Maddening Running Issue

[Bruce M]

Squirt a little brake cleaner into the air intake & see if that stops the hunting. The car will run on the brake cleaner when the fuel drops out, but if it’s a spark problem this will not act as a temporary fix.

[jwhillracer]

If it helps to try, I ought to have a fully functioning MFI lift pump that you could borrow available in a couple of weeks' time.
It is from our 2.4S and has been happily supplying the 3.2 short stroke MFI engine in our hillclimb car.
At least it would confirm or rule out the pump.

Cheers
JW

[willbrown]

Squirt a little brake cleaner into the air intake & see if that stops the hunting. The car will run on the brake cleaner when the fuel drops out, but if it’s a spark problem this will not act as a temporary fix.

Good shout - thanks.


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[willbrown]

If it helps to try, I ought to have a fully functioning MFI lift pump that you could borrow available in a couple of weeks' time.
It is from our 2.4S and has been happily supplying the 3.2 short stroke MFI engine in our hillclimb car.
At least it would confirm or rule out the pump.

Cheers
JW

JW that is a very kind offer indeed. Thank you.

I used knapman’s DIY fix on the check valve and reinstalled that today. Car immediately ran better but only showing 9psi at the gauge. Ran great for an hour or so then engine just died. Waited for a couple of minutes, re-started and off it went OK again. So I have pretty much convinced myself that it’s the pump.

A loan would be very handy, but I have Prescott coming up in a couple of weeks and would want time to test a different pump well before that. I think I’ll bite the bullet and get an OEM one from Design 911. If the problem turns out not to be the pump then at least I know the one installed is good. I think mine is the original and is making some pretty strange noises so after potentially 50 years of service it’s time for retirement

I think GavP is coming to Prescott - be good to meet up with any other DDKers - my car will be in the paddock parking (if it makes it )


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[jwhillracer]

Check the price from Porsche before you buy, several parts recently have been surprisingly competitive............

JW

[willbrown]

Check the price from Porsche before you buy, several parts recently have been surprisingly competitive............

JW

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[RobFrost]

A new pump after 50 years is probably a good investment even if the old one still works. (Just trying to make you feel better about it)

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[willbrown]

A new pump after 50 years is probably a good investment even if the old one still works. (Just trying to make you feel better about it)

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thanks Rob. That’s what I’m telling myself too.


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[stretch]

Will. Did you do the fuel delivery test.?

Pump.? I would take a quick look at the fuel tank filter before buying a new pump. https://www.design911shop.com/p/fuel-fi ... ggEALw_wcB

[willbrown]

Will. Did you do the fuel delivery test.?

Pump.? I would take a quick look at the fuel tank filter before buying a new pump. https://www.design911shop.com/p/fuel-fi ... ggEALw_wcB

Good point - I haven’t done the flow test. Will do that first and I guess it would be dumb not to replace (or at least inspect) the tank filter before fitting a mega expensive pump. Fun and games. It’d be much easier if the car was on site, but it’s in a lock up, but no point trying to take short cuts.


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[willbrown]

To update - did the flow test and got 900 mil at 30 seconds which is in spec.

That said I’m pretty sure I could have got in the car and it would have been fine to drive for a bit then the gremlin would return as it did yesterday….

Pressure still showing 9psi. I wonder if the 14 psi spec is measured directly from the filter console (whereas I am measuring from the fuel line). Would that make any difference?


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[willbrown]

Check the price from Porsche before you buy, several parts recently have been surprisingly competitive............

JW

Good advice. Thanks! Porsche price was £70 cheaper than I could find elsewhere so have gone for that...

[willbrown]

My fuel tank looks like it has had it (see video below apols for poor quality!). Is there any point in trying to have it professionally cleaned?

https://youtu.be/6RgHeKIi_Og

[RobFrost]

Nothing there overly concerns me. I'm more hands on than most, so this wouldn't be for everyone. But if it were me I'd chemically or electrically remove the rust then epoxy line the tank. It looks very thin, maybe less than a tenth of a millimetre thick on a tank wall probably 1.2mm thick. I'd be more concerned if there was crusty rust, especially in the seams or around the fittings. I wouldn't even be sure that's your problem, unless you have found a fuel filter full of crud.

[willbrown]

Nothing there overly concerns me. I'm more hands on than most, so this wouldn't be for everyone. But if it were me I'd chemically or electrically remove the rust then epoxy line the tank. It looks very thin, maybe less than a tenth of a millimetre thick on a tank wall probably 1.2mm thick. I'd be more concerned if there was crusty rust, especially in the seams or around the fittings. I wouldn't even be sure that's your problem, unless you have found a fuel filter full of crud.

you are definitely more hands on! i've ordered a new tank - they are not too expensive. agree - don't think its the cause of my problem, but i have a new pump on order and i would rather have peace of mind that everything upstream of the MFI is kosher than doing more fault finding. i'd much rather be driving the bloody thing