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Wiring Diagrams 1981 F100

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81f100custom

Wiring Diagrams 1981 F100

Anyone have any wiring diagrams for the 81 F100? Looking for all of them but in particular ignition wiring. I looked under diagrams up top but all I found was 85 and 86.

Thanks

Eddie,
81 F100 Custom SWB, 5.0L, 4x2, Single Rail Four-Speed Overdrive, 3.00 Non-Limited Slip Rear Axle, Non A/C truck to complete 85 F150 factory A/C conversion, Nutmeg interior color.

Hstrymkrs

Re: Wiring Diagrams 1981 F100

Here it is...

http://www.garysgaragemahal.com/start-ignition--carb-circuits.html

1985 Ford Bronco XLT, 4.9L, NP-435 transmission, NP0208 transfer case, 3.55 limited slip rear end,TTB Dana 44 with 3.54

Gary Lewis

Re: Wiring Diagrams 1981 F100

Administrator

Yep, the EVTM is better than the wiring diagrams as it breaks the schematics into individual circuits and describes how they work.

In the screenshot below you can see how to get to the 1981 EVTM's index via the red circle, and from there you'll see the Start, Ignition, & Carb Circuits. But you probably went to the yellow highlighted Wiring Diagrams, and there are only the '85 and '86 there now. I have the '81 in paper form, but just haven't scanned it - yet.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

81f100custom

Re: Wiring Diagrams 1981 F100

Thanks, you are exactly right I went to the wiring diagram that is highlighted. Trying to figure out maybe if I have a problem with the switch on the steering column as I am getting no fire. Will spin over just fine but not firing. It done this a few months back and I noticed when you back the key switch up as to the off position it would fire. It has been doing just fine since I started just giving it a quick twist and letting up until yesterday now it is back to not firing. Swapped the ignition module box on the fender but same thing just to try that.

Eddie,
81 F100 Custom SWB, 5.0L, 4x2, Single Rail Four-Speed Overdrive, 3.00 Non-Limited Slip Rear Axle, Non A/C truck to complete 85 F150 factory A/C conversion, Nutmeg interior color.

Gary Lewis

Re: Wiring Diagrams 1981 F100

Administrator

Check out the Ignition Switch tab here: Electrical/Ignition. It shows how to clean as well as adjust the switch.

Gary, AKA "Gary fellow": Profile

Hstrymkrs

Re: Wiring Diagrams 1981 F100

In reply to this post by 81f100custom

I had this same problem on my 1994 Ford Tempo a while back. FWIW, it was the contacts in the ignition switch "box" that was coming loose. What I mean by this is the plastic housing was coming loose from the metal base. I pinched the tabs back in and this tightened the "box" back up. No problems since. Please check everything else, but it seems odd that it fires when the switched is turned back. My Tempo would run as long as I held the key half way between start and run. As soon as I let go, the spring would disconnect it. After pinching the tabs back, it worked as it was suppose to work.

William

1985 Ford Bronco XLT, 4.9L, NP-435 transmission, NP0208 transfer case, 3.55 limited slip rear end,TTB Dana 44 with 3.54

81f100custom

Re: Wiring Diagrams 1981 F100

Thanks much for the replies and help. I believe and feel it is something simple just like you described.

Eddie,
81 F100 Custom SWB, 5.0L, 4x2, Single Rail Four-Speed Overdrive, 3.00 Non-Limited Slip Rear Axle, Non A/C truck to complete 85 F150 factory A/C conversion, Nutmeg interior color.

Gary Lewis

Re: Wiring Diagrams 1981 F100

Administrator

Let us know, we can help you work through it.

Gary, AKA "Gary fellow": Profile

Steve83

Re: Wiring Diagrams 1981 F100

Banned User

In reply to this post by 81f100custom

This caption explains how to test an ignition switch:

81f100custom

Re: Wiring Diagrams 1981 F100

Well just a quick update drove the truck to work Monday morning no problem cranking what so ever. Got off that evening motor just spins over not firing messed with it a little more nothing just spinning over. Head on home Monday evening after catching a ride and look over the wiring diagrams head back to work Tuesday and going to try jumping some things to see if it will crank. First tried jumping straight from battery to batt side of coil while cranking still just spinning over. Tried just putting the switch in the run position and jumping across the solenoid so the switch would not have to be moving still the same result. Tried checking the 12 volts that goes to the ignition module red/bl wire while cranking was showing voltage at that time. Swapped ignition boxes once more just to see if that made a difference still just spin over. Plugged back up the one still mounted on the fender and messed with the connections as it was spinning over. It sounded like a time or two it wanted to crank but did not. Running out of ideas to keep trying after staying after work late I decided I would just have it towed to the house Wednesday. Meet tow truck driver in the parking lot and he ask what is going on with it need a jump or something else. I told him it would just spin over but not firing and I told him just a sec and I will show you. Well what do you know I open the door reach in give it a quick start to show him and it cranks like brand new. Turned it off tried it again cranked just soon as you touch the switch. I cranked it once more back it out of the spot pulled it up to his truck cut it off let him load it and take it to the house. Got home last night cranked and drive it about 8 miles or so working like brand new again. I guess now instead of trying to get it to work I will have to try and not get it to work to try and figure this aggravating problem out.

Eddie,
81 F100 Custom SWB, 5.0L, 4x2, Single Rail Four-Speed Overdrive, 3.00 Non-Limited Slip Rear Axle, Non A/C truck to complete 85 F150 factory A/C conversion, Nutmeg interior color.

Gary Lewis

Re: Wiring Diagrams 1981 F100

Administrator

That has to be frustrating! At least it is now starting, but it is like driving a time bomb - you feel like it is going to fail to start every time you try.

You don't have a signature so I don't know what the truck is. But if it has an electric fuel pump then it may be a problem where the pump isn't running.

How 'bout creating a signature so we don't have to ask?

Gary, AKA "Gary fellow": Profile

81f100custom

Re: Wiring Diagrams 1981 F100

Yes I agree it is frustrating its like I can't trust it but not sure what to replace when it starts like new now. It is a mechanical fuel pump. This truck originally came with a 255 V8 but has had a 302 in since before I ever owned it. It has none of the smog equipment what so ever left on it. It is down to the very basics of what is needed to run with the Duraspark II ignition system that was original. Could the distributor itself cause this issue? I know the negative lead for the coil comes out of the ignition module but does the distributor still control when the coil receives the ground to fire like in the old points systems?

Eddie,
81 F100 Custom SWB, 5.0L, 4x2, Single Rail Four-Speed Overdrive, 3.00 Non-Limited Slip Rear Axle, Non A/C truck to complete 85 F150 factory A/C conversion, Nutmeg interior color.

1986F150Six

Re: Wiring Diagrams 1981 F100

Administrator

The electrical pickup unit in the bottom of the distributor can go bad. It generates a small electrical charge [millivolts?] which signals the ignition box.

Gary Lewis

Re: Wiring Diagrams 1981 F100

Administrator

Yes, David is correct. The pickup in the dizzy can go bad. But, the insulation to the pickup inside the dizzy is a known problem. Both he and I witnessed Paul/Rogue_Wulff troubleshoot Eli/SmokenChoken's problem wherein the engine would die if you put the vacuum to the distributor. Paul pulled the cap and pointed to the insulation falling off the pickup's leads. I had one in the attic, and we changed it out. Problem solved.

So, you might want to check that those wires in the dizzy aren't coming apart. If not, maybe replace the pickup for insurance?

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: Wiring Diagrams 1981 F100

Administrator

And Paul diagnosed this before even looking at it.

Gary Lewis

Re: Wiring Diagrams 1981 F100

Administrator

Yes, he DID. I was impressed!

Gary, AKA "Gary fellow": Profile