The Stovebolt Site Forums The Shop Area The HiPo Shop Vapor lock?

I've been trying to figure out why the truck has been running so irradically and someone suggested that it may be vapor lock. It runs fine when I initially start it but as soon as it heats up I notice that there's no fuel coming through the filter and it barely runs. The fuel pump is brand new so I ruled that out. I'm looking into an electric unit with a low pressure switch to see if that will help. Any other suggestions?

I don't have your answer(someone will) but the thing shouldn"t ( or wouldn't) vapor lock after it is running.

Is it electric or stock fuel pump? If electirc, mount it as close to fuel tank as possible.Most elc pumps push & don't pull. If stock, check to see if fuel lines are to close to heat source[ headers, pipes ext]if to close it will boil gas and produce these results.also new doesn't mean it's good.

"It runs fine when I initially start it but as soon as it heats up ...."

you might be putting the wrong things together, might have nothing to do with "heat", but with length of time things are vibrating enough for a piece of junk to plug the tank outlet - check how long it takes a few different times, do it with the hood closed [hotter] and open [cooler] - also if it actually is vapor lock, putting some spring type wooden clothes pins on the line between the pump and carb should either eliminate the problem or make it take longer to happen

also be a good idea to make sure the pump is actually moving enough fuel, the amount initially in the carb bowl will let it idle normally for awhile, but the pump may not be keeping up - does the filter show a good flow right from startup? does the carb inlet needle open properly? if the carb isn't allowing fuel in, there won't be any flow

Bill

The tank is clean, so I don't think there's any gunk in the line. There is good flow @ start up, but it falls off dramatically once it heats up. My brother-in-law told me to check the lines as it might be sucking air from some place. I forgot to mention that I'm getting some strange readings from the fuel pressure guage. Sometimes the needle bounces around wildly and then at times it holds steady at about 5-6 psi. Any thoughts?

I replaced the mechanical pump with an electrical one and most of the rubber lines with steel ones. Started and ran fine, Pressure guage held rock steady @ 5 psi. headed out for a test drive and it did the same thing...ran like @($%@&! & on top of that the brakes started locking up agsin!. The only other alternative is to check the carb. I'll see if one of my buds will let me borrow one just to test this theory. I'm getting pretty tired of this!!!!!!!

I'm outta ideas. I swapped the carb and it's still running lousy. The tank is vented and clean. New fuel lines, filters, fuel pump, distributer & coil. Using fresh fuel.

what happened with the "as soon as it heats up I notice that there's no fuel coming through the filter"? still that problem?
what does "still running lousy" mean now with the electric pump?

Bill

No problems with fuel flow now. Pressure holds steady @ 6 psi.

so the original problem wasn't really the problem ... what engine is this? .... maybe the "new" distributor has a problem, like vacuum or mechanical advance ... what exactly does running lousy include?

Bill

Mine acted that way and a very small adjustment in the advaance fixed it.

HEI ?
check ignition module.
get tempremental as they get old and hot.
usually due to lack of good heat transfere.
anotherwords always clean old off and put fresh dielectric grease on every time the module gets taken off. replacement or even inspection.
Like a processor for your pc it'll heat up and burn out without this grease acting as a heat sinkparts store prob has single use size packets of this stuff for less than a buck.

I had a bad coil that caused problems for a while.

It's a new coil & distributer. I changed it out earlier for a smaller unit to gain more firewall clearance.

First check your floats and then check for vaccum leaks. Look at the intake gasket and carb gasket and vacuum lines. Make sure that carb is setting perfecly flat on the intake.

I really wonder if some people even know what a vapor lock is.Sure does not sound like it according to some opf these posts.Not trying to be a smartass but but some of these posts make no sense at all.Only one that deals with why an engine will vapor lock,and that is checking how your fuel line is routed.

Dale - note that the original mention of vapor lock was questioning if he had it, which quickly turned out to be 'not', so the rest of the posts have to do what might actually be the problem

didja get it runnin Robert? find the problem?

Bill

Not yet. I verified that the tank is venting properly and is clean, checked all the lines for leaks, made sure the carb was clean, checked the timing and everything else I can think of. Only thing left that I can think of is to reinstall the old distributor to see if it runs the same way. It hasn't really ran right since I took off the TPI. (I was having trouble with it at the time but it turned out that there was water in the tank).

Having said that, I maybe starting over. I recently acquired another TPI unit. I know, I know..... I need to make up my mind, but through some "horse trading" I basically got it for free. The unit is complete with all sensors, harness, distributor, fuel pump, ECU and on top of that it's polished! Should be arriving soon. Will keep you posted.

Robert:
Have someone blow into the gas tank while the fuel line is disconnected from the carb.