WG start then stall ?? faulty lift pump

[Adrian D]

400cdi applications use an electric lift pump, and probably the same for c30. were you using only the lift pump from the 400cdi(c30) high-pressure pump?

[Deezelweazel]

The C30 uses both- an fuel lift pump mounted on the CP3 an an in line lift pump in the fuel tank.
That's a problem- because the elöectric fuel pump has the same amount of fuel all the time (to read as the same under all load conditions). It is just for starting purposes. I do use it in the same manner.

The pre lift pump delivers the fuel needed at higher loads.
I wouldn't trust on a pure electric fuel pump solution.

[Deezelweazel]

This is the CP 3with the added pre lift pump-it is always used in conjunction with an electric lift pump because it is very sensitive to run dry.
If you search the internet, or ask the local Merc dealer, they will tell, that they have a lot of problems with seized CP3'S after changing the fuel filter incorrectly.

[layback40]

Originally Posted by Deezelweazel

This is the CP 3with the added pre lift pump-it is always used in conjunction with an electric lift pump because it is very sensitive to run dry.
If you search the internet, or ask the local Merc dealer, they will tell, that they have a lot of problems with seized CP3'S after changing the fuel filter incorrectly.

In the KJ CRD (R42, they had the mechanical lift pump on the back of the CP3. The wiring is in place for an electric in tank lift pump. Very common aftermarket addition. The wiring is there because it shares the same wiring as the petrol version. The in-tank pump is an easy addition as the pickup in the tank is the same as the petrol except there is a piece of plastic tube where the pump is to be put in. The filter in the KJ has one of the best manual primer pumps on a filter I have seen.

[Adrian D]

Originally Posted by Deezelweazel

The C30 uses both- an fuel lift pump mounted on the CP3 an an in line lift pump in the fuel tank.
That's a problem- because the elöectric fuel pump has the same amount of fuel all the time (to read as the same under all load conditions). It is just for starting purposes. I do use it in the same manner.

The pre lift pump delivers the fuel needed at higher loads.
I wouldn't trust on a pure electric fuel pump solution.

Yes, the "onboard" lift pump of the CP3 is what I referred to. As I said, I know the 400cdi uses both the CP3 lift pump and an electric one.

[OffroadSpike]

Which engine on your WG? I'm going to assume the 2.7 CRD. I'm just going to copypaste myself on what I wrote on JoergM thread:

If you suspect having a fuel leak, the symptoms are hard to start car when cold (after hours of engine off) or visible bubbles on fuel lines. The fuel hose orings rot over time and end up leaking air inside. Also, the GC 2.7CRD which has the OM612 engine doesn't have an electric pump on the fuel tank, it has a low pressure pump and high pressure pump at the front top of the engine (black triangle shapped piece is the high pressure, small rectangle shaped piece that connects with it is the low pressure). The low pressure fuel pump sucks fuel from the fuel tank. Fuel isn't pumped before ignition, so is there's any air leaks in the system the fuel will go back to the fuel tank, when cranking the engine the low pressure pump has to suck all the air between the pumps and fuel tank first before any fuel pressure is reached in the common rail.

Other less common leaks can be the fuel pump gaskets or fuel filter orings.

I would buy the OEM orings from Mercedes and replace all of them (6 if I remember right). I ended up replacing the 3 hoses but was a pain in the arse, although not a complicated job but you need to remove some stuff to do so. New orings should do the trick. It fixed my long cranks in the morning, it now takes like 2 seconds to fire.

IMO installing an electric pump on the fuel tank is not fixing the problem, I would rather find the problem and fix it than cover the issue.

[OffroadSpike]

Also I would like to add what I think is happening in your case. It sometimes happened to my 2.7 before fixing the fuel hoses. When youn turn off the car the pressure is kept between the pumps and the common rail/injectors so when you first start it the pressude is enough so that it will start with no problems, then the low pressure pump sucks air in from the filter/fuel hose to fuel tank then common rail loses pressure and engine shuts off. After that you have to crank it for some time until low pressure pump has sucked all the air in then the car drives without problems until you turn it off again and let it sit for some time, that's when bubbles are sucked in again and fuel goes back into the fuel tank.

I'm also guessing you have very rough idle until all bubbles are removed.

See where the bubbles are in the hoses before starting the car, that may lead you to the oring or gasket that is failing.

Did you bleed the system after changing the fuel filter? There is a valve that sits near the thermostat that you are supposed to bleed when air gets into the system. You need a bleed pump and a hose that fits in to suck all the air out.