Fuel Pump wont shut off

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disturbed1980 - 23 Jun 2006 14:55 GMT

I have a 1999 sunfire GT 2.4 l I had a bad motor replaced the motor
and hooked everything back up when hooked battery back up fuel pump
engages and will not shut off. I unplugged fuel relay and fuel pump
fuse. The fuel pump still continues to flow Im lost I checked the wires
everything looks good but like i said im lost and any help would be
appreciated. and to note everything else on car was fine before just
had a bad piston so replaced motor. please help on here or send me an
e-mail therock_bs@hotmail.com Thanks in advance Brian

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William H. Bowen - 23 Jun 2006 23:17 GMT

Check the oil pressure sensor and wiring to it. The oil pressure
sensor has a set of contacts that are wired in parallel with the fuel
pump relay (acts as a "fail safe" so your engine will continue to run
if the fuel pump relay fails while driving).

Regards,
Bill Bowen

>I have a 1999 sunfire GT 2.4 l I had a bad motor replaced the motor
>and hooked everything back up when hooked battery back up fuel pump
[quoted text clipped - 4 lines]
>had a bad piston so replaced motor. please help on here or send me an
>e-mail therock_bs@hotmail.com Thanks in advance Brian

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Shep - 24 Jun 2006 00:58 GMT

My wiring diagram ( could be wrong) shows no circuitry from the relay with
the oil sending unit, strictly pcm controlled, possible the harness got
pinched somewhere and the fuel pump is powered all the time. Look for the
harness coming out of the relay box and see if the wires are shorted across
somwhere, or run a new wire from the pump to the power out of the relay.
bypassing that possibility.

> Check the oil pressure sensor and wiring to it. The oil pressure
> sensor has a set of contacts that are wired in parallel with the fuel
[quoted text clipped - 12 lines]
>>had a bad piston so replaced motor. please help on here or send me an
>>e-mail therock_bs@hotmail.com Thanks in advance Brian

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William H. Bowen - 25 Jun 2006 08:43 GMT

Shep,

I'll defer to you regarding the wiring of that car - I didn't have
my Sunfire manual handy and did this from memory (all the older 4
cylinder Sunfires and most other GM engines have that oil pressure
switch backup fuel pump feed). I looked at the Service Manual diagram
for that Sunfire and you are correct.

Rock, if you have a voltmeter handy, check for the presence of +12V
on the gray wire going to any of the fuel injectors: this is the same
feed that goes to the fuel pump. With the ignition switch turned OFF,
this voltage should be zero.

I'd go with Shep's idea that you've got a short to +12V to that gray
wire somewhere in the engine compartment. My first guess would be to
look very carefully around the throttle body and the fuel injectors -
there are some items in that area that get a constant 12V feed.

Regards,
Bill Bowen
Sacramento, CA

>My wiring diagram ( could be wrong) shows no circuitry from the relay with
>the oil sending unit, strictly pcm controlled, possible the harness got
[quoted text clipped - 22 lines]
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