Carburetor problem

[Bob from Northport]

We are in the final stages of rebuilding the engine on a 29 Cabrolet. The car starts very well, and idles great. The carb was completely cleaned out and redone. Initail driving was good, then a problem started. The engine acts like it's running out of gas, nad the manual fuel adjustment has to be opened two fulll turns to get the car to run. Is is possible there is something caught in the opening at the bottom of the adjuster? Possible problem with the cap jet?? The car runs great, but the problem makes it hard to trust the car as of yet. Any suggestions would help. Thank You!

[Rowdy]

Possible rust or junk in the gas tank is my bet. Also are you running one of the glass sidiment bowls? Some have had problems with them. Rod

[Mike V. Florida]

I would not blame the glass sediment bowls, used mine for thousands of miles. Each year I clean out the little rust that appears.

How long was the initial driving?
Vent hole pluged in the gas cap?
Do you have a mico filter installed?

[Kurt in NJ]

When I have had such symptoms it was usually some dirt or deposits in the main jet, It is very easy to take the bowl off the carb while it is still mounted on the car if you are using the original type Zenith, dissconnect the choke/GAV rod, take out the bolt, and lower the bowl assy, if you look carefully at the jet tips you will probably see the debris, a quick squirt with some air, or carb cleaner will flush it out.

A slightly spread cotter pin can keep the sleeve and spring in place on the gav rod

There is another quick "on the road" sometimes cure for debris ---with the engine running --step on the throttle and close the choke for a second, or covering the air inlet with your hand as you snap open the throttle ---this method sometimes will suck the debris through the jet.

It is not unusuall to fine a lot of debris in the screens, and they should be checked often, some of our members here will post pictures of a debris trap they install , a dead end dogleg , and others use a standpipe in the tank .

I have had problems in the last 2 years with this new gasoline making a gooey deposit in the tip of the main jet causing your symptoms, but it has happened only if the car has been sitting for 2-3 weeks, I have had to change 35 year old habits, now I turn off the gas valve before I back the car into it's garage to lower the gas in the bowl.

[Brentwood Bob]

try loosening the gas cap. Next unhook the gas line at the carb to see if flow is good.

[pat in Santa Cruz]

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sounds like some particles clogged something in the fuel line or a jet in the carburetor. Its not unusual after a car sets a spell or after the fuel system has been disrupted. Start at the fuel line into the carburetor, remove it and check the flow...it should be strong. If its good, the problem is in the carburetor. If its weak, its between the fuel tank and the carburetor.

In the carburetor, remove the plug under the main jet and drain the fuel into a cup so you can inspect it for debris. If there is debris, some probably clogged the main jet. Its easy to remove the bowl and check for particles in there too. Remove the jets and blow them back with compressed air or a can of aerosol carburetor cleaner. Hold them to the light to see they are clear. Back blow out the passages. Replace them and try it again.

Did you use any RTV sealer on the carburetor gaskets? Ethanol dissolves it and it gets everywhere.

[Grampy]

Hi Bob,

I know exactly what you’re going through! For a little more than a week, I’d been beating my head against the steering wheel because I’d be driving the car and in just a few blocks it would stop running. Symptoms were such that it could be no spark or no gas. I turned to the electrical possibility first because there was no debris in the sentiment bulb, nor was there anything in the fuel I drained through the gas line at the carburetor.

I tested everything and replaced a lot of the electrical system, retimed the engine, reset points, etc. etc.; well, suffice to say that now I’m positive there is absolutely nothing wrong with any of the electrical system! At the same time all this was going on, I was adjusting the carburetor, even replacing it with another that I had. One of the members of our club was even generous enough to take his working carburetor off his sedan and let me try it on mine. Nothing was solving the problem.

Last week I was in the hardware store for something and noticed a siphon device that would be perfect to vacuum the inside of the gas tank. I tried it last Friday. It was amazing how much rust and debris came out of the tank. I wouldn’t be surprised if Jimmy Hoffa’s body was in there! I was so amazed by the experience that I even posted to the Barn last Friday, the 8th, (It’s got to be the rust . . .) asking for suggestions how best to properly clean the tank. Some very good ideas were offered; you may want to check them out.

Today I followed through with some of them, and in addition, I completely drained the ‘old’ gas out and put in a few gallons of fresh gas. Then I went driving! I was out and about for over an hour with no troubles at all. It was exciting!

These problems can be solved, Bob; you just gotta keep trying everything. Good luck.

[Bruce Adams]

Is that Nothport Long Island?
If so, I there are a number of us who would be pleased to drop over and help, lend you a carburator, or whatever.
Bruce
Northport, Long Island, NY

[Bob from Northport]

Bruce,
I really appreciate your offer. But I live in Northport, Michigan, about 1500 miles from you. I own and operate a small garage that repairs and restores Model A Fords. I have a number of other carburetors, but was trying to solve this problem without changing anything. The car was restored about 30 years ago, then sat never used until we got last fall. The fule had turned to jelly, and we had to throw away most of the fule system except the carb. The engine was redone, and now we are road ready, excpet for this silly problem. With the help of the Fordbarn guys, we'll figure this out. Thank you again!!
Bob Campbell

[JoeWay]

I found out a couple of weeks ago that if you have a weak spark, the engine will run only when the mixture is quite rich. I had cut apart an original condensor to make dummy ends when I installed a set of Nu-Rex "modern" upper and lower plates. The "hot" end developed a short of about 50-100 ohms which didn't kill the primary, but cut it down drastically. It would run fair with the throttle wide open, or the GAV way open, but would miss badly or even quit altogether otherwise.

It's easier for the weak spark to ignite a rich mixture.

Just something else to think about.

Joe