Backfiring

[Felix]

Background: About a month ago the valves were adjusted, carb was tuned with a vacuum gauge, and the plugs/wires/cap were replaced. Due to a malfunctioning timing light, the timing was not set, but the truck did run very well. Carter AFB carb, non-USA dizzy, electronic ignition.

Problem: After not having drivin it for 3 weeks, I went tried to drive the Cruiser to work this morning. It was a little harder to start than usual, but I figured that was normal. I let it warm up for about 10 minutes. As soon as I pull out, it backfires through the muffler. I get multiple backfires during acceleration from a stop and the occasional backfire while cruising, all through the back end.

I know I need to get my hands on a timing light, but what could have gone wrong while it sat in my driveway for three weeks? It was running better than ever when I parked it.

Thanks for any suggestions on where to start.

 

[trucruiser]

Check, timing , Points, and for vacuum leaks.
Thats where i would start.

 

[Pin_Head]

Background: the plugs/wires/cap were replaced.

Problem: it backfires through the muffler. I get multiple backfires during acceleration from a stop and the occasional backfire while cruising, all through the back end.

Are you sure that you got the wires replaced in the correct firing order?

 

[petescoffee]

all of the above.
Try and move your distributor. the clamp may not have been tightened after you last worked on it and it moved.
Check firing order restet timing.

 

[Felix]

Thanks, I'll re-check the firing order and timing. I was just curious about what could have happened while the truck wasn't running.

It ran fine. I parked it. After three weeks of being parked it backfires all over the place.

 

[Pin_Head]

It ran fine. I parked it. After three weeks of being parked it backfires all over the place.

That's an important piece of information you left out. You can put the timing and firing order on the back burner and start looking at things like water in the fuel or dirt in the carb.

 

[camcruiser13]

all of the above.
Try and move your distributor. the clamp may not have been tightened after you last worked on it and it moved.
Check firing order restet timing.

x2.

 

[Felix]

Check, again. I didn't leave it out.

It just occurred to me that when I was pulling the coil wire before leaving for the holidays, I unplugged a couple plug wires to get a better grip. Maybe I put the those wires back on wrong like a dumbass. I'll check it all out when I get home from work.

Thanks for the tips.

 

[camcruiser13]

happens to the best of us

 

[cabron]

Also make sure if it was outside that nothing crawled into the motor and decided to knaw on a few things. Happened to me when my Cruiser was parked for awhile. When was fuel filter replaced? Condensation in the tank?

 

[65swb45]

Carter AFB on a 6 cylinder? Sounds like a backfire waiting to happen. Too much unburned gas getting into the exhaust. Check the color of the plugs.

 

[gladly]

usually first step I take when any of my vehicles starts to run like crap, add some methyl hydrate (gas line de-icer) and top up with fresh gas.
maybe too obvious, and you already did, but worth mentioning, surprising how often it's just a bit of water.

 

[Felix]

The condensation in the tank thing sounds plausible. I left it with almost an empty tank . The plug wires are in the correct order. All this backfiring was yesterday morning. I drove the truck last night and didn't get any backfires, but it did still run rough and hesitated from a stop.

If it was a little water, that would explain why it ran better last night. I only drove it for another 2 minutes after getting the gas, so it didn't have enough time to burn through the crap in the lines. Maybe?

Will the methyl hydrate still be effective after I've filled it with gas?

 

[petescoffee]

Carter AFB on a 6 cylinder? Sounds like a backfire waiting to happen. Too much unburned gas getting into the exhaust. Check the color of the plugs.

Sounds like MArk may be right one. Go Figure ,a carb Guru.

 

[Felix]

Originally posted by petescoffee:
Sounds like MArk may be right one. Go Figure ,a carb Guru.

Oh, don't get me wrong - I agree with Mark. I don't like the carter. That plus the Offy intake is too much for me, and going back to the stock carb is on The List. I'm just trying to get back to how it was running three weeks ago.

 

[gladly]

the methyl hydrate seems to work okay whether you add it before or after you fuel up, but I usually put in the methyl first just because.