New guy to bronco world. weird ignition coil problem.

hey yall. new year, great place for info! I got a question for you guys, kinda aiming to seabronc. He seems to have a good grasp on this topic. Bought a bronco for my plow truck. New it needed work. Its an 83 with 351 auto. replaced, plugs, wires, cap and roter, starter ign coil and ign relay. When i bought the truck from the guy it ran, batterys dead but it ran with a jump. Got it home and it all went downhill. First i smoked the starter relay. Replaced, started right up. Then the next day the ign coil went bad. was reading a dead short across + and -. Replaced it and it started right up yet again. Then so on and so on, did the starter and all that other stuff. Anyways, i had that thing running like a champ. A monster. last night i ran some sea foam through it, drove it around was really doing well. Came home today tried to start her up and no spark out of the ign coil yet again. Took it out, seems i killed another one. Reading a dead short. So il tell you what i dont know first. I dont know what kinda voltage i get between + and - when the truck is running. I read somewhere that it should be less than 12v after the truck is started. But i dont know, never checked it. I am guessing its supposed to drop lower and it is not, causing my problem. I got the ign relay from napa, i replaced wire for wire. HOWEVER i didnt use the "A" on there. I dont know where it goes /emoticons/[email protected] 2x" width="20" height="20" />. There was no wire on there. and i keep hearing about this ballast resitor and crap. The - wire off the coil goes over to this crappy old falling about harness, the wire is hanging on by like 3 copper threads. I know i gotta fix it. It goes to some funny plug, im not exactly sure what it does. the other side of the plug has 2 wires connected to it and goes somewhere. idk. im at a lost. and it sucks cuz its cold outside here, and i need to plow soon or i wont be about to get outa here! my driveway is the length of a football field. Any advice would be great thanks guys.

OK, you have a Duraspark II ignition on that truck. If you are eating up coils, it may have been rewired without the resistance wire, which prevents over current in the coil, (just guessing). Attached it the Ignition diagram for the Duraspark II with color codes marked on it. Note in diagram 18 how the coil gets it's voltage. In start it gets a strait 12V, in run it gets voltage through a resistance wire which when running drops the voltage at the coil to keep it from burning up. If that resistance wire is bypassed the coil won't last long. So check the wire connections and make sure that they all go to the right place. pages 12,13, 14, 15 show the power distribution 12, 13 (without an ammeter) and 14, 15 (with an ammeter).

These are from the EVTM (Electrical and Vacuum Troubleshooting Manual), it is one of the best books you can get for your trucks Shop Manual arsenal. It is what the dealers use to do trouble shooting. You can find them on eBay http://www.ebay.com/sch/i.html?_from=R40&_trksid=p5197.m570.l1313&_nkw=Ford+Bronco+EVTM&_sacat=See-All-Categories

I would recommend any Bronco owner get one for the year truck they have. Just make sure it is for a Bronco, F-series truck, not the Bronco II, unless of course you have a BII.

Good luck,

Oh yah! Welcome to the Zone /emoticons/[email protected] 2x" width="20" height="20" /> .

Welcome Keith,

If you are checking coils between the primary leads, the resistance should be 0.8 to 1.1 ohms. If you are checking continunity, it will read as a dead short. In a coil this is not the case. It is how a coil works.

Try this, the resistor should reduce the voltage at the coil to 90% of battery voltage, or about 10.8 to 11.88 volts. This is measured at the + terminal of the coil with the engine running.

I think you said that the wire from the - terminal went to a connector that then had 2 wires and one was frayed badly. This may be the root of your problem, as the coil gets it's firing command from a green and yellow wire that runs to a connector that leeds to a light green wire to the ignition module. If this wire is frayed, the coil will not fire, but will continnually be saturated to build voltage. That over time could burn up a coil.

Hope this helps.

you guys are allstars. i will check this all out tomorrow and get back to yall. thanks for your help!

RELATED QUESTION

Help me out here.... ^_^ /emoticons/[email protected] 2x" width="20" height="20" />

I was taught all coils are 12V these days (back in the day there were 6v coils, & points only.?)

Point being.., the ballast resistor., or "resistor wire" is there to protect the "points" i.e. extend the life., not to protect the coil...? Which is correct..?

The later FS Broncos have the resistor wire (even with pointless ignition) & I've always wondered 'bout that..

My homemade ignition runs on a "GM" HEI "4pin" module., hooked up to the later model Ford Duraspark dizzy. The instructions say "use any 12V coil and NO resistor or resistor wire."

It also states "the voltage is automatically adj. in the HEI." But, the HEI is downstream of the coil.

How does 12V harm a 12V coil...???? :blink:

You are correct on all counts Bob. The damage is done only to old oil filled coils if the module does not signal it to fire, and the saturation time is constantly too long. This is something that is a rare occurance.

Remember dual point distributers? Purpose was to increase dwell time for more saturation on the primary side. It gave hotter spark on the secondary side....but the coils would wear out sooner.

Newer HEI coils and aftermarket coils, like a MSD Blaster and the like are not oil filled and saturation time is no problem.

I believe the phrase. "the voltage is automatically adjusted in the HEI" refers to the secondary voltage. The early GM HEI units would increase voltage to 80K volts, as needed to fire plugs. Newer units could go north of 100K volts, as needed.

One thing Keith could do is go to a new blaster coil.....but I don't think the coil is the problem. For my money I would go with a HEI or blaster anyway.

I think the wireing he described as going to a"crappy old falling about harness" is the issue. Sounds like it is part of the command circuit to the coil.

It will be interesting to find out.

Bully Bob said:

\The later FS Broncos have the resistor wire (even with pointless ignition) & I've always wondered 'bout that..

Click to expand...

If he has a Duraspark II system, he needs the resistance wire or a ballast resister, this is a 28 year old system not a modern coil like a MSD Blaster. The object of a ballast in an electrical circuit is to prevent over current. Over current will overheat the coil. Granted his problem is probably the crappy wire, but if he follows the troubleshooting procedure given in the charts above, it will point him to the failing component, regardless of the theory of operation, the resistance wire being one of them as listed in the trouble shooting procedure. Since we are not there to actually see and help in the process, the simple troubleshooting procedure given in the above charts will point his nose to it.

If he can afford it, he probably would be better off in the long run to do just as Ron said, put in a MSD, or HEI system. Both could cost a lot more than fixing the Duraspark II.

And yes, the information provided with the modern MSD coil says that it doesn't need the ballast.

well i fixed it. silly me i was way off. The coil acually wasnt bad haha, i got a new one and compared the resistance to the old one and it was the same. It was a bad ign modual. got a new heavy duty one and she fired right up.

no i have a new, worse problem. kinda in a pickle. so i finally got it running good, dad went and got plates put on it.

we worked alll day today at my bro in laws house. working on the plow, and i redid the plow lights, and headlights. (they were terrible)

i was driving home and all of a sudden 2 loud pops, i think i saw sparks out the pipes. and truck turned off with NO sign of live. Power steering went out headlights, everything. Even the dome light doesnt come on. Starter relay doesnt put in. I think the sparks acually were just from it back fireing. its sitting in a ditch right now until tomrrow when we get it towed back to my house. Heres the only thing i found. We knew that the cable from the + battery to the one side of the starter relay had a bad lug. it was cracked. its VERY possible that it flew up and hit the bottom of the hood. But idk, seems kinda far fetched. its totally gotta be something electrical i would think but im at a loss. I thought maybe the key switch? but still the dome light should come on, and the headlights. idk guys. any ideas?

If you lost everything it almost has to be something up front electrical and close to what you are thinking or the main ground connection. Wait till you have a better chance to look at it.

Good luck,

Fred's right, wait till tomorrow. It might be super apparent as soon as you open the hood. I was flying down Hwy49, when I first moved up here, to check the place out & because I just dropped in a new motor in my '77 F150. I was flying down a 2 lane Hwy, one lane north & one lane south, when I suddenly heard a "POP" over my stereo and the truck just went silent and glided to the side of the road, dead! The truck was so close to the crown of the road, I heard it slide slightly in the gravel as the semi's flew past. I was almost afraid to get up onto the front bumper because I thought my weight was enough to send it over and onto it's side in the ditch!! I popped the hood, looked around for a few minutes, and saw the electrical wire had completely snapped off the coil under the nut. I loosened the nut, wrapped the wire around the stud, and tightened the nut and it started right up, thank God! [-o<

Sounds like something touched and grounded, or something with the ignition, because once it's started, it's started, unless something "turns it off"...but believe me electrical is not my strong suit. However, I am very interested in learning it and that is why I bought one of those manuals off a FSB member who had a bunch of new ones like Fred was talking about... > -Kevin-

Catching up to you Fred, I got 14 wait 15 posts......lol. > -Kevin-