Failure to start falls into two categories:
1) The engine wont revenues - the starter motor wont run
Or
2) The engine turns over but will not fire and run.
jeep grand cherokee transmission
This information will address the first cause. If you engine turns over and can not fire see my other article.
Start with checking battery voltage. Most Jeeps have a voltage meter on the dash. If the voltage is low - below 10 volts, check the following:
1. Fist check to see if you have a reason for your battery to become discharged. Were the lights left on? Doors left open or another power draining accessory left on? If thats the case, shut off the drain and use jumper cables to start employing a charged battery from the different vehicle.
2. If there is no excess power drain, look into the condition of the battery cables. Remove the cables from your battery posts and clean the contacts. Also check the connection of the ground cable for the vehicle body.
3. If the battery cables are clean and making good contact and the voltage is still low, verify how the alternator is working properly.
jeep grand cherokee transmission
4. If the battery is constantly on the dont start your Jeep, replace the battery.
In the event the battery voltage is normal nevertheless the engine still is not going to start, the most common cause is one of the safety interlocks. By using an automatic transmission there is a Neutral Safety Switch (NSS) that only allows the engine to start in neutral or park. The contacts inside the NSS can corrode and cause the change to malfunction. Move the shifter forward and backward while turning the important thing to start out. The motion will cross a spot around the switch that also works. The NSS may be disassembled and cleaned or simply just substituted with a brand new unit.
In the event the NSS is working properly however the starter still is not going to turn, you could have a defective starter or starter solenoid. The starter and solenoid are replaced like a unit on the XJ Cherokees. However before choosing as replacement starter, look into the wiring connection on the starter and also the trigger wire to the solenoid. Often these connections can be loose or dirty due to the rigors of dirt driving. Some individuals have reported that starters may be disassembled and cleaned to correct problems however i havent tried this procedure.
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