So I've been restoring a 1984 Cj7 for the last several months. With much good advice and help from this forum I might add.
258 I-6, T-5, 33's, 332's with factory differentials front and rear.
Nuttered, Team rushed, Weber 32/36 the engine is the original 1984 from what I can tell.
The jeep runs great for about 10-20 miles and then slowly you can start to hear a slight valve tap starting. Then within minutes it gets worse and starts backfiring or detonating through the carb where you have to pull over. In less then 5 minutes the tap and backfiring is gone and then you can drive for another 5-20 miles or so!
I've replaced the distributor, timed at 8 degrees with vac disconnected and plugged. Relocated the Ign module with added ground wire. Went through the carb (its's the good webber not a knock off) there are no vacuum leaks and eng will idle smooth and low. Runs and accelerates great until the problem starts. The PO unhooked the EGR. I hooked it back up but don't think it's opening.
The distributor is hooked up to S port and will idle at about 375 rpm with no vac at The S port with lean best at 1-1/4 turns out on the mix screw. I'm forced to turn the idle screw up a bit to get a more desirable idle after tuning. Idles set at 550 with a slight vac at the S port.
Went through and replaced the cooling system and it runs right at the proper temp.
Seems like there's a lot of heat under the hood when it starts popping? The only thing I haven't checked is the muffler. Had a cherry bomb when a got it. Possibly broken inside not letting the exhaust out fast enough?
Any thoughts or advice would be much appreciated. Sorry for the long post.
Not sure? It seems to run clean, not blubbery at all. I wouldn't think that would cause the valve tap that starts it going. I was thinking more on the lean side causing it to get a bit hot in the combustion. Not really sure at this point.
Well, that is what started me asking about a FPR to begin with. I had the same issue (albeit it quicker) when my regulator would get plugged with debris and lean out the motor until it died. Is it possible your filter is causing a lean condition after running for a bit?
Mine got way too much fuel without a FPR... I wonder if your filter is plugged and keeping pressure down enough to start, but then leaning out too much to run?
It doesn't die it will start popping and backfiring through the carb. There will still be a good squirt in the carb. The detonation is so bad that I just pull over and shut it off to prevent eng damage. Filter is new as well as the sensor and screen in the tank.
I'm still thinking fuel too, (but I am also a bit of an idiot, so do with that what you will ) do you have a line too close and are vaprizing it? What did you do w/ the return line when the weber went on?