Vapor Lock Confirmation?

[81_El_Homewrecker]

Yesterday after about 45 miles of driving I get on the highway and around mile 5 I start chugging and surging. The engine died and I coasted to a stop, pop the hood and take a look. My fuel pressure was zero at the carb gauge (mechanical Edelbrock pump) so I pull the rubber supply line at the pump and I have fuel. So fuel is at the pump but not the carb. Let it sit for about 20 minutes, crank it a few times, check the gauge and I have pressure so I get it home.

I have had this setup running for about 6-7 years and never once had this issue. It was hot and humid yesterday, but nothing unusual from other years. Temp gauge stays at 210 in traffic and on the highway can get down to 195-180. The only thing that changed was I adjusted timing a little (10 degrees base) and richened the carb this spring. I don’t want to go replacing the radiator and all kinds of stuff because I never had trouble before, but wanted your help confirming it is vapor lock that happened. I think I will try advancing the timing a few degrees and move my heater hose that is resting on the carb supply line

 

[Scoot-71]

Normally vapor lock occurs at low speed or after a hot soak, but not going down the hyway, I might suspect fuel pump is starting to crap out, getting any heat source away from fuel lines is a good idea. Some fuels do boil easier then others but on the pressure side of the pump you would think it wouldn't happen, do you have heat spacer under carb?

 

[81_El_Homewrecker]

Normally vapor lock occurs at low speed or after a hot soak, but not going down the hyway, I might suspect fuel pump is starting to crap out, getting any heat source away from fuel lines is a good idea. Some fuels do boil easier then others but on the pressure side of the pump you would think it wouldn't happen, do you have heat spacer under carb?

I do not. I pulled the pump apart and the diaphragm was not torn and the spring was not broken.

 

[airboatgreg]

Also check the rubber lines to the tank for cracks that could suck air. Possible sock in the tank restricted also

 

[81_El_Homewrecker]

Also check the rubber lines to the tank for cracks that could suck air. Possible sock in the tank restricted also

Just replaced the tank and those hoses a months ago no issues as I can tell. I had good fuel at the pump feed.

 

[lilbowtie]

May or may not be related but I had the same problem on my 1979 van which turned out to be the module. The dielectric grease had dried up and when things got hot the module went wacky. Replaced - no problem

 

[pontiacgp]

if there was fuel at the feed line at the pump and none after the pump I kinda think the pump is bad

 

[pontiacgp]

also if you have had the same configuration for years and driven in the same hot climate why would you think it suddenly developed a vapor lock....

 

[81_El_Homewrecker]

also if you have had the same configuration for years and driven in the same hot climate why would you think it suddenly developed a vapor lock....

That’s why I’m looking for advice...I’m not sure. I can’t understand why I would have fuel on the supply to the pump side, but empty float bowls

 

[pontiacgp]

That’s why I’m looking for advice...I’m not sure. I can’t understand why I would have fuel on the supply to the pump side, but empty float bowls

it's either the pump or the lobe on the cam is worn