Engine stalls at stopsign

[Rip]

Bought a 31 truck with previous owner fabricating wooden cab and bed. Earlier ran it as some kind of beach speedster. It Has Zenith and 12v system otherwise stock. Engine supposedly rebuilt. Shud have known better but liked nice older guy and only drove it around block successfully. Once home my problems started after 3 short 4-5 mile drives went well. Then on first drive to visit club prez, it stalled at 11 miles. Then with him trailing me home, it stalled many times. It would restart with shot of choke and one/twice cranks. Because we have a small show this Saturday at a local retirement center only couple miles away, I find that by going to neutral before stopping or turning or downshifting and keeping rpms up, it kept running. I want to go but can only do some much in the time left (old fingers and shipping parts too slow).

Reading a lot and using forums, Les Andrews, Tom Endy, etc resources:
After determining choke, gas adjust working but carb air mix inop, connected vac gage and tach.

Warmed up with full retard and idle at 250rpm, vac fluctuating tween 15-17 indicating (on the gage) late timing. Then with advance at normal driving position (for mine at 9), rpms increased slightly and vac almost to normal. Gage needles never entirely steady but sometime close.

What is the correct sequence to fix my problems? Check distributor and static timing then rebuild zenith? Or just drop carb half and see if cleaning it can resurrect it (my reason is fear of breaking off bolts tween carb top and intake manifold).

My fun background is shadetree car builder and homebuilt airplane builder in retirement. I disbursed all my stuff and now have to get some back to mess with my A. Any help would be appreciated. Sorry if too long winded. Rip.

[jg61hawk]

I had a stalling problem and found the float was not good. Be sure the float is not leaking and be very sure it is set correctly. The vendors sell small gasket "shims" to help you get it correct.

[Aerocraft]

Richen the mixture.

[Jim Brierley]

Your idle speed may be too low. Fix the easy things first!

[TinCup]

Float height is critical in preventing stalling at stop signs. Until fixed just increase idle.

[midgetracer]

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I agree with Tin Cup. That was my problem... Float set to low.

[Mitch//pa]

Always make sure your engine is set to specs before playing... IE , points, timing, plugs etc

[stouchton]

Have had this issue, and solved it - a couple times cause I keep tinkering.....

Some of this is mentioned above - I'm just rehashing what I have successfully done.

Make sure timing is correct, and make sure dwell angle is correct (point gap at .020"). Stay to the wide side of point gap, not narrow side - it effects your idle. Err on the wider side.

Make sure float level is correct.

Run engine up to temp, open GAV 1/4 turn. Advance and idle levers all the way up.

Adjust idle to slowest obtainable speed. If idle mixture is all screwed up, then start with idle mixture screw 1 1/2 turns out.

Adjust idle mix screw for best idle. Readjust idle speed to lowest obtainable, then readjust idle mix screw.

Rinse and repeat a few times. If you have a broad range (1/2T to 1T) where the idle mix seems good, set for in the middle.

When you are happy with idle mix, turn mix screw in 1/8 to 1/4T.... 1/4T might be too much. This makes the idle mix slightly on the rich side.

Now take advance lever 1/2 to 3/4 of the way down (normal running position). Advance idle speed to a comfortable idle. I set mine based on generator - spin fast enough to be at 0 amps or slight charge at idle with all lights and stuff off - just ignition drawing juice.

Now, play with GAV. Close it and wait. Open 1 turn and wait. It should have no impact to only a slight impact (slightly roughen idle). If it has too much effect, lower idle speed slightly. Mine has only a slight impact. If I lower the idle speed slightly it has no impact but my generator loses ground at idle (discharging slightly).

Put GAV back to 1/4 open.

Road test. This has always cured mine from stalling when stopping.

It has also cured mine from backfiring while coasting. For me the 2 issues seem to go hand in hand.

[ODFever]

This may sound like an odd question, but what condition is your battery in ? Is your alternator / generator doing an effective job of charging the battery?

[Jacksonlll]

My guess is that you have an intake manifold leak.

[Rip]

Thx to all. After Saturday car show, Will check electric (points, plugs, timing but batt fairly new & charging.) Have sprayed twice for vacuum leaks but with bad ears and TACH having too large a scale, can't really determine whether leak or not unfortunately. Inoperative air mixture on carb remains. What gets me is trial drive and 3 successive 15 minute drives were fine. That 11 miles to prez started this stalling problem..too dumb to understand why incorrect float level would occur? If after elec checks, I'll rebuilt carb I guess. Thanks.

[Mitch//pa]

Make sure your throttle shaft is tight (no play) when going through the carb

[George Miller]

250 rpms is way to slow, it is not going to keep running at that low speed when you stop. When you stop the gas moves forward in the carb, and changes the mixture of the fuel to air.

[Bob Bidonde]

More often than not, I find it necessary to adjust the float by trial & error until the stalling stops. There should be a float height between the onset of stalling and leaking gas that is ideal for each vehicle.

I find that many engines are not at the 3 to 3.5 degree angle they should be to use the factory float setting.

[Mitch//pa]

Originally Posted by George Miller

250 rpms is way to slow, it is not going to keep running at that low speed when you stop. When you stop the gas moves forward in the carb, and changes the mixture of the fuel to air.

Agree with George on the 250.... I missed that

[tbirdtbird]

what George said
make it 500

[Tom Wesenberg]

I also missed the 250, which is half of what the idle should be.

[Jacksonlll]

When you have the carb off, file the two flanges where the carb attaches to the manifold until they clean up, shiny all over the surface. Use a mirror on the intake flange. Then use a new gasket. I would do this easy job before rebuilding the carb.

[Tom Endy]

A little known secret about stalling at a stop is an incorrectly ground reproduction throttle plate, or a worn original throttle plate. If the throttle plate does not close properly at the throat of the carburetor to allow the small hole that goes to the idle circuit to just peek above, it will not allow the carburetor to transition from run to idle correctly when coming to a stop.

I had two Zeniths that would stall at a stop after rebuilding them. Snyder advertises in their catalog that their throttle plates have the edges ground to the proper angle as is an original.

I replaced the throttle plate in both Zeniths with Snyder reproduction throttle plates and the problem was resolved.

Tom Endy

[wizbang]

THANKYOU!!!!!!

Been dealing with this for a couple years - just stumbled on this and stouchtons directions fixed it!!!

Tried everything else and just gave up and advanced idle.

You guys got stickies for this kind of stuff???