Fuel pressure regulator???

[timfost85]

Hi all,

I'm not a frequent poster here, but I do really appreciate your advice when I have issues with my truck.

My 93 Ford Ranger (4l 4X4) wouldn't start the other day. I checked for spark, and narrowed it down to a fuel delivery problem. I lifted the bed and hardwired the fuel pump directly to a 12 volt battery. It did turn on. After I pressurized the line. I then turned on the vehicle and it started for a few minutes and shut itself off. After this, I would start it and it would only run for about 5 seconds. Since the fuel pump seems to work, I'm guessing that the fuel pressure regulator might have an issue?

I took a look at it today and pulled off the (vacuum?) line attached to it which was very loose. It seemed like there was some kind of fluid inside of it.

1. Am I on the right track with the FPR?
2. Is the (vacuum?) line to the FPR supposed to have fluid?
3. Anything I'm missing?

I also put a new battery and fuel filter in it. Thanks in advance for your help!

 

[Mark_88]

There is a vacuum line on the FPR and if there is gas in the line then that is the problem. It is a vacuum line and if the diaphragm in the FPR ruptures it will allow fuel directly into the intake...which will flood the engine and cause fuel delivery issues.

So...YES...replace the FPR if that is gas in the vacuum line...

 

[RonD]

Not sure if you are on the right track but the vacuum hose on FPR should be dry inside.

FPR is connected to the fuel rail and Fuel Return line, this line sends unused fuel back to gas tank
There is a spring inside the FPR that holds Return line valve closed until is it pushed open by fuel pressure above 42psi(approx.)
On the other end of the spring there is a diaphragm and vacuum chamber.

Since fuel demand changes quickly by RPMs and throttle position the computer would have a hard time adjusting fuel mix if pressure wasn't stable.
Engine vacuum is high at idle(low demand) and low when accelerating(high demand)

So engine vacuum is used to pull spring back, running engine pressure averages 30-35psi, at idle or while accelerating.

If diaphragm is leaking fuel then that fuel would be sucked into the engine via vacuum hose, which would cause Rich fuel mix.
Fluid in question could just be condensation, so smell it and check the vacuum hose for gasoline smell.

If FPR spring or valve failed then no fuel pressure could build up, so test for that.
There is a fuel pressure test port, schrader valve on the fuel rail, press center pin in to see if there is pressure in the rail, be careful, 30psi can spray fuel a long way, so COLD ENGINE is when you test.
Cycle key on and off a few times, fuel pump runs for only 2 seconds each time key is turned on, but you should get 10psi pressure added for each 2 second run time, if its not being lost at FPR.
So after cycling key off and on test for pressure at schrader valve, then wait a few minutes and test again, to see if its losing pressure when it sits.

Inside the fuel pump is the Check Valve(back flow preventer), this holds pressure in the system when pump is off.
A fuel injection system will hold pressure for MONTHS, not minutes, hours or days, MONTHS AND MONTHS, lol, so after a vehicle sits for 6 months it should just start up, assuming battery is OK

Change fuel filter, if it is clogged up it will let gasoline filter thru slowly over time, but once engine is started that limited amount of fuel will be used up fairly fast and not enough gasoline can get thru filter fast enough so engine dies and won't restart until it sits long enough for more gasoline to get thru filter.
Same situation can happen to fuel pumps "sock"/filter
Fuel pump itself can turn on but not pump very much fuel, because of impeller damage or motor speed.

 

[85_Ranger4x4]

Does the fuel pump run without being hardwired?

There is an inertia kill switch on the passenger side floorboard that kills power to the fuel pump in the event of a wreck. The one in my parent's '94 Explorer came unplugged once.

Make sure you have power to the pump...

 

[adsm08]

Just as a point of grammar, a "vacuum" line shouldn't have anything in it, ever. Otherwise it wouldn't be a "vacuum" line, it would be an "other thing" line.

 

[adsm08]

Inside the fuel pump is the Check Valve(back flow preventer), this holds pressure in the system when pump is off.
A fuel injection system will hold pressure for MONTHS, not minutes, hours or days, MONTHS AND MONTHS, lol, so after a vehicle sits for 6 months it should just start up, assuming battery is OK

Actaully, according to Ford it is considered "In spec" for a return type system see a sharp drop when the pump is turned off and then to loose up to about 1 PSI per minute down to 5 PSI where is should stay.

 

[timfost85]

Does the fuel pump run without being hardwired?

There is an inertia kill switch on the passenger side floorboard that kills power to the fuel pump in the event of a wreck. The one in my parent's '94 Explorer came unplugged once.

Make sure you have power to the pump...

Yes, I checked this. Thanks!

 

[timfost85]

Just as a point of grammar, a "vacuum" line shouldn't have anything in it, ever. Otherwise it wouldn't be a "vacuum" line, it would be an "other thing" line.

Haha, yes, I know. It looked like a vacuum line but when it was filled with fluid it caused me to second guess.

 

[timfost85]

Thank you all for the advice. I ordered a FPR online. I'll update you with the results once it arrives.

 

[timfost85]

I replaced the FPR and it's still not working. Measured voltage with a voltmeter and found out the fuel pump isn't getting enough juice (about 8 volts). My current plan is to run a new line from the relay back to the fuel pump. (Ugh, I hate wiring issues!)

The line to the FP is relay terminal 87, correct? If so, 87 has two wires coming out under the relay (see pic). Could someone please help me 1) determine if I have the right wire and 2) explain why there are two wires? Would I cut only one of these wires to splice the new one?

FYI (in case you haven't already noticed), I'm fairly ignorant when it comes to wiring, so please explain accordingly.

Thanks!

 

[timfost85]

I had my mechanic rewire the fuel pump. It's running like a champ. Thanks for brainstorming with me.