bad starting, fuel leaking back?

enery8 · Jan 21, 2011

While visiting a main dealer today my p38 seemed a little reluctant to fire up. The person I was dealing with told me that the problem is fuel leaking back and there is a suggested modification using a non-return valve in the fuel line just before the ip. Anybody heard of this? know where I can get a suitable non-return valve usable with biodiesel (viton or hdpe)

Datatek · Jan 21, 2011

First check the leak off pipes, if they are leaking, the fuel will run back. Many people seem to have fitted a non return valve also.

enery8 · Jan 21, 2011

Thanks Data, I will check the leak off pipes over the weekend, do you happen to know the inside diameter of the supply pipe? I have sourced some aluminium valves locally. They do 6.8 and 10 mm at just under £8.

Datatek · Jan 21, 2011

enery8 said:
Thanks Data, I will check the leak off pipes over the weekend, do you happen to know the inside diameter of the supply pipe? I have sourced some aluminium valves locally. They do 6.8 and 10 mm at just under £8.

Leak off pipes are fine with 3.2mm I.D, pipe, sorry I don't know the diameter of the supply pipe

enery8 · Jan 21, 2011

thanks datatek

JellySpanners · Jan 21, 2011

Pop to the scrap yard and get yourself a diesel fuel primer off a Citroen or Peugeot, it looks like a small rubber rugby ball with a pipe either end, not only does it have a one way valve in they are great if you run out of fuel or change the filter...

enery8 · Jan 21, 2011

Thanks for that JellySpanners, I will go look...

ovalandrover · Jan 22, 2011

i'm travelling in Europe and all of a sudden i got bad starting proble when hot and cold one time i read some reports on here and they said sometime if fuel is below 1/4 tank there is a problem after i topped up the car the problem went away.
It was the only time i let the fuel get that low.

dogsbody · Jan 22, 2011

ovalandrover said:
i'm travelling in Europe and all of a sudden i got bad starting proble when hot and cold one time i read some reports on here and they said sometime if fuel is below 1/4 tank there is a problem after i topped up the car the problem went away.
It was the only time i let the fuel get that low.

Both of these problems could be linked to the in-tank pump. If it's not working well you don't have any pressure in the fuel line, giving the appearance of fuel running back. Then, if your tank is low and the in-tank pump isn't working well you are relying on the pump up by the engine to pull the fuel all the way from the tank.

As the in-tank pump is electric it's fairly easy to check. Ignition on and disconnect the clear fuel pipe under the bonnet. If the in-tank pump is working well you should get a good flow of fuel. Obviously this is a lot easier and safer if you have a small bucket, maybe some rags and a second person to help.

Datatek · Jan 22, 2011

dogsbody said:
Both of these problems could be linked to the in-tank pump. If it's not working well you don't have any pressure in the fuel line, giving the appearance of fuel running back. Then, if your tank is low and the in-tank pump isn't working well you are relying on the pump up by the engine to pull the fuel all the way from the tank.

As the in-tank pump is electric it's fairly easy to check. Ignition on and disconnect the clear fuel pipe under the bonnet. If the in-tank pump is working well you should get a good flow of fuel. Obviously this is a lot easier and safer if you have a small bucket, maybe some rags and a second person to help.

Easier and safer to take the fuel pump relay out and stick an ammeter across the contacts. It should read 4 amps or so if the pump is working, a lot less if it's not

wammers · Jan 22, 2011

dogsbody said:
Both of these problems could be linked to the in-tank pump. If it's not working well you don't have any pressure in the fuel line, giving the appearance of fuel running back. Then, if your tank is low and the in-tank pump isn't working well you are relying on the pump up by the engine to pull the fuel all the way from the tank.

As the in-tank pump is electric it's fairly easy to check. Ignition on and disconnect the clear fuel pipe under the bonnet. If the in-tank pump is working well you should get a good flow of fuel. Obviously this is a lot easier and safer if you have a small bucket, maybe some rags and a second person to help.

If you switch ignition on, pump will only work whilst glow plug lamp is on. It will not run unless glow lights are on, engine is being cranked or engine is running.

The Mad Hat Man · Jan 22, 2011

Datatek said:
Easier and safer to take the fuel pump relay out and stick an ammeter across the contacts. It should read 4 amps or so if the pump is working, a lot less if it's not

Not if it's seized, or getting that way.

Datatek · Jan 22, 2011

The Mad Hat Man said:
Not if it's seized, or getting that way.

If it's seized or partially seized it will read a hell of a lot more than 4 amps, if it's dead it will read a lot less. Simples

The Mad Hat Man · Jan 22, 2011

Now, it's a long time since I did motor electrics, and I don't wanna hijack the thread, but don't that depend where the motor seizes and where the brushes are in relation to the commutator, as it can seize and look like a direct short? Or have I got it wrong?

fanatic · Jan 22, 2011

The Mad Hat Man said:
Now, it's a long time since I did motor electrics, and I don't wanna hijack the thread, but don't that depend where the motor seizes and where the brushes are in relation to the commutator, as it can seize and look like a direct short? Or have I got it wrong?

one could test with ones ohm meter for direct short

but you would get a stall current on a seized motor

The Mad Hat Man · Jan 22, 2011

fanatic said:
one could test with ones ohm meter

Could one?
Or should one instruct ones chauffeur?

fanatic · Jan 22, 2011

The Mad Hat Man said:
Could one?
Or should one instruct ones chauffeur?

One's chauffeur will just replace it

[nomedia="http://www.youtube.com/watch?v=dlPjxz4LGak"]YouTube - Dire Straits - Money For Nothing (From "Live At Knebworth" DVD)[/nomedia]

wammers · Jan 22, 2011

Pump flow test. Borrow wifes measuring jug. Remove pipe from filter place in jug. Remove pump relay. Take live + from battery and contact terminal five in relay socket for 10 seconds. Five is the one orientated differently to the other three. You should get 80 ml of fuel in jug. Simples.

PS Washout measuring jug.

enery8 · Jan 22, 2011

ovalandrover said:
i'm travelling in Europe and all of a sudden i got bad starting proble when hot and cold one time i read some reports on here and they said sometime if fuel is below 1/4 tank there is a problem after i topped up the car the problem went away.
It was the only time i let the fuel get that low.

I concur with this as after I filled up yesterday

I noticed the car started more readily. If the in tank pump is the same as the old Rover SDi it will be VERY expensive.

wammers · Jan 22, 2011

enery8 said:
I concur with this as after I filled up yesterday I noticed the car started more readily. If the in tank pump is the same as the old Rover SDi it will be VERY expensive.

That is a sure sign that your pump is not functioing correctly. Change it. Around £100.00 or less for a pattern one. Genuine silly money.

bad starting, fuel leaking back?

Active Member

Well-Known Member

Active Member

Well-Known Member

Active Member

New Member

Active Member

Well-Known Member

Very senior member

Well-Known Member

No longer with us, RIP

Well-Known Member

Well-Known Member

Well-Known Member

RESPECT IS EARNED, BEATINGS ARE FREE ;-)

Well-Known Member

RESPECT IS EARNED, BEATINGS ARE FREE ;-)

No longer with us, RIP

Active Member

No longer with us, RIP

Similar threads