Classic/Antique Car Repair/1940 Chrysler vapor lock?
QUESTION: Hi, i have a 1940 Chrysler Traveler coupe, straight eight, fluid drive. When driving on warm days, say above 70, the engine starts to sputter, a little at first, and gets worse until eventually it stalls. It will also stall at a traffic light, or stall when idling in the driveway. It will start again in 45 minutes. If the engine is hot and you shut the car off, it won't start for the usual 45 minutes. I thought it might be vapor lock, so i moved the fuel line away from the headers and insulated it. I also removed one of the stone guards for more ventilation. The car has had a coolant flush and a new coil. None of this has helped. I have talked to other MOPAR owners of 1940ish cars and they don't have this issue. Do you think the problem could be something other than vapor lock? At this point I'm willing to try/replace anything because the car is so unreliable. Thanks Bob
ANSWER: It sounds more like the carburetor flooding over than vapor lock. But to be sure test the fuel pump pressure. It should be in the 4 PSI range and with the fuel line disconnected and directed into a plastic container pump about 1/2 quart of fuel with the engine cranking in 30 seconds or less. If those tests pass I would look at the carburetor. Now when the engine stalls quickly remove the air cleaner. Using a flash light look down into the bore of the carburetor. If it is flooding over you will see fuel dripping from the main discharge nozzle. If this is the case the carburetor will need to be remove, disassembled, cleaned and rebuilt.
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QUESTION: Thanks for your advice, I'll try removing the fuel line this weekend. I should have mentioned that the fuel pump is original to the car. The carb was rebuilt 20 yrs ago. My father and i have had the car since 1992 along with the stalling problem. We just drive it on cool days. I also thought of the ritual involved in starting the car. If the car hasn't been started in 3-4 days: Pump the gas pedal about 20 times, pull out the choke, and hit the starter button. This usually works. Anything longer than 4 days: Pour gas down the carb, pump the gas pedal 20 times, pull out the choke, and hit the starter button. The engine will start after a few cranks then stall. Repeat all of the above and it will start and stay running. Does any of this extra info help?
ANSWER: Sounds more and more like the carburetor needs some TLC.
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QUESTION: I took the car out for a ride, parked it in the garage and it stalled. I disconnected the fuel line from the carb and cranked it over for 30 seconds. No gas came out of the fuel line. Thanks again.
OK, now we can go to work. The problem is either the fuel pump, the lines including the flex fuel line at the fuel pump, or the fuel tank including the gas cap. The easiest fix is the cap. The cap should have a vent in it. If it is the wrong cap or the vent is plugged a vacuum will build up in the tank and shut down the flow of fuel. To check the fuel pump, disconnect the fuel line that comes from the tank and put a vacuum gauge on the pump inlet port. Crank the engine and there should be at least 11 inches of vacuum there. If that checks then disconnect the line at the tank and put the gauge on the line. make sure that you have reconnected the line to the pump. Again crank the engine and the vacuum gauge should read the same as when checking at the fuel pump. If not there is a problem with the line, like a small rust hole in the line. Most often we found those up over the rear axle. This is the high spot in the line and it will not leak fuel but will allow air to enter the line. If everything is OK there is a problem in the tank like something floating around and getting drawn into the fuel pick up.