This truck is getting me worried

[Xxl2]

Heres what i have done so far truck is a 1991 c 1500. 4.3. I changed the ignition contorl modual. New fuel pump relay. Also checked the conector pin A is hot. Thats the only one i found power on with the key turned to on. I have checked my new fuel pump works fine. What am i missing could it be the oil pressure switch . I has spark becuase when i pour gas down the throttle body it runs. My issue is the fuel pump dosent run. I turn the key it dose nothing. I have it sitting out side right by my door. Also i conected pin a to pin c. Didnt do anything. Then tried a to f nothing the flow chart was telling me issue with crt 120

 

[Xxl2]

Okay checked code is 54 and i am not getting a rpm reading on live data when i crank the engine

 

[RichLo]

I understand your problem is the fuel pump isn't running when the ignition key is turned on but that would have helped to be stated from the beginning.

How have you checked the new fuel pump? I assume jumping it straight from the battery?

 

[Caman96]

I have checked my new fuel pump works fine.

My issue is the fuel pump dosent run.

Is it grounded?

 

[Xxl2]

I flowed this flow chart. It says issue with ckt 120. Could it be the oil pressure switch.

 

[Xxl2]

I understand your problem is the fuel pump isn't running when the ignition key is turned on but that would have helped to be stated from the beginning. Sorry

How have you checked the new fuel pump? I assume jumping it straight from the battery? Yes i had a 12v battery checked it on

 

[Xxl2]

Ill check tommarow how the ground looks isnt it up by the front of the engine? I thought i saw it

 

[Das Hatt]

Ill check tommarow how the ground looks isnt it up by the front of the engine? I thought i saw it

Fuel pump ground is by the fuel tank on the inside of the frame rail.

 

[CumminsFever]

*dusts cobwebs from old obd1 memories* If I'm recalling correctly, the fuel pump gets triggered from ecm when you turn the key on for approximately 2 seconds. Then the ecm waits for notification that the engine is running. This occurs by 2 methods. 1- crank sensor indicating engine turning, or 2- presence of oil pressure via oil pressure sensor.
Crank sensors can go bad, but it'll still run because of the secondary oil pressure sensor backup.
The fuel pump won't be running all the time the key is on. That makes one-man diagnostics a bit difficult. My personal trick is to remove fuel pump relay and place jumper wire between hot wire and load wire, thereby sending power to the pump. If the pump does not operate in this scenario, you have constant current being supplied to the pump, and you can then check if you have power to the pump.
These trucks are getting older, and on my 94, I just had a tail light issue that turned out to be a broken wire in the harness under the cab. I jammed a long extension between brake pedal and seat, grabbed test light, probed wire until I found the dead area.
I hope this gives you some ideas!

 

[Xxl2]

Thank you to everyone who helped. I finily found my issue My grounding strap on the driver side is broke. When i hooked my ground upo to the trans case the fuel pump came on. Ill be replacinging my ground strap tommarow i am looking for any other broken straps this is a 91 so its pretty old.