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turns over but will not start...no Spark...Tested:ASD,PDM,CPS,IAC,TPS, replaced O2

Camel013

NAXJA Forum User
Location
raleigh nc
I did a bunch of tests with all the info I could find and I'm listing it below with as much detail as I can find so if anyone has this same scenario or some advice as to how to proceed next it would be much appreciated by all who come across this page.


  • I had an erratic (fluctuating) idle that would want to die and would die sometimes unless I feathered the throttle.
  • I checked with wd40 for any vacuum leak all around the intake
  • No sign of an exhaust leak, audible or felt
  • I had already replaced the IAC, but I kept the old one to have a spare to test with (the vehicle ran with the old one, albeit not great).
  • I also have an autozone TPS installed (under a year old I think)
  • So I replaced the upstream O2 sensor with a new NTK O2 sensor (23151) this morning and the jeep will not start afterwards.
  • I then installed the old O2 sensor and the motor would still not start.
  • I checked the CPS (which had just recently been replaced): had OL measure @ B,C connectors. which according to my research is proper
    standard.jpg
  • Checked the ASD fuses and all the fuses in the PDB
    1997-1999XJPDCannotated.jpg
    (borrowed from Sidewinder CC)
  • Checked ASD relay (see above: upper right relay)for power and had power on both ends with the key on.
  • I have power in and out of PCM on the ASD circuit.
  • no spark when testing with a spare spark plug on the block.
  • I do not have power at the ignition coil.
  • I did not check for fuel pressure since I do not have spark.
This is where I ran out of ideas of where to go next....
Anyone have any ideas as to why I'm not getting any voltage at the Ignition coil?
 
You getting the no bus on odometer?
 
1998 Cherokee 4.0 4x4
seeing only normal info on the odometer.


The ASD circuit test on the PCM @ C3 &C12 on the grey connector, the voltage was tested to have 12 vdc at both with the key on.
 
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This is the same scenario I had several years ago.... on my 98 XJ.
Occasionally on the highway when I went over a bump the vehicles engine would lose power and then regain the power. One day not too far from home the engine just stopped; it would crank, but not start. Spent many hours troubleshooting voltages, continuity and resistance of circuits and components. Everything checked out except no voltage to the coil.
I found that the 12V wires to the coil had rubbed thru on the underside and were intermittantly touching ground. Reinsulated both wires and the problem was solved.
 
If ASD relay is energized, it passes 12 volts from Battery straight thru the ASD relay to Fuse 20 in PDC and directly to ignition coil.

So check relay output, fuse, and wiring to coil.
 
so this morning I've checked all my grounds over by the coil on the eng. brushed em with some fresh sandpaper to secure a solid ground.
No start still

I'm receiving a P1389 Code (I've got a scanner tool, not a real time data collector though)
I'll go look into all your suggestions.
 
P1398 (M) Mis-Fire Adaptive Numerator at Limit PCM is unable to learn the Crank Sensor’s signal in
preparation for Misfire Diagnostics. Probable defective Crank Sensor​
 
I'm not real familiar with the 98 specifically, but on most motors with a coil, the hot (in) wire is the supply voltage and constant when the ASD relay is closed. The out wire is the trigger wire and is triggered by the PCM to ground (the coil makes high voltage when the electromagnetic field is collapsed/grounded). You should be able to volt test for a pulse on the ground side of the coil, it should pulse battery voltage, then nothing, as you crank the motor. You are likely to get better results with an analog meter and the needle may just pulse and not show true voltage.

If it doesn't pulse, your PCM has shut down the spark (ground pulse) usually because of a faulty sensor someplace.

I you get nothing on the ground side of the coil, it usually means the coil is defective. The PCM isn't going to keep a constant ground on the out (ground) side of the coil so it doesn't overheat. There should be a pulse while you are cranking.
 
I do hear the fuel pump turning on when the key is turned on initially.
I took the coil out and tested it: tests good in my opinion.
+ to - leads: 1.3ohms/Low resistance
-/+ leads to coil out 12k ohms

key on eng off - At ign coil orange wire? is there 12v--no
any injector Dk/grn wire ....is there 12v – no VDC @ injectors
At CPS orange wire... 5v-----yes 5.16vdc?

Can the CPS test good and still be bad? maybe bad wire upto?[FONT=&quot]

[/FONT]
 
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I do hear the fuel pump turning on when the key is turned on initially.
I took the coil out and tested it: tests good in my opinion.
+ to - leads: 1.3ohms/Low resistance
-/+ leads to coil out 12k ohms

key on eng off - At ign coil orange wire? is there 12v--no
any injector Dk/grn wire ....is there 12v – no VDC @ injectors
At CPS orange wire... 5v-----yes 5.16vdc?

Can the CPS test good and still be bad? maybe bad wire upto?[FONT=&quot]

[/FONT]

Test the dark green and orange wire at the coil (or the same wire after a splice at the injectors) with the engine cranking, no voltage you have a fuse issue, a wire issue or the ASD relay isn't closing. The ASD relay won't close unless the PCM gets a good pulse form the CPS or (I've been told) the Sync sensor.

Some models the ASD closes with the ignition switch in the run position and will only stay closed if the PCM gets a good pulse from the CPS while cranking or running (or I've been told the sync sensor may cause the same symptoms as a bad CPS). On some models the ASD will only close after the PCM gets a good pulse during cranking. I'm really not sure with your 98. but testing while the motor is being cranked covers both possibilities and may disclose some low voltage issues, if present. You said you tested the ASD with the key in the run position and it tested good, so my thinking is you should have current on the dark green and orange wire and the same wire at injectors with the key in the run position, but check again with the engine cranking just to cover the other possibility.

I've had a CPS that tested good by the book, but was internally shorted and pretty much shut down my sensor voltage supply.

And don't forget to check the CPS wires for heat damage from the exhaust manifold.
 
1998 Cherokee 4.0 4x4
seeing only normal info on the odometer.


The ASD circuit test on the PCM @ C3 &C12 on the grey connector, the voltage was tested to have 12 vdc at both with the key on.

C3 is the line the PCM grounds to pull in the ASD relay.
C12 is the ASD 12 volt output line when the relay closes.

The PCM energizes the ASD for about 3 second when you turn the key to the on position.. That should put 12 volts at the coil momentarily also.

C12 on the grey connector is the same "electrical point" as the 12 volt coil input if wiring is good and no blown fuses.

Test the circuit again.
 
I tested the Coolant temp just to eliminate it
I had9.94kohm @75.5F Which is within the 9120-10880ohms range
Resistancetable.png

co: hubs97xj

I will test the C12/C20 circuit again.
I checked for grounding wires from the ign. coil and did not see any. even jiggled behind the valve cover and no diff in result, but worth a look. If it comes to it I'll remove the split loom and check everything.
Just cause: intake air temp sensor
Temperature / Resistance °F °C Ohms (Ω) 248 °F 120 °C 370-410 Ω 230 °F 110 °C 480-540 Ω 212 °F 100 °C 640-720 Ω 194 °F 90 °C 860-970 Ω 176 °F 80 °C 1,170-1,340 Ω 158 °F 70 °C 1,630-1,870 Ω 140 °F 60 °C 2,310-2,670 Ω 122 °F 50 °C 3,330-3,880 Ω 104 °F 40 °C 4,900-5,750 Ω 86 °F 30 °C 7,370-8,750 Ω 77 °F 25 °C 9,120-10,880 Ω 68 °F 20 °C 11,370-13,610 Ω 50 °F 10 °C 17,990-21,810 Ω 32 °F 0 °C 29,330-35,990 Ω 14 °F -10 °C 49,250-61,430 Ω -4 °F -20 °C 85,850-108,390 Ω -40 °F -40 °C 291,490-381,710 ΩEliminating anything and everything possible
 
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OK, so I traced all the wires for so many components, and ended up tracing from the PCM to the fuse box. I ended up on the fuse slot with no fuse in it....F'n gremlins I tell ya... either way put the fuse back in started it up, and it runs great now with the new O2 sensor. No hesitation, no rough idle, no issues at all.
Thanks for all your help everyone.
 
I have a 2000 grand cherokee limited, 4.7 v8. replaced both computers, asd and tcm relay, crank and cam position sensors. But have the same issue, wires look good, i have fuel in the rails but no spark in the plugs. any help would be appreciated.
 
I'm receiving a P1389 Code (I've got a scanner tool, not a real time data collector though)
I'll go look into all your suggestions.

Glad to hear you found it. A1398 means the pcm isn't getting anything from the ASD. I often pull mine to prime the oil pump after an LOF, and get that code every time. Funny how o2s is fused in along with that.

Computer-controlled engines suck. The next vehicle I purchase will have a carburetor. Newer ain't better.
 
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Computer-controlled engines suck. The next vehicle I purchase will have a carburetor. Newer ain't better.
Just because you don't understand or aren't willing to learn does not mean it is bad.

I knew you were not good with computers when I saw you were congratulating someone in a 3 year old thread.

:doh:
 
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