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rad99 · Joined: 22 Apr 2006 Posts: 24 Location: Santa Clarita, CA

When I turn the key on without starting motor, fuel pump keeps running and I hear hissing in front. I have been all over "top" of motor and no visible leaks.
Any suggestions or likely places?

_________________
77 924 n/a
Silver w/black int.
5 speed

Paul · Posted: Mon May 01, 2006 6:07 am Post subject:

Most likely it's just the fuel pressure regulator in the fuel dizzy releasing fuel back to the tank. Normal.

The question is, why is your pump running for more than a few seconds? Most likely a stuck or bypassed fuel pump relay.
_________________
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.

Tigger937 · Posted: Mon May 01, 2006 6:34 am Post subject:

Stuck air flow sensor contact.
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1981 931 (Concours)
1982 931 (Daily Driver)

"Think outside the box"

Paul · Posted: Mon May 01, 2006 6:40 am Post subject:

I can never remember which of the early years had the sensor on the airbox.....
_________________
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.

rad99 · Joined: 22 Apr 2006 Posts: 24 Location: Santa Clarita, CA

So, now I am confused, is it normal or not? I always thought a fuel pump would pressurize system and hold. So, should it hold or return to tank via a valve?
_________________
77 924 n/a
Silver w/black int.
5 speed

Paul · Posted: Mon May 01, 2006 6:49 am Post subject:

Sorry for the confusion and a poor memory....

It is normal for unused fuel to be returned to the fuel tank.

It is not normal for the fuel pump to run for more than a few seconds when the motor is not running. Someone may have bypassed this safety feature by jumping the fuel pump relay or the airbox switch to solve a hot start problem.
_________________
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.

Eturbo924 · Joined: 09 Nov 2002 Posts: 2212 Location: Londonderry NH

Paul that is what I was going to say.

I just purchased a 1977 and the previous owner bypassed many of the relays... including the fuel pump. So the pump runs all the time... well once the key is turned to the run position.

Not good. So I plan to put it all back. He also bypassed the headlights and the fans.

I have a lot of work to do!

At least I got the exhaust straight!

Eric
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1982 924
1992 968
2003 C4S
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rad99 · Joined: 22 Apr 2006 Posts: 24 Location: Santa Clarita, CA

Thanks to all of you for your help! Lubed and inspected seats. Working perfect. No bolts in the way. Drivers seat still 4" behind passengers seat travel distance. Can someone with a 77 check to see if their drivers seat indeed completely goes up as far as passengers seat? I cannot find a fuel leak, on top or below (how can you guys stand laying under a car on jackstands? It give me the kreeps here in earthquake valley). I traced noise that souds like leak to me. Line from fuel filter to pressure reg. I can feel/hear fuel going thru...also I can hear/feel on fuel pump at rear of car. No, leaks. I am looking for elect. bypass. There has been some re-wiring done, all work appears to have been done by a good mechanic on this car. In engine comparment, drivers side, I found 3 wires unattached and close to each other and cannot find in haynes manual. 1 large brown with a round attachment at end and grounded to motor. The other two are in a harness together and both are females, one is yellow with red stripe and the other is brown with white. Both very dirty so probably disc. for a while. Again, THANKS!
_________________
77 924 n/a
Silver w/black int.
5 speed

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2745 Location: Sydney, Australia

When either seat is fully forward the rear bolts holding the rails to the floor should be fully exposed.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

rad99 · Joined: 22 Apr 2006 Posts: 24 Location: Santa Clarita, CA

O.K. rear bolts are not exposed on driver seat. So, agian I looked, lubed, and scooted back and forth. I cannot see the problem. So I am obviously missing something. I will have to take it out. Thanks, thanks, thanks

Does anyone know what those wires are in my previous post?

Can I clean the airflow plate? And what sensor contact? An exterior electrical one? I can not locate it, I see an electrical connector in Haynes but I can not find it.

I am searching the wiring diagrams for the 1977 1/2 and earlier. My car was made in June of 77. Am I correct?
_________________
77 924 n/a
Silver w/black int.
5 speed

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2745 Location: Sydney, Australia

Click the "924 Registry" link at the top of the page and then click the "VIN Decoder" link. Key in your VIN and it will tell you the car's model-year.

For most things the `78 wiring is the same as the `76/77 and the `78 diagrams are a lot easier to follow.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you