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I need answers.. Ive got a 1993 jeep grand cherokee 4.0 6 cyl. Drove an hour, went into the store, when i came back out and started it it turned on fine. Soon as i turned the headlights on it died. It will turn over and over bt wont start. I have replaced the distributor, distributor cap, ignition coil, rotor button, pickup module (inside distributor), crank censor, and rewired the ground wire. My check engine light doesnt come on until after 5-20 minutes and when it does come on it'll act like it wants to atart but wont. Does this sound like it could need a new computer? Possibly re-flah the computer? Please help...i'm out of options...  

you could have a damaged computer...

i would really really really like you to check the grounds.. i know you said you rewired them..  

jeep 4.0s usually ground the engine on the left side down at the bellhousing.. and on the ride side at the bell housing..

the check engine light taking minutes to come on show there is some kind of power problem.. either on the ground side or the positive side...

i will work with you on this...  do you have a wiring diagram for the engine control... and a digital volt meter...

i would like you to do this test first...  

lets start with the simple and cheep stuff...

do you have a digital volt meter... if you don't.. they can be had for 7 bucks to 25 bucks..

a lot of parts stores have these from innova for about 16 bucks..



harbor freight stores have these for about 20 bucks



either will last you for decades..


next.... i would take a digital volt meter...

set it to 20 volts DC scale...

start the engine and turn on the headlights..

1. test between the positive and the negative battery posts.  14.1 to 14.8 volts is expected.

2. test between the negative battery post and the engine block. 0.04 volts is expected..

3. test between the negative battery post and the body... 0.02 volts is expected..

4. test between the Engine block and the body..  0.02 volts is expected.

if you get 0.00 on the last 3 tests.. change the meter setting to 2 volts DC scale.. and retest.. the last 3...

this test takes about 2 minutes...

post your results by test number..

if you get more than the 0.04 or 0.02 volts on the display...

you have a bad ground between those parts..



why do this test....   bad grounds will stop any new car in its tracks...

why... electrons flow from Negative to positive...  if you loose a ground.. or it becomes intermittent..  you won't have any power for that circuit...  just like a table light when the plug falls part way out of the wall...  the light will go out..



since the engine DOES not run....   please do test number two... with somebody cranking the engine..


post results by number...  please..  

you are going to want to print these individual diagrams..

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the most obvious thing i did not see that you replaced was the auto shut down relay....



i don't know where its stashed on your model..

if you look at the wiring diagrams.. you will see that this supplies power to a LOT of things under the hood...

it powers up a LOT of stuff.. like the positive side of the fuel injectors... the positive side of the ignition coil.. the ECM on pin 57. and the dark green and black stripe wire on the back of the alternator..  

so.. test the Dark Green with a black stripe wire..    when you turn the key on.. does that get power instantly???

i would check with a test light or volt mete that you are getting constant power on fuses F2 and F15...

and power with the key on,  on fuse.. ***

lets get back to basics...

spark when cranking?????

can you hear the fuel pump turn on.. when you first turn on the key.????

do you get fuel pressure at the fuel rail???

can you feel the injectors clicking when somebody cranks the engine????

are you sure the spark plugs are NOT fouled...

you might want to try to crank the engine with your foot to the floor on the gas pedal.. this puts the system in clear flood mode and reduces or shuts of the fuel injector pulse..    once it starts back off on the throttle but keep the RPMs up to around 2500 or 3000... for about 20 seconds.. this may burn the carbon and wet fuel off the spark plugs..   try not to blow the motor when doing this..

also.. pull the coil wire from the distributer cap.. position the end about 3/4" from ground..  i have found these ignition coils that have failed.. and won't throw enough spark to allow the engine to start...  the spark should be bright blue and snappy...  if it will only throw a 1/4 inch orange spark.. you need to replace the coil ..