VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 vapor locking

Where the 32s prone to vapor locking? Mine seems to have this problem. Is there something that was period correct to help? TIA, Tom

Chevrolets were not prone to vapor lock back in the "olden" days. The problem is with todays gas. It has a low boiling point and thats what causes the vapor lock. The gas in the line before the fuel pump and in the pump will boil, especially bad after engine is turned off.Installing an eletric pump back at the tank would be the best cure as it pushes the gas rather than pulls it. Your present pump location can not pull the air laden boiling gas. The eletric pump could be used just for hot weather vapor lock and filling the carburetor if the car has not been started for awhile. The mechanical pump could be left in place.

Modern gas with lower boiling point, high ambient temperatures and slow speeds will cause the gas to vaporize. I have installed an auxilliary electric pump midway between mechanical pump and gas tank that will compress the gas and allow the mechanical pump to work. It sure beats having the passenger jump out pour cold water on the fuel pump during a parade. That is when pulling out the choke barely keeps it running.

I assume the auxiliary pump is 6V, where might one source this unit?

Mike

Try your nearest NAPA store.

I buy them at my local auto parts store.

:) :grin:

Mr Chipper,

Mr Chipper,

Mr Chipper,

Mr Chipper,

Mr Chipper,

Mr Chipper, can you send me a good description of where and how you installed the electric pump? Thanks, Tom

If I can helpfully jump in..Tom, I've had exactly the same problem with my '32. Because I'm breaking in a complete rebuild, it gets hot fast. I have run into odd times when it stalls and floods, and I have to wait for it to cool down and the extra gas to evaporate. This seems to be getting better with time.

As earlier suggested, I bought a 6V fuel pump right from an auto parts store. It just had to be special ordered, that's all. Following the suggestion from a restoration guidebook, I installed it right onto the frame directly under the rear passenger fender (that is, right in-line with the fuel line). That makes it very discrete - there's no way to spot it unless you crawl all the way underneath and looked for it.

I wired the negative to the frame, and the positive wire under the body frame and up to the dashboard. I wired that to one of the lighting circuits (that is, where power is available regardless if the electrolock is on or not).

I can't remember if it was specifically recommended, but I chose to insert a small toggle switch on the positive line, and mounted that switch underneath the lip of the dashboard - that way, I can control if I want the electric motor on or not, and because it is discretely out of the way, it doesn't diminish from the original appearance.

Chipper or others may have variations on this strategy. Hope this helps.

I install mine essentially the same as above except closer to the middle of the frame. I also put a filter in line at the same point. If midway between wheels then it is easier to check, change the filter, etc.

I wanted to report in that Chipper's advice on this thread has been really, really helpful to me. My '32 has sputtered, died, and spilt gas all over the outside of the carb four times in the last 9 months, and it has increasingly frustrated me close to tears. It's happened at odd times, but generally it's when the motor is hot and I've pushed in the clutch to slow down on a turn or downshift. Each time I pull the carb apart to track the problem I find zero grit, so I'm increasingly skeptical and dismissive that the cause is a blocked float or jet.

Chipper, you mentioned the vapor lock occuring in the mechanical fuel pump, and the fact that you've had to pull out the choke to keep your car from stalling. If I run the electric pump while putt-putting around town, when I slow down should I also "nurse" the choke back a bit? In the past when the engine starts sputtering I've tried to pull out the throttle in a valiant attempt to rev the motor up, but it just seems to hasten the last dying sput-sput-sput of the falling RPMs.

If vapor lock is the problem, the carburetor is run low on gas which causes the lean condition (backfire). If you pull out the choke it richens the mixture helping the engine to continue to run. If running an electric pump as an auxilliary it will pressurize the inlet line to the mechanical pump eliminating the gas (vapor) bubble and restoring the function to it. You should only need to activate the electic pump occasionally when in hot and slow driving conditions or when working the engine hard (like climbing a long hill or mountain).

Because of the design the original 212S or 235S Carter carburetors are more prone to perculation or syphoning gas from the bowl to the carb throat. Later designs or modifications will eliminate or minimize this tendency.