Vapor lock...again
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 923
Likes: 4
From: Austin Tx
Vapor lock...again
Per forum members instructions from last time, I wired heat riser valve open, installed new fuel pump to eliminate that as a problem,installed heat shield along with 3/8 fiber gasket below carb...moved inline filter to push side of the pump instead of suction side. The filter I installed is one of those plastic clear ones so i can see what is going on. After driving around in city traffic, temp around 80 degrees, pulled into my office parking lot, popped hood while running, idle is smooth, temp is around 180-190, but fuel filter is empty, with an occasional bubble of fuel coming in. What the f#$@!!! This is a SB with no headers and it is not even summer yet. What is the BB with headers going to do in July!!! Next step is switch over to Chevron from Conoco. Maybe the conoco reg unleaded is the culprit. Or maybe should replace fuel strainer in the tank...I'm sure it is the original 33 yr old one. Help!!!
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
Try disconnecting line into fuel pump and let the rubber line hang into a can. Fuel should run out. If not, maybe you have a clog in the fuel line or vent into tank. I can't remember when they went to unvented caps. I think in later '69 or '70. Try removing cap if fuel is running slow. If removing cap fixes things, buy a vented cap. If fuel still runs slow, then put a compressed air hose into opening of tank, sealing the area around the hose with a rag and blow with the air hose. The fuel should shoot out and maybe clear whatever clog may exist. If not, then I'd start looking for crimps in the fuel line. Check inside of tank too, to check for rust on bottom.
If the line to the tank seems clear and the tank seems vented OK, maybe its the fuel pump pushrod or the fuel pump cam lobe.
Also, have you checked the fuel line pressure between the pump and the carb? Should be about 6-8 psi if I recall. If you can, maybe you can temporarily clamp the gauge so it's in view while driving (not in the car with you in case of leaks). That way you can get a read on whether the fuel pressure is dropping off while driving at any point.
Hope these ideas help. Good Luck!!
If the line to the tank seems clear and the tank seems vented OK, maybe its the fuel pump pushrod or the fuel pump cam lobe.
Also, have you checked the fuel line pressure between the pump and the carb? Should be about 6-8 psi if I recall. If you can, maybe you can temporarily clamp the gauge so it's in view while driving (not in the car with you in case of leaks). That way you can get a read on whether the fuel pressure is dropping off while driving at any point.
Hope these ideas help. Good Luck!!
