Re: Stalls When Braking
I’ve been chasing this problem for months on my 1929 sedan after reading about as many of the threads on this and other forums about it as I could find.
It seemed as though it MUST be related to the fuel level in the carburetor since that is the only thing that would be affected by applying the brakes other than the brake light coming on, which is easily discounted by disconnecting the switch. But it isn’t just the float level as evidenced by different people saying their problem was fixed by raising the float level, and others saying they had to lower the float level. On one thread these “cures”were proclaimed literally two posts apart.
I found it particularly interesting on my car that it would stall only when I put the brakes on going forward. I could back up at any speed, apply the brakes, and the engine wouldn’t even stutter.
I chased the float level up and down with no effect. I found a vacuum leak at the intake manifold so I bought new intake and exhaust manifolds. There was some improvement, but not a total cure. As it turned out, this was probably a waste of money.
I had been hesitant to mess with the carburetor since the guy I got the car from told me he had put on a brand new one, NOT a rebuilt one. And he hadn’t driven the car enough in the last few years to even mention.
But I got to the point where I had to check it out for plugged passageways etc. I followed some of the leads that had been posted on this forum to find the proper methods and the jet sizes. Interestingly, I found the idle jet had a burr from manufacturing that was partly blocking the orifice in it. I thought that I had finally found the root cause of my problem.
Clearing the jet did improve the situation some more, but it still wasn’t just right. So I bought a set of number drills on eBay for $8 so I could size the jets. Sure enough the compensator jet was a couple thousandths undersize. I opened it up to spec. (.035”), put two washers under it so it couldn't be hitting the secondary reservoir, and put it all back together again.
I think I have finally chased the demon from my car. I can now stop without the engine stalling. My assessment is that the comp jet was not allowing fuel to fill the secondary reservoir fast enough when the gas sloshes forward upon braking. This would explain why it wouldn’t stall when backing up. It’s hard to imagine that a couple thousandths of an inch could make that much difference, but it amounts to about 5% of the jet size.
I hope this helps someone else.
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