Q: 20 amp ignition fuse continues to blow

asked by on October 10, 2016

I have a 1986 GMC Sierra S15 with a 350 small block Chevy engine. I have an issue where my 20 amp ignition fuse continuously blows. I have an electric fuel pump underneath the driver side of the cab that has power going to it with a inline 20 amp fuse also that is still good, but the fuel pump is not engaging or turning on at all. My starter is engaging when I turn the key over but when I place a new 20 amp fuse Within the fuse panel it immediately blows. I have a Mallory ignition coil underneath the hood that when I place my test light on the positive side of the coil my test light barely turns on at all. Could the ignition coil be the source of my problems?
My car has an automatic transmission.

Hello. All of this depends on what was spliced into that circuit when the engine was swapped out. I usually isolate this problem by disconnecting the circuits in it until it no longer blows. This fuse usually has a problem with the wiring to the fuel injectors at the throttle body. It is common for the wires going to these injectors to wear on the throttle body and short out. It can also be the coil if it is shorted internally. If you need assistance diagnosing this short, consider YourMechanic, as a certified mechanic can come to your home or office to inspect the electrical system and repair this problem.

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