924Board.org

[JeepXJ]

Ok, I have two questions for you all. The first is about my fuel pump relay. Does anybody know a theory of operation for this relay? I suspect that this relay may have something to do with my starting issue. When I turn the key to the "ON" position i can hear the pump prime up for maybe 3 seconds, then it shuts off. This seems normal, as my other cars do it too, but the difference is that the Porsche doesn't do it all the time. I'd say that it only primes up about 70% of the time. I thought maybe it was bad contacts in the relay, so I removed it and popped it open. My goodness this thing is more complex than i thought. There is an IC inside that I'm guessing is a timer circuit of some sort, with the outputs triggering transistors to throw the relay itself. I could probably reverse engineer it, but i thought i'd ask here first if anyone knew what I'm supposed to be seeing here. Also, the relay smells kinda like its burnt out, so i'm looking to order a new one if i can't fix this one.

The problem is that a google search for "1980 Porsche 924 fuel pump relay" brings up a bunch of relays that look completely different than the one i have. Mine is a 5 pin unit with 4 large pins (#s 30, 87, 15, and 1) and a small pin labeled #31. I can't see the pin #s on the new units, but i can tell that there are at least 6 of them. I've done a bit of searching, but didn't really find what i was looking for. My relay is made by schier electronic, and carries the # 24.1000.10. Anyone know a good source for one of these?

Now for what appears to be my third question... even though i said 2... Anyways...

While searching around under the dash i found what looked like a relay, but it was emitting the loud annoying buzzing noises associated with having the keys in, or the door open. Is this just a buzzer, or does it actually do something. I pulled it out because it was pissing me off, but I can put it back in if it is actually important for something...
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-'80 924
-'89 Jeep Cherokee /w 6" lift
-'67 Ford mustang 302ci

[Rich H]

The fuel pump relay is a safety device of sorts. it will prime the pump initially but then it won't run the pump until it sees 300 (ish) rpm by checking the ignition coil firings. The idea being to cut the fuel if you crash and the engine stops. That is what all the electrics do.
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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

[D Hook]

I think the last fuel pump relay I bought was from Performance Products for around $17 or so. You might want to buy two and keep one in the glove box as a back up. They're known to go out at inoportune times.

Also, some of the cars have a little trick wiring were you can cycle the fuel pump by trying to adjust the drivers side rear view mirror. Whenever I move that switch, I can hear the fuel pump run for a couple seconds. At first I thought I should fix it but now it comes in handy for trouble shooting. I always know for sure if the pump is working. IIRC, you need to have the key on to do it. Give yours a try and see if you can hear the pump.

Cycling on for about 3 seconds is correct. Just enough to build pressure in the line before starting.

The buzzing relay is just an alert of door open, key in or seat belt not fastened. AFAIK, it has no other function.

Good luck.
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'80 924 n/a SOLD

[JeepXJ]

Would anybody be kind enough to grab their spare relay and take a few pictures of it? Mainly the lettered side and the pins. The one listed on performance parts looks like this:
[img]http://www.automotion.com/aux_incl/images.ashx?i=ID+112592.jpg&partNo=112592&w=280&h=210[/img]

However I haven't found a single round relay in the car yet. The one I pulled out is square. I'll take pics of it when I can.

The other ones i have found are the "DME" relays:
[img]http://info.rockauto.com/getimage/getimage.php?imagekey=1133909&imageurl=http%3A//info.rockauto.com/UROparts/993-615-227-00.jpg[/img]
These are the ones with too may pins

As noted in my sig, the car is a 1980, and i don't know if there was some difference in the years.
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-'80 924
-'89 Jeep Cherokee /w 6" lift
-'67 Ford mustang 302ci

[Smoothie]

That's the pic for www.rockauto.com 's later 924 FP relay - their price is $18.86. '77-'78 got a lower amp-rated relay to run only 1 pump. '79-up got 2 fuel pumps and the higher-rated relay. 924NA's from '79-up all use the same relay.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[JeepXJ]

oh very good, thank you. I see that my picture links didn't even work. Sorry about the noob questions, I just was having a bit of trouble figuring out why there were so many different choices. Thanks for the help!
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-'80 924
-'89 Jeep Cherokee /w 6" lift
-'67 Ford mustang 302ci

[JeepXJ]

Ok, I ordered up a new one. Funny thing is that I was on that site last night, but when i clicked of the fuel pump relay tab for the car i got an error message saying that the node wasn't active or something. I just assumed that meant they didn't have one. Tried it after your reply though and poof, it works.

Tomorow i'll be back at my old place where the car is, and i'll have access to some of my diagnostics equiptment. I know i've got a relay comming, but i really want to figure out the output patern of these relays, so i'll probably do a write up in the next few days on what kind of signal you should be expecting out of a healthy vs a bad relay.

Hopefuly i can get it running. If not, i'm sure i'll have more questions!

-Justin
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-'80 924
-'89 Jeep Cherokee /w 6" lift
-'67 Ford mustang 302ci

[Smoothie]

This one includes some discussion about the various 924 and 931 FP relays, but also a schematic of the 433.__ relay drawn up by Finbarr. -
http://www.924board.org/viewtopic.php?t=10360

(My own pics there are long gone due to a pic hosting site shutdown.)
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[JeepXJ]

Wow, I sure wish that had come up in my searches, would have made life a lot easier!

The good news is that the car now starts and runs. The relay is botched, but its intermittent, so as soon as the new one gets here i should be set.

I got the car added to my insurance, and it only raised my policy by $48 a year. Not bad, i was stoked, though when i went down to DMV the want $140 for the fees and registration. And i still have to get it to pass smog. Fun fun fun!
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-'80 924
-'89 Jeep Cherokee /w 6" lift
-'67 Ford mustang 302ci

[924er]

yea i had to change mines recently for about 15 bucks and now i dont hear the pump buzz when i turn the key anymore but it still runs, weird
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80' Porsche 924 NA - Slower then a S L O W
86' Porsche 951- New toy

[924er]