won't run right, driving me nuts

L

larry harding

Senior Member
i've been tinkering with cars, motorcycles, hit and miss engines most of my 81 years. a friend wanted me to get his 29 fordor running right. it will start up and idle roughly, if you open the throttle it won't rev, just spits and coughs backfiring thru the carb, it's getting plenty of fuel battery(12v) is up. i've been
trying to diagnose this for two days. i have a coil mounted on a bracket i use to test run engines, it runs great on the test coil, i even did a little wiring to run test coil from the hot lead on the car's coil and thru the wiring, ign, switch, to the distributor. ran great! next i took a good coil from one of my cars and mounted it on the firewall same bad running. its like just being on the firewall is doing something. i've been chasing electrical problems most of my life , but this has me stumped. the fix will probably make a fool of me when i find it. ideas please!
 
Coughing back through the carb indicates a lean condition. You can have plenty of supply to the carb inlet but still have internal delivery problems due to blockage. I'd have to ask how the GAV responds to adjustment? The same ask on the low speed idle adjusting screw adjustment since that's all there is. They should respond by improving the way it runs. Turning the choke/gas adjustment valve has to open the valve enough to get at least some throttle response. The idle should get better as the low speed screw is opened up until it gets too rich and then back it off a touch after it idles correctly.

If it doesn't respond, then it likely needs to be cleaned out. There may be a sticky valve or two so see if it has good compression on all 4. I'm not implying that there is no ignition problem but that could be a bad condenser or an intermittent connection somewhere. I try not to assume anything. Use known to be good components if trouble shooting. That little wire under the breaker plate likes to get intermittent too.
 
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I would take the carburetor off and clean it completely.

Sounds like a bad carburetor.
 
o.k. guys. i'm up for the dumb a** of the year award. the first thing i did on this car was open the distributor and polish up the points, they weren't in bad shape. racking my brain for better part of two days, i realised my test coil had an external resister, then the light came on. i got out my old simpson 260 that i have used for years checking condensers (capacitors on appliances and electric motors) sure enough the needle went up part way and stayed there not fading back as it should. the needle did not go all the way to zero as with a complete short. i found a used condenser and put that on, ran perfectly. this is not the first time i have litteraly beaten my head against the wall overlooking the simplest solution. i'm suprised the engine would idle much less rev up with a bad condenser. learn something new every day.
 
Larry, thanks for the update and your honesty. Your post will most likely help another person in the future.
 
Hello, the condenser is the first thing I look at also with a poor running condition. The location in distributor caused them to get “baked” .Some Model As have be converted to a newer point and condenser on the upper plate.
 
Here's a condenser story... I actually heard of this trick on this forum....and it worked great.

Quick story... At the Northeast Studebaker Zone Meet last week a "Bullet Nose" big 6 stopped on the road. We easily determined it had no spark. The cap was removed, points were opening but no spark. Test lights were used and we concluded the condenser was more than likely the culprit. Another member had spare parts but the distributor on this car is not user friendly on the side of the highway and removing the condenser was not something we looked forward to. The car is NEGATIVE GROUND.

Solution: We simply decided the car doesn't car care where the condenser is...so we ran a jumper wire to the negative battery terminal and to the spare condenser case. The spare condenser pig tail wire was attached to a jumper and attached to the negative side of the coil. The car fired right up. If the car was positive ground you would have to attach accordingly...condenser case to positive battery and jumper pig tail to positive side of coil.

This solution should work UNLESS the condenser has actually internally shorted itself out and is shorting to its own case. Usually they just open internally so this is a great solution. You could even make it permanent if you choose....I would remove the one under the cap or cut the wire so it can't internally short to its own case.
 
looking back at the replies i got and realizing i may not be the dumbest guy around i went for the carb too backfiring, not the problem! i bet the next bad condenser i encounter wont fool me like this one did. thanks for the effort guys.
 
Years ago condensers held up very well but now with the cheap manufacturing most likely in china the quality is suspect even new out of the box that's why most people run the burnout proof ones for the model A. that are made in the United States!!!
 
The Wretched Roadster came to me with the condenser mounted on the firewall. I was told the original placement in the distributor subjected it to higher temperatures. May be a case of true but irrelevant.
 
I had condenser burn out troubles back 34 years ago when I would be running an exhaust heater so I moved it up on the side of the coil. Have heard it's not good to run one up there but its still running there 34 years later and still the same condenser.
 
Cough and spit?
The carb must be it!
Adjusted the GAV and idle screw
Still backfires
I feel blue
Maybe a carb jet has some dirt?
Squirt of carb spray couldn’t hurt.
Cursing and hissing
What am I missing?
Ford Barn lore says it ain’t bull
9 out of 10 “carb” problems are electrical.
Check for corrosion on battery clamps.
Short in the meter that measures amps?
The distributor plate’s little wire
If flaky can cause misfire.
Intermittent shorts cause great sorrow
Fixed today, returns tomorrow.
FINALLY GOT IT! And it all makes sense
The condenser forgot how to condense.
I have five spares on the shelf
Next time I’ll try this first
I tell myself.
 
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