The Stovebolt Site Forums The Shop Area Engine Shop Engine stalls with touch of accelerator

'48 3/4T with the original 216. Starts pretty good and idles nice and quiet. I have it up on blocks working on the brakes and haven't had it out on the road yet. One thing I noticed is that if I touch the gas from idle, it will sputter and stall, however if I gently give it gas, I can rev it right up without issue. Sounds fuel related to me. Could this be something in the fuel lines? There are no filters to be seen anywhere. Where's the best place to start looking?

Thanks!

It is the accelerator pump's job to prevent this stumble.
Carl

The variables include, Timing, Accelerator pump, and Idle air bleed mix. There are plenty of ways to time these inline motors. I use a vacuum gauge. Set the timing at idle to the best(max) vacuum you can get. I don't have a timing light and with modern fuel, the timing mark(flywheel "BB") will get it started so the gauge works for me. Adjust the idle speed to about 500 RPM( a "Tach/Dwell meter is helpful). With about 30 degrees of Dwell you have checked the point gap and coil are happy together. Set the Idle mix screw to best(max) vacuum. Now we get to the "opinion" bit of the process. Set just as described, most engines will be a little advanced. It will be prone to "Ping" under load. I use a local hill and retard until it stops the "pinging". Tough to do on a set of stands. But at this point you are very close to the ideal. All that is left is the accelerator pump and maybe the power piston is sticking. Here is a good service manual: http://c777913.r13.cf2.rackcdn.com/Rochester%20Service%20Manual.pdf
Scroll to page 11 to see what the power piston is supposed to do. I have found that mine needed to be "polished" with 600 grit sand paper in a drill to get it to move freely. So if the Carb has not been serviced, then a good clean and rekit should solve any remaining issues. I hope this was helpful. Set the float as described and away you should go. Some have had issues with the accelerator pump, but all of the ones I have worked on have worked fine. I would rather be lucky than good any way.

Thanks Steve, I actually have the Carter Carb and I will look at my manual to see if i can find the power piston. The accelerator pump is the leather piston, I believe and may ned to be replaced. A carb kit is probably in my future.

Which Carter do you have? Some of them have diaphragm accelerator pump which doesn't get along with ethanol. I get about 2 years before mine goes bad.

As Carl says, most likely the Accelerator pump. I remember the long post about trying to get your motor started, which you did quite handily. Steve_H is right on the mark. (carb rebuild after brakes)

At the Ancaster Swap Meet on Sunday, talking to the guy that specializes in Carb repair. Said to clean up the edges of the leather and soak it in oil for a few days. I'll try this until I can find a rebuild kit for a W-1 that won't break the bank!

When you get ready, The Carburetor Doctor is in Alberta. May save some on shipping.

Just checked The Dr.'s site. It's in US currency and the shipping to Canada is more expensive than shipping to US! http://www.carburetor-parts.com/ seems to be cheaper, anyone have any experience with them?

You've been given some great advice here. In addition the heat riser between the intake and exhaust was always a problem for me. Actually had an "ice-cold" carb base on my Zenith, fuel just poured into the intake. Keep looking and explore all the options. - Joe

So I'm reviving this thread, but only because it was mine to begin with and this is an update. After quite some time looking into the carb I have, it has been determined to be a Carter 574s with the wrong accelerator pump put in it. Sounds like a no brainer to the earlier posts as the cause of the fast acceleration issue. I just got my new kit in the mail and installed the new pump piston today. Here's a video of it running with the new parts:

https://goo.gl/photos/JJAhE7Aak8ZjCTE2A

As you can see/hear, it idles nice and slow acceleration is no problem, but try and give it gas a little quicker and it would stall out.

Any suggestions on where to go from here? Thanks!

Advance the ignition timing a little and richen up the idle mixture.
Jerry

Thanks Jerry - Is that a clock-wise turn? How much is "a little" and do I do that while running? Obviously I don't do this often

Or missing or wrong check ball under accelerator pump.

Not sure how to tell that, but here's a pic!

https://goo.gl/photos/T631vhhqwCsCzN4q7

It's a W-1 like carb I think. Kaiser-Frazer 40's model. Don't see a ball in the rebuild kit. So I guess you don't have a ball. Can't tell by your pic. Is this the right carb for your truck?

Yes, 574's were in the '36-'48 trucks and then changed to 684s in '49. Do I adjust the dizzy counter-clockwise while it's running? I heard it will start to ping and then you adjust it back slightly until this stops. Sound advice?

Advance is counterclockwise when looking down on the distributor cap- - - -opposite the rotation of the rotor. Running or not doesn't really matter. A very slight movement changes the timing a lot, so don't overdo it. The mixture screw at the base of the carb needs to turn slightly CCW to richen the mixture, also.

The "ping" will show up under load, while pulling a long hill at 3/4 to full throttle.
Jerry

Goach,

The Carburetor Shop has an excellent tutorial on the Carter W-1:

http://www.thecarburetorshop.com/CarterChevroletW1.htm

It lists your carburetor as OEM on 1946 Chevies. I do my own carburetor rebuilding using NOS kits. From what I have read about "professional" rebuilders they commonly mix and match parts like jets and metering rods. Parts books list the correct metering rods and main jets for various carbs and verifying that those are correct is worth doing.

There is a linkage between the throttle shaft arm and the metering rod/accelerator pump bell crank. The bend in that linkage must be adjusted using a gauge that checks the distance between the bell crank and main jet orifice.

I have a fairly good stash of W-1 parts and the gauge if that would be helpful.

On my '36 Chevy PU engine I have a Carter Model 420S W-1 (1939-40 Chevy) with OEM 1937 Chevy main jet and metering rod. That works much better than the more primitive 1936 Chevy W-1 showing that mixing and matching can be a good thing if it's done properly.

Thanks Ray, I've been through every tutorial and forum that I could find online. That's how I was able to properly identify the incorrect piston in the accelerator pump. I didn't know about the linkage adjustment though, I will look into that. I rebuilt a few carbs in my teens, so I'm not too worried about putting the kit into this one.

I did notice that my dizzy octane meter was set all the way to one side. I moved it back to '0' and rotated the whole unit a bit. It seems to have helped, although it still has that air-sucking sound in the carb. It was popping out of the carb a bit too, but that may have been before I had the dizzy firmed up. I will keep on keeping on

Just looking at this link and it looks like it was completely retarded:

http://s47.photobucket.com/user/Tinys1938/media/Misc%20Pics/OctaneSelector_zpse0e754e7.jpg.html

I'm assuming with today's octane fuel, this should be closer to 10-advanced?

Also, when I was advancing the dizzy it didn't seem to rev up and then start coming back down again. Some of the stuff that I was reading said that once you go past the high-point, it should start to come back down and you bring it back to the high point again. Without a timing light (for now) is this correct?

Get a vacuum gauge and hook it up to manifold vacuum (vacuum wiper nipple). Advance or retard the timing until maximum vacuum is reached, tighten down the distributor and test drive it going up a hill to see if it pings. A slight ping is normal according to The Operator's Manual.

Goach,

My 1929-51 parts book lists a 93 main jet and a 66-42/75/562 as the original main jet and metering rod for your carburetor. Your engine may like other jetting. A little trial error experimenting will get you to the precise rod/jet combo that your engine likes.

The present symptom indicates an inadequate accelerator pump squirt. There are 2 check valves in the accelerator pump circuit that must be working correctly. Also the timing and quantity of the squirt are affected by the vertical link adjustment and slop in the bell crank bore and throttle shaft bores.

Rochester Quadrajet throttle shaft bushings are perfect for your W-1. A custom bushing is required to tighten up the bell crank bore if the bell crank is on a shaft that pivots in the float bowl cover. NOS float bowl covers are common on ebay too.

Have to ask a simple question,
Is the gas fresh?

Yes, fresh gas. I can't get it out on the road right now, due to the soft ground, so I will have to wait to see how it performs with the timing advance.

Don't worry about the degree the Octane Selector is on; it was of use when retarding or advancing the ignition for different grades of gasoline and then you could set it back to "0" when you wanted back to original timing - But note that you can still retard and advance by loosening the vacuum advance clamp up on the distributor instead of the bolt on the "Octane Selector" which will still read at "0" because you moved the distributor and not the Octane Selector. The simple thing, would set the Octane Selector to 0 and then time distributor by the top clamp. It is possible someone was fooling around with both, which wouldn't give an accurate timing at all. Keep us updated.