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Ian89C4 · Joined: 01 Apr 2011 Posts: 561 Location: North Carolina

I tried searching for and answer to my question but my searching skills suck. I do not have the secondary fuel pump hooked up to the fuel pressure regulator but wanted to make sure my wiring fixes worked. I put around 2 gallons of fuel in the tank (had emptied it prior) so that the pump was not running dry. I stuck the hose into a fuel can and switched the key to the run position.
At first there was nothing and then I remembered I had not hooked up the grounds in the trunk. The pump didn't want to work at first, so I went to turn the engine over and it finally kicked the pump on. When I turn the key to 'on' the pump comes on put runs intermittently. Both pumps work and put out a good volume of fuel, but I am curious about the intermittent flow. Should the pump be doing this? or do I have an issue somewhere?

Cheers,

Ian
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Ian Edgerly
North Carolina

Current:
1981 924 SCCA/ChampCar Weissach Race Car ("Serenity")
1987 924S ChampCar Endurance Car ("Der Weg")
1980 924 Euro ("Wahala")

Ozzie · Posted: Sun Jul 31, 2011 5:56 pm Post subject:

Normal.
Prevents pumping fuel when the engine is not running.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

When using the fuel pump relay, the relay shall not actuate unless it gets a pulse from the ignition. I believe this pulse occurs when cranking and running. It is a fail safe so that the fuel delivery system is disabled when the engine stops running when the car is in extremis due to a collision, rollover, etc. (and the engine stops as a result. It prevents fuel from continuing to flow.
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"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

Ian89C4 · Joined: 01 Apr 2011 Posts: 561 Location: North Carolina

Awesome! Thank you guys.
_________________
Ian Edgerly
North Carolina

Current:
1981 924 SCCA/ChampCar Weissach Race Car ("Serenity")
1987 924S ChampCar Endurance Car ("Der Weg")
1980 924 Euro ("Wahala")

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

The pump runs when the ignition is turned on to prime the fuel system but it doesn't run during cranking, This is to keep the engine from flooding in a no start situation. When the engine is cranking the 50 circuit only is activated. The 15 circuit which controls the fuel pump relay is bypassed.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black