OK, ... I'm Stumped * Solved *

BillCNC

BillCNC

Well-known member
Hey All,

This morning, I was on my way to a car show in my "A" and out of the blue and half way there, my car started backfiring out of the tailpipe, very loudly so I slowed down and noticed it stopped, so I started to go again and the backfiring came back. It only happens when I go over 35mph. I pulled over and removed the carb, split it apart and tried to clean it on the side of the road. I put it all back together and the same thing happens. I limped it home and removed the carb again and tore it completely apart. I blew out all the jet's and passageways and float valve and reassemble it all. During the test drive, I'm getting the same thing.

I do have strong flow from the steel line and the filter in the carb is clean. I tried opening up the GAV, but enriching thre fuel does not stop the backfiring.

I then thought it could be the condenser, but I can get up to 2100 rpm in 1st gear with no backfiring until the bowl drains, but I cannot get past 1200 in 3rd without backfiring


Any clues?

Regards
Bill
 
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Re: OK, ... I'm Stuped

Bill,

it sounds like maybe fuel starvation, how about the cap on the tank? try removing and run down the block.

But, back to the backfiring, a friend had his Vicky out on morning and driving to a small car show in a quiet little town.
The points slipped or the cam moved, in any event it backfired a couple times and he stopped.
About 5 minutes later a handful of sheriffs cars come flying around with the lights on.
I went over to chat with one and he asked if we heard any gunshots.
When I explained that it was the Vicky backfiring he couldn't stop laughing. It was comical to hear him calling it in, laughing the whole time. The dispatcher, who had a sense of humor asked if there had been a Dillinger sighting?

Best, John
 
Re: OK, ... I'm Stuped

The backfiring makes me wonder if your getting too rich a mixture. Try running with the gav closed. Also, if the brass seat for the gav is loose, that would get you a rich mixture. How do the plugs look? Also, the gasket for the carb, I would use a mirror, and a flat file on the intake/ carb surface, and dress up the top of the carb.
 
Re: OK, ... I'm Stuped

If the car is running rich unburnt can get into the muffler and ignite. If running too lean the same thing can happen if the engine is missing. Ignition problems can also cause backfiring. The condensor can be weak which would cause the spark to fail at higher pressures in the cylinders when driving in high gear at a higher speed. Or if the timing has slipped that can cause the backfiring. Or something is loose in the ignition system like the screw that holds the distributor or a loose wire. The pressure in the cylinders is lower when the engine is under less stress so the ignition has an easier job.

Look for something that broke in the carburetor or something that broke in the ignition system. The fact that it came on suddenly points to a broken part somewhere.
 
Re: OK, ... I'm Stuped

Things I have done or checked:

Checked carb throughly
Gas flow is high
Drive without gas cap
Points is .020
Rotor Gap is .030
Plugs are good
Changed Condenser
Fiddle with the GAV from closed and up to 2 turns open
Distributor connections are clean and secure
Inspected Cap components.

Regards
Bill
 
Re: OK, ... I'm Stuped

Did you check spark? Take one of the wires from spark plug to distributor body and position it about 3/8” from terminal on distributor body. Start engine. Is the spark blue or yellow?
 
Re: OK, ... I'm Stuped

One or more plugs may have gotten damaged but you say plugs are good.

Check compression on all cylinders to see if a valve is not seating or damaged.
 
Re: OK, ... I'm Stuped

OK, ... Found it, or I hope thats all there is.

My armor cable is shorting out around the spark rod. It will arc to the rod and if I pull it away, it's stops sparking, but if I bend the cable in that area, it shorts and the engine dies.

Can I fix the wire inside?

Regards
Bill
 
Re: OK, ... I'm Stuped

BillCNC said:
OK, ... Found it, or I hope thats all there is.

My armor cable is shorting out around the spark rod. It will arc to the rod and if I pull it away, it's stops sparking, but if I bend the cable in that area, it shorts and the engine dies.

Can I fix the wire inside?

Regards
Bill
Click to expand...





You might be able to change the wire inside it, but, I just replace them. I like the thin flexible after market cable,, but mine is not a show call.

Like many things, they can be a son of a gun to find the first time. A second or third is faster and easier.
 
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Re: OK, ... I'm Stuped * Solved *

I've seen a lot of those cables go bad.That fabric coated cable was never meant to last forever.I had one on my own go bad,the car would just randomly die.When I checked for spark,I would have it.It was blue but had no real strength to it.No big snap.I knew it was the cable because if I touched it the car would quit.I took the popout assembly out,then I saw scratches on the back of the switch and marks on the distributer end.Somebody had already tried to monkey with it before.I sent it to Mr Crabtree,he said it had a single strand of wire still intact,and one end was twisted.He repaired it and made me an extra key.
 
Re: OK, ... I'm Stuped * Solved *

Bill,

good job finding that, intermittent issues are always fun.

Thanks for sharing, John
 
Re: OK, ... I'm Stuped * Solved *

I think your original posted misspelled stumped…
I Misread your misspelling!!!!
Good job. Hope all works going forward
 
Re: OK, ... I'm Stuped * Solved *

Backfiring out the tail pipe? Backfiring from the carb lean mixture. “After firing” out the tail pipe ignition.
 
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