Kinda Vapor Lock Issue on a Vega

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Kinda Vapor Lock Issue on a Vega

Postby straws » Sat Mar 24, 2007 6:11 pm

OK, I have posted before looking for thoughts, but I need to give some more information.

My vega has a 350, with an Edelbrock Carb with the choke wired open, and a no-name mechanical fuel pump. I have a temp gauge that says the engine temp gets up to 210, but my problems start at 200.

When I am running constant (outside temp makes no difference) I am fine. When I idle for even 30 seconds, if I hit the throttle hard, it will take off, then after maybe 75 feet it will choke. I have learned that I can frantically pump the pedal, it will barely stay alive. If I do not frantically pump the pedal, it will die and take a minute to restart.

I have gotten the car even hotter during some tests with the hood off, and the see through fuel filter that sits on the valve cover is completely FULL of fuel!!!!

Does anyone know what is happening? Could this be something in the carb? But pumping the pedal keeps enough fuel going to keep it alive? Tips??????? Help???????
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Postby cjbiagi » Sat Mar 24, 2007 6:26 pm

The fuel could be boiling either in the line between the filter and carb or in the carb itself. I had a similiar issue years ago with my AFB and by insulating the fuel ine once it enter the engine compartment and making a return line from the filter back to the tank, I was able to eliminate it. You may want to try some simpler things like insulating the fuel line and using some type of heat insulator under the carb if you have enough hood clearance. Blocking the heat crossover in the intake manifold can also significantly cut down the amount of heat transferred to the carb. You may also want to check the carb itself, it could use a rebuild along with checking/setting the float levels. Cars with mechanical fuel pumps are more likel to have problems because the fuel pump acts as a ginat heat sink, pulling heat from the engine block and heating the fuel.
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Postby shytebucket » Mon Mar 26, 2007 3:50 am

Definitely sounds like a heat-related problem, however, I would suggest the next time you take your car out (a time where you can say, "yeah, it's gonna choke"), run it with only fuel hose between the pump and carb, i.e. no filter, and see what it does. Not sitting in the driveway with the hood up, but out on the road so the motor and engine bay get good and hot.
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Postby Sirshredalot » Wed Mar 28, 2007 11:48 pm

Hmm...youre problem might be volume.....not pressure.

Traveling at a constant state of engine speed there is a normal rate of fuel consumption....but once at idleit slows and then upon acceleration there is more demand for fuel than the pumpcan keep up with and the bogging lean sputter.
But also this could only become evident at the higher temps because the warmer intake temperatures make the air less dense and slows atomization of an already lean condition....perhaps....?

Might have enough pressure....but lacks volume. Most standard "hipo" "street" fuel pumps are only about 80GPH.
120GPH is more suited to a hot small block with high fuel demands.

Good luck
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Postby cjbiagi » Thu Mar 29, 2007 6:54 am

I still run the stock in tank pump and have no problems with my 350. I'm sure it is not rated anywhere near that high. Plus, there should be enough fuel in the carb to get you off the line.
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Postby Sirshredalot » Thu Mar 29, 2007 2:29 pm

He said that he does get off the line though...he said about 75 feet....enough to drain the bowls...which would lead me to believe they werent being filled back up quick enough....either a fuel volume problem or an improper float adjustment.

If it was a heat problem only...like fuel boiling than he wouldnt get off the line strong.

Just my .02
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Postby barebonesracecars » Fri Apr 20, 2007 8:14 pm

Maybe something as simple as the 'no-name' pump itself.

How old is it?

Plugged fuel filter? A see-through filter can fool you. Even though you see fuel, it's not necessarily going through the filter media.
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