Won't run smoothly unless accelerating

Bill in Al

Bill in Al

Senior Member
My '41 idles fine and runs smoothly while it's accelerating,but when trying to cruise at any speed it bucks and balks. I can pull the choke out half way and it runs ok. I have had the carb,a 94, off to clean it and replace the power valve before I got the engine running. I feel pretty sure it's carb trouble but don't know what to try next. Would a 97 be an advantage or is there an easy cure for my problem with the 94?
 
Obviously you are running too lean with out the choke. Sounds like the carb needs a thorough rebuild. What size jets are in it? Is the float set properly? Seems like the idle circuit is working properly, but not the main circuit.
 
if you have to pull the choke out to run right you have a fuel or vacuum leak problem, weak fuel pump, not enough pressure to carb, should have around #2 1/2, float to low, maybe a jet problem, bad power valve, vacuum leak in carb gasket at manifold, leak at maniflod gaske on engine leak at gasket between carb bottom piece and carb top piece, maybe a leak at throttle plate rod, check for vacuum leaks first, thats the easiest to do, then on to the fuel supply checks
 
Start with the fuel supply and then work your way to the pump and carb. Blow back to the tank. Don't go through all the other things until you have a fuel supply, it could be a waste of time. Gordon
 
Keep excelerating, .........just a little humor.

In all seriousness first thing to do is to check all the fasteners. A little vacuum leak will play havoc on your senses. When this is done take some starting fluid and spray it around the intake and carb bases. Be very careful as this stuff is really flamable. You are looking for a change in the exhaust note or RPM. That will tell you if you have an intake/vacuum leak. After that then put the fuel line in a plastic bottle and turn the car over. A good healthy squirt will let you know the pump is good. If it's electric then make sure the pump is turning on. If none of this solves the problem then you probably need to pull the carb apart and make sure it's clean. Fast idle jet and blown power valves will sometimes create this problem. Likely not a power valve though as it is designed to kick in under acceleration and if you have to pull the choke out it's not a flooding problem it's a supply issue. Anytime you have to run with the choke on a warm engine you got fuel ratio/supply problems. If it was running good prior it's probably not the jets. A 97 will be an option but a 94 is not a horrible carb. One thing to check is the throttle plate shaft for leaks.

Good Luck,

Tim
 
I think your fuel pump, tank, filter, and fuel lines are ok since your not having problems accelerating. Usually if a pump can keep up with the fuel demand during acceleration it should be sufficient to handle cruising. I don't think it is a vacuum leak, if it had a leak bad enough to cause a problem at cruise it would definitely have an idle problem. You probably have some dirt in the main jets. A real quick check is to pull the carb top off and take a peak inside.

I can tell you what not to do. After 35 years working on cars I still find new ways to break things. I have a 1948 Ford 8N tractor with an updraft carb that constantly gets junk stuck in the adjustable main jet. As a quick fix, with the carb still on the engine I remove the float bowl drain plug and the main jet mixture screw and blow air through the jet. I leave the fuel turned with flushes the dirt out of the bowl. The last time I did this I forgot to remove the drain plug first. Since the air pressure had no way out of the bowl it crushed the brass float just as if I had put it on the ground and hit it with a sledge hammer.
 
I would have somebody go through this thing,there are 3-4 very capable rebuilders on here.Could be wrong # power valve,wrong jets a plug up in the hi speed circuts. Charlie,NY,52 henry and ken ct are all good on these carbs. take your pick. ken ct.Were all on this web site.
 
New tank,lines,electric pump and mechanical pump.Have run with one or both pumps.Have cleaned all jets and internal .Am going to check for vac. leaks then go for another power valve and if that doesn't work I'll be contacting Ken. Thanks to all-Bill
 
I still vote for the carb. If you had a fuel supply issue, it would not accelerate because more fuel is needed to do this. Also if it runs that bad, you usually are able to hear a vacuum leak. And a vacuum leak would also effect your idle. At cruising speed, the power valve is generally not in operation.
 
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I had the same problem on a previous car ( excpet for the choke part ) and it turned out to be play in the distributor shaft, the timing would jump all around untill I rev'ed it up. Just an idea, good luck.
 
Sturgis39;I don't know why I haven't thought of that! I've had an "A" for years and that's a fairly common problem among "A" owners! 54bomb; I had the diz set up on a Sun machine and it's checked out ok. Thanks Ya'll--Happy New Year --Bill
 
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