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Unread 01-14-2013, 07:00 AM   #1
Nate_nev
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1997 XJ Cherokee 
 
Join Date: Jun 2012
Location: Sault Ste. Marie, Ontario
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First No Fuel, Now No Spark

so... it seems I am back to not starting again... strange this time...

my 97 XJ decided it would not start after driving about a half hour. it would turn over but not ignite.

I tried several times until I needed a boost, wiggled the shifter, tried in neutral, then sprayed a bit of quick start to see if it would ignite.. it fired up instantly then died because of the lack of fuel. brought it home, tried again no noise coming from the pump. changed the pump, bench tested the old pump and would not work. I figured this is it I have my Jeep back.... nope... turns over and now no spark. also checked all conections

parts that are within six months new:
crank position sensors (not auto zone)
cam position sensor (not auto zone)
plugs, wires, ignition, cap.
both 02 sensors
grounds all replaced
map sensor
throttle position sensor
temp sensor
air temp sensor on intake
SKF stethoscope to listen to injectors
not throwing any codes, reset computer with hand held and by disconnecting battery.

so... hopefully that is enough information for someone to help me figure this thing out..


thanks once again in advance for the help.


Nathan N.

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Unread 01-14-2013, 10:30 AM   #2
CCKen
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Swap the Automtic Shut Down (ASD) relay in the PDC with the elecric radiator fan relay, then see if it starts (gets spark).
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Unread 01-14-2013, 01:39 PM   #3
Nate_nev
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will try that tonight. willing to try anything at this point lol!!
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Unread 01-14-2013, 03:52 PM   #4
oakmckinley
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On my 00 XJ, we went through 2 crank sensors before I found a good one to work. It ran good for about a week before it started acting up again.
They can be bad right out of the box.
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Unread 02-22-2013, 12:15 PM   #5
Nate_nev
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well, figured I would update. tested the sensors and all seem to be fine. computer shows proper error readings when I unplug sensors. still no spark. cleaned all grounds again etc.. i am at a loss on what to do... checked the 02 sensors. what else can/should I look into?? ran perfectly fine until I shut it off one day and it has not started since.
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Unread 02-22-2013, 05:42 PM   #6
tjwalker
It's the crank sensor!
 
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I haven't seen any mention of "coil" here. Test and or replace. Critical component. Oxygen sensors will not affect spark.
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Unread 02-25-2013, 09:09 AM   #7
Nate_nev
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I swapped out the coil with known good working coil and no effect. wondering if this might be a computer issue?

also re-verified the grounds.

any other thoughts would be great.
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Unread 02-25-2013, 09:25 AM   #8
VBRubicon
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You're sure you have fuel now? If you said you bench tested the old pump and it wasn't working, it would be awfully coincidental if you had 2 seperate issues...

That's not to say it couldn't happen.

Assuming it's the same as the older xj's....Can you hear the pump prime when you first turn the key to "on"? Are you 100% sure on your pump polarity?
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Unread 02-25-2013, 10:35 AM   #9
CCKen
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Quote:
Originally Posted by Nate_nev View Post
I swapped out the coil with known good working coil and no effect. wondering if this might be a computer issue?

also re-verified the grounds.

any other thoughts would be great.
You can verify (to a degree) that the PCM has the ability to activate the ASD, which, as you know controls the ignition coil, fuel injectors, and O2S heaters. No ASD = No Ignition.

The ISO type relays in your PDC are controlled by the PCM by providing a ground to the control coil in the relay(s) when certain conditions are met. These grounds are called hot grounds.

In the case of the ASD relay, the PCM must see the crankshaft position sensor signal that the engine is turning.

The XJ has a CCD Data Bus. The Bus has two circuits (two wires), a (+) and a (-). The (+) circuit should have around 2.49 volts on it and the (-) circuit should have around 2.51 volts on it. The differential between the two is .02 volts. This is when the PCM is idle.

To check the control coil ground circuit from the PCM you will need a digital voltmeter.

Refer to the relay socket pin cavity arrangement below.

Remove the ASD relay. Touch pin cavity 85 of the relay socket with the (+) probe of your meter and touch the (-) probe to the battery negative terminal. With the ignition switch OFF/LOCK, you should see around .02 volts. Again with the ignition switch in RUN, you should see around .02 volts. If you see the .02 volts it means the PCM relay control circuit is good and the wiring to the relay pin socket is good. If you don't see the .02 +/- volts the PCM driver is bad or the wiring is open.

Just to verify, repeat the above procedures on the Fuel Pump relay and the Electric Radiator Fan relay.

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Unread 02-25-2013, 02:24 PM   #10
Nate_nev
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VBRubicon, I am sure. I tested the fuel pressure before I swapped the pump with new one and had no pressure. changed pump and had pressure. and even bench tested the old pump and it did nothing. assuming there are two separate issues at the same time.. which sucks.

CCKEN, thanks for the info. I will test soon and update.

thank you both for the input.
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Unread 04-02-2013, 08:55 AM   #11
Nate_nev
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back up and running. had extra parts sitting around. changed the computer because I was not getting the proper voltage to the crank position sensor. instantly had proper voltage then still did not run, changed the crank position sensor, almost started then threw code for the pickup changed that with spare and shes back up and running. now I am having an issue with temp gauge spikes... probably air in the coolant...? both temp sensors are new (within a couple months old). other thing i want to figure out is why everything went all at once? ie, fuel pump (bench tested and did not work), computer, pickup coil and crank position sensor (had no magnetic properties).. maybe got a power spike from somewhere? either way now i can continue my daily/off road build. thanks to everyone for the input and help.
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