1994 ranger 3.0 no fuel pressure

[trueblue2]

1994 ranger 3.0.Fuel pump runs with KO,EO then pump turns off as if normal,but there is no pressure at test port.
Engine turns over like normal,with new starter,battery,cables but will not start.
No fuel in vacuum line going to fuel pressure regulator.
Is there a pressure switch in the fuel pump,or elsewhere?
What tells the pump to turn off?
A sensor somewhere that I cannot find?

Thanks in advance for all assistance on this matter.

 

[RonD]

Welcome to TRS

Fuel pump comes on full time when engine RPMs are above 400
Cranking speed is 200rpm

There is no "driver module" that shuts off fuel pump once engine starts, its on full time
There is no fuel pressure sensor on Rangers

Fuel pump can run but not pump fuel, odd failure mode but can happen
Completely clogged fuel filter would also result in 0psi fuel pressure

Remove the larger air tube on the intake and spray fuel directly into the engine
Called 50/50 test
If its a fuel issue engine will start and run until the fuel you added is gone
But RPMs will be above 400 so fuel pump will be on full time while engine is running so should provide pressure at the injectors to keep it running

If engine stays running then your FPR(fuel pressure regulator) may be bad
The pump can provide 80+ PSI fuel flow
FPR is set for 43psi, so the extra fuel flows thru the FPR and back to the gas tank
If the FPRs valve is stuck open the fuel pressure should still stay above 20psi to keep engine running once its started and fuel pump is on full time

If engine just starts runs and dies then its a fuel pump issue, probably not FPR issue

 

[trueblue2]

The fuel pump turns on with key in "on" position,and then off after a few seconds,which indicates fuel pressure has been reached?But no pressure when I depress the Schrader valve at the injector rail,even when holding the key"on". What tells the pump to turn off? Is there a pressure switch somewhere that turns it off when it reaches a certain pressure?
Thanks again for your valuable time and attention to this problem.

 

[RonD]

No, the computer turns the fuel pump on for 2 seconds with key on, every time you turn the key off and on, it will run for 2 seconds, its a timer, there is no pressure sensor.
Its just to Prime the fuel system
Each 2 seconds equals about 10psi of added pressure

The Ranger fuel system should hold 15-25psi pressure with key off for MONTHS and MONTHS
The FPR closes and the fuel pump has an internal Check Valve so fuel can not flow backwards into the tank, backflow valve, aka check valve
So with key off system should hold remaining pressure for months and months
10psi is enough to start an engine if it can hold at 10psi with key on, it will stumble at start up but will start
Running pressure, pre-1998, is 30-40psi, 1998 and up is 55-60psi

 

[trueblue2]

Fuel pump runs for 2 sec,the turns off,as normal.When I check the pressure, it is zero
( I pressed the shrader valve detent,and got noting when switched on). I have friend hold key to run,still no pressure. Is this bad fuel pump or totally clogged strainer?How to isolate which one is bad?

 

[RonD]

One thing I forgot to mention is gas in the gas tank?
Gas gauge can not be trusted
Over my years working on vehicles I have spent useless hours diagnosing an EMPTY fuel tank
If anyone says to me "of course there is gas in the tank", then I send them out with a gas can and say "good, but get some more please", lol
If they say"not sure" then I will check if there is gas in the tank

Get a new fuel filter, they should be changed every 5 to 7 years regardless
Remove the old fuel filter
Try to blow thru it
Cycle key on to see if gas comes out, but be prepaired with a CLEAN pan or bucket to catch any fuel
If nothing comes out then bad pump OR............no gas in the tank

There is a primary filter inside the gas tank, called "the sock" its on the end of the pump and lays flat on the bottom of the tank to pre-strain fuel coming into the pump
These rarely clog but can
In any case you would need to access pump to check this