VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1937 with vapor lock??

Previous owner said that vapor lock occurred while driving on hot days. Ran the car yesterday for a 45 minute trip in 56F weather. About every 10-15 minutes, the car would appear to be running out of gas. After sitting for several minutes, it would start back up, run fine for another 10-15 minutes then quit. Operating the manual choke would sometimes allow the car to run longer...Any suggestions? I'm a new owner of this restored coupe so appreciate any advice. Thank you!

I've run thousands and thousands of miles in the last 30 years in a '37 Town Sedan, two different '37 pick-ups and presently my '37 Sports coupe (gee, I seem to be in a rut with '37's, don't I ??), in weather ranging from the high-90°'s to below freezing, and have never, ever had a trace of vapor lock. Based on my experience, I'd doubt it's vapor lock.

Check the timing and plugs, wires, etc. If they look old or suspect, give the old gal a complete tune-up, including new wires.

Trace the fuel line from the tank to the carb to make sure there's no extra fuel filters installed and clean / change any you find.

Check the fuel pump and maybe rebuild it, if it looks bad.

Check the carb for dirt, float level to specs, dirt in the passages, etc.

If everything looks OK there, I'd drain & remove the fuel tank and flush it out. May very well be some crud in there that partially clogs the fuel outlet.

A problem I experienced ened up being a piece of solder rolling in the tank and occassionally being caught by the fuel pickup pipe.
Tony

check the gas cap. a plugged vent will cause the symptoms you described.

Thank you all for your comments. Some good suggestions. Regarding the comment about an "extra" fuel filter: what would be the proper setup for a fuel filter? where should it be located? Without climbing under the car again, I believe there is at least one small filter installed right at the point on the carb where the fuel line attaches. Ignition stuff, gas cap and fuel pump are all new on this car, but I will double check those items. Fuel tank was cleaned and re-sealed about 1 yr ago. Regarding any dirt in the lines, I did have a similar problem to this on my '27, and found some dirt in the fuel line that was causing the problem, so I will check the lines on the '37 too.
Thanks...will update the list on any discoveries!
John H.

Your symptoms are classic for vapor lock. Replace the fuel pump & see if that fixes the problem. If it does you're good to go. If it doesn't you know to look for a plugged fuel line, etc. plus you have a fuel pump for when yours does finally go bad, and it WILL go bad eventually.

"Regarding the comment about an "extra" fuel filter: what would be the proper setup for a fuel filter? where should it be located?"

The only stock "filtration" was the glass sediment bowl on the fuel pump. I installed an aftermarket fuel filter between the tank and the fuel pump, to protect both the pump & the carb.

I will have to agree with Bowtie Bob, it is a rare thing for a Chevy six of these years to vapor lock. I would suspect a problem with the fuel pump, or in the carb (needle and seat, float) or something in the tank sucking down over the tank outlet, then with the suction removed to float back off the opening, it could be a piece of the tank liner, dirt or rust or even apiece of paper a leaf or a restriction in the fuel line or inline filter.

i had a similar problem a while back . all pointed to fuel but the coil was bad

Would be very easy to check both....when it dies does it loose spark or fuel. Remove plug wire from plug and hold terminal about 1/8" from bare metal on engine, have some on turn over engine with key on. A spark shold jump the gap. Remove air cleaner and peer down into carbruetor throat with flash light. When the throttle is opened you should see a stream of gas squirting from the accelerator pump nozzel.

gene the problem with mine was as fast as i could get out get the hood open check the fire it would be ok . may be in my younger days i could have moved faster . as long as i have been doing this i should have started with the easy stuff first .

Perhaps it was just stopping to catch its breath. :)

Check the fuel hose that goes from the pump to the line,they will collapse on the inside giving it symptoms of running out of gas. My 37 p/u done that years ago and it was just the hose. Jeff

All good suggestions and ideas, this will give you somethings to check out during the next few hours?, days? weeks?
Good luck!
And let us know what you find....

I have had a full summer of problems with the carb running out of gas after 10 to 40 minutes of driving. After replacing an in line fuel filter, rebuilding the fuel pump, replacing the fuel pump with another one, blowing out the fuel line, going through the carb, replacing the carb with an extra, checking for an oil leak on the bottom of the coil, (I have a 3 year old gas tank), I still had the problem. What turned out to be the solution for me was re-tightening my fuel lines before the pump. I was not getting any gas leak but was getting a little air leak. Now whenever I look at my gas filter by the carb it is 3/4s full of fuel. Before there were many times I could barely see any gas in the bottom of the filter.

Good luck, Mike

That is a chore we don't consider as often as we should. Simple things like a loose fitting can ruin your whole day. Kinda falls into the same category as "any fuel in the tank"?

Glad you "got her done".

Your experience is just another example of trying the simplist and cheapest first. Though none of us thought of it making sure that the fuel line fittings were tight (particularily those between the tank and fuel pump) would have been a good first step. In hind sight it sure makes sense to do that early in the process. Guess the gremlins kept you from it. Never know what those little guys will do next?

If you think it is vapor lock, try slicing a piece of 5/8" or whatever size you have, heater hose and sliding it over the steel fuel line to insulate it. You may also try covering the heater hose insulation with foil. I would try covering the section closest to the engine and manifolds first . Mac

Ok, everyone. With so many good suggestions, I spent a few late nights in the garage this week trying to work thru this issue. It's about 10:30pm here in Toledo, and just got back from a short drive. Probably not long enough,though, to really know if the problem is solved or not. What I've done so far: replaced all rubber hose portions of the fuel lines as well as installed new stainless hose clamps. I also removed and cleaned the "new" fuel pump which had a fair amount of debris in it. I also removed the small in-line steel canister "modern" fuel filter that had been installed just before the carb. Given the above changes, the car seems to happier even just at idle. Weather permitting, I will try to put a few more miles on this weekend to see if it continues to run well. Thanks again to everyone for the suggestions so far!
John