QUESTION ABOUT VAPOR LOCK

[Meck]

In the superhot weather that we've been having this summer I'm having trouble with my engine vapor locking. Three times after a hard run, I've stopped at a store only to come back out and have the car not start. After an hour or so of cooldown, fuel flows again and off we go. I've already rerouted the gas line from the pump to the carb, but yesterday it pulled the stunt again. Now, I've been told that the vapor lock is actually coming in the fuel line under the car boiling from the heat off the asphalt parking lot being trapped between the car and the surface. There is some evidence that this may be true because when the car has refused to start, the line at the fuel filter has also been empty. Is this the case? That the fuel boiling is under the car? If so, is there anything that can be done about it other than to stay off hot parking lots until we get back to more normal weather? Thanks.

[Petros]

there was a recent thread on this topic under a different name. I find it hard to beleive hot asphault would cause vapor lock in the fuel line, though I supposed it is possible. How about wrapping the fuel line under the car with aluminum foil? Or hot water pipe insulation? Carry around water in a large squeeze bottle and spray off all the fuel lines, that should stop vapor lock. If it still will not start it might be something else, fuel tank vent issue perhaps?

Where do you live where it is so hot?

[ARCHINSTL]

http://www.tercel4wd.com/forums/viewtop ... 15&p=41088
There is also a another link within the preceding.
Do an Advanced Search using vapor+lock as the key word combination; there are 32 posts (not 32 pages!).
It's been 100+/- in STL for the past three weeks and I've not experienced this - although I do have a Weber.
Even back in the bad old '50s I've never heard of your situation (parking lot manifestation) occurring with any cars.
What is your location?

OT maybe, but - you had a kinda similar thread last year about no gas getting to the carb - http://www.tercel4wd.com/forums/viewtop ... f=2&t=4747; you did not post a resolution. What was it?
Tom M.

[emmahumpfritter]

Arch, you are the search master! Serious kudos and thanks to you for that!

Just a random praise unrelated to vapor lock..

Carry on.

[sunray]

These vehicles use a return fuel delivery system with an evap system. The chances of vapour lock are pretty damn slim unless you are running winter fuel right now.

What does the car do when started? Are you sure its not flooded (ie black smoke when it finally runs?) I have seen a lot of carbed a series engines flood due to the high speed venturi air bleed being clogged with grit. This creates a siphon that doesn't stop after the car is shutoff. It pours all the fuel from the bowl into the manifold and floods the hell out of it. The bleed in question is about 10 thousandths across but is critical.

To verify if its this, drive the car making sure to floor it at least once and then shut it off. Now get a flashlight, remove the air filter housing lid and peek down the carb throats right after shutoff. Watch for fuel pouring out of the primary or secondary high speed venturis and onto the throttle plate.

If thats what you see send me a pm and I'll take some pictures to walk you through the fix.

[Meck]

Thanks for the quick and helpful replies. First, this is in Kentucky where we're having a sustained hot spell. Second, this "vapor lock" situation has happened to me three times in the last eighteen months. All of these have taken place since I changed carbs to a rebuilt Hitachi. The car is not flooded or boiling gas out of the carb after shutdown. When this has occurred, the car will fire up immediately, run for a few seconds until the fuel in the float bowl is used up, then fuel starve and die. At this point there is no fuel in the carb (the Hitachi has the glass plate on the bowl that lets you see into it), none in the line back to the fuel pump, and none in the fuel filter (and I assume the line in between). After the second time it happened, I replaced the fuel pump which was old and the gas cap. I had already blown out all the lines. The gas is not old.

This isn't the worst problem on earth, but it is aggravating. Part of the aggravation is that there should be a simple explanation, but I can't seem to hit on it.

Thanks

[RiggerRob]

FWIW, had this identical problem and replacing the fuel pump did the trick. If the fuel pump is even slightly marginal it will cause this problem. I can tell you from experience that vapor locking in rush hour traffic in Charlotte, NC is not a fun experience ... Good luck!

[Meck]

Thanks for your reply. I've been lucky not to have the car stall in heavy traffic as you have had. It has always been after parking on hot asphalt. As far as the fuel pump being the problem, it still could be, although I replaced the fuel pump after the first time it did it. (It wouldn't be the first time that a "new" part wasn't what it should be). Since it is finally cooling down here, I'm going to let it go and not do anything for now. Sometime this winter, though, I'm going to splice an electric pump into the line back close to the gas tank. I think that will do the job.

[takza]

You could have a leak in the "suction" line going back to the tank?

[gatemaster]

I had the same problem here in NM. The gas is boiling out of the carb and the fuel pump which is located on the engine also is too hot and cannot pull the fuel up into the carb. The weber deals with it better than the stock carb. Put an insulator plate between the carb and intake manifold and or get an electric fuel pump.