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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: chase.grantham.7 on December 07, 2013, 10:00:03 pm
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Have an 82 silverado with lq4/4l60e swap, the other day when I go to start it the gauges/ fuel pump come on but as soon as I switch the ignition to start I lose all power. I assumed I had another bad relay and it had drained the battery, so I used one of those portable jump starters and got it started. Amp meter showed 14v until stopped at a red light I lost all power again, no windows/locks/gauges nothing. I got jumped again and made it home before it lost power again. Battery shows 13v and I have voltage to the firewall bulkhead connector, Battery grounds to engine/frame are tight. Sometimes when I turn the key to on everything works until I turn it to start then I lose power. Trucks wiring is original, the only thing I have changed is using my distributors key on wire to power my lq4's fuse block. I'm about to take the steering column apart to get at the ignition switch and see if maybe that's the problem, the only thing that has me confused is that when I lose power my electric locks don't work; I didn't think they ran through the ignition since they operate even when the ign is off.
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I'm thinking neutral safety switch or fuselink
What's under the hood??? If you have to ask maybe we shouldn't race...
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I've checked the fusible link at the power distribution block, I haven't checked at the starter since I have it wrapped in conduit and heat wrap. Guess that next if I don't find anything suspect in the column.
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So when it happens you can't operate the door locks? Have you checked the junction at the firewall and the battery to starter wire?
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Losing all power is a big clue.
Replace both of the big battery cables. They rot out inside the insulation. They can also wear through the insulation and short to the frame rail. So if they are original, replace them.
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Checked the starter wires today, getting +12v on the starter to battery cable, and the solenoid wire shows continuity all the way to the firewall. It should only be energized when the key is at run correct? As I'm about to leave to eat lunch I put the key in and it starts right up, I let it run for a few minutes then turn it off and on about 4 times then about the 5th time suddenly no power agian. Still haven't replaced the ignition switch, but I don't see how that can kill all power to the cab.
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chase.grantham.7, I agree with you. The ignition switch truly is a long shot....
Reread the preceding posts regarding the battery cables and fusible links.
When the symptoms occur, connect your voltmeter across the positive battery cable, with the red voltmeter lead connected to the battery post and the black meter lead connected to the starter solenoid battery cable post. Follow the same process with the voltmeter connected across the battery ground cable (reverse the voltmeter leads) and the 12-gauge red cab feed wires that connect the starter solenoid battery cable post to the firewall junction block and bulkhead connector.
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I ended up replacing both battery cables, neither showed any signs of a break and both showed continuity so I'm not sure what the problem was. Anyways starts and doesn't lose power now so $20 well spent.
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They can show continuity but be so degraded under the insulation that they heat up when passing current and open up. Randomly. Very hard to diagnose, so, like you cay, for $20, if they're original, replace them.
Thanks for letting us know.
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...neither showed any signs of a break and both showed continuity so I'm not sure what the problem was....
Checking continuity through a battery cable using a test light or ohmmeter will very rarely detect a service problem, because neither tool will adequately 'load' the cable. An ohmmeter and test light flow mere milliamps of 'test current' compared to 150+ amps supplied to the starter for cranking and 30 - 50 amps received from the alternator for charging.
To check heavy gauge, high amperage cables, connect a voltmeter across the cable and measure the voltage used by the cable when under high electrical load (i.e., while cranking the engine, or charging the battery, etc.). A good cable will measure less than ~0.5 volt drop.
As Rich pointed out, one or both battery cables may be corroded under the insulation where it isn't visible. It's great that you got it fixed!