Fuel pump

porschedavid · 08-17-2019, 11:40 AM

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 .

Jfrahm · 08-18-2019, 04:00 AM

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.

Bukowski · 04:46 AM

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, I’d 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?

porschedavid · 08-18-2019, 10:45 AM

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.

Jfrahm · 08-18-2019, 02:58 PM

Good thought on the DME relay.

kdjones2000 · kdjones2000's Garage

The in-tank strainer is likely bad, allowing sediment from the tank into your pump. Has happened to many people on here.

thomasryan · 08-19-2019, 01:14 PM

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.

porschedavid · 08-20-2019, 04:34 AM

I bypassed the DME with 3 wires

thomasryan · 08-20-2019, 09:29 AM

what is the voltage drop with the jumper?

Jfrahm · 08-21-2019, 04:19 AM

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?

porschedavid · 08-21-2019, 04:34 AM

Yes used three wires instead on DME relay.Just in case it was the relay.Took pump off to free up

Jfrahm · 08-21-2019, 04:47 AM

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.

kdjones2000 · kdjones2000's Garage

Bukowski · 08-21-2019, 06:01 AM

awesome!

let's see how long the fuel pump lasts after it gets a clean fuel source!... it was Bosch, right?

porschedavid · 08-21-2019, 06:05 AM

Yes Bosch, pump fitted

Jfrahm · 08-22-2019, 04:35 AM

Thanks for posting that pic KD. Maybe they get clogged and the fuel pump collapses them until they split. Interesting.

curtisr · curtisr's Garage

Quote:

Originally Posted by kdjones2000

Luxury!

DannoXYZ · 08-22-2019, 10:04 AM

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?

kdjones2000 · kdjones2000's Garage

Not on the 3 I have tried it on. Non-Bosch seem to work better.