1997 Jeep Cherokee 97 Cherokee sport died, won't restart

Tiny
JBEAU70
  • MEMBER
  • 1997 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 234,000 MILES
My 97 cherokee sport w/ 4.0 liter died going down the road. My gauges died as well, but other items on the dash kept power, like the radio. I put gas in the car and tried to start it but to no avail(Thinking it might be out of gas because my sending unit doesn't work right all of the time). I checked voltage for the fuel pump and found that it didn't have voltage. I also didn't record voltage at the coil. I had no fuel pressure at the fuel rail. I had no check engine light nor did I get a code after cycling the ignition on and off. While checking electrical connections under the hood, I found that when I unplug the front plug of the PCM, the fuel pump and electric fan both start running. I don't have a diagnostic tool but will consider getting one if that's needed. Thanks for your help!
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Thursday, April 15th, 2010 AT 9:23 PM

18 Replies

Tiny
RACEFAN966
  • EXPERT
Ok so if I understand correctly you have no power to the fuel pump at any time until you unplug the PCM? Is this correct? Also do you have a digital mutli meter? Do you have a way of checking fuel pressure if needed? Get back to me and we will take it from there. Also is this a standard cherokee or grand cherokee? It makes a difference.
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Friday, April 16th, 2010 AT 8:59 AM
Tiny
JBEAU70
  • MEMBER
This is a standard Cherokee, Sport package. I have no power at fuel pump until I unplug the PCM. I have an analog multimeter and I do have a fuel pressure test kit. I have not checked pressure but after I heard the fuel pump kick on I pushed the valve on the fuel rail test port and got a good stream. I did swap out the fuel pump relay with the cooling fan relay and visually inspected the fuel pump fuse.
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Friday, April 16th, 2010 AT 1:24 PM
Tiny
RACEFAN966
  • EXPERT
OK one more question before going through testing. Is the check engine light on? If so what code did you get? If you don't have a scanner simply turn the key on engine off three times on the third time leave key on and count the engine light blinks. Example 1 blink = 1 2 blinks =2 is you get one blink and short pause and 2 blinks = 12 then longer pause and next code. Let me know what you find and we will go from there.
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Saturday, April 17th, 2010 AT 8:05 AM
Tiny
JBEAU70
  • MEMBER
The check engine light is NOT on and I have no error code after cycling through the key on-off sequence. I picked up a digital multitester yesterday, btw.
Thanks
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Sunday, April 18th, 2010 AT 10:12 AM
Tiny
RACEFAN966
  • EXPERT
Ok first check fuse 21 make sure it is good this powers the fuel pump relay on one term. Check fuse 11 too. Then I need you to check the brown wire to the fuel pump relay. What I need you to do with the brown wire is hook up you meter and set on 20 volt unless you have a 12 volt scale to check DC voltage. Now set the meter where you can see it and turn the key on with everything plugged in is there power there for about 3 seconds when you turn the key on engine off? If there great now crank it, is there power? Let me know what you find ok.
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Monday, April 19th, 2010 AT 11:15 AM
Tiny
JBEAU70
  • MEMBER
Fuse 21 is an open space in my Cherokee, fuse 19 is the fuel pump. The fuse is okay. With the fuse removed, I recorded 12 volts with the key on and around 10.5v while cranking. Fuse 11, Auto Shutdown and O2 Sensor, was okay as well. With the fuse removed, I recorded no voltage at key on and 0.1v while cranking. I also checked fuse 10, Auto shutdown engine controller. With the fuse removed, I recorded no voltage at key on and 0.1v while cranking. Fuse 18 is another ASD. I recorded 12v and 10.5 with the fuse removed.

At the fuel pump relay brown wire, I measured 11.7 volts at key on and about 10v while cranking. The voltage was constant at key on position, it did not fade after 3-5 seconds.

Thanks
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Sunday, April 25th, 2010 AT 8:27 PM
Tiny
RACEFAN966
  • EXPERT
Ok looks like my wiring diagram don't match yours as I only show one automatic shut down relay on any model not two. So if you would give the production date on the door so I can see if I can find the right diagram so we are on the same page. Now also I need to know if it a standard cherokee or a grand cherokee as they are completely different wiring and all. Thanks.
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Tuesday, April 27th, 2010 AT 9:46 AM
Tiny
JBEAU70
  • MEMBER
Standard Cherokee, not Grand.
Production date is 1/97
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Tuesday, April 27th, 2010 AT 8:13 PM
Tiny
RACEFAN966
  • EXPERT
Ok what I show is that fuse 20 powers the auto shut down relay (there is only one). I also show that fuse 6 powers the fuel pump relay. So at the red wire to the fuel pump relay there should be constant power. The brown wire is the switch power from the computer. Let me know what you find and we will go from there.
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Wednesday, April 28th, 2010 AT 11:12 AM
Tiny
JBEAU70
  • MEMBER
Okay, fuse 18 on my Cherokee powers the ASD relay, I traced the red/green wire and measured 11.8v with key on and 10.2 while cranking.
Fuse 19 powers the fuel pump relay. A green/black wire connects and I measured 11.8v where it connects to the relay at key on and 10.8v while cranking. At the brown wire of the fuel pump relay, I measured 11.6v at key on and 9.8 while cranking.
I measured key on and cranking voltage at all four connectors of both relays if the other measurements are important. I did have a green/white wire on the fuel pump relay and a red wire on the ASD relay that didn't show voltage at key on or cranking.
Additionally, I measured voltage at key on and cranking at all four contacts of the fuel pump plug-in(under the car at the fuel tank) and recorded no voltage.


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Wednesday, April 28th, 2010 AT 7:53 PM
Tiny
RACEFAN966
  • EXPERT
Ok first off lets check fuse 11 in the fuse box inside the Jeep ok. Ok having power with key on at the green/black wire is good this means the PCM is sending the power to the fuel pump relay. Now the dk green/white wire that goes to the fuel pump module (on tank) does this have power with key on and when cranking? Just making sure here you can feel the ASD and Fuel pump relay click when you turn on the key right? Let me know what you find here you may have just lost the fuel pump as the module for the pump is part of it. We will know with the tests.
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Thursday, April 29th, 2010 AT 9:13 AM
Tiny
JBEAU70
  • MEMBER
Fuse 11 inside the car fuse panel is okay, on my car that's a 20 amp fuse listed as the run/start ignition and daytime running lights(na).
I unplugged the connector for the fuel pump and checked all four contacts, measuring no voltage at key on or cranking on any of the contacts. I'm not sure about checking voltage at this connection, is there a way to check voltage while the connector is still plugged together? Or is unplugging it to check it okay?
I have not noticed a click from either relay when the key is turned on but did measure voltage change from 0v(key off) to 12v(key on) on the switched wire for both the fuel pump relay and the Auto Shutdown relay.
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Thursday, April 29th, 2010 AT 9:59 PM
Tiny
RACEFAN966
  • EXPERT
OK the black wire at the fuel pump if you would check continuity to ground should be near 0 ohms. Let me know what you find ok.
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Friday, April 30th, 2010 AT 9:43 AM
Tiny
JBEAU70
  • MEMBER
I checked the black wire from the fuel pump to the orange wire of the fuel pump and measured 1.1 ohms. Black wire of the fuel pump(while still plugged in) to ground measured 1.0 ohms.
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Saturday, May 1st, 2010 AT 10:30 AM
Tiny
RACEFAN966
  • EXPERT
Ok the dark green wire with the white stripe at the fuel pump relay does it get power when key is on and does it have power when cranking?
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Tuesday, May 4th, 2010 AT 11:47 AM
Tiny
JBEAU70
  • MEMBER
No, the green/white wire does not get power at key on or while cranking
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Tuesday, May 4th, 2010 AT 5:59 PM
Tiny
RACEFAN966
  • EXPERT
Ok first check fuse 21. Now if that is good then the dk green wire with the black stripe at the fuel pump relay does it get power with key on or cranking? Let me know what you find.
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Wednesday, May 5th, 2010 AT 11:24 AM
Tiny
JBEAU70
  • MEMBER
Okay, we've already covered this. Fuse 21 is an empty space in the power distribution center and fuse 21 in the interior fuse panel is unrelated. The green/black wire at Fuse 19(Fuel pump) that goes to the fuel pump relay does show voltage at key on and while cranking.
I appreciate the step-by-step process you're guiding me through in assessing the problem with my Cherokee but let's try something that we haven't already done.
Thanks
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Wednesday, May 5th, 2010 AT 8:00 PM

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