coil question
Thread Starter
|
New User
Joined: Feb 2011
Posts: 19
Likes: 0
coil question
My 76 f100 died on me the other day. Tracked it down to a bad coil. Had an old one in the bed swapped it out and it ran fine. So I went to auto store and bought a. Accell super coil. 12 volt universal. After installing it I noticed a power improvement but it backfires horribly through the Carb. Went back to the old one in the bed and the backfire stops but doesn't have the same power output. The manual says 8volt oil filled coil. Is the voltage the problem? Any suggestions would be great before I return the coil. It's either a 360 or 390 motor. Will dowel test the stroke when I can to be sure.
Senior User
Joined: Feb 2011
Posts: 243
Likes: 3
From: Spokane, Wa.
That is an odd problem. I have never played around with coils much so I don't know what the deal is with the 8 volts, that just puzzles me since all cars I have ever heard of are either 12 volt or 6 volt systems. Not to say 8 volts is wrong, I just don't know much about coils. As far as backfire with one and not the other, sounds to me like the supermarket coil is either putting out a hotter spark or its getting to the plugs faster. Try playing with the distributor a little to adjust ignition timing and I would imagine that will fix that problem. Hopefully someone smarter than me will help us both learn a little about coils and answer your electrical questions.
Thread Starter
|
New User
Joined: Feb 2011
Posts: 19
Likes: 0
Ya the Guy at Oreilly told me to retard my timing a little also. So I think I'll mess with that this weekend. Unless someone else has another suggestion. I think my Haynes manual says 8 volt oil filled coil is the specs page. Which seemed odd to me also. I just checked the replacement coils at Oreilly and they all say 12 volt. So I don't. Think that was the issue
Posting Guru
Joined: Mar 2006
Posts: 1,182
Likes: 1
i agree with the guy at O'Reilly's- try retarding the timing a bit.
as for 6v/8v/12v coils....the old-school stock coils can't handle 12v all the time- they'll burn out. to prevent this, Ford used a resistor wire (pink) between the key switch and the coil to knock the voltage down from 12v to 7 or 8.
aftermarket coils can generally handle 12v all the time. (double-check yours to make sure.) if so, then to get the most out of it, you now need to bypass that resistor wire. follow the instructions that came with the coil, it'll probably have all this in good detail, including what to do with your external (ballast) resistor.
as for 6v/8v/12v coils....the old-school stock coils can't handle 12v all the time- they'll burn out. to prevent this, Ford used a resistor wire (pink) between the key switch and the coil to knock the voltage down from 12v to 7 or 8.
aftermarket coils can generally handle 12v all the time. (double-check yours to make sure.) if so, then to get the most out of it, you now need to bypass that resistor wire. follow the instructions that came with the coil, it'll probably have all this in good detail, including what to do with your external (ballast) resistor.
Senior User
Joined: Feb 2011
Posts: 243
Likes: 3
From: Spokane, Wa.
Ok, that makes sense. The old one he had was an 8 volt that requires the resistor wire and the new accell super coil is a 12 volt capable so it pumps out more juice to the plugs resulting in a quicker and more complete fuel burn which is starting while the intake valves are still closing and shooting fire up the intake. Bypassing the resister wire will result in even better burn which is good for power but creates more back fire without adjustment. Retarding the ignition timing by turning distributor counter clockwise will delay the spark a little and thus let the intake valves close completely before the cylinder fires. Makes sense to me 
I love learning new stuff.
I love learning new stuff.
Posting Guru
Joined: Mar 2006
Posts: 1,182
Likes: 1
almost forgot- you may also be able to gap your plugs a little wider to take advantage of the hotter spark.
Trending Topics
Thread Starter
|
New User
Joined: Feb 2011
Posts: 19
Likes: 0
Thanks for the info. The ccoil has hardly any instructions. I'll just make sure I get 12 v to the coil. Eliminate the resistor and dial in the timing and se how it goes from there
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Tuned
Joined: Feb 2009
Posts: 370
Likes: 0
From: Near Nashille, TN
Did you get the Accel 140001 to replace the Duraspark coil?? If so, the Accel coil has a lower primary resistance than the Duraspark coil... so you should also use the Accel ballast resistor (.83 ohm) in place of the Fords 1.2 ohm resister.
With ignition on & engine not running, you should have 6~8 volts at the +coil connection. You probably have less than 5 volts using the original resister. If you run straight 12v to the coil, you risk burning up the duraspark module.
Also, don't just GUESS at your timing... check it using a timing light! If you still have trouble with backfiring after all of this, I'd replace the duraspark module (they're fairly cheap). What ever killed the coil could have damaged the the module too.
Let us know what you find out..
With ignition on & engine not running, you should have 6~8 volts at the +coil connection. You probably have less than 5 volts using the original resister. If you run straight 12v to the coil, you risk burning up the duraspark module.
Also, don't just GUESS at your timing... check it using a timing light! If you still have trouble with backfiring after all of this, I'd replace the duraspark module (they're fairly cheap). What ever killed the coil could have damaged the the module too.
Let us know what you find out..
Posting Guru
Joined: Mar 2006
Posts: 1,182
Likes: 1
%^@%@@%@!!!
i completely missed that he's running a 76, which would have the Duraspark setup. all my stuff is older, pre-Duraspark.
forget what i said- just get a OEM-style coil and don't worry about it.
jmf66- thanks for catching that.
i completely missed that he's running a 76, which would have the Duraspark setup. all my stuff is older, pre-Duraspark.
forget what i said- just get a OEM-style coil and don't worry about it.
jmf66- thanks for catching that.
Thread Starter
|
New User
Joined: Feb 2011
Posts: 19
Likes: 0
Ok got home and started looking again. Put the coil in. My vacuum advance on the distributor has 2 ports. They were just jumped to each other. I need to get them tied in. Where do they need to connect? All I can see in my manual only shows one port. I need to get all my vacuum lines set up and go from there. Any help would be great
Senior User
Joined: Feb 2011
Posts: 243
Likes: 3
From: Spokane, Wa.
I have never dealt with a distributor with 2 vacuum advance units, but I know the distributors with one vacuum advance, the hose runs to manifold vacuum port on the bottom of the carb. On my autolite 4100 the port was on the back and was tapped. A piece of flared steel tubing with a brass fitting on it ran around to the front where a rubber vacuum line connected and ran to the distributor. On the holley 4160 I have now the port is on the passenger side of the primary fuel block and the rubber vacuum line just plugs onto the barbed fitting on the carb. I don't recall where it goesbon the edelbrocks or the motorcraft 4200, and I have never had a 2 barrel.
Thread Starter
|
New User
Joined: Feb 2011
Posts: 19
Likes: 0
Okay I think I figured out my vacuum tubing and advance hookup. Got a coil and external resistor. Mine was missing. Where does the resistor hook up? The way the auto parts Guy told me didn't work. It wouldn't even start that way