Posted this in the 1st Gen section, but also applys to 2nd Gen. I really do have a need to know on this one.

About how much fuel PER HOUR would you expect to flow back to the gas tank via the return fuel line during normal operating conditions?

Related, knowing that there is about 30 psi between the fuel pump and the injectors, how much psi would you expect to find at in the return fuel line at the gas tank?

Another 30 psi?

 

I'm not too keen to do this myself, but why could you not take the return line off and run a long hose from it to a container, start the engine for one minute, shut down and then measure what you have. It still would not be 100 percent accurate because the pressure regulator would not be switching from 28 to 42 psi like we recently found out it does during normal driving. If you want to know what the return pressure is you can just tee into the return line with a gauge. I don't see exactly how that would tell you how much in volume is displaced in a given time period. Seems like there are a lot of factors like size of line, how much one gets on the gas etc.

 

Excellent idea about pulling the return line and running it for a measured amount of time. Thanks.

Also, I don't need to be accurate about the return line pressure. What I'm trying to figure out is if the pressure in the return line is anything above, say, 7 psi. Logic (but not knowledge) is telling me yes. I think the whole system gets pumped up 30 psi.

Any of you knowledgeable rotor heads wanna share your thoughts?

 

Depends on the engine load. Under severe load, there will be a trickle going back to the tank, unless you have a mongo good pump.
-Les

 

Why don't you just put your pressure gauge on the return line on the left side of the engine bay(tee it in) and run the engine. I might do this in the next couple of days just for something to do, but my plates pretty full right now. If I remember right someone did this by accident recently on this site, but I do not remember just who. He was trying to read the rail pressure but was hooked up on the wrong side of the pressure regulator. Also the pump is putting out about 80 pst and the regulator is bleeding off the excess pressure so that you have 28psi in the rail except when you put the pedal to the metal and then you get about 40psi.

 

Unfortunately, I don't have a pressure guage. No rush to find out, so whenever you check yours, post me back.

Also, to be clear, I'm talking about the return line fuel pressure at idle.

Thanks for you help.