Non return valve in fuel system?

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luggsey

luggsey

Active Member
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209
Can anybody tell me if there is a non return valve in the fuel system on my 98 L series diesel? I *think* mine is simply letting fuel drain back into the tank making starting hard. All the usual stuff has been checked for air leaks but this problem is still driving me nuts! I was going to try an inline non return valve between the filter and the tank...anybody tried that??
TIA
Paul.
 
Hi mate, What made you come to the problem starting diagnosis? have you had the injectors tested and checked the leak off pipes are in good condition etc.. also has it just started or always been this way? I have read that advancing the timing some times cures slow starting problems after garages replace the cam belt and diesel pump belt and get it slightly out.
You could also check the condition of the seal on your fuel filler cap, also low compression can cause start up problems.

A bit more info would be helpful, like is it just the first start of the day, does the glow plug light come on and go off and how long does it stay on for. does it smoke just after starting etc?

Cheers.
 
Hi Marty, all usual stuff checked and/or replaced.
New glow plugs and tested all ok.
New prime pump.
New fuel filter. (bleed screw seals ok)
New blee3d off pipes.
No sign of failed fuel lines.

Now, the reason I suspect fuel draining problems is this:

Car running normally and hot or cold, turn off engine, within 5/10 minutes car will be hard to start just as if air is in the fuel, it fires while on the key but needs full throttle and then runs rough and clears to run normally.

Now what I discovered is that if I simply blip the throttle and turn the engine off while the revs are at 4k then the next time I start the engine the car will start instantly and normally up to a week later! I have tried this many times and the result is always the same.

This makes me think there is a dodgy non return valve somewhere, the primer pump is new so it's not that one.....

That's as far as I can go, I have heard there is a valve in the fuel pump but I don't want to tackle that if it's a hard job, I will live with the fault rather then throw money at it, but if I can do it myself I will.

Thanks for your help.
 
For fuel to drain it would have to be replaced by an ingress of air and would happen whatever revs you shut off the engine.

Have you checked cam and FIP belts and pump timing?

It seems more likely that shutting off at high rpm is trapping fuel in the timing device which is countering otherwise retarded injection timing.
 
that's fine as long as the pump hasn't ever been removed without locking it.
 
Not while I have had the car, it looked ok and untouched when I got it but has had this problem all along, I was told by someone else that the injectors don't hold pressure while the engine is off is that right? That would mean it should not be injector related. I would like to find out if the fuel pickup in the tank has a non return valve, I would assume it has but I don't know for sure. If it has then I can simply repair this by fitting an in-line non-return valve above the tank?
Any other ideas that I can try?
(Only paid £300 for it so I don't want to throw cash at it really!)
 
Hi mate, try advancing the pump timing it's quick to do just 2 bolts on the pulley if I remember correctly, the pump belt may have been put on incorrectly at any point in it's life, The cam belt would still have been lined up correctly so wouldn't show up. I wouldn't recommend reving the engine before switching it off as it can cause damage. if that doesn't help I would get a compression test done as low compression can cause starting problems but not necessarily cause running problems.
 
The way to prove or disprove that it is fuel running back to the tank would be to park nose down on a steep hill and see if it starts ok, this always worked on citroen hdi's when they had this problem.:scratching_chin:
 
Martyfreelander said:
Hi mate, try advancing the pump timing it's quick to do just 2 bolts on the pulley if I remember correctly, the pump belt may have been put on incorrectly at any point in it's life, The cam belt would still have been lined up correctly so wouldn't show up. I wouldn't recommend reving the engine before switching it off as it can cause damage. if that doesn't help I would get a compression test done as low compression can cause starting problems but not necessarily cause running problems.
Click to expand...

I can't get my head around this one, how could it be pump timing/compression when it starts normally after blipping the throttle while turning the engine off? Are you saying there is some sort of mechanical advance system in the pump? I know almost nothing about diesel pumps! :confused:

The steep hill test is going to be hard, but I will try when I can. When we say steep in a normal road hill steep in this respect?

The more things I try the more likely it is I will stumble on the cause!
:)
 
I had a problem with fuel running back on an old Escort Diesel.

I bought a small cheap in line non return valve from ebay and cured it, started instantly after that.:)
 
landowner said:
I had a problem with fuel running back on an old Escort Diesel.

I bought a small cheap in line non return valve from ebay and cured it, started instantly after that.:)
Click to expand...

That's interesting, where did you place the non return valve?
 
luggsey said:
That's interesting, where did you place the non return valve?
Click to expand...
in line just before the fuel filter. I think the one in the filter housing was faulty, that's what I thought so I put a cheap one in rather than a new filter housing.
 
landowner said:
in line just before the fuel filter. I think the one in the filter housing was faulty, that's what I thought so I put a cheap one in rather than a new filter housing.
Click to expand...
There is a manual primer before my fuel filter but I replaced that and they have a non return valve in them, I wonder how good they are though?
I was thinking of placing a non-return valve tank end...
:rolleyes:
 
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