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1989 F150 ignition info please

27076 Views 9 Replies 3 Participants Last post by  93FordPickemuptruck
Please bear with as I'm new to the forum, but I've been trying to find a schematic on 1989 F150 ignition system. I HAVE the #%@ Chilton for this vehicle and it is crap. I need a wiring schematic for the complete ignition system for the 5.0. I had a burnt wire near the solenoid that seems to feed ignition coil and ignition module. Replaced wire all the way to firewall and still only have 4.7 volts to coil and ignition module. Changed out coil, ignition module, ignition switch, distributor, computer, and even ran jumper to hot side of coil. Coil still won't fire. Checked eec and fuel pump relays and they work and have 12 volts coming out of them. Need to know location of fusible links in detail and a complete ignition schematic including underhood and inside cab. Can someone Please help me out with this.
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Anyone???? Dad's without a vehicle so I really need to get this resolved. Thanks in advance for any help or ideas offered. Thanks
Sorry for the delayed response but I have been searching all over for any kind of schematic for your ignition system and the best I came up with is the 1990 F-150 (with 5.0L). I just don't know what changes were or weren't made between the two model years. Still, no harm in posting what I have, I just hope it helps.

Also, welcome to the forum!


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I can't tell you how much I appreciate your response. That schematic is great. One thing though, do you have any more. That one goes into the starting circuit in pretty good detail, but not much into the run circuit, or maybe it calls it engine control, I'm not really sure. The problem I'm having is that although the engine will actaully turn over, it just doesn't have enough voltage at the coil or the ignion module(4.7 volts) and I've already followed original source wire all the way through the engine compartment until it disappears into the firewall into the cab of the truck. Seriously, I appreciate your response.
The only other one I have is the charging schematic, there really isn't one for the ignition system itself, all i have is this diagram that I hope shows up right...


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Turned out it was a bad fusible link on the drivers side fender well inside the wiring harness. Dark color wire on one side of it and white with a blue strip on the other side of it. Again, I really appreciate you providing me with what info you could. Good info is hard to find and buying the book anymore just seems to be a waste of time. Chilton is completely worthless for wiring schematics, and although Haynes is a little better, it is far far from complete usually only touching on highlights if you are lucky enough to get that.
Glad I was able to offer something better than the manuals we can all get from the parts store and even happier you found the problem!

Ignition failure

Having issues on the ignition side. No power to anything after turning the key. I can jump the relay with a screwdriver to get it to start….briefly. Also, checked the continuity between the ignition switch under the column and the ignition wire at the relay: no continuity. I tried moving the pin on the ignition switch to start it, but no bueno. The battery is strong, and I checked the fuses in the engine and cabin fuse boxes: all good. A few more clues: Once jumped, the starter fails to disengage, the engine surges when the lights are turned on, and the engine cuts out eventually. I also disengaged the neutral safety switch on the transmission to see if that changed anything, but nothing. Are there any fused links or other fuses (say on the PCM) that I should check? The ignition switch and starter relay have been replaced. Greatly appreciate any help.
If you have checked for continuity and see none where there should be then you need to look for broken/chaffed wires within the ignition system itself.
Thanks Mr. Mac. I was hoping I missed some special magic relay or fuse that would make the process easier. I put the meter on the ignition fuse holder contact points in the engine fuse box, and was getting resistance there. Time to start digging into the wires!
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