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Coil gets HOT and engine cuts out. 1984 F250

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Starliner

Coil gets HOT and engine cuts out. 1984 F250

The old coil had a condensor which attached to the bracket and came off the hot side of the coil, (so there were 2 red wires coming off of the coil pick up.
The new one just had the 2 wires, red and green, (no condenser wire), so I just left it disconnected.
My understanding was that the condenser was just a noise suppressor for the radio so I just left it disconnected.
But MAN, this coil gets hot. And given time it cuts out. Luckily I have a spark box and hooked it up and was able to drive away.
Than God I kept this handy tool, never thought I would use it again.

Anyway, any guesses as to why she is getting so hot.
Here is a picture of the OLD coil and pick up. You can see a grey plug which went to the condenser. Sorry for the bad shot, best I had. Thanks.

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Gary Lewis

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

The condensor isn't the problem. And it is indeed a noise suppressor, so isn't needed.

I can think of two reasons the coil would get hot. First, the wrong coil. Where did you get it? What brand is it? And why did you replace the old one?

Second, if you've bypassed the ballast resistor. Have you changed any of the wiring to the ignition? Are you still running the original ignition module with a blue grommet?

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

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

In reply to this post by Starliner

Today my plan is to sand down everything from the battery, solenoid, starter, all grounds. Check voltage at the coil, (or course), but after that I will just have fingers crossed.

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Gary Lewis

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

Did you not see my reply with several questions?

Gary, AKA "Gary fellow": Profile

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

In reply to this post by Starliner

Gary, because it had been baking for 10 years, and since I was having fuel and ignition issues, I figured anything with plastic or resin was going to fail eventually so I replaced a lot.

Coil, rock auto, not sure but maybe Standard. I will have to get back to you on that.
ICM, changed but kept the old one because the swap didnt help.
Cap, rotor, plugs, wires, battery.

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

I also changed the ignition switch

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Gary Lewis

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

In reply to this post by Starliner

I'd put the original coil back and see if it gets hot. If not, it is the new coil that is the problem.

And if the coil is getting that hot the ignition module is very likely to fail as it is carrying way too much current. So you may have fried it.

Gary, AKA "Gary fellow": Profile

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

Amazing, my buddy just made the same suggestion.
I hope it's not in the garbage and gone.
If it is gone I might just swap out another one to be safe. I consider it a 20 dollar troubleshooting measure.
Btw, I see no resistor in my system.
The replacement coil was a cheap one made by WVE (rock). Mine is over 8500 lbs so it specified that.

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Gary Lewis

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

The resistance wire/ballast is in the harness and you won't see it. But it is there.

Gary, AKA "Gary fellow": Profile

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

When the truck is running I'm getting 14.3 volts from the red wire going to the coil, (about what it is also putting into the battery).
Key on, not running I see 12.7 volts.

Does that sound normal?
Thanks.

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Gary Lewis

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

Do you know German? If so, jein. That means yes and no.

14.3 volts going into the battery while running is about right, as is 12.7 at rest. But, you should not have 14.3 volts at the coil while running. Something is mis-wired.

You can see in the schematic below that the ignition switch is supposed to bypass the resistance wire in Start and send full battery voltage to the coil, but that in Run the power flows through the coil and the voltage gets dropped.

Did you adjust the new ignition switch when you installed it? Instructions for that are on the page at: Documentation/Electrical/Ignition and then the Ignition Switch tab.

Gary, AKA "Gary fellow": Profile

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

This post was updated on .

Thanks very much.
I did not adjust it when I installed it.
Thanks for the voltage info will pull up that tab.
I think I'm in the right direction.
I saw the scans you did in the resources section. Thanks, that must have taken some time.

This is an interesting issue to trace, the fact that the coil is getting alternator voltage, not battery voltage which would have passed through a regulator, (if I am saying that right).

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

In reply to this post by Gary Lewis

I will adjust the ign switch tomorrow. If that doesn't help, until I can track down the real issue, wouldnt a ballast resistor bandaid the issue for in the meantime?
Also, I will check to see if someone has accidentally bypassed the resistor wire or replaced it with regular wire by mistake.

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

Gary Lewis

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

Yes, a Chrysler ballast resistor would work as a bandaid. But you won't have full voltage for starting so it might not start as easily.

But I seriously doubt anyone has removed the wire as it is deep in the wiring harness. However, they may have wired around it.

Gary, AKA "Gary fellow": Profile

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

OR, like you said, it might very well be a simple ignition switch adjustment which is preventing the use of the resistor wire!

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

ArdWrknTrk

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

Look at the diagram above.
You can ohm from the coil hot to the white/light blue of the ignition box plug.
I don't have the reading in my head, but it won't be 0, that's for sure.

The coil WILL get hot if you leave the ignition on, not running.
Once the field is saturated the windings have to dissipate that current as heat.
There's an awful lot of filament in that can.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ArdWrknTrk

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

Look at Matt's thread here: http://www.garysgaragemahal.com/#nabble-f63

He shows the pink wire wrapped up in the dash harness.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

Jim - Don't miss that he has 14.3 volts at the coil with the key in Run. Wait!

Starliner - Was that with the key in Run but the engine not running? Couldn't be 14.3 volts DC with the engine running as the duty cycle, the equivalent of the points opening and closing, would have it far less than that. Unless you are reading the ringing.

So, please confirm how you measured 14.3v at the coil.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Coil gets HOT and engine cuts out. 1984 F250

Administrator

Yes, I noted that.

A) I'd check the batteries in my meter. They use battery voltage as a reference, and a low battery will cause a high reading.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Starliner

Re: Coil gets HOT and engine cuts out. 1984 F250

I read that 14.3 while running, measured off the hot connector splice.

You have all been great BTW.

I do see on that diagram where in the "on" position the voltage should drop via resistor wire. I thing Gary is right on, that I need to focus on ignition switch adjustment first.

High voltage readings with low meter battery is very good to know. I will say though, that the standing battery at 12.7v tells me it is correct. I will definitely use that knowledge in the future.

Also, I did sand down battery/solenoid connections and it may have helped, certainly couldn't hurt.

JOE
1984 F250 HD 2wd auto w/air,
351W, 2bbl, Dana 60 3.73, no EEC

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