TheSamba.com :: View topic

Wed Nov 18, 2009 6:05 pm

I've got a problem with my '72 Bug, 1600 dual port, 041 dist, carb 30 PICT. When I get below half a tank of gas the bug runs awful, no power, feels like it's running on 3 cylinders. But when I stop and fill the tank, it runs great. I don't mean I have to drive for a while and it starts to run good, as soon as I start it at the gas station it runs great. The fuel filter is fine, the mechanical fuel pump is good. I've thought about crud in the 30 plus year old tank, but seems that should be a consistent problem, not just below half a tank. Would really welcome any and all suggestions. For now I just make sure I stay above half a tank. Thanks in advance.

Wed Nov 18, 2009 6:11 pm

Sounds like your fuel tank vent is plugged. Or vent lines are old and collapsing internally causing vapor lock of sorts.

Thu Nov 19, 2009 6:36 am

Check your fuel pressure when it's acting up (below half a tank). Could be a fuel pump going away. When the tank's full, the pump'd get an assist from the weight of the gas in the tank pushing fuel into the pump.

Thu Nov 19, 2009 6:27 pm

Just wanted to say thanks for the ideas of where to look. I was baffled. Now I have my Saturday planned. Thanks again.

Thu Nov 19, 2009 8:37 pm

sturgeongeneral wrote: Sounds like your fuel tank vent is plugged. Or vent lines are old and collapsing internally causing vapor lock of sorts.

I'm agreeing with the sturgeon. Next time you get to half tank and it runs like crap, just take off the fuel cap and put it back on - that's all. If that makes it run normally, then you do have a plugged vent.

Mine got plugged in the middle of the desert 110 *F between Desert Center and Blythe in 1984; I couldn't figure out what was wrong so I drove on the shoulder the remaining way to Blythe at about 35mph. When I pulled into the gas station in West Blythe, almost empty, the air just sucked right in and I knew then it was a plugged vent. It took me several weeks of burping the fuel cap every two days until I found a small "tee" in the vent system that was blocked.