Jeep CJ backfire

[themuscleyard]

I have a 1979 Jeep CJ5 Golden Eagle . It has a AMC 304 3spd 2-1/2" Lift, Holley 4barrel and an alliance high lift cam. The engine has been rebuilt. Standard bore, new rings, bearings, gaskets, timing chain, cam, lifters etc. Now after all of that here is the problem. The jeep has run great until about a month ago. My son took it out and when he came back the idle was real rough. After it cooled off it fired right up and idled fine. A few days later he took it out again and it stalled just as he turned out of our neighborhood, he said it made a weird sound. I tried to start the jeep and it would just turn over and not start. After it turns over several times it will backfire out the side pipes and shoot out a flame about a foot long, it will not try to start just backfire. Any thoughts or ideas would be great

 

[Old Dog]

my first thought is it jumped time.

 

[themuscleyard]

What would be the best way to check / fix this problem, I have heard of this but have never experienced this before.

 

[Old Dog]

It could be as easy as the disturber was loose and moved or as bad as the timing chain jumping a tooth or 2.
I'd start by finding TDC and see if the timing marks line up and the rotor is pointing at #1 plug wire. To check the chain you need to take the timing cover off and check the marks.

 

[BlackOmega]

My guess: Your boy took it out and ragged the hell out of it, and most likely, overheated the out of it.

It sounds like you have fuel pooling up (a dead cylinder) then one of the other cylinder fires the pooled up fuel and shoots the flame out the pipe.

I have never heard of a chain actually jumping time. If it did, then there's something else wrong. Or the chain is horribly stretched out.

 

[tarry99]

I have a 1979 Jeep CJ5 Golden Eagle . It has a AMC 304 3spd 2-1/2" Lift, Holley 4barrel and an alliance high lift cam. The engine has been rebuilt. Standard bore, new rings, bearings, gaskets, timing chain, cam, lifters etc. Now after all of that here is the problem. The jeep has run great until about a month ago. My son took it out and when he came back the idle was real rough. After it cooled off it fired right up and idled fine. A few days later he took it out again and it stalled just as he turned out of our neighborhood, he said it made a weird sound. I tried to start the jeep and it would just turn over and not start. After it turns over several times it will backfire out the side pipes and shoot out a flame about a foot long, it will not try to start just backfire. Any thoughts or ideas would be great

Sounds like a timing issue..........late timing normally is a backfire out the exhaust valve..........and early would most likely be out the Carb.
An overly rich fuel mixture will also create a backfire.........that is caused when there is un-burned fuel in the pipe that gets lit off by the next cylinder firing. Is it both sides of the motor or one?
A broken or crack in the Dist. cap or bad wires will sometime allow for cross firing.........check the timing first, if the motor is rich you should have smelled it.

 

[themuscleyard]

I will check timing and make sure it is TDC on # 1 on a comp stroke, and that it is also under # 1 on the dist cap. It has new plugs, wires, dist cap, and also timing chain and gears. I will let you know, thanks again for every ones thoughts and ideas.

 

[Jimbos76cj]

So what came of this?? letting the boy still drive it?