30 Zenith Carb

William Kelchner

William Kelchner

Senior Member
My 30 appears to have a carb problem. Idles great but put it under load and it starts coughing back through the carb. Forum member and I think it is acting like a float problem. Has good fuel flow. No starting probs, no overheating issues. Tried numerous GAV settings all to no avail. I have read that a sticky/hung float can exhibit symptoms like this. Now to the point I could not make it 1/8th of a mile back to the driveway this morning . Thanks
 
If this just started, I would suspect it's not the carb. My first thought is condenser.
 
kenparker said:
In the model A world 85% of the carburetor problems are electrically generated.
Click to expand...

:confused::confused: Yep it is a constant problem and prevents me from even attempting to venture out with the car. Love the quote. One thing that stumps me is the car will idle great, rev the he$$ out of it and it is flawless, but don't try to drive it. Oh well - thanks for the responses. Have a good weekend.
 
also check your coils, plugs inside cap. when there is a load on the engine it takes more spark energy to fire the plug and the spark may be finding an easier path to ground than across the plug gap.
 
Couple of thoughts here:
you may want to check to make sure the jets are not clogged in the carb.
condenser could be the answer.
is it timed correctly? Is the timing advance working properly?
make sure your distributor and coil are working properly. ie point gap, timing setting, good coil, good condenser.
We would like to hear the ultimate answer here. Please report back.
 
Backfiring Under Load (throttle wide open at relatively low rpm’s) often indicates a problem in electrical/ignition/timing.

Culprits include:

Insufficient point gap (should be set at .018 to .020)
Timing
Bad condenser
Bad distributor body
Frayed wire between upper plate and lower plate on the distributor
Intermittent connection of the ignition switch

As Mitch said I, would start with point gap.
 
Ok you guys thanks. I shall go through everything over the weekend, saving the carb for last, hopefully the culprit will be identified. I replaced the dist with an original type from Bratton's, the Zenith was also purchased from them, all this about 2 years ago. I also replaced the timing gear around that time.

I shall report back. Thanks again.
 
I've heard of this happening with bad muffler. A baffle collapses inside and restricts the exhaust flow. It'll start and rev in neutral just fine. Once you put it under a load it has no power. It's very rare but sometimes it happens.

William Kelchner said:
...One thing that stumps me is the car will idle great, rev the he$$ out of it and it is flawless, but don't try to drive it. Oh well - thanks for the responses. Have a good weekend.
Click to expand...
 
Well installed new points (orig style), the others did not look well and seen better days. Re-timed, checked spark (Tesla would be proud) :) Tried to make it around the block, almost made it but coughed several times. Carb tomorrow, another trip around the block. If no better there will be a lot more room in the garage. Have a good weekend.....

Bill K
 
Are you sure the fuel flow is OK? Too lean a fuel mixture for what ever reason can cause low power/backfiring. I took a very short video of my fuel flow after flushing my fuel tank and adding a new filter screen above the shut-off valve. I thought it was OK too, at first. Once I started getting it running better and producing more power it wasn't getting enough fuel.
https://www.youtube.com/watch?v=FAUI8MWo_Io
 
Thanks Art. Yep my fuel flow is robust, disassembled the Zenith today, clean as a whistle, blew everything anyway. Did not go for a ride as it is in the high 90's. I plan a compression test tomorrow and that will do it, told the wife to cancel her Father's Day gift order (car cover for the A).....:confused: Cheers and thanks for all the suggestions.
 
Devorce is to easy, she is testing you. There is nothing in the relationship that cannot be overcome, it just takes work and understanding. I love my mother's favorite quote, "it is easy once known". You have a simple problem that can be overcome, it will only happen once because next time you will know the answer. Be patient work it through, except the challenge.
 
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