I recently purchased a Haynes manual hoping to find some specifications or a procedure to check the ignition coil, but it just says replace it.

Does anyone know if there is a method to test the ignition coil?

I have a 390 that is exhibiting some popping, sputtering, hesitation, and backfireing out the exhaust.

Thanks!

 

Betcha money it ain't your coil doing that. ;)

The way to check your coil is two ways.
First with an ohm meter (a coil is nothing more than a transformer) check
both windings for resistance...
Primary is 1.0 to 2.0 ohms.
The secondary is 7,000 to 13,000 ohms.
That's straight from my Ford Shop Manuals. ;)

The other way is to test how long of a gap it can jump with a coil tester.
I've never used one of those and so far hadn't needed to. ;)
Anybody suggest I get one? ...and "why" would be cool. :)

Want to post more about the problems and what you've done to it lately?
A progression of how it got to acting up like it is, if it didn't happen all at
once, would be helpful.

Alvin in AZ

 

i thought exhaust valves are the problem with exhaust popping and what not. I also don't think its the coil.

 

I have read a few threads about similar issues and I am trying to pick the low hanging fruit first. Initially when I got the truck, it was having a hard time idling from a cold start. I went through and checked the vacuum lines and found an open port at the front of the carb. I plugged it and it seemed to run a little better, but not great. I set the timing (with a light) and found that the open port on the carb was for the EGR. After reconnecting the EGR, the cold start issue seemed to come back. Basically, I have to start it and stay on the gas until the engine warms up a bit and then it will idle on it's own. However, the real issue that I'm having now is; after the engine is up to operating temp I can take off at low RPM, but if I give it some gas the truck will shudder like it is starved for fuel. As I mentioned, I have read a few threads on this same issue and I plan to check; coil, timing, vacuum/mechanical advance, fuel delivery, etc...

 

Sounds more like accelerator pump - look down the throat of the carb, and pump the throttle, it should squirt quite a decent amount of gas down the throat.

 

I think both your cold idle problem and the acceleration issue are carb related. The cold idle is a maladjusted choke and cold idle speed issue. I'm with Krewat on the second, sounds like a dead or badly adjusted accelerator pump linkage.

 

Im having a coil problem with my 1981 Firebird with a 267 V-8, I bought a new one and it fried it again, is it the resistor.

 

Does you ignition system even have a resistor? Originally the resistor was a point protection thing. A well designed electronic system should not need or have one. I would suspect the ignition box or computer. Quite often in you situation you will be better off replace the coil, sensor and box to prevent the exact issue you had with the new coil.

 

Bear, I just looked at some Duraspark schematics I have in my Motor's manual (1979 truck repair) and it shows resistors for most of the setups.

Ford 1973-74, 1975, 1976 (all called "Breakerless" not Duraspark) have them.

Duraspark I does NOT.

Duraspark II DOES.

However, it alludes to something being different with California for 77-78 Duraspark, saying "internal regulation" for the coil reduces overheating of coil and module, and non-California using a reduced-value resistor to achieve higher spark voltage.

From what it looks like, Duraspark I was just California, maybe using a resistor internally to the box.

 

A lot of the resistor with electronic ignition was due to there being point ignition systems going into the same vehicles that also had electronic available. Cheaper to only have one wiring harness.

 

he said he has an 81' Firebird.. hello....

 

Wasn't responding to that post but to krewat's. I could care less about the Firechicken.

 

 

Well Guys...I wanted to let you know that my issues seem to have been solved by a good tuneup, i.e. points, condensor, cap, rotor, and plugs. I put everything in, gapped the points and set the timing. It all seems pretty good now with the exeption of my choke. I will be tweaking the choke and checking the carb settings this weekend. I'm also installing headers and duals...can't wait to fire it up after that.

 

In my much younger years....Redneck way is to pull the coil wire from the distibutor with your hand while it is running... if it shocks the hell out of you then the coil is good. Made my arm hurt for 3 days. Guess the stock coils don't put out nearly what the new ones do. Here's your sign LOL