Cutting out after driving for about a minute.

A cupful of methylated spirits will do no harm at all, I would not have suggested it if it would. So you could well have moisture in your tank and that could be the problem. Next alternative is to drain the tank completely and then refill with new fuel.

What grade of fuel are you using?

Where did you locate the pump? Are you 100% certain that this replacement pump is designed to pull fuel as opposed to pushing it?

Can you run the pump without the engine running? If so, disconnect the fuel line from the pump to the filter and run this line into a large fuel resistant container. Start the pump and allow fuel to flow from the tank to the container. Does the line become aerated after 5 mins or so? If it does you will have removed heat as being a problem, so vapourisation is not the issue.

Ron.
 
SydneyRoverP6B said:
A cupful of methylated spirits will do no harm at all, I would not have suggested it if it would. So you could well have moisture in your tank and that could be the problem. Next alternative is to drain the tank completely and then refill with new fuel.

What grade of fuel are you using?

Where did you locate the pump? Are you 100% certain that this replacement pump is designed to pull fuel as opposed to pushing it?

Can you run the pump without the engine running? If so, disconnect the fuel line from the pump to the filter and run this line into a large fuel resistant container. Start the pump and allow fuel to flow from the tank to the container. Does the line become aerated after 5 mins or so? If it does you will have removed heat as being a problem, so vapourisation is not the issue.

Ron.
Click to expand...
Sorry Ron, I wasn't trying to be disrespectful, I will add some meths tomorrow, how long to leave it? cap off? I had drained the tank previously though.
I have one of those Sealey vac pumps which I connected to the fuel pump supply line (before the pump) and whilst the vehicle was faulting, I tried sucking fuel through, I got lots of air. After being left, no problem. I am certain my new pump is of the correct type as I went to great lengths on the phone to make sure they knew what I wanted. It even says on the reciept. I could try disconnecting the coil and running the pump cold, good idea. I can't see anything can be wrong with the system. The only thing I can think of is the fuel line running under the exhaust manifold, seems a little odd but if it didn't cause isse for the mechanical pump, why would it for the electric?
 
No worries Phil :wink:

Hmmm, So having drained the tank previously, there shouldn't be too much moisture present. Just a cupful will be fine and no need to leave the cap open.

What grade of fuel are you using?

The fuel line runs under the exhaust manifold,...how close are we talking? When the mechanical pump was fitted, the original location of the fuel line is across the back of the engine and then down and along the n/s just above the sump. After the reserve tap, where does your line run?

Ron.
 
SydneyRoverP6B said:
No worries Phil :wink:

Hmmm, So having drained the tank previously, there shouldn't be too much moisture present. Just a cupful will be fine and no need to leave the cap open.

What grade of fuel are you using?

The fuel line runs under the exhaust manifold,...how close are we talking? When the mechanical pump was fitted, the original location of the fuel line is across the back of the engine and then down and along the n/s just above the sump. After the reserve tap, where does your line run?

Ron.
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Hi Ron, using standard unleaded which is 95 RON I think with an additive for lead with octane booster.. The fuel line comes out of the tap on the driver side as plastic and couples to a metal pipe as it passes behind the passenger side head, it runs down below the exhaust manifold. I guess it is between the sump and the manifold, still close I'd say for a fuel pipe.
 
Hello Phil,

I know that 95 octane fuel will give far more running problems in terms of heat related vapourisation. In fact, in the same situtions where 95 gives contant stuttering and then shutdown, with 98 there are no such problems, so that may well be your problem. Even though you are using an additive with an octane booster, the underlying fuel is still 95 so fill up with 98 and see what happens.

As far as the fuel line goes, you can insulate it to minimise heat soak. I think Richard (quattro) uses a silver covering, although I may well be thinking of someone else.

Ron.
 
Hi Ron, when fuel evaporates, does it litterally leave air in the lines? Do you have an electric pump and have you changed the routing?
 
From your discription of the fuel line route it does sound like it is all pretty standard and as such I cant see that running 95 grade fuel is a problem, I myself exclusivly run 91 grade fuel with no issue.
I think it is a good idea to run the pump (engine off) to see if there is any issue with what is comming out of the tank as it may show a blocked pickup filter or point in the fuel tank, if that works OK then you are into a heat affected problem of some sort be it fuel or electric.

Graeme
 
ghce said:
From your discription of the fuel line route it does sound like it is all pretty standard and as such I cant see that running 95 grade fuel is a problem, I myself exclusivly run 91 grade fuel with no issue.
I think it is a good idea to run the pump (engine off) to see if there is any issue with what is comming out of the tank as it may show a blocked pickup filter or point in the fuel tank, if that works OK then you are into a heat affected problem of some sort be it fuel or electric.

Graeme
Click to expand...
Hi Graeme, I'm certain its fuel starvation as the line supplying the pump, when I attach my vac pump to it, draws air.. only after the engine has been run. That kind of says to me that the pickup must be clear as it wouldn't even draw air if it were blocked would it!? I will try pumping the pump with the engine off. The tap isn't leaking, there are no other leaks.. Have you an electric under bonnet pump?
 
Hello Phil,

It does, you will get vapour in the line, one of the main reasons why the fuel pump is best down near the tank. Vapour is very difficult if not impossible for a pump to pull, whereas vapour in front of the pump presents no problem at all. The fuel will just push it along and no problems are encountered with the engine cutting out.

Can't use 91 octane in Australia as it is an ethynol blend, and trust me..95 will give running problems in anything like warm weather whereas 98 in the same situation won't. Certainly that is the case here, it may be well be different in New Zealand or in other countries.

I have an electric pump and I also retain the mechanical pump. The fuel lines around the engine are as they were originally,....except I use an OEM sheath over the fuel line.

P4090073.jpg


Ron.
 
Hi Ron, your fuel line looks nothing like mine. Mine is steel and is unprotected. Could low fuel level - less than 1/4 tank cause issues here?
 
Hi Phil, I used to have an electric pump under the bonnet located just behind the ignition coil had no troubles for a couple of years but eventually it caused problems and engine would not restart when hot! caused me no end of grief as the pump when in the no start condition was still delivering fuel, go figure? Took me a long long long time to to work out that the pump was my issue, the cure was to take the old mechanical pump which thankfully I had retained ( a justification to all you hoarders out there) which was hanging on the garage wall for the last 7 or 8 years and reinstall it, problem solved!

As to the indicated fuel level, mine reads off the empty mark when the fuel runs out, very disconcerting when you are driving along and the engine dies and a glance at the gauge shows fuel in the tank, cure is simple pull the reserve tap and the roar comes back. I use the reserve tank probably every 2nd fill so it gets good use.

Standard fuel line is just a bare iron pipe not to say that its good practice when so close to a hot manifold but it should not be the cause of your drama.

Graeme
 
I am utterly stumped Graeme!! I'm sure the problem is now before the pump. The tap is dry so that only leaves vapour lock, surely?!
 
I would be inclined to install a mechanical pump were one available just so that system was back to factory standard as a start point. Until you can eliminate the fuel pump doubt you will be floundering around in the dark. My advice would be get a known good mechanical installed then you can move on with certainty if the problem is not resolved.
Vapour lock would not occur on a cold engine and it would take a lot longer than a minute to transfer the manifold or block heat to the fuel line to cause a vapour lock.
P6's have a fuel return system so that fuel is continually being circulated which helps to ensure that fuel line temperatures are reduced.
 
Hello Phil,

I am going to disagree with Graeme (sorry Graeme) in that a mechanical pump won't fix the problem either, if as you suggest the problem is before the pump. That would seem likely given what you are describing, so relocating the pump down beneath the tank would be a permanent solution. Alternatively, fill the tank with 98 octane fuel..afterall what have you got to lose?

Fuel which is the problem will vapourise in what is essentially a cold engine, I know having experienced this before on more than one occasion. It defies logic, the dashpots on the carburettors are stone cold and the temperature gauge is reading in the white, you just shake your head in disbelief. It does happen especially when moving from Winter grade fuel into Summer, a warm day with the former fuel and bingo..vapoursiation.

My fuel line is the OEM steel and plasic pipe, it is just insulated, and of course I use a rubber hose between the metal pipe and my mechanical fuel pump, whereas your metal pipe will have been cut at another point I suspect so as to accept the line across to your electric pump. Have you got some pics that you can post of your fuel line, the exhaust manifold and your pump?

Ron.
 
:LOL: :LOL: thats OK Ron, I was only concerned in eliminating the pump as an issue.... also rememeber that a cold OZ morning in winter would be considered a once in a 100 year heat wave in old blighty.

graeme
 
Hi Phil

The mystery deepens. Your reported running time before problems sounds far too short for it to be conventional P6B fuel vaporisation. But your results with the vacuum pump do sound like it. I'm suspicious of a plain steel pipe alongside the engine, and the new pipe work up towards the electric pump must go pretty close to the manifolds too.

I think my next step would be to re-plumb the fuel line from the reserve tap via the suggested new route outside the engine bay, then you know this possibility has been eliminated. If you don't do this you will keep coming back to wonder about it.

I wouldn't fill the tank all the way up just yet, as one of the possibilities has to be something awry with the fuel pick up in the tank. It would be a shame to reach that conclusion with a full tank!

Have you tried the effect of running the engine with the reserve tap operated to reserve? That could help eliminate the pipework between tank and tap.

I'd be about 65% certain of success for the replunbing from tap to pump. If not I think you ought to simply work quietly down the system to the tank. So new O ring in the reserve tap, then new lines tank to reserve tap, then oick up out of tank. But here's hoping it's solved at the reserve tap to pump stage!

I wonder if this is why the car came off the road originally?

Chris
 
dont know if it relevant but I have seen iron fuel lines split before along the seam.
 
Hi, I will post some pics later. I have tried it on reserve and main, it makes no difference. When I reroute this pipe, do you cut the original? I don't see how you can't to do it satisfactorily.
There are no petrol leaks. As for engine temp...
If I start the car up cold. It will now run on the drive for half an hour with no issue, if I take it up the road it vonks out after a minute or so. I guess the bonnet shut, engine loaded produces more heat? When I come back from a run the fuel keeps becoming aerated when run on the drive, after a run.
 
Gee Phil, that puts a different complexion on it. If the car will idle fine on the drive for 30 mins but dies if you take it for a one minute drive, that is really bizzare. With no air circulating, the engine will be hotter than driving for one minute. When it shuts down after a one minute drive, is that from stone cold or after idling for 30 mins?

Ron.
 
That is after idling for ages as I have been tinkering with various bits to check it won't break down! (Which it still does.)
 
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