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1996 Chev. PU 5.7 engine fuel pump control


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gmgmdave
New User

Feb 28, 2008, 11:02 AM

Post #1 of 2 (2524 views)
1996 Chev. PU 5.7 engine fuel pump control Sign In

When key turned to "on" position should I feel the fuel pump relay "click"? Does the VCM (computer) energize the relay coil for 2-3 seconds? If the engine starts, is the voltage to run the fuel pump controlled by an engine oil pressure switch? I'm getting this from the electical diagram in a Haynes manual. With the engine running, should the fuel pump be heard running inside the tank at ALL times? Anyone have a trusted source of true information (as compared to opinion) I can telephone to educate me on proper operation of the fuel system on this vehicle? I'm willing to pay for education.


Double J
Veteran / Moderator
Double J profile image

Mar 2, 2008, 2:52 PM

Post #2 of 2 (2512 views)
Re: 1996 Chev. PU 5.7 engine fuel pump control Sign In

Hi

Fuel pump electrical circuit operation goes like this.....

When the Ignition switch is turned to the ON position (before engaging the starter), the VCM energizes the fuel pump relay for 2 seconds causing the fuel pump to pressurize the fuel system. If the VCM does not receive the ignition reference pulses (engine cranking or running) within 2 seconds, the control module shuts off the fuel pump relay, causing the fuel pump to stop.

As a backup system to the fuel pump relay, the fuel pump oil pressure switch can energize the fuel pump. The switch has 2 internal circuits. One circuit operates the oil pressure indicator or gage in the instrument cluster. The other circuit is a normally open switch which closes when the oil pressure reaches about 28 kPa (4 psi). If the fuel pump relay fails, the fuel pump oil pressure switch runs the fuel pump.

An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The fuel pump oil pressure switch energizes the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi).
Yes the fuel pump should run at all times with the engine running......you may not hear it..if its very audible it may be time to replace it..
Hope this info helped you..
Now then, Hmmmm willing to pay?
Just kidding...If I got paid for this...I'd probably call in sick...LOL
Jim






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