Title.

Just wondering at what pressure the injector pump return actually starts to return fuel to the tank.

Like on a second gen truck it's typically between about 25-35psi.

 

All the time, there is no spring in the overflow valve on a VE pump, there's a small hole that is sized for the particular application, case pressure is over 100 psi and increases with rpm, that's how the variable timing of the pump works.

 

you could put a pressure gauge on the case and see what it is. I think it gets to over 200psi internally? A lot of the high horsepower guys know because they will manipulate it.

 

ahh gotcha. good to hear, and that makes sense. I was kinda thinking that it wouldn't make sense that it would return the same way as a ppump. I wonder what kind of pressure it would go to if it didn't have a return... or if you were able to push enough fuel to actually make it drop a lot to have a shut off thing on there if the pressure dropped below a certain PSI.

 

I'm a little confused. I was under the understanding that case pressure shouldn't exceed 20 psi without making the input shaft seal positively retained with a snap ring.

 

Trendz, case pressure and inlet pressure are 2 different things.

The vane pump is separated from the main body. So inlet pressure puts direct pressure on the seal.

 

Ahh... That clears up a few questions for me. Thanks!