The Stovebolt Site Forums The Shop Area Engine Shop Possible vapor lock

I understand what vapor lock is but I am not 100% clear on the symptons. I was making a Home Depot run in my 47. It was running good and all of a sudden it started cutting out and died like it was out of gas. I called for help and my son in law brought me a can of gas. Took about 30 minutes. We added the gas and I was able to start it again but I could not get very far without it doing the same thing. If I waited a few minutes, it would start again and I could drive maybe a 1/2 mile before cutting out and dieing again. It was exactly the same as if I was running out of gas. Today was the first day we were in the mid 70's. Does this sound like vapor lock or do you have any other possible culprits I should check?

That really doesn't sound like vapor lock. he simplest thing to try is to remove or loosen the gas cap. If the vent is plugged up no air can enter the tank & it develops a vacuum. After that you probably have a plugged up fuel filter or the sock on the end of the fuel intake. The 47 doesn't come with a sock on the end of the tube so thats probably not it. It may have a shutoff valve under the tank. That can get clogged up also. Test the fuel pump. There are directions on fuel pump tests in the Tech-tips or the search on this website.
Let us know how it turns out.

George

Sounds like a clogged filter or a dying fuel pump to me. It fills the fuel bowl when you crank it and runs until the bowl empties because it is not filling as fast as you are burning it.

I would check the pump first because that is free.

When I had a serious suspicion of a vapor lock (very hot day, sitting at red light for 3 minutes), it was a chuga chuga kind of thing.

True vapor lock is about as common as finding a chicken with lips, the Easter Bunny, or an honest politician. It's caused by the liquid gasoline upstream of the carburetor boiling and turning into a gas that can't be pumped. Unless you've got a metal fuel line lying on the exhaust pipe or something similar, try to find the real cause of the problem.
Jerry

Could be fuel percolation.

New gas tank. New fuel line. New mechanical fuel pump (no guarantee it is not failing). I did recently add an inline electric fuel pump that is supposed to work as a stand alone pump or as a priming pump. I use it to prime the line when the truck has been sitting for a while.

What happens when you turn on the electric pump when the truck starts to die?

I need to test that. I was trying it but was not sure if that is what kept the truck running. It is on a spring loaded push button, not a toggle switch. I need to jumper the switch to see if that solves the issue, or at least rule out the mechanical pump.

You may or may not have read my thread about the similar problem I experienced last year with 2 brand new mechanical fuel pumps.

One failed after just a few hundred miles with symptoms that you describe leading up to total failure. I too, posted a question about possible vapor lock. The second brand new mechanical pump wouldn't pump a drop of gasoline straight out of the box! I thought for sure the cam lobe that drives the pump was wiped. After all, what are the odds that two brand new parts don't work?

Well, these days, new doesn't mean Jack Shiite. I sent my original glass bowl fuel pump to Then and Now Automotive for a rebuild and the problem has not returned. If you have your original pump, rebuild it. If you don't have one, buy one on ebay or whatever and have it rebuilt.

https://www.stovebolt.com/ubbthread...63250/fuel-pumps-and-other-nonsense.html

More on the fuel pump problem I experienced.

https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1458111/1.html

Thanks. I did not see your post but I am aware of the problem with the new fuel pumps. That is why I put in parentheses (no guarantee it is not failing) This is the second new one since I got the truck running. The first one lasted about 30 minutes before the pin for the pump arm popped out and a piece went into the oil pan. The one on there now is a Carter. I was hoping it is made a little better. It came with a spot of epoxy on each end of the pump arm pin. They are clearly aware of the issue with the pins staying in place. If it turns out to be the fuel pump as much as I dislike the idea I might go 100% electric fuel pump instead of taking a chance on a third one. .