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I've got a buddy who's family owns 1991 F-250 5.8 that hasn't ran since 2014.
The first problem we noticed was that you can't start the truck from the key. When the key is in the on position everything seems to be working, all the dash lights come on (besides the check engine light). The ignition switch is in good shape, it's just not getting power to the starter solenoid. It turns over just fine jumping the solenoid, but it's still is a no go. After that we checked spark, and it had nothing. The coil is working and getting power, but it will only trigger the ground when the computer is disconnected. I wouldn't be surprised if these two problems are connected. I don't know if the computer is bad, or if someone knows of a relay or fuse that could be causing this.
Ask any questions as needed, I won't be able to look at it until we can get together again and work on it. All input is appreciated.
Is there anything that could be just in the ignition circuit? I saw someone say the sensors wouldn't have power if the computer is bad, but the map had power going to it when the key was on.
Is there anything that could be just in the ignition circuit? I saw someone say the sensors wouldn't have power if the computer is bad, but the map had power going to it when the key was on.
Subford is probably the most knowledgeable on this forum. If he told me to rub dog poop on my hood to fix something, I would find a dog.
Is there anything that could be just in the ignition circuit? I saw someone say the sensors wouldn't have power if the computer is bad, but the map had power going to it when the key was on.
The #351 BR/W wire to the map sensor is the Ref Voltage of 5 volts DC an a bad computer may not send this 5 Volts out.
You say your Computer (PCM) is supplying the 5VDC out so it is getting power on pins 1, 37 & 57.
So you are saying you only getting spark when the computer is disconnected.
Do you mean by this you are unplugging the Computer plug or are you removing the SPOUT shorting bar?
Either way you are setting up a stand alone Ignition system for testing the Ignition system.
From that we know the Ignition system is OK and the SPOUT wire is keeping you from getting spark when it is connected to the Computer.
I know I wasn't disconnecting the SPOUT, because I didn't even know what it was until just looking it up lol. I'll remove the PCM next time I'm able to work on the truck, and check it over for anything that looks out of place. I'm going to a local junkyard here soon so I can see if they have some PCM's that match.
Thanks for the replies, I will report back with what I find out.
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