Engine Performance problem
1989 Ford F150 6 cyl Two Wheel Drive Automatic 188000 miles
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4.9 liter EFI F150 (1 fuel tank with 2 fuel pumps - 1 on rail, 1 in the tank.)

Engine shuts off intermittenly while parked, runs better while in gear with parking brake on but in park then it shuts off. I'm wondering if it's fuel pressure or electrical. Replaced fuel pressure regulator and symptoms have not changed.

Would like to know how to check fuel pressure? Can't locate valve stem to hook gauge on.

Can something happen internally with the idle solenoid switch to affect vehicle turning on and off?

Given any thought to a transmission problem?
Does it start in park and idle?
Will it stay running in neutral?
When it stalls is it sudden like key off or slow death like low fuel or something bogging engine down?

Transmission I think is okay, it will sit and run sometimes, sometimes won't

Yes it will start in park and neutral and idle for 30 seconds and shut off, 2nd time start in neutral and it ran for a minute and half, then shut off. Then restart this time and it continued to run in drive, neutral and park with no hestitation.

Will it stay running in neutral? Sometimes

When it stalls it is sudden like key off, yes ~ then sometimes when you restart it right away, then it feels like it's not getting fuel.

I don't know where on the fuel rail is the valve stem for the pressure tester?

Thanks for your help..