air in fuel, help please.

[gareyt]

OK, so I got a guy to replace my diesel fuel filter but now there is definitely a massive amount of air in the system and I dare not let the fuel drop below 1/4 as the gauge is also not reading accurately. When I start the car it doesn't start like it did before either as it needs to turn over more and then when it has started you can hear and feel it struggling at first to get enough fuel.

Once its going its fine and if I stop and start again it does it no problem.

I have tried bleeding the air myself a number of times but I think Im just making it worse. Also there are 2 lines coming out of the filter into the engine and this is confusing as there is only one fuel line going into the filter and one electrical connection.

Its a 2004 1.5dci megane, if anyone has any advice or knows a quicker or better way please lmk as its very annoying.

[Steffan]

gareyt said:

OK, so I got a guy to replace my diesel fuel filter but now there is definitely a massive amount of air in the system and I dare not let the fuel drop below 1/4 as the gauge is also not reading accurately. When I start the car it doesn't start like it did before either as it needs to turn over more and then when it has started you can hear and feel it struggling at first to get enough fuel.

Once its going its fine and if I stop and start again it does it no problem.

I have tried bleeding the air myself a number of times but I think Im just making it worse. Also there are 2 lines coming out of the filter into the engine and this is confusing as there is only one fuel line going into the filter and one electrical connection.

Its a 2004 1.5dci megane, if anyone has any advice or knows a quicker or better way please lmk as its very annoying.

I suggest tht you call the mechanic who fitted the fuel filter first. Why would this not be his responsibility?

Edited by Steffan on Saturday 31st May 22:47

[Vipers]

Confused............

[Locknut]

Sounds like the filter seal is letting in air. I can't explain it but it seems that a bad seal can let air in but not allow fuel to leak out,so there is no visible clue. As already suggested, you should go back to the mechanic who fitted it.

[gareyt]

I would go back to the guy, I say guy because Im not sure he deserves to be called a mechanic. I also had him change all my CV joints due to clicking noises when steering at slow speeds. After he said it was all done I couldn't help but notice that nothing had changed. When I finally got round to putting the car up on a ramp and having a look I could see that 3 of the 4 joints had their gaiters loose and were leaking grease. Also they had been fastened with zip ties and nothing looked new.

Im not going back to him, in fact Im doing everything myself now and have recently done all my brakes and discs so I want to crack this fuel thing.

If I fit a new filter and do it by the book surely there will still be air in the system or will that cure it.

[Steffan]

gareyt said:

I would go back to the guy, I say guy because Im not sure he deserves to be called a mechanic. I also had him change all my CV joints due to clicking noises when steering at slow speeds. After he said it was all done I couldn't help but notice that nothing had changed. When I finally got round to putting the car up on a ramp and having a look I could see that 3 of the 4 joints had their gaiters loose and were leaking grease. Also they had been fastened with zip ties and nothing looked new.

Im not going back to him, in fact Im doing everything myself now and have recently done all my brakes and discs so I want to crack this fuel thing.

If I fit a new filter and do it by the book surely there will still be air in the system or will that cure it.

Follow the workshop procedure to the letter and this should sort the problem out. Best of luck..

[mygoldfishbowl]

If you've still got the old seal your mechanic removed I'd try refitting that first before anything else. I've had this problem a few times.

[Jimmyarm]

Those engines don't have any seals on the fuel filter you can replace iirc, it is just a whole throwaway unit.

They do however have a drain on the bottom of them, check that is done up tight (I've done this early in my career, assuming the drain would be tight out of the box).

If that is tight, there is probably a crack in one of the low pressure pipes or one of the connector ends isn't sealing properly. If the filter is fine, unfortunately it is usually a case of replace the entire low pressure pipework set.

There are 2 pipes going to the engine, one feeds the pump and the other is the return from the injectors. The other line is the 'in' from the fuel tank.

It is struggling to start after you leave it because air is entering the system, allow fuel to drain away from the pump and back into the tank. You will never bleed that air out permanently when there is a leak. Once it is started, the system self bleeds and as the leak is small will start again quite happily until you leave it for a few hours.

Edited by Jimmyarm on Sunday 1st June 11:24

Edited by Jimmyarm on Sunday 1st June 11:26

[gareyt]

OK, This makes sense. When I next get chance I will replace the filter and follow the procedures for priming and bleeding. If it doesn't clear it I guess I will have to look at getting some new fuel pipework.

It didn't do this before the filter was fitted so fingers crossed it is filter related. I really appreciate this advice jimmyarm, thanks.

[Jimmyarm]

gareyt said:

OK, This makes sense. When I next get chance I will replace the filter and follow the procedures for priming and bleeding. If it doesn't clear it I guess I will have to look at getting some new fuel pipework.

It didn't do this before the filter was fitted so fingers crossed it is filter related. I really appreciate this advice jimmyarm, thanks.

No probs.

Before you replace the filter, check if the drain on the bottom is done up tight (finger tight, not plier tight!). The metal filters in particular have a plastic drain on the bottom that won't be tight enough out of the box occasionally and allow air into the system causing poor starting.

[gareyt]

Ok, so I replaced the fuel filter for a bosch one. Everything went ok and was far easier than I expected. Primed it and it started after the second turn. Tightened up the water drain screw as well.

After a few days I start the car and everything is fine but it doesn't start perfect. Its much better than before, it doesn't hunt for fuel or feel lumpy anymore but the starting just doesn't seem right.

It is a diesel and a 2004 megane so am I just searching for perfection or could it be the starter motor that is letting it down a bit. I don't think its the air thing anymore.

If you are a diesel driver and have a ten year old car how does yours fair when starting.

[Steffan]

gareyt said:

Ok, so I replaced the fuel filter for a bosch one. Everything went ok and was far easier than I expected. Primed it and it started after the second turn. Tightened up the water drain screw as well.

After a few days I start the car and everything is fine but it doesn't start perfect. Its much better than before, it doesn't hunt for fuel or feel lumpy anymore but the starting just doesn't seem right.

It is a diesel and a 2004 megane so am I just searching for perfection or could it be the starter motor that is letting it down a bit. I don't think its the air thing anymore.

If you are a diesel driver and have a ten year old car how does yours fair when starting.

All modern cars ought to start on the button. If not then there is a fault somewhere. Time to try some local friendly garages who will see if they can find the fault(s) with diagnostic equipment. The days are long gone when guesswork could solve IC engine faults. You need serious equipment and model specific knowledge to be able to ignore everything else and find the fault. Way it is with modern higher tech motoring. Best of luck. I would get this sorted otherwise let down time will be when you can least afford it.