Broke down at rest area

[chrismh]

Always possible of the soft cam with a soft exhaust lobe worn out?

[Glenn and Kathy]

Originally Posted by Unplanned

I have 3 cars and 3 motorcycles with carbs on them, and I'm old.

I may not be an expert (only worked as a mechainc for 40 years) but I'm thinking it's loading up the muffler with air/fuel, then it fires off.

Did you ever do the old "Big Bang" trick? Coast down a hill, pump the gas with the key off, then turn the key back on. KABOOM! Big bang, and flame out the exhaust! Worked fine with the old Trush straight throughs, but blew apart a few old rusty mufflers on some of my buddies cars!

That big bang trick can backfire (pun intended) on you. Back in the 50s my brother had a 39 dodge and we and some buddies were out cruising around. Big brother started popping the exhaust and suddenly the back seat was full of smoke. The floor mat was on fire, took 2 beers to put it out.

Glenn

[T12]

I had a 72 Ford that did that. Turned out to be a real cheap fix. After washing my under britches I ran a couple of tests. The condenser was going bad. If your RV has one try replacing it. Also check it before installation could be bad, that happened to me once. Also if you get it from a parts house, if the clerk is young prepare for some strange looks when you ask for one

[bluehaven]

vacuum advance might not be working, take it to a shop and have it looked at.

[Jimddixon]

Might want to check your ignition control module located in distributor Had same intermittent failure and backfiring. Ignition module was culprit. Not letting ignition advance properly causing backfires

[My First Rig]

Sorry to hear of your problems, IF it's a FORD engine, and from the description, I bet it is, the problem is most likely the electronic ignition control box,they have been known to fire intermittently and blow mufflers up/out, it's external to the distributor, they go bad on a regular basis, just identify, unplug and dismount the old one, mount and plug in the new one ! It's possible it could be that the pick up inside the distributor could be bad, but very unlikely ! .. If it's a CHEVY engine it most likely has a HEI distributor with a bad module that's mounted internally, mostly they run or don't, but I've never known a HEI to go bad and blow out a muffler. The HEI module is very easy to replace by removing the distributor cap and rotor, it's mounted with 2 screws, remove the screws, unplug and replace, be sure to coat the metal bottom of the module with dielectric grease.

[hforward]

Your vehicle most likely carb a air pump blows air in the exhaust under constant cruise conditions. However when you let up on the gas there is excessive fuel headed to the exhaust. The air pump check valve under deceleration is suppose to vent the air pump valve air to the atmosphere If it doesn’t the air and raw fuel are sent to the hot muffler and a explosion takes place.

Regardless upon deceleration you have to much fuel going to the exhaust. Look for cracked or rotted or disconnect vacuum lines and the air pump diverter valve could be shot

Keep it simple. Test don’t guess.

If no air pump system you may have a stuck float or I’d fuel injection a over rich condition.

[falconview]

Originally Posted by MandyRH

It's a 454. Chassis I believe is a p30. So far we have replaced: spark plugs and wires, cap and rotor and fuel filter. We have checked the fuel pump, vacuum advance and looked for anything possibly clogging it up. It's weird that it's only doing this on the driver side. Boyfriend is starting to think it's a lifter or valve issue. And believe me when I say we would have drove it home without a muffler already if there wasn't a battery issue too. Something is draining it and we haven't been able to figure it out yet. But we did manage to get it going at almost 3:00 this morning. Still not home. But we are getting there!

Backfiring like that is ONLY one thing the carburetor is TOO rich. Unspent fuel is getting in the exhaust and then it ignites and goes BOOOOOOM, goodbye muffler. Have the carburetor rebuilt or buy a new one. Another thing the choke could be partly close causing a rich fuel mixture or the air filter is clogged. That problem is solved.

As for the battery going down, it could be as simple as a plate in the battery shorting out thus new battery. Have the battery checkout at a parts store that does this. Or you have a short to ground somewhere or light or something that stays on. that stays on. This would be impossible to figure out here.

[Kountry_star]

Originally Posted by MandyRH

I have a 1985 fleetwood pace arrow. When I first got it. It backfired so badly it blew out the muffler. Replaced it and for a couple months. There were no backfiring issues. But nearly 2 weeks ago we took it on its first trip. Only 2.5hrs one way. A few days later when we got ready to go home it happened again. So we replaced it and got on the road. About an hour into the drive it started backfiring while going down the highway. Then, you guessed it, a big boom. We got to a rest area and parked for the night. Replaced it again the next day. And the muffler blew again. We've been here since. Boyfriend thinks it could be something in the manifold. But says replacing it is his last resort. Anyone have any ideas?

Hope I'm wrong but we had a similar problem with a 1996 Pace Arrow on F53, Ford 460. Turned out to be a burned valve. Dumping in raw fuel but not igniting until in the exhaust. In my experience (not professional) backfire is almost has to be fuel related.

[Down South]

Well, so far I think we have at least several thousand or more dollars worth of solutions here. You can try em all and may still have the same problem.

[F43jet]

Sounds like a timing belt issue. Worst case scenario is the timing belt skipped. If the engine hasn't blown yet better get that fixed or it will. BOOM!!

[Mded40]

Take it to a place that has an exhaust gas analyzer .
Measure the exhaust gas in each tailpipe at idle 1500 rpm and 2500 rpm
Evaluate the results, it will tell you if you have a problem all the time or just during specific situations or on each side.
It should determine if you have a carbeurator problem, ignition or valve issue
Regards

[Roadgypsy]

There are a few things that you can do that won't cost you any money.
1. take off air cleaner and start engine and observe whether fuel is coming up thru the vent. (If fuel is coming thru vent then you have a float that is not seating properly or is worn out and causing the problem to be sporadic).


2. Take screw driver and adjust the fuel mixture screws at the base of the carb it could be running super rich.


3 If you are experiencing a hi speed miss (sometimes that can go unnoticed) it can cause issues. (Tune up is in order)



As others have suggested get carb rebuilt and a good tune-up. (Cap and Rotor, spark plugs and a quality spark plug wire harness)


That should take care of it.



Happy RV'ing

[dennyof]

hello friends sorry for your destress!
replace the complete ignition distributor !! you should be able to get one from Oriellys/napa/autozone. that will get you a new cap/rotor/coil/ignition module/pickup coil and distributor housing all in one swoop. should be able to get one $75-110. while the carb could be the cause, the engine should be running noticeably rough (really rough) before a backfire like you are experiencing would happen. Note: an intermittent pickup coil problem or for that matter any intermittent ignition distributor component is really hard to diagnose; if the ignition shuts off for a fraction of a second your exhaust system is loading up with fuel ready for a spark! kkkboom!
i have an 1984 p30 / 454 eng on a fleetwood southwind eagle (30yrs. on the road) and have replaced carb/parts and distributor/parts. it's not that complicated. most likely in my opinion your problem is in the ignition distributor. forget the all the noise in these posts. fire /fuel/ air: thats what makes these things work.
Note; one bolt to get the distributor out, however take a picture with distributor cap off before you take it out so you can put the new distributor in with approx. the same orientation. as you pull the old distributor out the rotor will rotate. make sure you account for this when putting in the new one. it doesn't have to be right on; close, should get it running then adjust with timing light or best running condition at idle. that should get you home!!
hope all goes well
o'l denny

btw way my ol 1984 eagle is for sale $4000 maybe. after 30 yrs figured it was time to update
again good luck