92 Ranger 4.0 Fuel Delivery Issue

[Deppdog]

I have a 1992 Ranger with a 4.0. It has always fired right up, but the last couple of weeks it has taken a couple of cranks. All of a sudden it just wouldn't start. I found a split in the fuel line on the engine side of the fuel filter and have replaced that. It started up right after and I drove it 20 or so miles since then. Ran an errand yesterday morning, came back out and it wouldn't start. A few minutes later it started, ran fine but hiccupped a couple of times on the way home. This morning, started right up, but now will not start at all. Fuel pump is turning on, fuel is getting to the fuel rail, starts with starting fluid into the throttle body. Haven't had time to look at it any closer than that yet. Just looking for advice on where to start. Check the fuel pressure at the Schrader valve & check out the fuel pressure regulator? I would assume since there is some fuel pumping, that at least the relay and inertia switch are working properly. Any thoughts or ideas would be appreciated.

Thanks in advance!

 

[TxGasRacer]

http://troubleshootmyvehicle.com/ford/4.0L/how-to-test-the-fuel-pump-1 http://easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/fuel-pump-relay-tests-1 http://troubleshootmyvehicle.com/ford/4.0L/how-to-test-a-no-start-condition-1

 

[RonD]

Have you checked new fuel line for leaks at the fittings?

Ford only runs the fuel pump for 2 seconds when key is turned on, it is a safety feature, after engine RPMs are above 500(engine started) the fuel pump comes on and stays on.

Fuel pressure should be above 25psi at the rail even if truck has been sitting for several months, there are 2 things that hold system pressure, the fuel pump has a Check Valve on it's outlet, basically a flap so fuel can be pumped out but can't flow backwards, and the Fuel Pressure regulator(FPR), this is a diaphragm valve held closed by a spring, spring will hold against 45psi above that it opens slightly, FPR is on the fuel rail and connected to the Return Fuel line, it also has a vacuum line attached, when engine is off FPR valve is closed to hold system pressure, when engine is running the vacuum will pull open the valve and allow excess fuel to flow back to tank, at idle fuel demand is lowest and vacuum is highest(valve opens more), when accelerating fuel demand is highest and vacuum is lowest(valve closes more).

Fuel injectors and fuel lines can also leak and pressure will bleed off.

To test if fuel pressure is being lost, turn key on and count to 3, then turn key off, repeat this 3 times, then try to start engine.
Each time key is turned on fuel pump runs for 2 seconds, and that should increase pressure 10psi, so 3 times on should give you 30psi at fuel rail.
If engine starts every time after doing this then you are losing pressure when engine is off, check for leaks, check vacuum line on FPR for fuel(leaking FPR diaphragm).

 

[Deppdog]

No leaks on any of the fuel lines. Everything seems to be working. Fuel pump cycles correctly. If I cycle key on / key off several times, it is still no start but there is fuel pressure in the rail and what does come out when I open the Schrader valve seems minimal to me, but I won't be able to do an actual pressure test until the weekend. Hopefully its just the FPR and not the pump itself.

 

[Deppdog]

Still fighting this thing.

My no start issue continues. I put a fuel pressure gauge on the rail today. It went up to about 45 psi and held for quite some time and never dropped below 40 psi. Still, it is acting like it is not getting fuel and the plugs are dry. When I squirt starting fluid in, boom...fires right up and will run until it burns it up. I am at a loss. Any suggestions?

 

[RonD]

Now reads like fuel injectors are not getting signal to open.

The fuel injectors all get 12volts when key is turned on, this voltage comes from the EEC Relay, EEC relay also powers the computer(EEC) and coil, so if coil is working, i.e. starting fluid starts engine, then that means EEC Relay is working, computer and Crank position(CKP) sensor are working.
CKP sensor tells computer when to spark #1, #2, ect....

If you have a Cam Position sensor(CPS) then each fuel injector will have a "Ground wire" that runs back to the computer, sequential fuel injection.
If no CPS then there will only be 2 "ground wires" going back to the computer, batch fire injection(3 injectors are opened at the same time).

You can test if fuel injector has 12volts with key on, if connected either wire should show 12volts(battery voltage) if disconnected then just 1 wire will show 12volts, usually a red wire, red wire is just daisy chained from one injector to the next.
Injectors are only 14ohms, also most a dead short(0 ohms), so if connected that is why both wires would show 12v.

Injectors make a distinct "tick" when they open and close, Fords almost sound like a bad lifter sometimes, lol
With dry plugs I am betting injectors are not opening.
If you have a stethoscope or long hose you can put against injector and your ear, you will be able to hear injector "tick" when engine is cranking, if they are working.

You can try hooking a test light to an injector's wires and then cranking engine to see if light flashes(computer is grounding other wire)
BUT............that often doesn't work since the pulse(ground) is so fast.
You really need a Noid light to test if injector is getting a steady pulse.

 

[Muslhound]

45 psi is to much on a pic 4.0. Check your fuel pressure regulator.

 

[Deppdog]

Injectors

So, I disconnected the one injector that I could reach. I have 12 volts on both sides of the plug. I plugged a NOID light in and nothing when I cranked it over. Listened with a stethascope to the three injectors I could get to and am not hearing anything. Stumped again at this point.

 

[Deppdog]

Mystery Solved

Mystery solved! We have been having a pretty serious rodent problem around here! Squirrels, ground squirrels...you name it! They have chewed up more wiring than I even care to speak of. Anyway, I seem to have a short somewhere around the intake manifold. Guess I will pull it off and mend some wires! After that, squirrel hunting! Thank you to everyone for your advice and help!

 

[RonD]

Stop feeding the cats, let them hunt the rodents

Anyway, if you look here: http://www.therangerstation.com/tech_library/EDiagrams/index.htm

Then click on "3.0/4.0 Electronic Engine Controls - 2 of 3", you will see the fuel injector wiring for Batch Fire setup.
the Tan(T) and White(W) wires come from pins 58 and 59 on the computer(EEC), they control the Grounds that open 3 injectors at the same time, since no injectors are working at least those two wires are bad could even be problem at computer end of harness.


This is a general EEC-IV pin out diagram: http://www.auto-diagnostics.info/ford_eec_iv