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Jeep will not start

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  • Jeep will not start

    Help Needed. I have a 1997 Jeep Wrangler with a 2.5 4-cyl with automatic trans. One day Last summer I went out to go to town and it would not start. I Noticed the check engine light would not light up with the key on and the Gas Gauge stayed on empty. A friend of mine found a Blown 40 amp Maxi fuse in the fuse panel under the hood. I do not know what it controlled but he replaced it and it fired right up. Been running great until a couple days ago. Again I went out to go to town and it would not start. Again no check engine light and gas gauge stays on empty with key on. I just filled it up with gas the day before and gauge was working. The Fuses are all good this time. I checked the ones behind the Glove Box also. We Hooked a scanner up to it and it says No Communication. We have no spark or Injector Pulse. I replaced the Coil - the Distributor - and the Crankshaft sensor. Still No start. Could it be the ECM ? Is there a ground wire somewhere that could be the Problem ? I Tried to find a wiring diagram and had no luck. Can anyone tell me what the Power wire and ground wire are going to the ecm. I would like to make sure I have power and ground Before Buying a $300.00 ecm. Thanks

  • #2
    My understanding is that if the check engine light and gas gauge do not activate with key on, then your ecm is bad. Went through this when my 97 Cherokee wouldn't start. We ended up having a poor connection in the power center under the hood. Had to take it apart and clean all connections.
    1979 J-10, 258 with 2100 conversion, T-18/D-20
    1979 Cherokee Chief WT, 360, T-18/D-20, rust
    1967 Pontiac LeMans Convertible, 400 4sp
    1968 Mustang 5.0 conversion


    • #3
      Ok Thanks. I will check the Power center tomorrow.


      • #4
        I have a 97 wrangler with a 4.0 and M/T. I've seen these symptoms several times. It is usually caused by a bad CKP, but could be caused by any of the 5 volt sensors --CKP, CMP, ECT,MAP,TPS or Oil Psi sender. I've also seen an O2 sensor wire shorted to the exhaust manifold cause this. What is happening is a bad sensor is taking down the "BUS" communication network. The dash is part of that, which is why certain gauges and lights don't work.
        I suggest you disconnect each one of the sensors listed above, one at a time. (Key on) If this is the problem, you should hear the fuel pump relay click and the pump prime when you disconnect the defective sensor.

        Edit: Forgot the IAT (Intake air sensor).
        Last edited by Curly5759; 02-05-2016, 09:05 PM.
        77 Cherokee S 360/TH400/QT


        • #5
          Ok Thanks I will give that a try.


          • #6
            Parts stores usually have a hand scanner you can rent for just a couple bucks a day - sometimes they are free rent. you should ask for not just a code reader because those can lead you astray - but one that provides real time data like TPS voltage, coolant temp, MAP etc.

            the only thing is you would need to google the typical values for instance TPS is .75 volts with throttle at closed/idle and wide open at 3.75 volts ( i am making up those figures) and that 5 volts goes into the sensor on the blue wire and the output is the yellow and black. this tells you why the ECM is unhappy

            there are alot of folks here that know way more than I do about fuel injection
            Last edited by Tripwire; 02-06-2016, 08:06 PM.
            Abort? Retry? Ignore? >

            86 GrandWag. Howell fuel Injected 360. MSD Ignition + Dizzy. 727/229 swap BJ's 2" Lift and 31's

            88 Wrangler 4.2, Howell TBI and MSD - Borla Headers w/ Cat-back + winch and 31's AND a M416 trailer (-:


            • #7
              Gotta 97 2.5l too

              Did you clean off the battery connections lately? I keep mine fairly clean but last week I had the same problem deader than snot nada click chime nothin even went as far as popping the clutch had a nice person help just to have the voltage reading shoot up after it got running. Gave the terminals a cleaning when I got home and got back to jeepin.


              • #8
                Yes I have checked the battery Cables and they are clean and tight. I Unplugged all the sensors and still no Luck. I have a scanner and I do not get any communication. The fuel pump relay clicks when I turn the key on. The gas gauge will not work with the key on and the check engine light will not light up. I,m at a stand still.


                • #9
                  Try adding a ground wire (even just jumper cables) from the battery negative to a clean frame spot to make sure it's grounded. Did the automatics come with an ASD relay? If not, is there power at the main terminal on the alternator? (fusible link may be blown)
                  I drove mine home with a jumper lead bat + to main alternator terminal
                  Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental.


                  • #10
                    Ok I got to work on the Jeep again today. I got a wiring Diagram and went to checking wires. I checked the fuse + at the ecm and I have 12 volts. It shows 2 ground wires at the ecm and I have 12 volts ground on both wires. It has two 5 volt reference wires. One of them feeds the Map Sensor - Crank Position Sensor - and the TPS Sensor. The other one feeds the Speed Sensor on the transfer case. I only have .478 volts on both wires. I unplugged all of these sensors and the voltage stays the same. That tells me all the sensors are good. I even went as far as unplugging Both 02 sensors - the ECT Sensor and the Distributor and coil. still same voltage. So I,m asking is it the ECM Bad or the Ignition switch shorted or something else. I even cleaned the battery ends. I also checked the wiring for broken or burnt wires. All looks good. O,reilly's and Advance cannot even get me a ECM. They say A1-Cardone does not have any. Help me Please.