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Old 02-13-2010, 05:48 PM   #1 (permalink)
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Unhappy engine troubleshooting: 88 cherokee 4.0

Almighty and knowledgeable bretheren of the powerful PBB, I need help.
Stats: 88 cherokee 4.0 auto (all stock)
no spark, no fuel injector pulse, fuel at fuel rail.
I have replaced the engine, everything ran beforehand.
Engine cranks, but I am not getting spark and cylinders are not getting fuel.
I have fuel at fuel rail.
Crank sensor tests good (its new, it should, right?)
new cap, new rotor, new plugs, new plug wires.

I am out of troubleshooting steps, so I am starting from ground zero. I have read, researched, searched, searched some more, and now I have to ask because I just flat need help.

What am I missing? There must be a key to this puzzle that I have not figured out and it is escaping my grasp.

Asking, praying, begging and buying a sixer of your choice to the person with the nugget I desire.

Thanks for any and all help.

Wally
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Old 02-13-2010, 09:43 PM   #2 (permalink)
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Was your jeep a 2.5 and you just swaped it over to the 4.0 Just curious from the sig it says 2.5. If you did the swap did you get wireing harness and computer??
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Old 02-13-2010, 10:40 PM   #3 (permalink)
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Quote:
Originally Posted by Huff_Diesel View Post
Was your jeep a 2.5 and you just swaped it over to the 4.0 Just curious from the sig it says 2.5. If you did the swap did you get wireing harness and computer??
Nope, this is a different rig altogether. Everything on it is stock.
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Old 02-14-2010, 04:18 AM   #4 (permalink)
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This is the Daimler-Chrysler technical doc on how to troubleshoot and repair the Jeep Renix fuel injection system. Hope it helps!

http://www.eriejeeppeople.com/Jeep_t...ion_manual.pdf
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Old 02-14-2010, 07:01 AM   #5 (permalink)
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might also want to check the stator, or the pick-up in the dist., dont know if there the same , but my 93 yj, had the same symptoms, and thats what it was. good luck
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Old 02-16-2010, 04:01 AM   #6 (permalink)
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OK, I have gone through that manual Link, and have nothing conclusive to return with.

All my sensors check good. I am getting zero spark. Spark plugs are dry (not getting fuel). What in gods name am I missing?

Going back to basics tomorrow with tdc#1 and making sure I did not jump time anywhere with my distributor.

The only thing that keeps coming up is my O2 sensor relay is clicking like a mofo. (on-off-on-off repeatedly)
What is going on there????

Thanks.
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Old 02-16-2010, 05:46 PM   #7 (permalink)
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Did U change the flywheel?
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Old 02-17-2010, 04:28 AM   #8 (permalink)
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....JeepinJ...I am trying to follow you on this.

Did I change the flywheel? No, same. Did I put it on right? Only one way it goes on.

Throw me a bone, what are you talking about??
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Old 02-17-2010, 05:30 AM   #9 (permalink)
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Quote:
Originally Posted by ogreshooter View Post
....JeepinJ...I am trying to follow you on this.

Did I change the flywheel? No, same. Did I put it on right? Only one way it goes on.

Throw me a bone, what are you talking about??
the flywheel on your replacement engine may have a different relucter wheel on it that the ecm may not be able to read.
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Old 02-17-2010, 08:43 AM   #10 (permalink)
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The clicking O2 sensor HEATER relay could indicate 1) wiring or relay problems, or) bad a bad ECM.
The fuel pump relay supplies 12v to the O2 heater relay, EGR relay, AC relay, fuel pump, and fuel injectors. The fuel pump relay is controlled by the ECM, as are the others. If the ECM is getting intermittent power, let's say from the Power Latch relay, it may cause the O2 heater relay to chatter (click on/off).
I'd check the fuel pump and power latch relays, wiring, and grounds.
EDIT" Not sure the power latch relay does anything but keep power applied to the ECM for 3-5 seconds AFTER the Ign key is turned off; purpose: reset AIC for the next start up cycle.

The fuel pump control signal is on for ~3 seconds after the Ign key is turned on, but before Start is engaged. This allows fuel pressure build up, and you should here the pump run, and get fuel pressure at the fuel rail. Once Start is engaged, the CRANK signal is applied to the ECM, insuring the fuel pump relay stays engaged while cranking; this circuit is a wire from the starter relay to the ECM. If this wire is open, or intermittent, you would not get fuel pressure, etc, etc.
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Last edited by Bubba_Jeep; 02-17-2010 at 09:03 AM.
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Old 02-17-2010, 08:48 AM   #11 (permalink)
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i have an 89 xj with a 4.0 that i swapped motors in and my dad helped me.
we had the same problem and it ended up being this simple ground nut that wasnt bolted on. its been a while but i remember it being close to the oil filter.
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Old 02-19-2010, 12:11 PM   #12 (permalink)
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Sandaddik2, how right you are. We were missing a simple ground at the oil dipstick (well, 2 actually). So, now I have spark and I have injector pulsing (via screwdriver stethascope). Is not starting though.

Now, where do I go from here?? Fuel pump kicks on, so I am getting fuel. Spark, tested and good (nice blue spark), possibly no fuel from injector??? Possible plugged injectors??

Any thoughts now?
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Old 02-19-2010, 09:21 PM   #13 (permalink)
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FIXED!!!! Was just the ground. Stabbed the gas pedal, cranked it over, shot some "go juice" in the intake and WOOMF!

Happy as a clam.

Thanks all.
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Old 02-22-2010, 10:57 AM   #14 (permalink)
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Good call Sandaddik2!
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Old 02-22-2010, 10:14 PM   #15 (permalink)
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Yea, good remembering there Sandaddik2! It's always the "little" things in life. Are you going to claim your free 6er that ogreshooter put up for grabs in his first post? If not, I"LL TAKE IT.

Last edited by MrMoose; 02-22-2010 at 10:17 PM.
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