No start TBI - fuel pressure drops to zero after priming

[PlayingWithTBI]

If the diaphragm failed, wouldn't there be gasoline pouring out the bottom of the regulator?

Yeah, that too.

 

[haroldwca]

If the diaphragm failed, wouldn't there be gasoline pouring out the bottom of the regulator?

No. It's internal in the throttle body unit, not a self contained regulator like some vehicles have.

Desert Old Guy, I missed the mention of the 12 psi. That would indeed eliminate the regulator as a culprit.

 

[Schurkey]

The underside of the diaphragm is what the regulator spring presses against. The spring housing is vented.

A hole in the diaphragm fills the spring cavity, drains out the vent. Gasoline all over.

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The vent in the spring housing

 

[Griffin Meeks]

I had a similar problem in my 1992, where I had fuel pressure and the truck would crank, but not start. It ended up being a blown fuse from me not being careful with my pick as I was playing with wiring harness.

Look for the 10 amp fuse labeled "INJ A + B." It provides power to the injectors when the key is on. If the fuse is blown, it could be because the insulation on the power wire wore through somewhere and shorted the circuit to ground (there's also a possibility that one of the coils has shorted in the injector, though I'm not sure that would be enough to blow a fuse, considering the injector are only on for milliseconds at a time).