Dirt In Fuel System - What To Clean?

[David S]

Hi - Driving up to Donnington all was well for about 80 miles and then the car strted to hesitate, which felt like fuel starvation. The high pressure fuel pump also sounded laboured. I pulled over and let it rest and when I started off about 5 minutes later, it seemed better, but still had some of the symptoms. I spoke briefly to Richard on the GBS stand to see if they had any reported issues int his area, but he thought not (not really a fair question when he had no chance of looking at the car).

 

Anyway, when I left to go home, the pump all sounded fine and I got part way home when it happened again. This time it was far more dramatic and the car nearly stalled on me. I managed to limp in to a service station and filled up with fuel in case that was the issue (the guage said I had half a tank) and it seemed to be a bit better. I got home by sitting on the motorway all the way at about 2000 rpm. I drove it again over the weekend and it still feels a bit like the problem is still there.

 

Is it possible that the dirt could just work its way through the system, or am I being naive? I have never really worked on engines so I am not sure.

 

I though about changing the filter in between the tank and the low pressure filter at the back of the car to see if that helps, but what else should I do?

 

I am running a Zetec with the GBS plennum chamber, swirl pot and high pressure pump at the front.

[brumster]

Without knowing your car, I'd have to make some assumptions...

 

1) You've got a low pressure pump taking off the tank, through a filter, and filling a swirl pot (probably up front somewhere I'm guessing). There's a return line from the swirl pot back to the tank to dump back any excess fuel.

2) You've got a high pressure pump taking from the swirl pot, through another suitable high-pressure filter, to the fuel rail, via regulator then back to the swirl pot.

 

Which pump is sounding laboured, I assume the high pressure one, which begs the question how has any dirt found it's way through the filter in the low pressure circuit.

 

If the filters are the kind that can be disassembled, strip then down and check for dirt. Make note of positioning of filter when you take it apart, and ensure you put it back together and that you put the same fitting back onto the same hose (ie. don't turn it around in the process!).

 

I'd have thought it would have to be some fairly major dirt buildup to make a pump sound so obviously laboured - it sounds more likely that maybe the regulator, filter or return back is in some way affected and the pump is having a hard time pushing against it - outside it's specification. Be careful not to run the pump hot, if it is being laboured, you could knacker it up - especially if it's actually running dry due to some serious blockage.

 

If you can at least isolate which circuit the problem is in (low pressure or high pressure). If it has found it's way into the high pressure circuit past the filter, then realistically I'd want to be stripping down the fuel rail and checking the injectors - but focus on the state of the filter first, and let's take it from there.

[David S]

Cheers for the response, Brumster. Your assumptions are correct about the set up, except there is no high pressure filter before the fuel rail. It is the high pressure pump that sounded laboured, although if I run it now, it sounds fine.

 

I will start with the filter.

[spg]

Is there a vacum building up in the system, Try removing the filer cap if it happens again and listen for a sucking noise when you open the cap.

 

HTH

 

Steve

[brumster]

Further to Steve's post, has your tank got a breather pipe on it? If not, that is bad. Assuming it has, it should have a one-way valve in it that allows air in freely, but not out (or, if it's a nice one like we use in motorsport, it allows pressure out once it reaches a certain pressure difference - more for safety really - and closes if inverted so fuel doesn't spill out everwhere!).

 

If you have got a valve, check it's on the right way round (you can do this by simple blowing/sucking through it - but detach it first lest you want to be sucking in fuel vapour!).

 

I'd consider a second high pressure fuel filter anyway, even though you've got one in the low pressure circuit. The low-pressure transparent ones are excellent to verify that you're getting fuel flow, and see the state of the filter/dirt presence.

[Al Milton]

I've got one of the clear plastic filters bewteen the tank and HP pump (fuel injected engine).

It is amazing to see how much crud this filter has removed and stopped it from getting into the pump.

 

Cheap as well, so very good value for money