I have 1987 GMC 1500 in tank fule pump with no power. I changed fule filter ,fule punp, fule line relay and the ECM. I'm at the point now that I'm thinking of running a hot line to the punp side of the plug back to the fuse box. Controled by the keyed switch! Any idies welcome. Can the fule pump stay on all the time? Thanks from under the truck,Whiskyjoe
Another thought, look on the firewall, there will be a second connector with a red wire. (Red is the usual color)
Put a voltmeter or a test light in that connector, ground the other lead or the negative lead to the voltmeter. Have someone turn the key, and you should see 12 volts for three to five seconds. Also you should hear two distinct clicks, which will be the fuel pump relay going on and off for three to five seconds.
If you don't see voltage for three to five seconds, that's an indicator that the problem is electrical. The popular use for this wire is also to power the pump, with twelve volts, directly from the battery or another twelve volt source under the hood. After doing this for so many years, I still frown on that practice. The pump failed for a reason, and powering it can turn the truck into a grenade.
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