hi all,
i'm new here, and have a question or two about my motor. '94 250 318 or 5.2 motor. i'd like to know about the air pressure within the intake fuel line for this motor. how much air pressure should be in this system? thanks for any info. rick.

 

Carb, TB injection (2 injectors), or MP fuel injection (8 injectors)?

Are you asking what the intake vacuum reading should be or the what the fuel pressure should be?

 

Hey Alloro,
its the intake with 8 injectors.
MP fuel injection, what does the MP stand for?
thanks rick.

 

Intake vacuum should be around 20 at idle.
Fuel pressure should be around 45 psi at idle.

MP - Multi-Port or MPFI - Multi-Port Fuel Injection. This means there is one injector per cylinder. The fuel gets mixed with air right at the intake valve of each cylinder.

TB - Throttle Body or TBFI - Throttle Body Fuel Injection. This means there are two injectors mounted in the throttle body on top of the intake which serves all of the cylinders. It's kind of like a high-tech carb where the fuel gets mixed with the air as it enters into the intake.

 

hi allaro,
thanks for the info.
onthe gas filler, on the driver side tube of the intake, there is a round tube with the airfiller valve, just like a filler valve of a tire, than a tube that goes up over the intake than another round fuel tube that feeds the passenger side. this air filler valve within the fuel delivery system is what i'm wondering about, the airpressure.
later on, rick.

 

That's the port for connecting a fuel pressure test gauge to. Those lines contain fuel, not air. If you were to connect a fuel pressure gauge there, it should read about 45 psi at idle.

 

it's called a schrader valve... press it and fuel should come out. no fuel means your check valve on the fuel pump is most likely bad and the fuel is draining back down the lines away from the fuel rail. if you turn the key on 1x you should hear the fuel pump turn on for about 2 seconds, then off. after that you should have the 45psi @ the rail.

 

steve and alloro; thanks a lot for the info, you've been real helpful, & happy holidays to all!
steve my van responds exactly as you described, i'm worry free now, on that schrader valve.