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Fuel pump

1989 Porsche 944 2.7 lux
Do the fuel pumps get jammed with lack of use ?



Put new pump on for second time and when i start car a few months later.Fuel pump was stuck.IT as happened 3 times now.This time i freed the pump up by taking it off and connecting to 12 volt battery i freed it up .
Old 08-17-2019, 12:40 PM
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No, but they can get jammed if there is crud getting to them from the tank. The tank filter (strainer) might be no good (Not likely) or the line to the pump can be disintegrating.

If you want to look at the tank filter take care not to twist the threaded insert out of the tank, I think some people use a hose clamp to clamp it good to the neck of the plastic tank before spinning out the insert with the hose barb and strainer.

I'd first see if there are bits in the pump when it's stuck, backflush it into a clear container. What sort of fuel pump did you get? Maybe it's dodgy or counterfeit?

-Joel.
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1992 968 cabrio
1994 968 cabrio - Supercharged
Old 08-18-2019, 05:00 AM
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I took my possibly original Bosch pump out of my 87 944 NA, simple gravity drained it, let it sit for a ... very very long time - many many months - Put it back in, worked perfectly for many years. I only recently changed it for another new Bosch pump because I was troubleshooting. Gonna keep that pump.

... hope that helps!.... lesson is : get the Bosch....

Re-reading the OP, Id think if there is debris, and it made it through the pump, the debris is now in the filter... where is the ground for the pump? ... could this be another case of a flaky DME relay?

Last edited by Bukowski; 08-18-2019 at 05:46 AM..
Old 08-18-2019, 05:43 AM
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Fuel pump

Hi
I got a OEM Bosch fuel pump and also changed the fuel hoses from tank to pump and to filter and the one after filter to hard line.
Old 08-18-2019, 11:45 AM
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Good thought on the DME relay.
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1987 928S4
1992 968 cabrio
1994 968 cabrio - Supercharged
Old 08-18-2019, 03:58 PM
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The in-tank strainer is likely bad, allowing sediment from the tank into your pump. Has happened to many people on here.
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NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 08-18-2019, 07:57 PM
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yes on checking the strainer. order a new gasket before you pull it.

I would also pop the cover on the dme relay to see if the points are pitted on the pump side. it would be worthwhile to also check the voltage and current draw AT the pump.
Old 08-19-2019, 02:14 PM
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Fuel pump

I bypassed the DME with 3 wires
Old 08-20-2019, 05:34 AM
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what is the voltage drop with the jumper?
Old 08-20-2019, 10:29 AM
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Do you mean you bypassed the DME relay with the typical jumper wires? Is that what you think freed up the pump and got the car going again?
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1987 928S4
1992 968 cabrio
1994 968 cabrio - Supercharged
Old 08-21-2019, 05:19 AM
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Fuel pump

Yes used three wires instead on DME relay.Just in case it was the relay.Took pump off to free up
Old 08-21-2019, 05:34 AM
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Sounds like you are down to the tank strainer then. I've never seen one that had failed and was passing chunks to the pump but it sounds like others have. As a test you could try an inline fuel filter before the pump but it might limit overall flow. A clear filter would tell the tale though.

Taking the tank strainer out can be difficult and in some cases people twist the whole tank insert out so be careful on that route.
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1987 928S4
1992 968 cabrio
1994 968 cabrio - Supercharged
Old 08-21-2019, 05:47 AM
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In the Fires of Hell.....
 
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NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 08-21-2019, 06:06 AM
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awesome!

let's see how long the fuel pump lasts after it gets a clean fuel source!... it was Bosch, right?
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87 944 NA
Old 08-21-2019, 07:01 AM
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Fuel pump

Yes Bosch, pump fitted
Old 08-21-2019, 07:05 AM
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Thanks for posting that pic KD. Maybe they get clogged and the fuel pump collapses them until they split. Interesting.
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1987 928S4
1992 968 cabrio
1994 968 cabrio - Supercharged
Old 08-22-2019, 05:35 AM
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Quote:
Originally Posted by kdjones2000 View Post




Luxury!

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1977 924 Guards Red (parted and sold)
1987 924s Alpine White (sold)
1987 924s Kopenhagen Blue (my Lowencash tribute track car)
1987 924s Garnet Red
1982 928 Silver (sold)
Old 08-22-2019, 05:37 AM
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yeah, fuel-pump failure is extremely are. Factory pump is about 4-5x size of pumps in other cars of similar power. So these pumps aren't exactly having hard life. It's crud from tank that's clogging them up.

I wonder if running them in reverse would clean them out?
Old 08-22-2019, 11:04 AM
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Not on the 3 I have tried it on. Non-Bosch seem to work better.
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NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 08-22-2019, 07:31 PM
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