popping/missing and overheated control box..related?

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TylerW

TylerW

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Hey everyone...

Got a 318 2bbl that's developed some ignition problems suddenly.

When the engine is cool, it runs good and revs cleanly, but after some heat gets in it, it will miss and backfire out the tailpipes when you load it.Holding the gas down will make it either run badly with some major backfiring out the exhaust or it will simply peter out and die.

It starts back up quickly and idles ok, but before this actually happened I noticed at idle there are random pops out the exhaust at idle.

I noticed the Ignition control box has gotten hot and melted the epoxy down the fender, just like nearly every one I've seen in the junkyard.Could this be related?

The only other thing that might possibly be related is that the ground cable has been seriously overheated in the past.Everything works and the battery stays up, so I don't know what that is.

Also, what's causing the ECU's to melt?

Where would you guys start testing on this?

Thanks!
 
If the resin is melting out of the back of the box I would definitely replace it. And make sure that the new box is well grounded. It's not a good sign when the resin melts out of the back usually a big easy sign that it's gone bad.
 
Break out the timing light and hook it up to check your timing. With the engine cool your timing will probably look right on with maybe a slight variation now and then. When the engine warms up and the popping starts watch what happens to the timing. If it retards or moves around any at all you have a bad timing chain. Learned this 32 years ago with a '74 Charger. Unfortunately, I didn't know what it meant until the car quit running and I had to have it towed. I had 12 bent valves and all the pushrods were bent, so check for that when you get things sorted out. You probably haven't done that much damage yet, you are still on your first ECU. I went through 4 with the Charger. The current needed to fire a plug with the cylinder pressure at or just after TDC kills stock ECU's pretty quick. The stock timing chain is the Achilles heel of the smallblocks. By the time you have 60 or 65 thousand on the clock they have stretched to the point of causing problems like you describe and around 80 thousand they're dead. Do yourself a favor and put in a double roller. They last a lot longer. Just my $.02.
 
Mine started popping & missing bad the last time I drove it. Melted the ECU & blew the ballast resistor & burned up the voltage reg. It was all I could do to limp it home. Its time for a total re-wire in my case, but it could be something simple like the guys have stated.

What about going with a gear drive in place of the timing chain? I know they are a pretty penny but are they worth it??
 
Hey guys:

Did some further testing, and it appears this may not be an ignition problem after all, or it might still be.

I found that whatever happens to make the engine start breaking up starts happening at about 1/8 throttle.It will begin to run rougher, and the more you push on it, the more likely that it will die completely.

If it dies completely....with the throttle closed it takes about 3 seconds of cranking to fire up again, and it runs fine at idle then.

Here's a big BUT:

If I pump the gas hard and get it past the running rough and trying to die crap, it will stay running and rev hard.I didn't do that too much since it's an old engine.


The only thing I noticed other than this was, there's a faint noise like a vacuum leak when this stuff starts happening most of the time.I've been all over the vacuum lines and such and it's not just a loose or broken line.

The carb isn't the original..it's the Holley copy of the BBD I guess it is, and I've heard those are terrible for vacuum leaks and things.

Thoughts?
 
TylerW said:
Hey guys:

Did some further testing, and it appears this may not be an ignition problem after all, or it might still be.

I found that whatever happens to make the engine start breaking up starts happening at about 1/8 throttle.It will begin to run rougher, and the more you push on it, the more likely that it will die completely.

If it dies completely....with the throttle closed it takes about 3 seconds of cranking to fire up again, and it runs fine at idle then.

Here's a big BUT:

If I pump the gas hard and get it past the running rough and trying to die crap, it will stay running and rev hard.I didn't do that too much since it's an old engine.


The only thing I noticed other than this was, there's a faint noise like a vacuum leak when this stuff starts happening most of the time.I've been all over the vacuum lines and such and it's not just a loose or broken line.

The carb isn't the original..it's the Holley copy of the BBD I guess it is, and I've heard those are terrible for vacuum leaks and things.

Thoughts?
Click to expand...

It still sounds like the ECU to me.

They crap out under load and at higher rpm's.

I would swap it out first to see if it makes a difference, or you will be chasing all other kinds of culprits.

I would bet you have a newer orange box. Get a chrome one. It's made for racing, which you probably don't need, but it's just built better.

I went with the FBO kit. It has been flawless since I put it in.

Like Bigmack, I checked and replaced a lot of wiring after that. Went over all my grounds, took the bulk head apart and cleaned it and did an amp bypass.

Don't waste you time on the carb unless your electrical is up to par first.

Jim
 
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