Just bought a 1995 3500HD with the 7.4
While cleaning it out I noticed a newer looking coil in the glove box. I didnt think much of it and left it there for the time being. Drove to the DMV and went to start it again and nothing. I tried a few things and eventually decided to throw the other coil on and it fired right up.
Drove home and tried to start it again and again nothing. Swapped coils and truck fired up again.
Can these coils get too hot and stop working? It never hesitated or sputtered at all while driving. They are both Autozone store brand coils. I know theres something to be said about running OEM.
Let me know your thoughts.
Thanks!
Greetings StumpPuller454,
Welcome to the GMT400 forum! Congrats on your good taste in trucks.
Big block 3500HD? Heavy on the beef, light on the frills, a solid ride.
Now to get it to start on your timetable, not when it feels like it. :0)
The short answer is Yes, a coil forced to work so hard that it heats up
and loses it's ability to deliver the necessary spark is a real thing. Especially
if everything has stacked up in your engine bay so that the coil is forced
to work harder than necessary.
Before I discuss how you can give a new OEM quality replacement coil a
lot easier work environment to not only work, but at the same time
stay working,
check out what an elder had to say about the underlying electrical and
temperature variables on how coils work. It has the ring of truth:
You must be registered for see images attach
(credit: H.A.M.B. For many 1st-person 'coil heats up and puts me on the side of the road' stories, go here: (
Real World hot coil failure stories, a good read.)
Suggested Recovery Plan:
* Ensure that all the involved connections are clean as HotWheelsBurban mentioned, so that there isn't a voltage
drop on the 12v side of your ignition system anywhere. (Both the +12v side and the ground connections. Corrosion
has a 29-year head start on you.) Consider every volt a precious one, for we are working with so few of them. :0)
* Buy an OEM quality ignition coil. In the spring of '24 I don't know which brand is currently the best, hopefully others
will chime in with their firsthand experience.
* The higher the voltage required to jump the spark plug gaps, the more heat generated in our coils. If possible, this needs
to be brought down, especially if the PO subscribed to the "If it runs, leave it alone" mindset. A fresh set of plugs set
to the '95 factory specified gap (.035"?) is the way to go.
Fancy plugs here are not the answer, the only real difference they make on your 454 is to lighten your wallet the most.
Instead, a set of AC Delco (for the purist) or a set of affordable NGK V-groove (my go-to) will take care of business.
*New dizzy cap, rotor, and spark plug wires. Route the wires
exactly as the factory did -- a lot of engineering
man-hours went into that, for cross-firing spark plug wires = less customer satisfaction + more emissions.
NOTE: If you change your plugs, please lay them out in such a way that we can read them, and at the same time
look for any other issues. (Take a family photo laid out exactly as they were installed.) See attached as an example,
showing what I found when a big block '99 C2500 followed me home.)
****
Apologies for the length. But I didn't want you to just buy a new coil, only to have it
also fail prematurely. But if you replace the coil & refresh the high voltage side (to include
the plugs) I'm thinking that you won't need 2 coils (one cooling off while the other one works :0)
in order to enjoy your new (to you) ride.
Best of luck. If possible, please share sharp pics of what you find.
And let us know what you discover.
