Ok so I just drew this out and it leads me to to points. Either the relay isnt getting coil voltage to close the main contacts, or the wire off of pin 8 of the relay to the pump is open. Quick jumper to ground one end checking for the ground on the other end will rule that out. BUT.....BUT the other possible cause could be the coil voltage. The fuse to the coil is good, so quick check in socket 4 for the relay will prove voltage is present....the return out of socket 6 goes to the PCM. Here is my question, is it the PCM's job to provide a ground when the key is in the run or start position thus making the coil energize and closing the voltage feed contacts to the pump?

Thanks.

 

The fact that it wouldn't turn over in neutral would make me think somethings going on with the NSS. Electrically the same pins that are connected in park are also connected in neutral. How about running through the different selections on the shifter and see if it turns over anywhere other than park.

 

Tburk

Here's the NSS pinout

 

Swap the ASD relay in the PDC. That's linked in as well.

Rob

 

Ok, well when I jumper voltage to the pump is comes on and I have fuel pressure. Still wont start though. What is the relationship of the CPS to the PCM and timing? I verified that I had spark yesterday (on cyl 6) and now I have gas....the fact that the PCM isnt allowing the relay to turn on and its relationship to the firing timing does it look towards a faulty PCM?

I'll run out to verify the N switch also! Thanks for the pin out of it.

Todd

 

Still only turns over in P none of the other shifter positions. In fact after I cycled through all of them and went back to park I wouldnt turn over then either. I waited a couple mins and it would turn over again in P only.

I put in a different relay in the ASD relay socket before doing all of this as well.

 

How did you test at the pump connector? Meter or test light? You tested between the 2 pins?

Another option for test would be to ground the test light lead to the frame and test the DG/WH wire for +12, then put the test light lead to a +12 source and test the BL wire for ground.

 

In a nutshell, yes.

Fuse 22 in the PDC is permanent positive feed to the fuel pump relay.
Fuse 11 in the Junction Block is ignition switched positive to the fpr coil.
Switched output from the fpr feeds the fuel pump.
The PCM switches the negative to the frp coil.

Rob

 

I tested the plug with a meter and got 12 V between the darkgreen/white and the black wire. I had 5 volts from the BL/GRN to BRN/YLW (fuel level ckt). I also checked the DG/W then the BL wire to ground with no voltage applied. When I jumpered the relay outputs I heard the fuel pump kick on and verified I had fuel at the rail. This was with the jeep in P and the key in the run position.

I may be barking up a tree here, but I have to think that when I have it all hooked up normal and I dont get the pump on (i.e. no relay coil voltage closing the contacts and sending 12V to the pump) and the PCM is tied into that ckt, that there may be something going on there? If the CPS was bad wouldnt I not have any spark?

Do replacement PCM's need to be programed to your VIN?

 

Todd

PM sent

 

Just read in my manual that both the ASD relay and the fuel pump relay will be energised for 3 seconds only, when the ignition is switched on (unless engine running or starter engaged).

Rob

 

Also;

If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the
engine, it will shut down the fuel injection system.

Rob

 

Todd

PM's and email sent

 

I dont even get the fuel pump to run for 3 seconds turning the key on (only when I jumpered voltage to it) and I checked the CPS pins B and C and read an open so I have to assume Haynes is correct in saying It should read open.

And all the stuff Ive looked at offline of cherokeeforum points to a lot of stuff going on in the PCM? Is this something I can buy used to reduce my out of pocket expense or do I actually have to buy one programmed to my VIN?

Thank you again everyone for showing interest in helping me work through my situation.

Todd

 

Todd

Did you get the emails?