Truck cranks but will not start. Ran fine, shut off and left overnight, next day would not start. No stumble or pop. WOT, closed, partial, doesn't matter.

4.2L V6. Not equipped with anti-theft. Fuel topped and ran about 1/4 tank.

No codes
Fuel rail 40-50 lbs during ignition ON and crank
Fuel smell from exhaust after extended crank
Injected known good fuel behind throttle body, no difference
Fuel inertia switch button depressed
Good spark
Shotgun replace crank position sensor
Swapped around relays
Battery voltage nominal

Thoughts?

 

I'm assuming it is a 97-98 M/Y.

Have you checked the compression in the cylinders?

Those years were notorious for bad intake gaskets leaking coolant into the cylinders causing hydrolock.

 

More info...

KOEO results in P1000 and P1116. Hard to imagine that an engine coolant sensor would cause a no start.

 

When mine did that it was the relay that powers the computer.

 

How have you verified that you have good spark?

 

Removed #4 spark plug, connect plug wire to plug, ground plug case and crank. Also tried #5 spark plug. Both resulted in what I would consider to be healthy sparks.

 

Replaced new, it is not the P1116 ECT sensor.

Brake booster holds a vacuum. Vacuum lines do not appear to be compromised.

Plug #1 is also sparking.

Tailpipe is pumping air during crank. Was thinking a clogged catalytic and still maybe so, but at least some air is passing through.

 

In your first post, all items reported show normal operation.
Crank sensor should have not been replaced under those condition because everything was working including relays.
Assuming nothing was missed, the ECT code suggest a simple 'flooded' condition.
An ECT code can cause excessive richness because the sensor controls 'average' fuel delivery level at all times.
Be awhere on a V6 there may be two sensors. Be sure you got the one that feeds coolant temperature signal to the computer. At cold starting, the sensor indicates to the computer the coolant is cold along with the intake air temp sensor. This causes the fuel tables to be set rich, advances ignition timing and opens the intake Air Controller to raise the cold idle.
All the same things a carbed engine does with automatic choke.
I would be sure the motor is not flooded first before taking any other action.
The gas smell in the exhaust would be the tip-off because fuel injection does not just stop with a no start unless there is a fuel system fault or extended cranking without ignition. This would be a normal result.
Check the fuel regulator vacuum line for presence of gas. If yes it indicates gas is leaking by the vacuum side into the intake and causing excess richness.
Good luck.

 

If it's flooded, pressing the pedal to the floor will shut the injectors off.

 

Cranked numerous times and at length with WOT. Got the correct sensor; P1116 went away when replaced new.

The fuel regulator vacuum line check seems plausible.