Fuel problems, won't continue running after startup

[franklin2]

UPDATE: This morning, it again started right up and continued running. I took it for a short, easy ride down our lane and back and there was no indication of any problem. Then I took it out on the county road and drove it normal until it warmed up and then turned around and drove it hard -- up a hill, full throttle, foot to the floor, winding out each gear (shifting at about 5,200 rpm). Not a single indication of a problem, it was exactly as it has always been. If I hadn't experienced the last few days with this issue, I'd say there was nothing wrong. I find it difficult to believe that replacing the fuel filter had any significant impact on this situation.

I greatly appreciate all the time spent sharing your thoughts. At this point, I feel to monitor this for a while. Thanks to "HawaiiMud" on another forum, I found the test fitting (it is on the back end of the passenger-side fuel rail -- see photo) so I'll get a tester and check the pressure. Assuming that is good, I'm going to wait and see if I have another instance of the "won't start after coming back out of the store". If that happens, I'll call it done and replace the fuel pump.

View attachment 57944

When you get your tester and if it tests good, keep the tester behind the seat so you can test it real quick when you have a problem. If you do that, you will never have the problem again

 

[RodBarnes]

When you get your tester and if it tests good, keep the tester behind the seat so you can test it real quick when you have a problem. If you do that, you will never have the problem again

I call that the "umbrella policy" -- like carrying an umbrella with you so you know it won't rain.

 

[RodBarnes]

Harbor freight has a fuel pressure tester for $24.00

UPDATE: I purchased this kit and it worked great. Read 65 psi running, 61 psi after turning off the engine, and leak-down to 59 psi after 5 minutes.

 

[RodBarnes]

BTW: Out of curiosity, I cut open the old filter 'cause I wanted to see how it worked. Got it open but wasn't successful seeing anything about how the return mechanism works. But I did confirm the filter was pretty brown, so seemed pretty dirty.

 

[RonD]

The return line in the filter has no "mechanism", its just an OUT back to Fuel Pressure Regulator in the fuel pump assembly

 

[RodBarnes]

@RonD Can you explain then how the return mechanism works? There has to be something that determines that the fuel pressure is sufficient and then "opens" the return line (or whatever) so the fuel goes back to the tank instead of to the engine. In another thread, you said the Ranger doesn't have a fuel pressure sensor. Is the return activated by the fuel pump mechanism in the tank? So if it senses an increase in pressure there it then opens the return line at the tank end to allow fuel to return to the tank?

 

[RonD]

On the 1997, and earlier, EFI Rangers there was a Fuel pressure regulator(FPR) on the engine

(gas tank)Fuel pump-----------filter------------engine fuel rail===injectors===(30psi)FPR-----------------(gas tank)

So if pump is capable of say 80psi, the FPR lets out any pressure above say 40psi, so pressure at the injectors is stable, at 30-40psi regardless of fuel demand

On the 1998 and up Rangers the "Returnless" system moved the FPR to inside the gas tank, so still a return just heats up the fuel less, it also used higher fuel pressure

(gas tank)Fuel pump---------/filter--------------------fuel rail===injectors
(gas tank)FPR(60psi)--------/

So pump sends out 80psi to filter, but the FPR lets out 20psi keeping pressure at injectors stable at 50-60psi

I think Ford did try a true "returnless" with FPR in the tank but ON the fuel pumps OUT hose, for a few years
I think the pressure fluctuated too much at the injectors with that system
Also tried FPR on the IN line at the fuel rail/engine, no return, but caused fuel pumps to run harder and fail earlier

An FPR in these is just a spring holding a valve closed until spring is pushed open at the set PSI for that FPRs rating(spring size, lol)


Then in full size trucks they used a Fuel Pump Driver module to eliminate a return, computer would power the pump on and off to try and maintain a consistent pressure at the injectors
That system can work but the driver modules had problems, common failure point, may be a bad design??

I think overall its best to just power the pump full time when engine is running, and let it run at max flow/pressure, and then Return unneeded flow/pressure back to the gas tank
Electric motors work best when left on and at normal RPMs, constant on/off or limiting flow/rpms would cause problems in my opinion

To maintain good operation the computer needs a consistent pressure at the injectors, +/- 10 psi is OK
Needed because computer calculates injector open time based on pressure and size of injector

 

[franklin2]

Then in full size trucks they used a Fuel Pump Driver module to eliminate a return, computer would power the pump on and off to try and maintain a consistent pressure at the injectors
That system can work but the driver modules had problems, common failure point, may be a bad design??

I think I read something about that system and the failures. One of the big reasons was the location of the module, above the tank area in all the road salt/debris under there.