Ok. Hi Guys any help is greatly appreciated,
I have a 1998 chevy blazer 4wd 4dr 18 gal tank (plastic) I replaced the fuel pump 2 months ago and there are 2 red wires running from the pcm to the plug on the fuel pump. They were obviously installed aftermarket. This vehicle has 235k on it but was running awesome until it would not start yesterday and I am not getting any fuel at the schrader valve and can not hear the pump with the key on. I checked my fuel pump and believe what is the return line had a kink and am thinking it made the pump overwork and burn out quickly. Or maybe these two additional wires that were run by the previous owner for whatever reason are adding extra voltage I don't know. Can anyone tell me why they think these wires may have been added? could they be causing a problem with the new pump? how can I tell what they were actually added for. or should I attempt to rewire the whole fuel pump harness itself? Any help would be greatly appreciated. Also after replacing the pump 2 months ago my fuel guage would only work intermittently.
Thanks,
Rob

 

Grab a wiring diagram for your year truck. See what the 2 pins the red wires are hooked to on the pcm and supposed to be doing. The PCM is not supposed to be powering the pump.

 

It's very difficult to tell what they tap into...to be honest I am afraid to touch the PCM but I imagine unplugging and properly probing those wires would at least tell me if they are sending voltage. I was just hoping someone could tell me why this person would have run them to the PCM in the first place? If anyone else has any idea I would love to hear from you. I have a haynes manual but it only covers a limited degree of wiring diagrams. Any Idea where I might find a diagram for the PCM? Any help is greatly appreciated.
Thanks,
Rob