No fuel from fuel pump

[jamox2]

I am new here. I am having trouble finding out why my 4.0 will not stay running. I do not have enough pressure at the fuel rail. If I connect direct 12 volts to the fuel pump, then start it everything works fine. When I check the power going to the fuel pump it supplies 12 volts long enough to read it then goes back to zero. Fuses in the PDC are all good along with the ones behind the glove box. I have swapped and checked the relays, and they seem to be working fine. I don't know what the pins are coming out of the PCM to check for power. I am thinking I might have a pcm issue. Any suggestions? Thank you in advance for any help. I miss my Jeep. The hurricane just came through and I would like to use it to help clean up.

 

[Wildman]

I am new here. I am having trouble finding out why my 4.0 will not stay running. I do not have enough pressure at the fuel rail. If I connect direct 12 volts to the fuel pump, then start it everything works fine. When I check the power going to the fuel pump it supplies 12 volts long enough to read it then goes back to zero. Fuses in the PDC are all good along with the ones behind the glove box. I have swapped and checked the relays, and they seem to be working fine. I don't know what the pins are coming out of the PCM to check for power. I am thinking I might have a pcm issue. Any suggestions? Thank you in advance for any help. I miss my Jeep. The hurricane just came through and I would like to use it to help clean up.

Stock your pump is only going to run for a few seconds when you first turn the key on & then supplies fuel once the engine is running.

Factory Service Manuals area located here and you can find the wiring diagrams & pinout charts in them.

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

 

[macleanflood]

When you hotwire the fuel pump what pressure do you get?

-Mac

 

[MIGHTY97TJ]

Fuel pump relay is a good start.