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1978 924 fuel pump / fuel pump relay

 
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stan_5150  



Joined: 01 Sep 2006
Posts: 11
Location: Minnesota

PostPosted: Wed Aug 19, 2020 12:48 am    Post subject: 1978 924 fuel pump / fuel pump relay Reply with quote

I've read a couple threads on here regarding the fuel pump vs. the fuel pump relay. I'm going to see if I'm getting power to the pump. After wiping away some grime I'm assuming that the orange wire is positive and the green/black is negative.....if I'm wrong I'm sure someone will let me know.

Anyhow, not being the mechanical type I'm wondering if anyone has any quick pics (or YouTube links) of the fuel pump relay and what needs to be done to understand the wiring in the bundles. As far as I know there hasn't been any modification to the wiring/electrical to the car. In fact, all the electrical seems to be working fine. Any suggestions are welcome. Thanks.
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winddude  



Joined: 15 Jan 2020
Posts: 54
Location: Vancouver Island

PostPosted: Wed Aug 19, 2020 4:36 am    Post subject: Reply with quote

yea, green/blk would be positive, I think the orange wire should be brown...
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!tom  



Joined: 28 Aug 2006
Posts: 1905
Location: Victoria, BC Canada

PostPosted: Thu Aug 20, 2020 3:31 am    Post subject: Reply with quote

I've discussed some of my findings about my fuel pump relay (also from a '78) in this thread.
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stan_5150  



Joined: 01 Sep 2006
Posts: 11
Location: Minnesota

PostPosted: Thu Aug 20, 2020 12:19 pm    Post subject: Reply with quote

!tom wrote:
I've discussed some of my findings about my fuel pump relay (also from a '7 in this thread.



Awesome stuff. Thanks!
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stan_5150  



Joined: 01 Sep 2006
Posts: 11
Location: Minnesota

PostPosted: Sun Aug 23, 2020 7:45 am    Post subject: Reply with quote

Ok an update on my troubleshooting attempts. Remember, not a mechanic here so if I get some terms wrong please don't be too harsh

I pulled the fuel pump relay and tested it tested 12.2 volts between 87 and 30. So I think that the relay itself is still serviceable.

I pulled the leads going into the fuel pump itself, and when engaging the starter it registered between 8.09 - 9.17 volts.

I'm leaning towards changing out the fuel pump. Am I missing anything in my rudimentary testing?

Any ideas or suggestions are welcome. Cheers.
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Paul  



Joined: 02 Nov 2002
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Location: Southeast Wisconsin

PostPosted: Sun Aug 23, 2020 11:28 pm    Post subject: Reply with quote

If the fuel pump runs when the relay is bypassed with a jumper and if the car runs fine, the fuel pump is not the issue.
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Silver 98 986 3.6l 320 HP "Frank N Stein"
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Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.
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stan_5150  



Joined: 01 Sep 2006
Posts: 11
Location: Minnesota

PostPosted: Mon Aug 24, 2020 2:18 am    Post subject: Reply with quote

Paul wrote:
If the fuel pump runs when the relay is bypassed with a jumper and if the car runs fine, the fuel pump is not the issue.


The car will crank but not fire, and I can't audibly hear the pump running while the key is in the run position. Guess I didn't properly elaborate that! Cheers.
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Paul  



Joined: 02 Nov 2002
Posts: 9451
Location: Southeast Wisconsin

PostPosted: Mon Aug 24, 2020 3:27 am    Post subject: Reply with quote

If you haven't already, pull the fuel pump relay and put a jumper between 30 and 87 and see if the pump runs. If not hit the pump with a rubber mallet a couple of times while the jumper is still in place. If the pump doesn't start remove the jumper before the pump overheats.

To further test the pump remove the wires and use an ohm meter between the terminals. If you get infinity the pump is shot.

https://www.harborfreight.com/7-function-digital-multimeter-63759.html
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.
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