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Vapor Lock - The cure
Evidently, these things are notorious for Vapor Lock. . . I did not know this (all these years…). After all these years, and all the miles, and all the road conditions, I had never personally experienced Vapor Lock. Didn’t show up until I left on the trip from WA to CO - Like to drove me nuts!!! I thought I had a defective pickup, or clogged sock, or a hole in the fuel line, or anything but vapor lock.
For the Jeep, as probably ANY vehicle suffering this problem it’s the HEAT, literally “boiling” the fuel. Add to that Alcohol, and the boiling point gets even lower. Add to that the “vacuum” of pulling the fuel forward from the tank, and the vaporizing point gets lower still
The cure – I finally found a mechanic outside of Cheyenne, WY, that was familiar with these vehicles, and their inherent problem. The solution. . . install an electric fuel pump (PSI/GPM for carbureted vehicle) just off the output/pickup from fuel tank – as close as possible. PUSH the fuel. You don’t have to bypass the original mechanical fuel pump – it’s fine where it is. DO REMEMBER that on these vehicles (these model years) the fuel filter has a vapor bypass/return – this needs to be turned/twisted so it’s at the ‘top’, so that any vapor that comes through the line rises and goes out THAT return line.
Connect the power to the ignition, or an AUX switch. Insure the proper wire size (AWG) and circuit protection (FUSE). Good luck.