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Hi
My old and faithful 2002 C270 diesel saloon has now developed a new fault, which only shows when I am trying to start from cold. After preheating, the first turn of the key and the engine starts immediately, but then cuts out immediately. It then takes 30 seconds of engine spinning, before the motor fires again. Then all is well for the rest of the day ....until the next morning. I have just changed the fuel filter, but no noticeable difference. We are in the middle of our summer, so I can't even blame the weather
I know we all hate mornings, but this is ridiculous!
Would appreciate any suggestions or help in tracing this problem.
Many thanks!
Thanks Glyn.
Cold starting has never been a problem and even now, when it eventually starts, the engine is smooth with no white smoke. Do you think the glow-plug relay could also be a culprit? Where is that situated?
Thanks
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Cold starting on diesels is directly effected by:
- Engine compression ~ do a compression test
- Glow plug issues ~ even one out will compromise cold starting
- Glow plug controller issues ~ not user repairable
- Pump & injector calibration ~ have this checked.
- Clogged exhaust or Cat ~ your car is pre Cat & you would know if the exhaust was clogged. The car would not pull the skin off a rice pudding.
What mileage has the vehicle done? Has it been correctly maintained & only used Benz approved lubricants?
Mileage 195K.
Oil and filters changed every 5000 miles. I use High street brands of 5W-30 fully synthetic, so not sure if Benz approved. It uses no oil between services.
Not trying to interfere but if the glow plugs were at fault then the injectors would still be pumping fuel into the engine on starting and would result in a black cloud when the engine did start. I would lean towards the mechanical fuel pump if the car has one or if not a leak in the supply fuel line or faulty electric pump. Some have a combination and use both the electric and the manual, not familiar with which system yours has. But then again I think it is fuel supply related. Faulty check valve will allow the fuel to go back to the tank. Next try to remove the gas cap while cranking for the 30 seconds and see if the time is reduced before startup (reduced vacuum from the gas cap being installed) this is just for test and would probably give you a cel if left to run this way.
Good Luck, let us know what you find.
Many thanks for your help Critter. I have checked the glow-plugs as instructed above and from the readings, they all appear good. I have also checked the glow-plug control unit and that is delivering just over 12V to each cylinder, so that's ok. As yet, I haven't had the injectors checked/compression check, but saying that, the engine has never missed a beat and despite the high miles, still manages to return over 60mpg on motorway runs. The 6th gear obviously plays its part here.
I must say it feels like fuel starvation, similar to when changing the fuel filter and not priming it sufficiently. It gives a short clean rev and then dies instantly. Then doesn't even fire for a good 20-30 seconds until it gradually catches and finally revs as if nothing wrong!
Does the car have a mechanical fuel pump or electric or both?
Yes it does sound like a fuel supply issue, any fuel dampness around the fittings of the fuel lines.
Did you have issues before the filter change?
I'm sorry, I have no idea about the type of fuel pump on the vehicle, or even where it is located.
Yes, the problem arose out of the blue only last week, so I immediately reached for a new fuel filter, thinking that would cure the problem. The old filter was 15K miles old, so it was time to change anyway. Unfortunately it had no effect
The only other thing I did recently, was to remove the air filter cover, to see if that required changing. Could I have disturbed something on that side of the engine, which would cause this problem? What about the air-flow meter thingy?
As I said before, it seems that there is just enough fuel present for it to start instantly and then it cuts out, as if starved of fuel, followed by the winding over for 20-30 seconds, maybe to replenish? I have quickly checked the flexi fuel pipes around the fuel filter, but all appear dry and ok.
The car has never behaved like this and has never failed to start instantly, no matter what the temperature or conditions. Even now, once started, the problem goes away until the next time!
Looking into what type of fuel pump you have, 2002 C270 diesel.
Just thinking out loud but next drive and when you stop at night, remove the fuel cap for the tank to see if there is any vacuum from the fuel being drawn out. Possible when you drive a vacuum is created in the tank and when you shut it off overnight the fuel is pulled back into the tank from a faulty fuel cap check.
Looking now
Quick search looks like you have an electric pump in the tank which feeds another pump at the front of the motor, you should see a plastic line and a regular fuel line with metal fitting. A check to see if the electric is working would be to loosen a fitting on the front engine pump and then turn the key on, or more ideal would be to open the fuel cap and another person turn the key on while a person is listening for the hum of the electric pump, it may only work for a few seconds until the fuel pressure comes up to spec. Maybe someone else could chime in if they have another idea.
Do you have something similar to this? High pressure fuel pump has the white square on it, middle of picture, this feeds a manifold in which the injectors are plumbed off of it, Check for low pressure from the tank to this from the plastic line behind the visible steel line. So there must be a mechanical or electric "lift " pump to bring the fuel to the high pressure unit.
By the way this is my first picture on MB, thanks to the moderators for fixing that crazy setup they had before to apply pictures.
Hi
Yes, that is the same type of pump.
It is now 7.20pm, so I have removed the fuel cap and we'll see what the morning brings.
I will let you know tomorrow.
In the meantime, thanks once again for your kind assistance...it's very much appreciated
You can replace it now as this was just to ensure there was no vacuum in the system to draw fuel back. Have someone listen for the electric pump to switch on at the fuel tank opening, you should hear the hum, chances are the relay for this unit it toast or the pump itself, reading the above in tank thread it seems similar to your issue so some surfing may also assist you. Good Luck, keep in touch.
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
You guys seem to be doing well. Yes you have an electric feed pump to the HP pump & then amplifier injectors.
If you have a feed pump problem the car will generally not perform at high (for diesel) RPM or WOT. Remember that diesels run excess air. You accelerate them by giving them more fuel.
Most really high miler Benz passenger diesels hard start cold due to a drop in compression. Once started they will run normally as compression ignition is sustained due to temperature.
That's why I asked mileage.
Last edited by Glyn M Ruck; 07-12-2014 at 03:39 PM.
Hello Glyn,
Not to interfere, I do agree on your statements, But the op is getting 60mpg which is telling me he does not beat on the car but rather lets the torque do the work, so is it possible the lift pump is inoperative or the relay is toast, any other ideas?
Does the pump relay use a contact during the actual start function and then switch over to a normal run when the key is released??
This is fresh ground for me, although have had a diesel truck in the past, it just seems that it is a fuel issue, with the fact of no black smoke when cranked for 30 secs and the fires some what normal
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
If the lift pump or relay were at fault the car would never run. If the pump was lazy or the filter was clogged the engine would flat spot the minute you made power demands.
Fuel pump relay is in cavity A in the rear SAM on the LHS of the trunk.
When you read voltage. You must read it while cranking or you could get a zero reading. The LP pump on a diesel builds pressure to the HP pump & then auto shuts down until a pressure drop on the feed line. i.e it holds the feed rail at a specific pressure.
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Sorry ~ been scratching my head & we are ignoring a very simple possibility. The CPS.
Replace the crankshaft position sensor. It is located at the back of the motor mounted above the flywheel approximately behind the diesel injection pump.
CPS's usually give trouble hot but there are exceptions.
07-10-2014, 03:36 AM
