WEIRD no start problem? (details)

Alright so I did a bit of searching and couldnt find anything that would point to my problem.
Heres a little history on the car.
2000 xj 171k
Recently converted from 2wd to 4wd.
Was told the trans had a newer CPS. Shortly after car was experiencing a rough motor running, (barely fired and ran without stalling). Had misfire code on all 3 coils. Traced to bad Cam PS, then car ran great!
I would say it still always had HARD starts.
And sometimes would not start at all until a long period of cranking, while at 100% throttle.

Yesterday hit a snow bank a little hard in 2wd, and then tried to muscle it out in 2wd, (I was flooring and spinning the crap out of the open rear end). Got it out but the car stalled when I got off the gas (has happened before plenty of times after a high RPM tire spin) and would not start again.
Cranks forever but again would not start and had it towed to my house.

Today checked:
Fuel pressure- While cranking 49 psi
40 psi off the key, about 3 minutes to under 10 psi.

TPS- replaced with new just to be sure, no help I reinstaleld the OE.
KPS (w/ entire new cam synchronizer)- new quality napa parts as always.
CPS- new'er' according to donor car owner.
battery- very good deep cycle, holds 14V while off.

Checked over all the connections and everything appeared to be tight and fully connected. Tried to check spark but I think I couldnt get a good ground with the pos tester I have.
Will not start at 0% throttle, 50% throttle or 100% throttle.


Can anyone point me in the right direction?
I really thought it would be a fuel pump or TPS but everything is pointing away from that?

After some more reading on other sites, IAC maybe?

I hear its either lean, or rich no inbetween with a bad one

Check for weeping fuel injectors.

Test the O2 sensor operation. If the O2 sensors have +100,000 miles replace them.

Test the CPS. If it isn't a genuine Jeep CPS, replace it.



Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when engine gets hot, but works again when it cools back down.

Symptoms-
- Starter cranks and cranks but engine won't start up
- Fuel gauge and voltage gauges may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

If the CPS/CKP is failed sometimes the OBD-II code reader cannot make a connection to the computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed.

Diagnostic steps to confirm the CPS is the cause of your no-start

-You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now displays correctly, replace the CPS.
-Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.
-Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.
-Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?
-Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will lose communication.

If you buy a new CPS, get a genuine Jeep CPS, or the premium one from NAPA. Cheap crappy “Lifetime Warranty” parts are often out of specification or even failed right out of the box. They usually also have a shorter service life than better quality parts. Buy good quality repair parts and genuine Jeep sensors for best results.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU will behave oddly until you remedy this.

Crankshaft Position Sensor Connector (CPS/CKP)
.

.
.
CPS Testing

TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines
1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to the 10K-or-2OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

TESTING PROCEDURE for 1987 – 1990 4.0 L engines
Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.
Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector is on the passenger side, near or
on top of the Transfer case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.
.

Dont really think any of my injectors weeping would be the cause, 3 minutes of time before I get below 10psi is pretty long to hold fuel pressure for.
I was getting a CEL for secondary o2, but nothing for primary o2.

As far as checking the gauges I am charging at 16.5V on a 14V system. Not sure how I could use the volt gauge in that instance, since it is always wrong.

But looks like I will be checking spark a little more thoughly. Then testing the sensor itself if I have none.
I admit I probably got a good amount of trans fluid all over the CPS connector and the sensor itself, (By accident of course while being lazy during install).
Would that damage it?

Doesnt look like I am getting spark
I used an inline tester inbetween my coil and plug.

So #1 Crank PS it is?

That 3 minute fuel pressure loss is a big concern, as it it maybe flooding the engine if the injector(s) are leaking. It is either a bad pressure regulator, loose hose in the gas tank, leaking injector(s) or a combination of the above.

But, it also sounds like you need a new CPS, and I hear the only good ones are Dealer ones.

What is with this 16 V system? On the 2000 XJ the PCM has a voltage regulator inside it that controls the voltage and alternator, I doubt it is at all happy about the voltage increase!!!!!

x91evo said:

Dont really think any of my injectors weeping would be the cause, 3 minutes of time before I get below 10psi is pretty long to hold fuel pressure for.
I was getting a CEL for secondary o2, but nothing for primary o2.

As far as checking the gauges I am charging at 16.5V on a 14V system. Not sure how I could use the volt gauge in that instance, since it is always wrong.

But looks like I will be checking spark a little more thoughly. Then testing the sensor itself if I have none.
I admit I probably got a good amount of trans fluid all over the CPS connector and the sensor itself, (By accident of course while being lazy during install).
Would that damage it?

Click to expand...

Ecomike said:

It is either a bad pressure regulator, loose hose in the gas tank, leaking injector(s) or a combination of the above.

Click to expand...

One of the injectors was seeping around the bottom seal funny you mention that. One more thing to add to the money pit

Ecomike said:

What is with this 16 V system? On the 2000 XJ the PCM has a voltage regulator inside it that controls the voltage and alternator, I doubt it is at all happy about the voltage increase!!!!!

Click to expand...

I originally started with this for the speaker system I no longer have, but decided to keep it for lighting.
And I'm running an external regulator

I also noticed the sensor looks like it might of hit against the trans tunnel?
All mounts are pretty firm, but like I said I did hit a snow bank.

I used a cross member form a 98 when I swapped out because it looked like it mounted a little higher than a 2000. Should I opt for the 2000 cross member?

Tim_MN said:

Check for weeping fuel injectors.

3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

Click to expand...

Thanks for the info!

Sensor read 4.97 ohms
Guess this "newer" sensor wasnt so new, add to that the top of it looks like it was damaged as I said before.

Just realized I was reading sensor in milli ohms.. (moron)
Replaced it anyway and still no start help!
I am out of ideas with this Jeep and have no idea where to look now.

So I am going to go back to my original problem,

Always intermittent starting, getting worse and worse with time.
Until I hit a snow bank now NO start at all.

Fuel is good, new KPS, CPS.
New plugs.

Somebody help me out please

let me add to that NSS is bypassed!

And there is alot of fuel I can smell it out of the tailpipe (cranking for a long period of time hoping)


So my guess would be there still isnt spark. Somebody with experience please chime in and point me where to look

Is the ground strap from the head to the firewall in the middle of the engine bay important?

It broke a while ago but car was running fine after that.

I have giant 0 gauge wires running from the block to the chassis and battery so I kind of didnt think that little ground strap did much.

tried clamping ground strap straight to battery, no help

Hello? Am i on cherokeeforum

x91evo said:

One of the injectors was seeping around the bottom seal funny you mention that. One more thing to add to the money pit




I originally started with this for the speaker system I no longer have, but decided to keep it for lighting.
And I'm running an external regulator

Click to expand...

Then I suspect you are creating serious problems for the PCM and its voltage regulator. And that is out of my league, advise wise.

x91evo said:

let me add to that NSS is bypassed!

And there is alot of fuel I can smell it out of the tailpipe (cranking for a long period of time hoping)


So my guess would be there still isnt spark. Somebody with experience please chime in and point me where to look

Click to expand...

Guessing at a "No Spark" is a waste of time, get a second person to crank, and check one plug wire for spark.

Have you tried holding the gas peddle to the floor and cranking it?

I would pull the fuel rail and check for leaking injectors now, AFTER verifying I had spark!!!!

And no, you are in Jeep Gremlin Twilight Zone #III now.

Ecomike said:

Then I suspect you are creating serious problems for the PCM and its voltage regulator. And that is out of my league, advise wise.

Click to expand...

I was told by Mechman alternators there is nothing dangerous about running that voltage. They told me they run 16 volts on wranglers and many other Jeeps.

Ecomike said:

Guessing at a "No Spark" is a waste of time, get a second person to crank, and check one plug wire for spark.

Click to expand...

Ok, I dont have spark!
I am sure there is no spark. I checked it 2 times, then had 3 other people watch the inline spark tester while I cranked it. Without light, so we should have seen something??
Couldnt be more lost as to why there is no spark.
All new sensors all at different times, car ran fine until that snow bank.

Ecomike said:

Have you tried holding the gas peddle to the floor and cranking it?
I would pull the fuel rail and check for leaking injectors now, AFTER verifying I had spark!!!!

Click to expand...

Yes I have tried all throttle positions, 0% 50% 100% nothing.
Injector on #5 leaks a little around the seat,
I figured it would still fire at least!?

Ecomike said:

And no, you are in Jeep Gremlin Twilight Zone #III now.

Click to expand...

I wanna laugh at this but I am more scared!

I think next chance I get a ride to somewhere I will try replacing the coil rail for shits and giggles.. how fun

x91evo said:

I think next chance I get a ride to somewhere I will try replacing the coil rail for shits and giggles.. how fun

Click to expand...

Ask Mechman alternators if they will warranty a HV spark coil that fried itself from too much voltage (Just a guess on my part, but I could be right). An extra 1.5 V times XXXXX winds on the HV coil can up to huge over voltage IMHO, that knocks out the insulation and fries it.