Detroit DDEC IV Fuel Pressure?

Does anybody know what the fuel presssure should read coming out of the low pressure transfer pump?
I am getting a reading of basically zero at idle and 18 PSI at full throttle. I suspect this is my issue, but I don't know what the pressure is supposed to be.
Thanks
Floyd

 

Thank you very much for the info small truck.
I think your right that it's the pump. The truck has nearly a million miles on it with what looks like an original pump on it.
Now if I am not mistaken I think there is a 90 degree elbow on the back of the motor on the fuel return side. Is there an actual valve in there somewhere, or is it just a small hole that restricts flow to control the amount of system pressure?

 

Thanks. I wish i could get at the back of the engine to check and see if it might possibly be that check valve, but I can't without tearing apart half of the truck interior! Hopefully it is the pump 'cause I ordered one yesterday. Should be here Thursday.

 

Cool. Makes sense. Thanks

 

Freightliner Columbia.
Hopefully the pump came in yesterday so I can change the old one out and see if that fixes my problem.
Cross your fingers.