All Small Six Fuel Pressure to Weber drops once hot

[ncpe2001]

I've noticed that the fuel pressure to my Weber DGS drops significantly once the engine is at operating temperature. Starts at 6psi then drops to 0 once the engine is at top temperature. The engine continues to run so fuel is passing through the Weber, just no back pressure on the gauge. Electric pump fed. Anyone else seen this?

 

[akidwithacar]

I had a similar problem and was getting fuel starvation. It turned out to be hydro lock I think is what it was called. Basically the fuel lines are getting so hot that the gas is evaporating before it gets to the carb. I would try to move your gas lines away from the hot parts or insulate them

 

[bubba22349]

If you upgrade the Fuel line size to 3/8 inch it should help by the way Webers usally like to only have about 3.5 PSI. Best of luck

 

[R_Calris]

to verify if its hydrolock, put some thermal insulation tape on the fuel line where it seems to get close to anything that gets hot; next to the header/manifold, for example. or you can take a small piece of aluminum and cut it so you can use two carb bolts on the side the fuel line enters, and use that as a small heat shield to keep the heat from effecting the line. Aluminum would work pretty good here, even if you decide just to leave it, as it has decent thermal conductivity, and by bending one side up slightly (probably the closest to the valve cover, or toward the rear of the engine) it can also give you a warning if the line is leaking.

 

[78_200_C4]

The low pressure may not be "engine temperature" related but the time the electric pump has been running. The pump could be failing or the fuel tank has a plugged vent. Run the pump without the engine running for the same amount of time it takes the engine to reach operating temperature, check fuel pressure. When ever you get low pressure remove the gas cap as a vent check.
Is your elec. fuel pump mounted near the tank with a siphon supply of fuel reaching it?

 

[ncpe2001]

The low pressure may not be "engine temperature" related but the time the electric pump has been running. The pump could be failing or the fuel tank has a plugged vent. Run the pump without the engine running for the same amount of time it takes the engine to reach operating temperature, check fuel pressure. When ever you get low pressure remove the gas cap as a vent check.
Is your elec. fuel pump mounted near the tank with a siphon supply of fuel reaching it?

This was actually a very good guess, and I wished it was the issue, easier to fix. Turns out, looks like it's the heat from the muffler on the electric pump and hoses near the tanks. I have headers and flowmaster mufflers to install next which should resolve the problem.