VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 Engine only Idles with choke and throttle pulled out Slightly

Hi All,

Started my car (36 std) and will only idle if the Choke and Throttle are pulled out say 1/4 inch. If you put either one in the engine stalls. No issues when last run in late fall. Figure its the Carb, but usually when the idle jet is clogged only need to have the throttle pulled out. Once cleaned no issues. Never had it where both had to be pulled out to keep the engine running. Is there anything I am missing why both are needed? Hoping just to have to take the carb off once. Thanks

I would check the end of the idle speed screw where it pushes against the linkage to open the throttle slightly. It could be that the screw has backed out and is no longer opening the throttle at all.

While I am not familiar with the actual set-up on your carburetor I expect there is something that provide resistance so the idle screw will not turn easily by hand.

Try letting the car run and pull the choke out all the way and push back to 1/4 several quick rapid times. This will attempt to clear the carb by sucking. If that fails then check the screw that sets the idle. It should be after gently screwing all the way to stop...backing out one and a half turns.This will clear any crud that was in there. If that fails then you will have to go into the carb and see where your blockage is. Also note that on your standard and mine there are fine filter screens under the plugs on the bottom of the carb. You will have to remove the carb and turn it up side down to see the plugs. I am hopping you will not have to go that far, but if you have let it set with 10% Ethanol Gas then as it evaporates it leaves a powdery stuff that will plug your carb. I use only old time Regular in mine. I have learned my lesson the hard way. Good luck and hope that pulling the choke out while engine running several times and do it repeatedly at least three times...don't let the engine die. you will hear it start to pull down. then shove back into 1/4. Then try all the way in...good luck. My 1936 Standard has been a learning experience Oh! forgot to say I had the exact same thing you are having.
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You can put a drop of Loctite Blue 242 Thread Locker on the threads of the idle screw to prevent it from backing out.

Cheers, Dean

"You can put a drop of Loctite Blue 242 Thread Locker on the threads of the idle screw to prevent it from backing out."

Good morning Dean.

Are you recommending Loctite on the idle speed screw? If "yes" doesn't the spring hold it in place without any thread sealer?

My '36 used to get blockages in the idle jet occasionally. Then I discovered a couple of different AC fuel filters that are a perfect fit in the '35-'36 fuel pump where the original but crude filter screen goes. Using an actual filter rather than the screen that only filters out the big stuff solved the idle problem permanently.

It's pretty amazing what fits what. For example a '35-'40 Ford fuel pump diaphragm fits the '35-'36 Chevy fuel pump and is available separately from Ford vendors and makes it possible to get only the diaphragm rather than having to buy a whole "kit" just to get a diaphragm. The ones I bought were from Sacramento Vintage Ford for about $7 each.

Ray W

Hi Ray,

Yes, the spring is supposed to keep the idle screw from moving around, but if Robdi1's idle screw is moving around (maybe the female threads are worn) then some extra tension in the threads might help.

Cheers, Dean

Thanks All - Will try these this weekend. It didn't look like the idle screw was loose - but will be on the list to check. The choke was throwing me off - just wanted to make sure I wasn't missing something.

You may have developed a vacuum leak. Could be wiper hose, vac.advance, intake manifold gasket or insulator under carburetor.

Good idea from Gene to check for vacuum leaks. If the car sat over the winter a hose could have cracked.

If you have checked thru all of the above suggestions, you might try (I'm not sure it would work) spraying carb cleaner directly into the vent of the fuel bowl. Possible it may break down and flush any "crud" out of the smaller circuits of the carb.

Here again, this is only a suggestion before having to go the rebuild route if everything else fails.

I had a similar problem like this with my 36 Standard. Car would not idle unless I gave it more throttle. Turned out to be a dirty low speed jet which I removed and cleaned.

It dosen't cost anything and takes only a minute. Cross #3 and #4 spark plug wires. Remove air cleaner and start engine. Punch down accekerator pedal seveal times so engine back fires through carburetor. this will blow out the low speed jet.

Thanks All, I think it is time for a rebuild and ordered a kit from the filling station. I did take check the wiper lines and the vacuum advance. didn't see any change. Any other way to check the vacuum advance other than spraying a little carb cleaner on it and see if the engine speed increases? Also tried playing with the choke. Nothing changed. I do see the engine now bog down if I press the accelerator so I assume the accelerator pump is partially clogged. I think time to clean it all out and rebuild it. At least start there. Its been an number of years since last time it was done. Anyone know where to get the brass screws in the carb, they are usually not in the rebuild kit? (just in case the are stubborn to come out)

I have not tried Gene's last. will try and switch the 3 and 4 wires and see it that clears anything out.

When a six-cylinder Chevy of this vintage requires choking to run, suspect air being sucked in, probably at the intake manifold. Try tightening all the manifold bolts. Be sure the manifold bolts are not too long, as they can bottom out, leaving the manifold loose enough to suck air in. You can verify an air leak when the engine is running by spraying Mapp gas at the manifold connection area and at the base of the carb. If engine accelerates, you have found your leak.
Jay