I need to know exactly what causes vapor lock and have any of you guys had any trouble with it? I have been driving my truck to and from work for about the last month or so. Haven't really had much trouble, except for the fact that about once a week the fuel pump decides not to pump. I seriously doubt that it is faulty since I just replaced it, but you never know. One day the gas'll be flowing like a champ and the next day, on the way home, the line will be dry!! Is what I'm experiencing actually vapor lock or could it be something else?
As far as the backfiring, that just started today, on the way back from lunch...what the hell causes that??

Just getting frustrated....need some guidance.

 

Vapor lock happens when the fuel in the carburetor inlet bowl, fuel inlet line, and/or fuel pump becomes so hot that it boils and turns to vapor. Once this happens, your engine will typically stall when the vapor reaches the carburetor.

Typical causes are:

1. Poor fuel line routing
2. Engine running excessively hot
3. Problem with radiator, fan, or other cooling system apparatus
4. Very high air temperatures - as in the desert or southern climates
5. In a few cases, low fuel pressure (usually requires one or more of the above causes as well)
6. In rare cases, oversize fuel lines (usually requires one or more of the above causes as well)

The fixes are fairly clear - keep fuel lines away from exhaust manifolds or other hot areas, check for engine overheating, keep your cooling system in good working order, check fuel line pressure, use the proper size fuel line.

 

Nawlins56_F600,
Maybe someone can pipe up with known specific problems with a big truck like your F600. Does dumping ice water on the fuel pump help?
But in the meantime, anything upstream of the pump suspicious? No plugged filters? Clean tank? Clean pickup tube? Any rubber sections that could be either leaking air in or soft and collapsing shut under vacuum? Vented fuel cap? Gas line routed close to hot object like muffler?
How 'bout the pump? I had a weird one last fall. Installed a rebuilt fuel pump. Would starve and die if the tank was low took a hard left and accellerated. Finally disassembled the pump on the side of the road and discovered that one of the staked-in valves had backed out of the casting. So it 'sorta' worked. Anyway, drove it back into its seat, and staked it over throroughly with hammer and screwdriver, and been haulin' butt since then.
If all this stuff is OK, then maybe time for some reengineering. Move lines away from heat sources. Any sort of insulation slipped over the fuel line will help, even just slitting lengths of rubber fuel line and slipping them over the metal line. You may have heard of using clothes pins; they basically work as heat sinks. Worse case scenario you could add an auxillary electric pump by the tank.
Good luck!
Brett

 

When I bought my truck, the hose that connects the gas filler tube to the gas tank had rotted and hunks of rubber were falling into the tank. The gas pickup in the tank is just a tube that has no screen. Making matters worse, the tank had a lot of varnish from years of old gas.

The previous owner obviously had similar problems, in the box of extra parts that I got when I got the truck, was the original fuel pump. On the engine was a new pump.

I bought a new hose, dropped the tank out and cleaned it with lye, and pulled the fuel line out and blew air through it to try to clear it out. That fixed my fuel starvation problem.

 

Well, as it turns out, I think it was more of a starvation problem than a vapor lock. I had a filter in the line between the pump and the carb. Took that out and have not had a problem yet. I had already pulled the tank, cleaned it out, blew out the lines, and replaced the fuel pump. Just hope that by the process of elimination, I won't take a two hour trip just to get home from work anymore!!! Thanks for all your help fellas.