642 bobcat "84" fuel problem

[kevsblading]

So I have a 1984 642 bobcat with 1.6 for industrial. It has all new fuel lines had electric pump near mechanical pump that is not being used. I have replaced electric inline fuel pump couple times. I insulated the fuel lines in the engine compartment. When the engine gets warm. Engine compartment will get roughly 150° on a manifold side. Engine temp usually around 180. I will start starving for fuel to where I can barely keep it running and then I will die I can hear the electric fuel pump being louder because it's not getting fuel. If I unhook the fuel line from the carburetor and key the ignition it will pump fuel pushing air out until it's a solid stream then I hook it back up and start it and it runs good for about 5 minutes and then I start sucking air again and it starts vapor locking again and can barely keep it running. And then it will die then I have to pull fuel line off again and let it completely prime and hook fuel line up again to get 5 more minutes

 

[Dave1234]

Sounds like you have an air leak ahead of your fuel pump where it sucks in air and looses prime. Might be a crack, lose clamp, and might be made worse by a clogged fuel inlet in the tank. I'd pull the inlet screen, and just replace the hoses ahead of the pump. I suspect the increased volume pumped without being connected increases the ratio of fuel to air in the line and that lets the pump function properly and continue to pump while when the fuel volume is lower air gets left behind in the pump eventually causing it to lose prime. That is my guess.