Lift pump filter

[nathanrobo]

I have an S204 (2009) which can be difficult to start. At first I thought it was glow plug related and allowed the glow light to come on a couple of times before starting. But then every now and then it feels as though there's fuel starvation.

You can hear the pump in the tank pressuring up which takes about 20 seconds. If you wait for the pump sound to stop the car starts normally.

Does anyone have any experience of this? Am I on the right track? Should I pull the rear seat, extract the sender unit and inspect the filter on the lift pump? Is the filter separate? Appreciate your comments please

 

[a111r]

Sounds more likely that it's purging air ingress from the fuel filter and fuel lines?

 

[nathanrobo]

Sounds more likely that it's purging air ingress from the fuel filter and fuel lines?

Not sure... In the summer I replaced the fuel filter as part of a big service and it's done a couple of thousand miles since. There shouldn't be any other way of air getting in should there?

 

[alecmascot]

Sounds more likely that it's purging air ingress from the fuel filter and fuel lines?

That will be it. There are warnings in WIS to be careful to not damage the fuel hoses when replacing the filter.
After changing the filter the pump runs till it is filled, then I never hear the pump run gain...of course it must but for only a short time every now and again.

 

[Alex]

I'd measure the fuel pressure first. Could be the pump on its way out or the FPR.

 

[nathanrobo]

I'd measure the fuel pressure first. Could be the pump on its way out or the FPR.

I did wonder about the fuel pressure regulator as I had something similar on my IL6 W211. Although you can definitely hear the lift pump for a while each time the car is cold. Is this more likely to be a lift pump or FPR fault? I take it that there's no question of a problem with the high-pressure pump as it's just a gear pump.