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'91 Chevy C1500 fuel pump wiring problem?
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mbsmith9
New User
Oct 17, 2008, 6:36 AM
Post #1 of 3
(5784 views)
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'91 Chevy C1500 fuel pump wiring problem?
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It appears that my 10A ECM fuse circuit controlling the fuel pump has a short - a new fuse burns out the instant the ignition is turned on. Bypassing the fuse and hot wiring the fuel pump delivers fuel to the throttle body but not to the injectors or engine, I assume because the ECM fuse is necessary to do so. I've inspected all wiring from the fuel pump to the firewall and it's okay. I have also replaced the fuel pump relay.
I now want to remove the fuse block to check the wiring and connections to locate the problem. Any suggestions would be much appreciated.
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Jeff Norfolk
Enthusiast
Oct 17, 2008, 8:44 AM
Post #2 of 3
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Re: '91 Chevy C1500 fuel pump wiring problem?
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Check the plug that goes into the fuel pump. These have a history of burning up and causing the problem you are having.
Jeff
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DanD
Veteran
/ Moderator
Oct 20, 2008, 4:48 AM
Post #3 of 3
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Re: '91 Chevy C1500 fuel pump wiring problem?
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If the ECM/IGN 10amp fuse, is the one that keeps blowing; you may be chasing the wrong circuit?
This fuse powers up a portion of the ECM, along with a few other devices, such as the EGR (exhaust gas recirculation) solenoid, AIR (air injection reaction) diverter valve solenoid and the ESC (electronic spark control) module. According to my wiring diagram this power wire is a pink/black wire.
With this fuse blowing as soon as the ignition is turned on, I would try disconnecting these modules & solenoids one at a time; to confirm that they are not internally shorted.
I understand your thinking; you turn on the ignition and you should hear the fuel pump run its prime cycle but you’re not seeing/hearing fuel pump because a portion of the ECM that controls the fuel pump relay pull-in coil, is not being powered up.
The actual fuse (In-line 20amp) for the fuel pump to tank circuit (after relay) is located under the plastic cover, on the right side of the firewall with the fuel pump relay.
An easy way to confirm that the wire(s) from the relay, the oil pressure switch, to the fuel pump are ok is to jumper the gray and orange connections at the oil pressure switch. This should cause the fuel pump to run; more or less by-passing the relay.
The oil pressure switch is used as a back up method of turning on the fuel pump if the relay fails.
Here’s an example of how that’s suppose to work on a vehicle where’s nothing wrong other then the fuel pump relay. Most GM’s of the same model years as yours used this method of wiring their pumps..
You begin cranking the engine and it doesn’t start as fast as “normal”; you continue to crank the engine. Once oil pressure builds to 4psi, the switch in the oil pressure switch closes and completes the power feed circuit to the fuel pump, once the fuel pressure builds the engine starts.
Like I said this is not likely a fuel pump issue.
Dan.
Canadian "EH"
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