454 Southwind Popping back at carburetor solved-- revised

[jyrostng]

My 1989 Southwind 454 P30 chassis with 48,000 miles on it started popping back at the carb. I had a hard time figuring out if it was fuel, (vapor lock) or ignition. I searched all the internet for days trying to figure this out and ended up more confused than before. I changed the rotor, the distributor cap, the ignition module, the wires, fuel pump, all the fuel filters and the plugs, it effected nothing, the popping was worse than ever. I still couldn't separate it from fuel or ignition. I even contemplated pulling the fuel tank when I finally figured out it had a internal fuel pump to supply the mechanical pump. I changed the fuel pressure regulator diaphragm (A Holley kit #12-807)and made sure the tank pump was working, still no help. I then realized it was popping before it got hot so I thought that might eliminate the fuel vapor lock issue. The last thing left to check before buying a new distributor was the coil. I took off the cap and removed the coil cover and the screws holding the coil. The old distributor cap was black, the new Borg Warner select was grey. Inside the coil area where the coil sits in a pocket in the HEI distributor was black with carbon, I had a ah-ha moment--- the coil was bad and arcing through the plastic to some of the plug terminals causing the backfire through the carb. Some of the other things that were mentioned on the internet were, accelerator pump, burnt valves, a vacuum leak and a quadrajet rebuild.

It was a bad #4 plug wire that caused the coil to arc inside the cap. High voltage HEI WILL find a place to put that arc.

[cj7365]

jyrostng wrote:

darsben wrote:
I am adding this to my knowledge base

Even with the new cap and rotor it started popping again. I found a bad plug wire on the #4 plug, no damage to the outside of the wire. I had to use a Ohm meter to find it. I suppose the HEI dist has so much voltage the spark found the lowest point of resistance with the bad wire was another post inside the dist cap causing another cylinder to fire while the intake valve was open causing the carb pop.

I also did this to fix the over heating plug wire problem on all these p30 chassis.
P-30 P30 plug wire and header overheat fix

Great info, I have a 95 and it does have that metal wind channel on the right side

[darsben]

I had this happen in May 2015 and it turned out to be exactly as the OP posted well almost exactly mine was #2 wire. Put racing boots on the new wires to try to stop recurrence. The old wires where one ear old with less then 6000 miles on them. Replaced under warranty.

[darsben]

BULLETLS1 wrote:
I found in the SUMMIT RACING store in Ga, an offer: complete billet HEI distributor, with hi perf coil, module, and cap-rotor for $57!!!, still carry the old one (of course had installed new wires).

They also carry the fuel pressure regulator that is mounted on the frame if you ever need one

[BULLETLS1]

I found in the SUMMIT RACING store in Ga, an offer: complete billet HEI distributor, with hi perf coil, module, and cap-rotor for $57!!!, still carry the old one (of course had installed new wires).

[RedG]

The second I read the title of your thread, I said "coil".
I've had a lot of people I know complain about popping and backfiring upon acceleration or load. When I tell them it's probably the coil, they look at me like I'm crazy. 9 times out of 10, it's been the coil.
Been driving GM vehicles for nearly 50 years and had this happen to me many times.

[DSDP_Don]

Anyone with the 454 and HEI ignition (OEM) should always check the distributor cap when issues arise. You need to turn it over and with good lighting look at the plastic near all 8 of the plug wire contacts on the inside of the cap. They were notorious for cracking, then arcing between each other. If you have a bad cap, replace it with a higher quality aftermarket model.

The 454 with the HEI ignition and quadrajet was a great set up when everything is working.

[jyrostng]

darsben wrote:
I am adding this to my knowledge base

Even with the new cap and rotor it started popping again. I found a bad plug wire on the #4 plug, no damage to the outside of the wire. I had to use a Ohm meter to find it. I suppose the HEI dist has so much voltage the spark found the lowest point of resistance with the bad wire was another post inside the dist cap causing another cylinder to fire while the intake valve was open causing the carb pop.

I also did this to fix the over heating plug wire problem on all these p30 chassis.
P-30 P30 plug wire and header overheat fix

[Mike_Hohnstein]

Always carry a complete spare HEI distributor, always.

[2bzy2c]

I and others in here really appreciate your posting the answer to what seems to be a common problem.

Far too often, people post a question for a certain problem, they get many answers, and never come back to tell us what the result was, if any. Very frustrating.

[Stim]

The GM HEI Distributor was one of the best ever invented!
It is simple and easily plug and play.
I have used it to retro older points systems.
During the same time period Ford had the Brain Box system. A total DOG to troubleshoot! The only way to check the box was to replace it and when they first came out they cost $150.00 !!!

[Grandpere]

Good to know, I would have gone with the timing being off. Thanks for sharing. I will keep this in mind if my 87 454 does this.

[darsben]

I am adding this to my knowledge base

[turbojimmy]

Good to know - thanks for sharing.

My cap and rotor are new (600 miles). How long until yours failed?

[BrianinMichigan]

Same vintage same amount of miles. I will print this and put it in my portfolio of possible issues in the future.