POP POP no power

William Kelchner

William Kelchner

Senior Member
Wonder if anyone has experienced my problem and a possible solution.

Last year I was cruising around and heard a pop through the carb. Pulled off the road and gas pouring out of the carb. Engine started right up and idled well. Let out the clutch and pop pop and zero power. Went home on a rollback. Next day was like nothing ever happened.

This Sunday drove about 15 miles to a show. Ran great. When I returned home shut the engine off to juggle my cars around. Started the A and POP followed by a creshendo of POPS just like the previous incident. This time the carb was not spewing gas but dry. Let the clutch out and car had no power and went beserk, barely made it 6 feet to the driveway.

Today started right up. I can rev it up and sounds great.

Checked the fuel flow to the glass sediment bowl - drained the bowl and took 4 seconds to fill back up.

Checked the filter in the Zenith - clean

Drained the carb into a glass jar - no junk

Left the carb drain plug out and turned the gas valve on. Good flow no junk.

Fresh Ethanol in the tank - old stuff from the winter was drained prior to putting in the fresh stuff.

Could this be a heat problem with the coil or cap breaking down? or, my fairly new Zenith carb. I could probably drive for months until this problem surfaces again.

I am well aware every voyage in the A is an adventure but this problem is sapping the enjoyment.
 
Hi Wm.,

Intermittent Model A problems are the most difficult to resolve.

This one may take a Model A "Whisperer" with experience in listening to a Model A Pop-Pop; e.g., one who can try various things when it goes Pop-Pop-No Power.

If you don't feel up to it, maybe call a local Model A Club for a Model A "Whisperer" -- most clubs have one or two -- "Whisperers" will either have grey hair or be bald, wearing some type head gear -- most need reading glasses -- easy to spot them when they get out of their vehicles.
 
Intermittant backfiring and loss of power could be caused by a condenser that is beginning to fail. Easy enough to swap in a new one and see how it goes.
 
Sounds like condenser or coil. Both are heat sensitive and some coils can play up at a certain temperature. Go beyond that temperature and a coil can run ok.
 
My first thought was a sticking carb float or valve. Sometimes sticking closed which could cause the pop, and sometimes sticking open which could cause the flood.
 
Back firing through the carb means the engine was exhausting on an intake stroke. This is usually electrical as in bad cap, rotor, condensation etc. The condenser is a good starting point. I would not suspect fuel with those symptoms.
 
Thanks - trying new condenser tomorrow - I have one of Brattons newer plates and finally found a replacement concenser - now working on getting the bracket off the condenser and on to the new one.
 
May be starving for gas. May want to check the gas cap. If it is clogged, then it can prevent the gas from going down and into the carb. Loosen the cap & see if all returns to normal & if so, then the three breathing holes under the cap may be clogged up creating a vacuum. Certainly worth a try. I have seen this happen several times over the years.
 
If the motor was still running when you said you had no power, it's most likely not a gas problem....Sounds like a retarded spark issue to me:
1. Coil
2. Condenser
3. Distributor Cap & wire, and body
4. Rotor
5. Shorted (Ignition) wire under advance/retard cam. (spray some penetrating oil on the spring to make sure it's extending the whole way).
 
If the condenser is bad, it probably burned the points a little. Check file and re set the points. If the points gap is closing up, it would cause loss of power. I set mine at .022 . Anything from .018 thru .022 will work. The wider gap will slightly advance the timing and give more time before the points will have to be set again. If that doesn't work, it could well be the ammeter or resistance in the terminal box as said above by Bill Edstrom . I've had problems with both. A bad ammeter on my Sept 29 really gave me fits, it caused it to backfired and it wouldn't be good to get out of the yard with.. Several years ago when I drove the coupe to work , it started running ruff and shut off. I coasted to a spot,pulled off the road and tinkered with it for a while. Several people pulled over and proceeded to give directions on how to set the timing as they were all sure that was the problem. I wasn't sure what I did but I got it started and made it to work. On the way home it quit again!! No amount of tinkering,cussing or praying would get it cranked . Grasping at straws this time, I removed all of the wires in the terminal box, I cleaned the terminal ends and nuts with fine sandpaper and re connected the wires. After cleaning the connections in the terminal box , it came back to life.
 
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