91 2.9 not running

RonD said:

Yes, fuel pressure would have been the thing to check first if it was firing with starting fluid.

'91 should have 30-40psi at the rail.
The 2 things that hold the pressure are the Check Valve in fuel pump, and the Fuel Pressure Regulator(FPR) on the fuel rail.
Check valve is basically just a flap on the output of the pump, when pump is off(key off) the flap closes to prevent fuel from flowing backwards.

FPR uses a valve, spring and engine vacuum
FPR is connected to fuel rail and Fuel Return line.
When engine is off spring holds valve closed so fuel can't go into the Return line.
FPR also has a vacuum hose, when engine is running(fuel pump is on) the intake vacuum pulls valve open, at idle vacuum is high and fuel use low, so FPR valve is open quite a bit, when accelerating or at higher RPMs the vacuum is low so valve closes maintaining approx. 35psi fuel pressure.

First check vacuum hose on FPR, if valve is leaking there will be fuel in that hose, replace FPR if there is.

On the fuel rail there is a Schrader Valve, this looks like a tires air valve because tires use Schrader valves too, lol.
If you push in the center pin fuel will spray out, same as air would on the tire, and at 30psi there would be alot of pressure, same as 30psi in a tire.

Fuel system should hold pressure for a few months, not minutes, hours, or days.

Fuel pressure gauge isn't expensive, $15-$25, but just testing for pressure by pushing in center pin can tell you alot, but be careful, fuel is flammable and if pressure is good it can spray 30+ft

You could also remove the Return line from FPR, put a towel down under FPR outlet, turn key on, fuel pump should run for 2 seconds then shut off, that is normal, if fuel comes out of FPR and continues to come out, so 0 pressure left in rail then replace FPR

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RonD said:

That would be FPR failure or Fuel pump's check valve.

Unless there is a pool of gas at the engine or under the truck

Check vacuum hose on FPR for gas first.
The Fuel Return line is connected to the FPR as well, you can squeeze it closed with vise grips, although you need to be careful not to damage the hose, this would prevent gas from flowing out of broken FPR valve.
If system holds pressure with Return line pinched off, or there is gas in vacuum hose, replace FPR.

If there is no gas in vacuum hose and pinching off Return Fuel line still shows 0 pressure after pump shuts off then Fuel pump will need to be replaced.

In the fuel tank the pump does connect to a lift hose that then connects to the outlet hose on the outside of the tank.
The lift hose can crack, this would also cause the loss of pressure without the smell of gas outside the tank.
Long shot but not a no shot, and you would still need to get into the tank to check it out.

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RonD said:

"New" used to mean "tested and works"

"New" now means "never tested but warrantied", we are the Quality Control Department for most manufacturers now.

So ".....the Fuel Pumps is new", is more of a "hmmmmm", than a "well that's not the problem" thing.
If the fuel pump was 5 years old, so fairly new but not "new", that would be the less likely failed part IMO

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