the seals and O-ring were compltely worn out. infact the O-rings were C-shaped due to wear. I simply replaced the seals and the engine starts and runs fine. My only worry is that the O-rings I used might not last long because the original O-rings were purplish (or blue) but the seal kit I got had black seals.

If you bought them from Benz then these will be the modified seals. I think the original ones were once green!
 

izo11

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Pump change

Hi everyone

can a cdi pump for a 612 engine (5 cylinder) part No 6120700101 fit in a 611 engine with part No 6110700701. I want to bid for it online because my pump is still leaking and I am not sure if it will fit.
 


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