Turbo fuel issue

Hi all

Been trying to get to the bottom of my GTA dying after running for about 30mins. After much testing, the rear pump starts to squeal like it's dry then the car the car splutters and stalls. Car won't run properly again until it's cooled down.

So far I've cleaned out the tank, replaced the front pump, front filter (which was full of muck hence why I washed the tank out) and fuel regulator.

It had a new rear (and front) pump and filter about 4yrs ago. The rear pump fitted at the time is the uprated Walbro unit.

Thanks in advance!

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If you had issues with muck in the fuel tank and the rear filter is 4 yrs old, then I'd replace it.
The rear filter is KL57 and is a shared part with Porsche and not too expensive. I can dig out the cross reference part numbers if you need them.

Found an old thread with part numbers so just about to order. Can't understand why it only happens when it gets up to temp tho. Even if I don't drive the car and let it warm up on the drive the same thing happens. Starts fine and runs well when cold.

Hoping this is correct to order: https://www.ebay.co.uk/itm/Knecht-Fuel-Filter-Metal-Type-Porsche-944-928-924-911-Targa-993-964-Service/232583975200

Umm, slighty different porschr code to the one I have which is 928.110.147.05 Mahle KL22

I recall having to reuse the old brass connectors from the existing filter.

The thread stated either the KL21 or 22. I'll order the 22! Thank you

I believe there is a small reservoir between the two pumps, it could be the flow rate from the front pipe is insufficient to refill the reservoir. you can always do a flow check...how long to fill a bag of fluid. I bought some empty drip bags to do this and not have open petrol to spill i the garage...ebay is a good source.
One thing to check for is there is a bottom of the fuel tank strainer still there on some cars- hard to get to through, and on my atmo the front to rear metal fuel pipes were blocked or partially blocked...flushing through brake cleaner(and air line pressure behind it) cleaned them up for me.
Different symptoms on an Atmo, but could be the same cause.

Rear filter changed for the KL22 which was the correct one but still having the same problem. I don't have the luxury of anything to clean the fuel lines out. Another rear Walbro pump ordered, where is the reservoir that's been mentioned? Thanks

Might be of use - viewtopic.php?f=2&t=3217

if it's the rear pump thats starving over time, its must be the front filter , the front pump or the fuel lines connecting them....looks like I was wrong about the fuel reservoir at the back...that's the fuel filter you have changed.
The parts book is confusing, here are the two images, as you can see there are many potential blocked pipes, I think the outlets from the tank would be where I would start and they are easily accessible.
page 13 is the pumps (includes atmo version on the RHS), page 19 is a rhd GTA turbo. You can see a strainer filter shown (18) around the flow/return distribution block...that could be blocked too, but either way it sounds like a fuel system clean out will be needed.

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The fuel system on the GTA turbo looks complicated but is actually quite simple.

At the front of the car there is a high volume low pressure pump & an inline filter. I bought a filter from Amazon for about £8. I used a Fram G12-1. The filter is situated on a crossmember in front of the pedals. It should be replaced every 30,000 miles.
This pump feeds an auxiliary tank near the rear pump. The rear high pressure pump draws from this tank via a filter with screw fittings. This is available from Euro car parts. The one I got was a Mann 503330039. From memory it was about £15. It fits a Porsche 928. The rear pump supplies the fuel rails on the engine.

Because of the high pressure that the system uses (3bar) it is necessary to have fuel return pipework to send any excess fuel back to the tank.

Incidentally, I also fitted a Walbro pump. Overhauling the system made a huge difference to my car.

Thank you gents. The front has already been apart, tank out, pump & filter replaced. Pipes looked ok at the bottom of the tank.

Seems what I replaced on the rear at the weekend is jointly referred to as the rear filter or reservoir.

I'll replace the Walbro rear pump again (on order). What I don't understand is why it only happens when the car is up to temperature. The rear pump squeals because I presume it's running dry, how would a slightly blocked return line cause the inlet to have problems?

Just a thought !
Have you checked the pressure regulator ? Maybe its stuck & is returning the fuel to the Aux tank

It may not be the return line, it could be the feed line. There is a strainer shown in the rear file system and the front to rear pipe may be restricted.
If the fuel pressure regulator is retuning too much, I suspect the rear pump can outstrip the front pump and starve itself...seems a possibility.
Sadly its check everything until you find it.
I had similar issues with my Atmo that had sat for 20 years.

The fuel pressure regulator was one of the first things I replaced (after much searching!) after reading that it could have a hole in the diaphragm which could change with heat, that made sense but changing it made no difference. I'll have to work back from the rear pump if it's replacement doesn't cure the fault and see what I find.

"This pump feeds an auxiliary tank near the rear pump. The rear high pressure pump draws from this tank via a filter with screw fittings"
hi im looking at a GTA with fuel issues and am about to replace a seized rear pump, your quote implies the fuel is drawn through the filter is this correct ?it looks to me that the fuel is pushed through the filter by the pump
there is no fuel coming out of the low pressure pipe which goes onto the fuel pump even on cranking so i am wondering if the seized pump may be due to running dry or crap in the system causing a front pump or blocked pipe issue?