1990 XLT strange ignition issues
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8th Gear
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1990 XLT strange ignition issues
1990 XLT Lariat 5.0 4EOD. Had previous issues getting it rolling, sorted that out with new TPS. Pulled the ECM and sent it off for repairs, reinstalled today. There is intermittent loss of power at the ignition switch, sometimes there is power there and sometimes not. Couldn’t get it to start, put the battery on a charge as it sounded like the solenoid would click but that’s it. After a few hours of charging switched the charger to start mode and got it to fire up and idle nicely. Then it died as soon as I put it in reverse. Hasn’t started since, same intermittent power issue at the key. The only things I did while the ECM was out was swapped in new headlight assemblies, new wiper motor, new stereo, and welded in new floor / inner cab panels. I will start checking things out with the meter tomorrow, just thought I’d ask in case anybody else had already beat their heads against the wall over something like this.
Fleet Mechanic
Joined: Oct 2025
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Not second guessing you, but how do you know you’re losing power at the ignition switch? On the starter solenoid battery terminal, make sure those are secure. Since you changed headlight housings, did you unhook any wires? Like a ground? Battery terminals themselves are very tight and in good order?
Last edited by 90project5.0; Yesterday at 05:00 PM.
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8th Gear
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I’m happy to be second guessed, the only wiring I touched doing the headlights and wiper motor were the harnesses to those items. I will go back over the areas to make sure I didn’t knock anything loose. I’m not sure yet whether power is making it to the ignition switch, at this point all I know is the when I turn the key either to accessory power or ignition nothing happens. Until it does lol. I can cycle the key many times when it isn’t working with no results, then I can walk away for a while and come back and get power but no ignition. Battery clamps are nice and tight, I don’t a load tester but the meter shows me 13.4 volts so at least I know there is enough potential to at least get the solenoid moving.
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