924Board.org

[924-76]

As per title, I get low voltage at the fuel pump which result in fluctuating fuel pressure and on long run it overheat of the relay and fuse.

So far, I cleaned the ground points at the front of the car (left and right), 2 behind the relay box and the one at the back between the taillights.
I also installed a homemade ground kit to ground points behind the relay box and the one at the back between the taillights.

I'm getting the following reading:
at the Alternator: 13.6V
at the battery: 12.8V
at the fuel pump fuse (#2): 11.5V
at the fuel pump: 10.8V

Haynes manual says that fuel pump voltage should be min 12.5V

Where should I look next?
Thanks
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

[fiat22turbo]

Sounds like the power side of that equation is where you get to dig in.

You can disassemble the relay panel and clean it internally, but you can probably start with cleaning the positive connections.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Rasta Monsta]

Ugh, you need to toss the alternator harness, and the run between the battery and fuse box. FP fuse should be 2v higher.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[fiat22turbo]

[924-76]

Thanks guys
Tonight I removed the starter/alternator harness, rebuild it and re-installed it.
Now I I'm getting the following reading:
at the battery: 13.1V
at the fuel pump fuse (#2): 12.2V
at the fuel pump: 11.2V

Things are slowly improving.
Next, I will change the wire from the battery to the fuse box.
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

[924-76]

Replace the fuel pump wire from the battery to relay and th one from relay to fuse and another wire from battery to fuse box (not fuel pump related).
Now I I'm getting 12.0V at the fuel pump. BTW all my fuel pump voltage reading are from the in-tank one.
Now Haynes manual says that it should be at 12.5V, but I'm going to try it like that and see how she goes.
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

[924-76]

So, heading for a test drive after diner thinking all should be fine and planing on upping the boost to 12lbs if all well.
Drove slowly to the main road at the end of my street, got here in second gear and stepped on it and...could get pass 2800RPM!
Engine is cutting, probably fuel or spark; and I'm guessing fuel since it was running lean. 14 Air and Fuel Ratio at idle, then between 15-16 after the engine cut out.
Why? The fuel pump was running on 10.8V and it's now getting 12.0V, it should run better not worst!
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

[924-76]

Good old weak overboost connection...good to go
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP