busted

Hey guys im new to this forum and i would like to say hi and thanks in advance to any help you have to offer with this problem.

i have a 98 jeep cherokee 4.0. i started it up and drove it for about a minute from parking lot to parking lot. i stopped to put it into reverse and it just stalled out and would not start back up. it just cranks and cranks but wont fire.

What i've found at first:
No spark
the fuse for the fuel pump was blown so no fuel pressure (20 amp under the hood)
The gauge cluster does not read faulty at all for the voltage or gas gauge.

What i"ve replaced:
CPS (old one tested good)
Coil (old one tested good but was really cracked)
The fuel pump fuse
The ecu (got 2 from the JY out of wrecked xj's one 99 and one 96)
The cam sensor (JY wrecked 99)

The fuel pump started working immediately after i replaced the fuse.and still works

I checked the voltage to the coil and it was inconsistent with the old ecu.
i checked it with the new ecu and it has no voltage to it until it starts cranking over then it jumps to .3 volts. both terminals on the connector do this. i dont know if this is right at all but it seems fishy..

im totally confused on where to go next or maybe i missed something simple.
any help, advice, or pointers would be greatly appriciated

BatmanXJ

I would get an ecu from a 98. 96 is different from all others I have heard. I would also think 99 is a different ecu aswell. Sounds like you have checked the normal things.

Still no spark?

Let's check basics. When u replaced CPS are you sure you plugged it back in? Did.u replace with new OEM cps?

busted

Nope still no spark. i checked to make sure i plugged every thing back in and i had every thing right. i also rechecked the cps and on pins b and c i get about 1800 ohms of resistance. so i put the original ecu back in it and checked for voltage at the coil again and here is what i got

i got 0 volts to the coil with the key on (the green and orange wire jumped to the batterys negative terminal)

i jumped the ASD relay between 30 and 87 and got voltage to the coil through the green and orange wire

then i plugged the connector back into the coil

i checked for output voltage from the coil to make sure it was flowing through the coil and it was.

then i checked with a test light on the gray wire to see if it would flash when cranked and it remained on constantly

i then checked for continuity from the gray wire to the ecu (pin 7 on the black connector) the wire checked good

then i checked the ground pin (31) and it checked good too

so it seems that the ecu isn't receiving a signal from the crank sensor or the cam sensor. or it is and its just fried .

is there a procedure for checking the cam sensor just so i can rule it out as a suspect all together?

jeepXreaper

Have you checked the ignition relay. I know this because my buddy had an issue starting and I replaced the relay n then it started rite up

Programbo

I was going to suggest this. This is what had me sitting on the side of the highway awhile a few months ago. Checked all the complicated stuff and overlooked this simple thing.

busted

thanks guys, i checked all of the relays and interchanged them and they all seem to be good.. i did discover one thing tho that the coil would get momentary power then i popped the asd relay back in, then like a breaker the relay would flip off and cut power. soo maybe all of this is just a bad ground somewhere i haven't checked yet???

i also stumbled upon another thing. when i turned the key on with out the cps plugged in and with the key still on can plug and unplug the cps and the injectors will fire and the asd relay trips on and off again. i have no idea what that means at all haha. but maybe i should try another new cps.

freegdr

Theres a issue some times with o2 wires rubbing on ds causing no start iss it blows a fuse in the pdc have you rechecked them for power in and out ?

salad

Where did you buy your new CPS?

busted

hey, sorry i cant get back everyday i got finals and moving and career hunting to take care of in the last and nest few weeks but i will try to keep the post updated with what i find when i can.

the wires from the ds o2 sensor appear to be good it doesnt look like the wires are shorted anywhere. and the crank sensor one was from az and the other came from a tranny we had lying around from when we did a stick conversion. neither of which worked. could there be a bad wire to the fuel pump would that cause the relay to trip.

is the fuel pump on the gen twos like the gen ones? is there a ballast resistor somewhere for high rpm?