I did one more round of observations on the engine and fuel pressure. I started the truck with just the manual fuel pump. the fuel pressure was 4 - 4 1/2 PSI ideling at 600 RPM. I continued to allow the truck to run and get up to operating tempreture. Over a 20 minute period the fuel pressure slowly dropped from the starting 4 PSI to less than 1/2 PSI. I used a digital thermometer to double check some tempretures around the enging. The block was too hot to register with the thermometer. I think the limit it will read is 200 degrees. The goose neck on the engine at the radiator hose was 184 degrees. I peeled back the insulation on the fuel ine about 20 inches from the carbruetor and the metal fuel line was about 125 degrees. The metal fitting at the carbruetor where the fuel line attaches was about the same. 125 degrees.
Can this slow steady drop in fuel pressure be contributed to a failing fuel pump? If based on this latest information it still points to a fuel pump issue I think I will go with an electric fuel pump replacement. Is 125 degrees too hot for the fule line. should I switch to a rubber fuel line or is the metal one better. I am using Nickle/copper line for my fuel line.
The truck continued to idle and run okay with just the 1/2 PSI but I assume if I had waited longer it would have dropped to nothing and died.
Last edited by dgrinnan; 07/19/2025 7:50 PM.
