HELP! 97' Grand Cherokee turns over but won't fire!

NC919.4x4_XJ

NC919.4x4_XJ

Member
Joined
Mar 21, 2011
Location
Holly Springs
My buddy has one, it's a 97 GC. 4x4 with the 4.0.
One day he came home from work, and parked the jeep.
Came outside to move it, and the jeep didn't wanna fire up.

It'll turn over all day long, but i won't fire.
It won't fire with Starter fluid, and it has fuel at the rail.
The fuel pump is turning on.

Now heres the thing, the gauges didn't work.
Checked fuses, and one blew..
Gauges are back up...

GC still won't start.

I assumed it wasn't getting spark but it didn't fire with starting fluid.
We replaced, coil, plugs, cap and wires.
Replaced fuses, and relays.
CPS, TPS.

After reading around on some forums... alot of folks said
that they had a bad ECM. He's had 2 and that did nothing.

Any suggestions?
 
Check wiring looms to make sure they are not rubbing anywhere.
 
Think I'd find a good shop and have them take a loo before it becomes anymore expensive. No reason to pull out the parts cannon. It's usually no more than a 1 hour diag
 
The gauges were dead because the BUS was down due to a blown fuse. Usually on late model ZJs that is due to the downstream O2 sensor harness coming loose from it's retainer and rubbing on the driveshaft until it causes a dead short to ground. With that fuse replaced you got the BUS back up but it may have indeed shorted the PCM.
Do you have spark now? Do you have injector pulse? You can have fuel pressure, but if the injectors aren't opening, you won't start.
 
mysterync said:
Think I'd find a good shop and have them take a loo before it becomes anymore expensive. No reason to pull out the parts cannon. It's usually no more than a 1 hour diag
Click to expand...


this route was mine on my 93 zj

ended up being computer
also took them 6 hours to diagnose it, 300 before parts.

you'll never see my vehicles at a shop again for a diagnosis

waste of money , for the 500 i spent i coulda had every new senor on the jeep and had spares to boot.
 
Cory said:
this route was mine on my 93 zj

ended up being computer
also took them 6 hours to diagnose it, 300 before parts.

you'll never see my vehicles at a shop again for a diagnosis

waste of money , for the 500 i spent i coulda had every new senor on the jeep and had spares to boot.
Click to expand...

Sounds like you found the wrong shop. Don't throw us all in that category lol. Don't think I'd have approved a $300.00 diagnosis on that type of issue in the first place :D
 
Jody Treadway said:
The gauges were dead because the BUS was down due to a blown fuse. Usually on late model ZJs that is due to the downstream O2 sensor harness coming loose from it's retainer and rubbing on the driveshaft until it causes a dead short to ground. With that fuse replaced you got the BUS back up but it may have indeed shorted the PCM.
Do you have spark now? Do you have injector pulse? You can have fuel pressure, but if the injectors aren't opening, you won't start.
Click to expand...


Sorry for the late response, i have had my own issues with my XJ lately.. And just recently had surgery.
Haven't spent much time on my buddies ZJ.

but Anyways, we have checked all the fuses... many of times. it was his Cluster fuse that blew. Why? i don't know..
i will check the o2 sensor but i doubt that was it.. We've replaced the PCM, 2 or 3 times now. including LKQ PCM/ECMs

I even read about the BCM going bad, grabbed a few a LKQ and that didn't work.

I haven't checked the fuel pressure or pulse.
It just doesn't seem like any spark.
 
Cory said:
this route was mine on my 93 zj

ended up being computer
also took them 6 hours to diagnose it, 300 before parts.

you'll never see my vehicles at a shop again for a diagnosis

waste of money , for the 500 i spent i coulda had every new senor on the jeep and had spares to boot.
Click to expand...


my buddies wife already had it at the jeep dealership here in fayetteville and also
a mom and pop shop.

they said it was the computer.. but it didn't fix this issue.
 
It sounds Ike you need to start at the basics. Check them off your list and move on. Don't second guess yourself. Be methodical about it....like


You need 3 things for an engine to runs simply put
Fuel.
Spark.
Compression.

Outline it

fuel...
Fuel pump...~
Pressure at rail
Injectors
Spark....
Electronics(computer controlled sensors )
Coil( too and from on all electric)
Sparkplugs(wires )
Strong battery and starter( you said it was good )
GROUNDS!!!!!!!!!! (Very important )

Compression....
All cylinders
Fast starting rpms


Now you have the basics starts investigating and write down your findings.
Note, ECUs have to have 5 things to function....
Switched power
Un switched power
Ground
CAN hi
CAN low.

Hope this helps
 
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