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Octane · Posted: Sat Oct 17, 2009 7:38 am Post subject: Fuel pump not turning on

'77 924 N/A, has been running all summer no problem.

Went to start it the other day and it did it's usual stumble a few times until it finally starts and runs (cold weather). However it stopped "trying" to run and now just cranks and cranks with no result or any firing sound.

I tracked it down to the fuel pump not pushing fuel through the system, I removed the line-in to the fuel distributor and no fuel is coming out with key on or when cranking.

What should I look at first? Is there a fuel pump fuse and if so, which one is it? All the fuses look ancient but I don't know where to start. There is a relay (very top left of the fuse board) that is clicking when I'm turning it over and then releasing the key back to the off position. Not sure if that's new or if I just haven't noticed it before.

Any advice would be great, thanks.
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- Brendan
1977 Porsche 924

Octane · Posted: Sat Oct 17, 2009 8:30 am Post subject:

Alright, I traced it and no 12v to the pump. It doesn't look like the stock pump, in-line right out of the bottom of the tank. It's a rubber-coated Pierburg (made in Germany) unit and was suspended by a large hose clamp.

Anyway, there's a black with green stripe wire and a dark red/orange wire. Which is positive and which is ground? I jumped 12v to both and no result, although that doesn't rule out a bad ground - I need to get my small 12v battery (motorcycle battery) with jumper leads that I usually use for this kind of thing from work tomorrow. Until then I still have no idea which fuse or etc. is causing it. I have no problem running a switched 12v line as I am doing a race car conversion this winter with carbs/different pump and will need to do this anyway, I just need it to run to drive it to my new shop right now though.
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- Brendan
1977 Porsche 924

9XX Girl! · Posted: Sat Oct 17, 2009 9:06 am Post subject:

Fuse Board and Relay Layout

Fuse #2 is fuel pump fuse on Aux fuse board

Fuel pump relay is #2 on relay board

if fuse is good, try removing the relay (they do fail) and shorting pins (30) with (87) if the fuel pump fires, its your relay

you can find the rest of the wiring diagrams here
http://www.pelicanparts.com/944/electrical/944_electrical_diagrams.htm
you want 924 part 1 page 2
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924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY

CorsePerVita · Joined: 25 Jul 2008 Posts: 1992 Location: Redmond, Oregon

The way i tested mine was to open up the boot where the metering plate was, lift it up manually by hand, this turns the relay on and lets it turn on the pump.

Take the plug off the pump and hook up a voltmeter. This is with the key turned on (not ignition on, just the key turned over). It should test out at 12v.

If it does not it's likely the relay or the switch in the metering plate.

If you do get 12v with the metering plate lifted up, bench test the pump. I was able to disassemble and rebuild mine with some patience. Not recommended if you aren't okay with chancing the potential consequences that can come with a horrible pump failure...

Thing is that if you didn't lift up the plate, then when you go to test the connectors the switch isn't on and the relay hasn't kicked in. So lift up the metering plate, then go test it and make sure the plate is up. Easy cheesy.
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

9xx:

Thanks for posting that picture. I printed it off and am going to post it in the back cover of my Haynes manual for quick reference.
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'80 924 n/a SOLD

Octane · Posted: Sun Oct 18, 2009 11:04 pm Post subject:

Thanks a lot 9xx girl! I gave the Haynes book but it's packed up as we are moving soon and I don't have easy access to it. I'll go out and try that today, thanks!
_________________
- Brendan
1977 Porsche 924

Octane · Posted: Tue Oct 20, 2009 9:51 pm Post subject:

Where are the aux fuses? I looked everywhere and couldn't find them.

Thanks.
_________________
- Brendan
1977 Porsche 924

Rich H · Posted: Tue Oct 20, 2009 9:53 pm Post subject:

Look at your fuse baord - now look up under the dash

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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Octane · Posted: Tue Oct 20, 2009 10:13 pm Post subject:

Rich H · Posted: Tue Oct 20, 2009 10:43 pm Post subject:

Ah - Oh dear. Might be a US/UK thing.

Afterall you have a steering wheel where I have a glovebox...
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

The reason you can`t find it is simply because 77s don`t have one. The fuse panel layout is different to the picture posted and most likely the diagram shown is for a later model too. Use the correct diagram for a 77. The relays and system of operation is different too.

Learn to use the search function to locate all the useful and relevant information that members couldn`t be bothered repeating just for the sake of those too lazy to search for themselves.

http://www.924board.org/viewtopic.php?p=268021&highlight=fuel+relay+different#268021

PopUpProject · Joined: 06 Aug 2025 Posts: 88 Location: NE Ohio

scm924s · Joined: 22 Oct 2010 Posts: 296 Location: Gloucester UK

The fuse/relay layout above will be fine for your car.
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1984 n/a Ruby Red Metallic
1988 924S Guards red- sold
1986 924S Guards Red - sold
1984 n/a Black - sold
1980 n/a Le Mans#1 - sold
1980 n/a Le Mans#2- sold
1977 Martini - sold

Nobbi · Joined: 24 Aug 2006 Posts: 1394 Location: Germany

The early 924`s have a fuse on top of the relais!! Check fuse and when lucky you have a starting 924.
Today its difficult and expensive to buy a new relais, maybe you have some luck and simply replace the fuse.......

regards ,

Nobbi
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NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1969

PopUpProject · Joined: 06 Aug 2025 Posts: 88 Location: NE Ohio

Thanks guys!!!

I'm playing the game of figuring out which relays I'm missing and then going to figure out (if I can) why the relays were pulled, and check for blown fuses

I noticed I have the two part fuse box Nobbi, or at least I think thats maybe what this upper part is. It looks really crusty. Poppy actually runs in her current state with a fuel pump switch, I just don't trust her to not catch in a ball of fire based on the way this looks: https://drive.google.com/drive/folders/1xzBC2eWB-sdo6HnXnI4oy0NbFIUMfBgI?usp=sharing
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Just trying my best to figure this out without total failure

Poppy the '82 924 Resurrection in Progress