Fuel, Spark and Air...still does not turn on

[Simkins12]

1990 with the 4.0L. Checked other threads regarding this issue and did what they said in terms of troubleshooting and/or replacing the part. Ranger still does not start.

A little history:

I changed plugs & wires (Motorcraft and gapped correctly); changed fuel filter all about 4 months ago. Ranger was running great, no starting issues, no rough idle or it cutting out.

About a month ago, the Ranger got harder and harder to start. I could start it, but after trying many many times. Once it was running it was fine. I could shut if off and then come back and it would fire up.

Finally got to a point where it will crank and crank but not start. So I started listening for the whirring of the fuel pump...I heard it but it sounded weak.

What I have done so far:

-New fuel pump (complete hanger assembly with strainer)
-Checked that I do have spark at each of the cylinders
-No burned or frayed wires or bad spark plugs
-Gap on spark plugs is set to factory specs
-Battery terminals and battery are good and clean
-No Inertia Switch; it was removed and bypassed by previous owner; wiring and connection is tight and making contact
-Replaced fuel pump relay
-Fuel pump relay fuse is good and new
-Plenty of fuel in the tank
-Cleaned/inspected IAC

After all of this, engine cranks but does not start

With the new fuel pump relay and new pump, it is not coming on at all. I am not getting fire at the fuel pump harness connector.

This definitely seems like electrical, where else can I check between the fuel pump relay and the fuel pump?

Can the system be OPEN? It just seems that the issue kept deteriorating rather than an all out fail of a part.

Any help is greatly appreciated.

 

[adsm08]

There could be a wiring issue to the fuel pump. The problem with testing voltage to the pump is that it only gets a brief prime and then its off until the engine starts. The best way to test power is to unplug the pump and hook up a headlight bulb in it's place, then turn the key and see if the light comes on.

There is also the possibility that the PCM relay, the PCM itself, or the inertia switch have failed. All of them are part of the fuel pump's power flow.


You might also have a wiring issue.

 

[RonD]

Fuel pump 12v wiring

Battery + -------Fuel pump fuse----fuel pump relay------inertia switch--------fuel pump----Ground

Fuel pump relay gets 12volts when key is ON, computer(PCM) is the Ground control for this relay.
When key is turned ON, PCM Grounds the relay for 2 seconds, it closes and 12v from fuel pump fuse passes to Fuel pump for that 2 seconds.

There is a tester for this PCM Ground, on the OBD I test connector.
Look here: http://www.therangerstation.com/tech_library/OBD_I.shtml


You will see a diagram of the OBD connector
The connector is in the engine compartment by the firewall on the drivers or passenger side.

In the diagram of connector the fuel pump slot is shown
If key is on and you Ground that slot you are doing what the PCM should do, ground the fuel pump relay, you should hear a "Click" and if everything else is OK the fuel pump should start.
If this happens then PCM could be bad or have a bad Ground so can't control the relay.

If you hear the "click" but no fuel pump sound then the 12v wire to pump is bad OR......the fuel pumps Ground is bad, that one is often overlooked.
12volts is only 12volts if there is a 0volts(ground)
On some Rangers the fuel pump is grounded on the frame near the tank, on others it is grounded near the inertia switch in the cab.

This is a wiring diagram for 1990 4.0l and shows the wire colors and VIP test port Ground for pin 22 or PCM: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Enginecontrols4_0_3_0_1of3.JPG

 

[Simkins12]

Thanks for the replies. Checking things now using the info provided.