Carb issues when stopping headed down-hill...

[Special Coupe Frank]

I live in town, on a hill. Leaving home and going anywhere ( in any direction ) means heading down-hill for several blocks, with stop-signs at most cross-streets.

I have noticed that when coming to a full-stop for stop-signs / red-lights, with my foot off the accelerator and the throttle lever all the way "up", the engine will bog-down and sounds like it's loading up for several seconds, then it settles-down and idles normally.

This is only when descending steep hills and/ or during very hard braking when all the fuel tends to slosh towards the front of the car.

This doesn't happen on level ground, or going up-hill.

I added a washer under the float-needle housing last night, but that made no difference on this mornings' drive...

Any ideas what might be going-on here ?

Thanks,

SC Frank

[ford1]

there are two things basically that will cause that, (1) the float is to low, when stopping going down hill it lets the fuel run away from the main jet, (2) the float is two high letting the fuel be sucked into the engine causing it to run rich. my guess is the float is to high or its to heavy to allow it to put enough pressure on the needle and seat to keep it fully closed. check float real close to see if any fuel as seeped inside, has it been soldered on making it heavier? double check float higth buy an american made needle and seat, china crap is junk and they will cause you no end to problems

[BILL WILLIAMSON]

I believe that this is a typical quirk with the Zenith carb.
After all, it is very early technology, and not a very refined design.

[bogdonj]

In my 31 Tudor my rebuilt zenith also does this... didn't before but notice now when i'm coming to a quick stop it wants to die out. I have to keep the throttle going until i stop completely.. then it will run fine. I'm going to look at my carb very soon!

[BILL WILLIAMSON]

Originally Posted by bogdonj

In my 31 Tudor my rebuilt zenith also does this... didn't before but notice now when i'm coming to a quick stop it wants to die out. I have to keep the throttle going until i stop completely.. then it will run fine. I'm going to look at my carb very soon!

Yep! you learned how to deal with it. It's just the character of the beast.

[Gary/IA]

Sponsored Links (Register now to hide all advertisements)

I experienced a very similar problem. I open the GAV just a little more and it cured my problem. You might try playing with the GAV to see if it helps.

[mrtexas]

Originally Posted by BILL WILLIAMSON

I believe that this is a typical quirk with the Zenith carb.
After all, it is very early technology, and not a very refined design.

The Tilly is as old of technology. Does a Tilly do the same thing?

[Gary WA]

Might check the tank for blockage at the valve moving around, but float could also be the problem as noted.

[TinCup]

Sounds like example 2 from Ford1. If they die going downhill it has always been my experience that the float is too low. I would suspect the float.

[Purdy Swoft]

I think it is the float level, thats the only thing that I know of that would cause stalling when the brakes are applied, unless the battery is loose enough to move around and ground out against the brake pedal rod.

[1931 flamingo]

Mine would do the same thing, approach stop sign shift into neutral, right foot on gas pedal, left foot on brake, fun. Had to replace float and re-adjusted, now it doesn't stall when stopping. Just my experience.
Paul in CT

[Ned]

Had the same problem, engine died when stopping going down hill. The float level was too low, fixed it and no more problems.

[Special Coupe Frank]

Thanks all - will check float level.


Regards,

SC Frank

[bogdonj]

let us know what you find!

[Special Coupe Frank]

will check into it tomorrow and report back.

[Mark in MT]

Check to see how the throttle plate is centralized in the bore. With the carb off the car, back off the idle stop screw and hold it up to the light. The throttle plate should almost black out the light. If there are big gaps, loosen the throttle plate screws and while holding tension on throttle shaft against stop, tap on plate with screwdriver. This will center the plate in the bore. If it is scarred up, lightly deburr it with a file or a stone. When it is as tight as possible, tighten the screws. The throttle plate needs to be very close to the idle discharge port to run on the idle circuit. Reassemble and readjust. You should be able to idle at 400 rpm and stand the car on its nose and keep it running.

[Special Coupe Frank]

Quick update - dropped the carb bowl this morning, there was maybe 3/8" fuel in the bottom (after starting the car, moving around to the garage and shutting down).

Dropped the float-needle cage and found a stack of three washers. Left two out, put one back. Also set the needle cage on my anvil and gave the needle a whack with a heavy ball-peen hammer to "set" the needle & seat.

Put it all back together and went downhill into town via the usual route.... no stalling / junky idle at stop signs.

Will get out my U-tube float gauge and check it when I have more time to play.

Thanks for the replies !



SC Frank

[BILL WILLIAMSON]

Originally Posted by mrtexas

The Tilly is as old of technology. Does a Tilly do the same thing?

I don't know yet as soon I will be trying my first Tillotsen.
I've been told they are better on fast stop because of the small crosswise fuel bowl and crosswise float design.

[cars56]

Had the same issue, purchased a Viton tip float needle and stacked 2 white neoprene gaskets from Bert's, that solved it. Realized how important the fuel level in the carb bowl really is.