Perhaps you need to go back in the tank and have a look around for the check valve. I haven't been in one of these tanks myself but there's always the chance of a leak internal to the tank (o-ring, etc.) that is allowing the fuel to flow back as well.

https://dodgeforum.com/forum/dodge-r...-to-start.html

 

When I run the fuel pump with a shorted ASD relay output, the fuel pressure stays up at 14 psi. That removes all transients of start cranking or turning off the ignition. Not safe to run that way long term, but it's a pretty good test.. Either low fuel on startup IS the problem, or giving it more fuel sooner on startup is mitigating the effects of the real problem.

 

With the relay jumped, does the pump run constantly?

The pressure falling off immediately after depriving the pump of power is what concerns me. It really isn't supposed to do that.

 

Is there anybody out there that would be willing to "T" into their fuel line supply just before the carburetor and shoot a short movie of the CORRECT pressure? I'd love to see what a working van is doing. Is the idea that the pressure in the line *stays* at 14.5 PSI even after the engine and ignition is off for seconds, minutes, or days?

It seems really small chance that the old fuel pump failed by not checking back pressure, and then a new fuel pump just ~happens~ to arrive new with the same problem. I didn't notice any external check valve in the tank separate from the fuel pump. What a pain if I have to gamble that's the problem and tear down the entire tank again.

My backup plan is to buy a separate $9 check valve and put it into the line somewhere coming from the tank. If I ever get into the tank again, I could always remove the external check valve.

 

It should hold at least 10 PSI for several hours, if not a day or more...... And, I would point out, it's an AirTex pump...... failures right out of the box are not unusual.

 

Is there anyway you (or anybody else who reads this thread) could video their fuel pressure before engine start, start the engine, and then for about 15 seconds after the engine is turned off? In the meantime, sounds like I should go buy a check valve to put externally in the line from the tank.

 

And that may be all you need to do.

If you can find a service manual for the van, it will describe exact behavior for you. I don't have anything handy for TBI though.