94 Ranger Fuel Pump wiring pinout

[ThatGuy1988]

I need a wiring pinout for the 4 pin connector on the fuel pump assembly so I can bench test the pump. I think I have an electrical gremlin causing my fuel pump to not work. On the connector, I measure at Ground (4) and The 2nd wire in and only see 8 volts with the key in the on position, and 5v on the wire next to it (The one next to ground). The battery does have 12.5V on it but it is an older battery.

 

[Curious Hound]

I don't know which wires are in which pins. But...

Pink/Black wire is power to the pump>Battery voltage
Black wire is ground for the pump
Yellow/White wire is power for the level sender > 5volts
Black/Yellow wire is ground for the level sender

8 Volts means there is a dirty or loose connection somewhere.

With engine OFF the pump only gets voltage for a few secinds when you turn the key on. You will have to jumper across the relay contacts or use the diagnostic connector to get continuous voltage for troubleshooting.

 

[Heather’s94]

Perfect timing. While the bed is off, going to swap fuel pump and fuel filler anyway.

 

[ThatGuy1988]

OK! Thanks to CH here, I was able to determine that I do not have bad wiring. The fuel pump assembly is bad...nothing coming out of the sender, and the pump is weak or the fuel filter is clogged...or both. I also have three bad relays in the box. They click but too much resistance and it's causing the voltage drop I was seeing. I jump the relay and I get the full 12V. I was intending to replace the fuel pump assembly in time, but now that I have the bed off, now may be the time to replace the crunchy filler neck, and drain the tank.

 

[Curious Hound]

I'm curious what you mean by "nothing coming out of the sender."

 

[ThatGuy1988]

It's not sending anything to the fuel gauge. It's always shown Full.

 

[Curious Hound]

It's not sending anything to the fuel gauge. It's always shown Full.

Ok. By switching your meter to read ohms, you can see what the resistance is across the 2 pins for the level sender. (Connector unplugged). It should read somewhere between 145ohms (full) and 22.5 ohms (empty), depending on how much fuel is in the tank. If you take it out, you can move the float to either end of its travel and should get those values. If that is good, then something else is wrong. I believe the slosh module sends 5 volts to the level sender. I was just looking for something to confirm that. But haven't found it yet. That is why I felt that the 5 volts you measured earlier was good (for the fuel level). Maybe another old-timer can confirm that for us. The 5 volts is used because 5 volts can not produce a "hot enough" spark to ignite fuel vapors if there is a problem with the sender.