Technical Why Does My Fuel Pressure Drop When Engine Gets Hot!!

I looked a lot online about why my fuel pressure drops when my engine is up to temp (180-190 degrees) and it said could be a faulty fuel regulator or fuel pump.

I've since changed both AND checked for leaks in the line (nothing) and checked my gas cap is vented...and still, the fuel pressure drops.

I have been driving my car with an electric fuel pump and fuel regulator for many years and never had this problem.

It has perfect pressure from cold and initial starting. Engine idles great and is very responsive and runs great etc....then the fuel pressure gauge that's mounted in my fuel block on the firewall, drops the hotter the engine gets.

I have 4 strombergs and always set the pressure at 2.5 pounds and set it when its warm.

I'm really scratching my head on this one. Any help is much appreciated.

 

Maybe the gauge is not working right. Cold shows right reading?

 

I thought that too…but the way I initially found out was that I was driving the car and it died on me like it was starved of fuel.

checked that I had gas and then checked at the carbs and no they had no gas.

So the pressure is definitely dropping

 

Are you boiling the fuel (vapor lock)?

 

I've seen this before..
In a hi end build, They tried efi, Didn't have success, Went back to carb, But regulated the pump down to 4psi., The pump would eventually shut off, Let sit, fires up...
Changed the pump out to a 5psi.
Problem solved...
Higher psi pumps regulated down run very hot... Not knowing Your pump can't say, Just something to look into..

 

When did you last clean/replace the fuel filter?
Also, gauges can read low when things heat up.

 

This problem can/has also happened with liquid-filled fuel pressure gauges. Removing the liquid could solve the problem.