need coil info.

[thestrange]

So the trucks been running great, then at 5am i went out to head to work and the beast wouldn't turn over. its getting fuel, and air but no spark. i did the quick test of watching for a spark from the coils and i got nothing. both wire terminals have 12v when the keys on, 2v from the center terminal(where the wire goes out to the distributor cap). i checked the primary and secondary resistance (secondary 9k / primary 1.70) Im guessing i need new coils because the primary reading was not with in the 1.04-1.27 spec? so can i just buy any coil, or do i need a specific model#?
My other question is, is there a mod to just run 4 plugs, and 1 coil like a normal 4 cylinder?
thanks in advance.

[Davezilla]

It could be the ignition module inside the dizzy that just went out, the coils are out of spec but they should still fire with those resistance numbers, and more than likely one coil would still work if the other failed... very unlikely that both would fail at the same time...

[thestrange]

How do i properly test the ignition module? I have been searching for a few week for a fsm online but i just can't find one. I thought the same thing, there's no way both went at the same time. however, the PO had a jumper running from one coil to the other with a.10amp fuse, could that have been used as a bandaid fix for one bad coil?

[Davezilla]

I can look it up when I get home since I got a FSM for an '86. I just find it hard to believe both coils would go out at the same time, but it could happen. To get a FSM for these things isn't easy and took me a few months searching ebay before one came up for sale, then I had to pay like $65 for the book and another $20 for shipping, normally I wouldn't pay that much but it was the only copy I've seen up for sale in several months.

From what I was reading in the turbo forums it's a common practice to jumper the coils together so they both fire at the same time in order to simplify the ignition system or if one side loses spark, they'll just jumper the coils together so they both still fire. The ignition modules in these are also quite expensive so it's highly likely that if one side went out the previous owner jumpered the 2 coils to keep them both going, then somewhere in here I was also reading where someone found the ignition module from an ebay seller who was selling them dirt cheap, and I've seen a few places selling the dizzy fully assembled with everything installed inside for less than the normal cost for the module by it's self.

As far as the coils go, there shouldn't be anything wrong with using a coil off another car to see if you can get it to fire, but if you're replacing your coils you would want them to have close to the same primary resistance as the stock coils to prevent overheating the module.

[thestrange]

Ok i tested the voltage at the icm, all 3 points had 12v. I have been looking for the relay that's for the icm to check it, but i can't locate it at all. I have read that its to the left of the battery, i see where it would have been but i simply have no relays under the hood. I have the 2 relays above the fuse block (fan and headlights) and one on the passenger side that is for the coils? I swapped relays and it is good. I am still thinking its both coils. They both have 12v at both connections, but absolutely no spark what so ever. is there any way to pop these open to repair them? I am super broke and just need it to get to work for a few more days. lol.

[Davezilla]

Did you check the ground circuit for the I.C. Unit in the dizzy? the other 3 readings are good, but there's also the ground circiut that should read .5 volts or less, if you get a reading of more than .5 volts the I.C. unit is bad. The coil's primary side does read out of spec on yours, but unles tehy read as open they should still be able to fire, even tho the spark may be weak, but with the wrong resistance here it could overheat the I.C. unit and cause it to go out. Another symptom of a bad coil would be that it would work intermittantly, meaning it may fire when cold but won't fire at all after it's been run for some time.
I'd also be checking all the wiring connections and relays going into the coils and I.C. unit as a dirty connection somewhere could also be the culprit.
The next step to confirm it's the coils would be if you got a known good one you could borrow from a different car, or if you could take your coils out and wire them into a different car and crank it over to see if they fire at all.
The reason I'm stressing that you should further check the coils before running out and buying anything is mainly beacuse both of them going out at the same time is so unlikely, and normally coils don't just die instantly, but they do die slowly making your car unreliable about starting and the solid state components like the I.C. unit are far more likely to just die instantly leaving the car stranded wherever you turned it off last. I have seen ignition modules in other cars go out slowly and intermittantly where they will start one time and nothing the next time, but eventually start again... again, making for a very unreliable ride at best. The other part about troubleshooting the ignition carefully and thouroughly is that ignition parts can get real expensive real fast and most places won't refund electrical parts. These engines will run off just one coil tho, so if you checked everything else, you can go out and buy one coil to see if it starts and runs, then if that fixes it, you can buy the second one... This might be your best bet right now since you're low on funds and you won't be out too much if the coils aren't the problem. From what I saw in the manual, the only thing that's out of spec right now is the coil's primary resistance, so if you're sure all your electrial connectors and wiring is ok, then I'd say it's safe to buy a coil and see what it does.

[thestrange]

Where is the ground circuit? Would i just be testing the actual grounding of the unit, or is there a forth wire concealed under the icm?
thanks for all the help btw.

[Davezilla]

From the pic in the book, the grounding is measured from the dizzy housing to the battery negative terminal, The procedure says to pull the coil wire from the dizzy and ground it, then to observe the voltage reading while cranking it over so you'll either need a remote starter switch or a buddy to crank it over while you take the reading.

[thestrange]

Oops, sorry i forgot to update that I got a pdf of the fsm and did the test. I got about .46v. I will be taking the dizzy to a autoparts store to have it tested just to make double sure. thanks for all the help.

[Davezilla]

Glad you found that in the FSM since all the tests are there on the same page and it'll better point you to what needs to be replaced. Just be sure to check and clean all your electrical connections and be sure your relays are all working properly etc as well since a dirty or bad connection, a broken wire, or an electrical short somewhere can cause the same problems and make you waste your money on new parts. Lastly,check all your fuses since there is a fuse for the ignition coils and also for the clutch switch (if yours has one) or inhibitor switch (automatics only) that'll prevent it from firing the coils if they're blown. There's also an ECM under the driver's seat, check the electrical connections there too since this ECM controls the module inside the dizzy... You'll see this in the manual and it's also worth checking before spending any money, this part is usually pretty reliable so it's not as likely to be the problem, but just in case...
Hope to see you up and running again soon

[thestrange]

I do not believe my 720 has the ecm under the seat, although i will check thank you.

[thestrange]

Well i took the over priced icm in to have it tested and it past 3 times. so i know its not the icm no for sure. i think now Im going to have to trace each and every wire involved with the ignition system.

[Davezilla]

That's a good thing on the ICM... those things are way overpriced for sure... but yeah... spark chasing is the next step, and try to cllean every connection as good as possible before plugging them back in, it don't take much corrosion in the wrong place to give you an intermittant or extremely difficult to troubleshoot problem... Good luck and you'll find the problem as long as you test every part of the system.

[thestrange]

Well i got the icm back in yesterday, before i put it in I used some sand paper under the dizzy cap and cleared up some rust. well I have strong constant spark from one coil, but the other seems like hit and miss. after cranking the engine for awhile it still wouldn't start so i swapped coils and it still won't fire. I did notice that I can turn the rotor with the ignition off, a good inch each way before it'll stop. I don't remember it being able to move that much before?

[thestrange]

Figured it out. the rotor shaft and governor weights were not properly lined up. That and the rust in the dizzy were my problem. I would like to thank everyone for helping.

[Davezilla]

Glad you got it all figured out... and I'm sure you know this ignition system very well by now too...

[thestrange]

yea, I learned a lot in a short amount of time lol. I drove it yesterday and it ran awesome! I was cleaning up the engine bay a bit and realized in my mad dash to get it running I left the #1 exhaust plug disconnected, it runs fantastic now, haha.

[Davezilla]

Awesome!!...