i have a 93 grand cherokee with the 4.0, i have replaced crank sensor, coil, dist,computer still nothing, motor rolls over have power to both sides of the coil???? and power to the crank sensor,i can jump a hot to the fuel pump relay and pump runs but still no spark, it had a after market security system in but the po removed it before i got it need to know how to check for grounds at the computer and what to look for next, thank you for your time!

 

don't know the cherokee that well in and out but i can tell you that i would start with getting the schematic and testing relays. start with the fuel circuit, correct that, see what happens.

 

You should have +12V at the (+) coil terminal, and roughly 6-9V at the (-) terminal while cranking. The (-) terminal pulls up to +12V, the PCM switches it down to ground to fire the plugs..back and forth...the reading you get with a DVM will be 6-9V or so.
Is it just sitting at +12V while cranking?

 

coil has power to both post, ill bring home a good meter from work monday and check voltage , relays all are good,as is the fuses what worries me is this jeep had a aftermarket security system in it i tracked down a cut wire under the rear seat for the fuel pump, if i send 12v to it the fuel pump runs,keep getting told there is a ecu ground problem somewhere but not sure what to do next, also if i unplug the crank sensor there is power to 2 of the 3 wires??? does any one know what wires should be grounded for the ecu?only wires i can find thats not hooked up is a light blue under the dash and a small black wire beside the battery i have grounded them both still nothing??

 

Being a Grand Cherokee I'm shooting in the dark, but have you reviewed all the grounding points for corrosion and/or bad connections? Battery cables @ both ends, engine to frame ground, chassis ground, any sensor grounds...that sort of thing?

 

well its going !! found a bad fuse location in the front fuse box for the ecu, fuse fit loose wasnt making contact!