Testing fuel pump wiring harness

[panamarojo]

So what pins should have how much volts? My haynes doesn't say. I know for sure one pin had 12 volts and one pin had 6 volts and one is ground, the other I am not sure.

Should I be getting volts with the key on the on position? or only when its cranking? Becuase I get this reading with the key on the on position.

 

[steve]

Please update your profile. I had to go digging to try and find out what car you have. I know we figured out it was a 91 but I don't know if it's AWD or FWD and no one should have to go digging for that information to answer a question.

On the 1G AWD cars:

Pin 1 thick black/white wire Fuel Pump power.
Pin 2 yellow wire Level sensor.
Pin 3 thick black wire Fuel Pump and Gauge ground.
Pin 4 yellow/blue Warning sensor.

On the 1G FWD cars: There are two connectors, one from the pump and the other from the senders merging into a single four pin connector.

Pin 1 yellow/blue Warning sensor. (pin 1 of the flat 3 pin gauge unit connector)
Pin 2 thick black wire Fuel Pump and Gauge ground. (pin 1 of the round pump connector and pin 2 of the flat 3 pin gauge unit connector)
Pin 3 yellow wire Level sensor. (pin 3 of the flat 3 pin gauge unit connector)
Pin 4 thick black/white wire Fuel Pump power. (pin 2 of the round 2 pin pump connector)

The fuel pump only gets power while cranking or engine running. During those times you should see battery voltage between the power and ground wires.

The level sensor and warning light have voltages on them any time the ignition is on. The voltage on the level sensor will vary depending on how much gas is in the tank. With the connector off and measure the resistance of the sender it should read between 3 and 110 ohms, full to empty.

The warning sensor has a voltage on it and will ground that once the gas drops below the empty point in the tank to turn the light on.

 

[panamarojo]

My bad Steve. I was up late and had this question in my head. Last time I ask question when I am falling asleep . But thanks, imma try and see if anything comes up different when I crank it. I just find it wierd I find the volts on the harness side when the key in on.

 

[steve]

I just find it wierd I find the volts on the harness side when the key in on.

Sounds like your still sleeping. There will be voltages on two the the wires when ever the key is on since both the warning sensor and the level sensor are active.

 

[CT_DSM]

What guage are the wires on the harness?