1979 Jeep Cherokee Chief backfires

[Brody93]

Okay so here is the story. My dad bought me this Jeep as a graduation present a year ago. I had always wanted a Jeep and this one is perfect. It drove great until around summer. (I had got it in about March as an early gift) I was trying to move it and it wouldn't budge. I had the tanks switch on the wrong tank so it would not stay started. I put a little gas in my carb and it started up but died but the carb had started up on fire and ever since then it has had problems. The guy I had bought it from had taken off the pollution controls, so it has no egr. It did not backfire until around August. I had driven it cause it had just idled bad and died as a consequence. So, all summer I drove with it just dying at idle basically. Now it idles great and just backfires from the second I touch the gas pedal. I have retimed it and it runs perfect for that day and then goes back to crap the next day. I have replaced the fuel pump, fuel filter, distributor, rotor, air filter, spark plugs, spark plug wires, battery terminals, and battery. I have also checked for vacuum leaks everywhere. I have plugged off every single line that is left open. I am at my wits end. I don't know what to do. Any help would be great.

[710 Burner]

A question and a possible solution:
First, the carb needs to be rebuilt.
Second, you are setting the timing repeatedly? and its not where you left it when you check it? If so, you need to pull the distributor and see why.

[mattparliament]

definitely check the distributor, sometimes they die slowly...

[Brody93]

I have thought about that but also have debated on just buying a new carb to get a fresh start. The timing will stay in place, but it will still backfire. For example, under the hood it said that it needs to be 8 before TDC so I time it to 8 at the correct RPMs and it will drive great for that day but go to crap the next day but still be at 8. I have also tried programming it to the timing it should be at for the earlier models that had no egr cause mine was removed.

[bg2pres]

I don't think a carb will cause backfire, it's just putting fuel in the engine, it's the timing off the valves that would cause backfire. Is it out of the carb or out of the tail when it backfires? It's all timing, my friend. Did your distributor gear rotate on you when you installed and you may be off a tooth or two? Went to an HEI and it did the same thing. I bought a new HEI and it was perfect. My first distributor spring and vacuum module was bad on delivery. Take the distributor back for a replacement, first and reinstall carefully making sure you are at TDC when installing. If you have a book, make sure you reinstall to perfection or it will drive you nuts... What about your ignition module? Check your voltage too, just in case...

[Brody93]

It comes out of the carb, but I am trying to determine if it is a backfire or misfire. I checked the distributor and it is flawless and installed right, it seems. I tightened it very tightly so the timing can't move. There is a vacuum can looking thing behind the carb towards the cab of the truck. That burnt up when my carb lit up cause it was just plastic. I was wondering if that could cause all this. I just discovered that it was burnt up today.

[seventynine]

Have you replaced the coil? Or possbily the ignition module?

Oddly...I just had a similar problem with my '79 CJ-5 which has a 304 in it. Last weekend it was running poorly stumbling and backfiring at speed and would stall out at idle some of the time.

I swapped the coil out with a spare and it's back to normal.

[will e]

Welcome to the forum!

How about a picture of that carb and what is burnt up? That might help.

I take it you poured gas down the carb, cranked the engine, it back fired and caught on fire? (It is always best to put the air cleaner back on before cranking for this very reason).

Do you have a vacuum guage? That would help in the trouble shooting.

[Brody93]

I have thought about replacing the ignition coil. I will probably do that when I get payed at the end of this month. This car doesn't come cheap at all. I poured a little gas down it and it started right up. No backfire or anything, just died. I do not have a vacuum gauge. I will probably pick one of those up as well. I burnt up the vacuum canister when the carb started on fire. Could that be causing the backfiring?

[Brody93]

Also, thanks for the welcome, good to be here. It is a lot more help than just the plain Jeep forum.