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No power to fuel pump

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Old 01-13-2012, 10:29 PM
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No power to fuel pump

Ive tried searching but got nothing ive got no power to my fuel pump on 92 f150 300 i6 I tried to hot wire it but it dumps fuel out the exhaust then dies?
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Old 01-13-2012, 10:55 PM
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Use a test light, or a voltmeter and see if voltage is getting to the injectors. If there is no voltage going to the injectors I would say the computer is toast.

I had a 87 F150 with a 4.9 EFI. The computer was fried, the computer wasn't grounding out the injector relays or fuel pump relay, so power wasn't getting to the fuel pump or the injectors.
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Old 01-14-2012, 12:44 AM
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Is it ok if I just hot wire the positive to a fuse that comes on with the key
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Old 01-14-2012, 01:27 AM
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Quote:
Originally Posted by SCRebel View Post
Use a test light, or a voltmeter and see if voltage is getting to the injectors. If there is no voltage going to the injectors I would say the computer is toast.

I had a 87 F150 with a 4.9 EFI. The computer was fried, the computer wasn't grounding out the injector relays or fuel pump relay, so power wasn't getting to the fuel pump or the injectors.
I second that! I have a 94 Ranger that kept giving me the old "ground to fuel pump" code, and would not keep the fuel pumping running. It would act as if it ran out of fuel or vapor locked. I tried bypassing the harness to the pump and it worked, momentarily and the computer fought my bypass.
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Old 01-14-2012, 09:17 AM
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Quote:
Originally Posted by SCRebel View Post
The computer was fried, the computer wasn't grounding out the injector relays or fuel pump relay, so power wasn't getting to the fuel pump or the injectors.
Well there is no such items as the "injector relays".
You have the PCM power relay but the computer has nothing to do with picking (grounding) that relay or sending power to the injectors.
The PCM power relay coil has one side permanently hooked to ground and the other side is powered by the Ignition switch.
The PCM power relay does send power to all of the injectors, fuel pump relay coil and other solenoids.
You can unhook the computer and take it out of the truck and turn on the key and still have power to all of the injectors and the fuel pump relay.

The 1992 is the same as the 1993 wiring below.


/
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Old 01-14-2012, 09:30 AM
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Quote:
Originally Posted by rangergirl94 View Post
I tried to hot wire it but it dumps fuel out the exhaust then dies?
Sounds like all of you injectors ground wire is shorted to ground.
It could be a bad computer.
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Originally Posted by rangergirl94 View Post
Is it ok if I just hot wire the positive to a fuse that comes on with the key
Yes you can bypass the Ignition switch for a test. Do you have open (bad) fuses?
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Old 01-14-2012, 09:35 AM
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Have you checked the inertia switch? Just throwing that out there. I always overlook the easy stuff
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Old 01-14-2012, 09:56 AM
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How 'bout the relay?
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Old 01-14-2012, 10:10 AM
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Hmm...this computer thing would make sense...my truck also gives the fuel pump circuit open, EEC processor to motor ground...never knew if that ground was the EEC itself or not. My truck has a surging idle, but always runs fine...

And Rangergirl, sorry to hijack. Seems to me that however you jumped it before, it bypassed the EEC (possibly because it's fried) and made all the injectors fire at the same time, instead of in sequence...causing it to ultimately dump fuel out the exhaust, when it had nowhere else to go. If my theory is correct and it would have kept running, it would have hydro-locked the engine. Good luck, I'll be keeping an eye on this to see what fixes it...
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Old 01-14-2012, 04:07 PM
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Can I change the fuel pressure regulater without pulling the intake manifold
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Old 01-14-2012, 05:35 PM
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Can I change the fuel pressure regulater without pulling the intake manifold
Yes you can.
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Old 01-14-2012, 05:38 PM
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If you want to fix the truck , listen to Subford.
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Old 01-14-2012, 05:59 PM
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I hot wired the pump to a fuse thatsl comes on with the key it runs but dumps gas out the exhaust? What would cause that
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Old 01-14-2012, 06:03 PM
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I think your computer is not telling the injectors when to open or close. so they are probably, open. And you hot wiring the fuel pump, the fuel pump is constantly running. This will fill the combustion chamber with fuel and the fuel will pour out the exhaust and get into the oil.

I believe you need another EEC.
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Old 01-14-2012, 06:16 PM
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Maybe verify this is so by pulling an injector and see if its dumping. If so focus on that circuit.
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