Im tracing a robbit...
truck was running on sunday, monday it wouldnt start.
So since then I've swapped my starter, starter solenoid, Alternator, and tested my battery. New plugs a few months back. Can smell gas so im pretty sure its not a fuel problem. Its got a solid crank now but its like its not getting spark?
its a 1976 with a 390.
its got power to all the lights and fan.
maybe its the ignition coil? Im at a loss
maybe time to swap cap, rotor, wires, coil?

 

Have you checked your ignition control module?

 

no but it has been added to my list. Ill probably swap coil and wires tomorrow. Also laster this week re doing the key ignition with a new harness just in case.

 

I haven't had one completely crap out that it wouldn't start but have had them make the trucks run super crappy. Good thing to have an extra of...

 

Always good to keep a spare. They used them in Jeeps until they went EFI. My experience with them is they tend to completely die, or will die, then after cooling down, may run again for a short while, then die again. Sadly the part's store units tend to be junk.

As to the OP, instead of throwing parts and money at the problem, have you taken time to diagnose the issue? There's a number of things that can cause no-spark.

 

ive swapped the ICM and the Ignition coil. I have diagnosed it to i am not getting any spark/power from the coil. Its a new coil so what would cause it to not send a charge to the distributor?
am i missing a blown fuse or something?

 

 

pulled the dash off to inspect the ignition wires and found the problem. The previous owner had re wired the old melted wire harness up to a 15amp ignition, but left everything open. Asuming over time it melted the wire to the coil.
i already have the new wiring harness and key ignition as i was planning on swapping it this weekend.

 

skyhawc's point was to test individual items and circuits rather than replace them. Diagnose the parts, not the problem. You know you don't have a spark, so the point was to find out if you can see what's obvious first. Before spending money.
Glad that you found the problem no matter what! But you could have saved a few bucks had you found the bad wires first. The sheer number of electrical "fixes" that are perpetrated by previous owners is epic with these things!
For example, checking for voltage at the coil's positive tower with the key on. Or checking the resistance on the distributor's magnetic trigger being between 400 and 800 ohms between the Purple and Orange wires. Or verifying that there is a good 12v signal to the Red wire to the ICM.
Stuff like that.

You did dig deep to find that wire under the dash. That was good detective work.
FYI the alternator can't cause a no-start situation unless you were experiencing a dead battery from no charging.
By the way, what were the original symptoms? Would the starter not crank the engine at all? Or was it spinning/cranking/turning over very slowly? Something else?

And one last thing since you now have some new parts. KEEP YOUR OLD PARTS!!! At least for a short time.
The reason is that so many of the new parts (especially the new Ford starter relays/solenoids) are so crappy these days that they often fail within the first week. Or even within the first few cranks! Yep, it's that bad.
So at least keep the starter relay just in case.

Glad you got it running again.

Paul

 

 

well i was positive this would work considering the old one was melted but it still aint running with the new wire harnes and ignition. Still no power to the coil. I cant find why. Might have to have it towed to my shop so i can have someone else look at it.

a little over a month ago, the starter started to go bad, so i swapped it. Everything was going fine till monday when it wouldnt start, id been starting it to let it warm up every few days. But monday night it just wouldnt start.
turn the key and it would just turn over really weak. Thinking it was just a bad reman starter, i swapped it to no avail. Then the starter solenoid, no difference, then descovered my battery wasnt fully charged so i put it on the charge and swapped the Alternator. Has alot more powerfull of a crank but still wouldnt start. Swapped the icm with recomendation, no change. So i moved onto the coil, put on a new one and did some digging. My distributor is turning but not sparking, so i checked the coil and from what ive been able to tell, no spark at the coil. Tried testing the power to coil with a light but no light. As far as i can tell everything else on the truck has power to it, just not the coil and i cant ping why.

 

So no power to coil with key on and this is after all the swapping of parts and not before?

Other than the fist part of what 1ton said
What do the rest test out to?

When you swapped out the solenoid you did put all the small fuse link wires on the same large post as the + battery cable is on and NONE went on the starter cable side did they?
If they are all on the battery + side of the solenoid, then take your test light and test for power down a little bit from where it connects to the stud. It is best to check down where the wire is "normal" as it will be pass the fuse part.

If that checks ok then it is time to back trace from the coil to find where the power is lost at.
Could it be a bad IGN switch? You said you had to repair a repair someone else made are you sure this was power out to the coil and if so did you check for power after your fix?
Just some things to start checking as there are not many more parts you can throw at it.
Dave ----

 

I dont have a voltmeter currently just the test light, but when i wired in the new ignition switch i checked to make sure it worked in on, off, run , start. They all lit up when they were supposed to. So the switch is good. I traced the wire out to the ICM, got power to the icm on the 2 wire plug "red and white on icm side" on run. Then checked the 4 wire plug coming out and no power and any of those when in run.
i can connect to (+ )on the battery and either wire on the horseshoe clip to the coil will light up when in run.
all my solenoid wires are on (+) besides the one thats on (i)
and its been a no spark problem since before the new starter and ect parts. Wasted money on new parts instead of testing to figure that out.

im going to reinstall my old coil and test it again due to not confirming no spark at coil till after switching it.

 

Not a bad idea to have one. Even a cheap $5 one would do very well here. Sometimes test lights are fantastic, but sometimes they just don't tell the full story.
Yes, you can judge that a dim light something is wrong, or that with a bright light you probably have a good circuit, but it's not fool-proof.

To just one, or both wires? Should be just one with the key in RUN and the other one in START only.

That's correct. All of those are for sending and receiving signals from the distributor and coil.

Something does not sound right with that test. You turn the key on, ground the alligator clip, then touch the probe tip to the wires on the coil.
Doing this will show you that power is reaching the coil through the wiring. If you're doing it the way you described then all you're doing is verifying that what you're touching eventually will reach a ground somewhere.
If that's what you did, re-test with the clip on the negative side of the battery (or a known-good grounding point on the vehicle) and then touch the probe tip to the coil. You should see no light when the key is OFF, but bright light when the key is ON. But only on the "+" side of the coil.

Also, if you tested the ICM this way, re-test that as well.

You can test a coil more accurately with an ohm-meter, but a sure-fire test as well, is to connect the positive side of the coil to 12v, and intermittently ground the negative side. Each time you "catch and release" so to speak you should get a big fat healthy spark out of the center tower.
Obviously doing this test it's best to have the coil wire inserted into the tower and the other end laid over on the engine or somewhere away from you and/or delicate electronics.

An ohm-meter will also let you test the distributor's trigger mechanism which has that specific range of readings where it's good.

Paul

 

just an update. The problem was no power to the coil, i never did track it down, a break in the wires somewhere but i just hooked up a toggle switch for power to the + coil off the ignition switch. Also, stupid me, the new Alternator i installed, i forgot to attach the regulator so i wasnt getting correct readings and alot was misleading. Was looking for a power draw that wasnt there.
this thing is goin to have more problems i know it will, im still lost about how it used to run because throughout old photos of the wiring, i dont see where the coil ever got power.
I'm dang close to just building my own wire harnes. I opened up the wrap and there is a rats nest of wires. Ive looked at the woring diagrama and have no idea why there are so many wires there, let alone some bundled up that don't seem to go anywhere and misolanious plugs with nothing pluged in.
unfortunately the ford dealer in town closed a few years ago so not much options for help locally on this stuff. More back yard/project guys you have to find to get help.

but it runs and after a little adjustment, i can shoot flames too.