Engine turns over, but won't start.

Today at school I got in my jeep, (93' cherokee sport, I6, 5 speed manual) turned the key and the engine turned over but didn't start. After trying a little more I got it started and seemed fine. So I drove it off the school property and was turning onto the main road ruuning through our town. When I did so it almost stalled but managed to save it. I went on a little more and as I was driving and the thing just died on me while driving. (3rd gear about 2200rpms) When that happened the motor went out along with the power steering but all electronics stayed on. I luckily managed to roll safely into a car wash where I parked by the vacums. There it did the exact same thing as it did at school, turned over but wouldn't start. My friend managed to get it started again. When he did, he was giving it some gas in neutral and it backfired and died again. I got back in tried a few more times unsuccesfully, I eventually got I started and took it to the nearest mechanic where it sits now. That time it seemed to run fine.

Not quite sure what the problem is. I drove it this morning and it behaved just fine. It's completly random when it does start. If any more info is needed, please say something.

My money is on the CPS (crankshaft positioning sensor) being bad.

When you turn the ignition on can you hear the fuel pump running?

Check to make sure you have good strong spark, it sounds like the coil went bad.

X2 on the coil...mine has gone 3 times in 3 years due O'Reilly's crap coils.

Most common issues for a non start are:
1) a Bad CPS, which is obvious as there is no spark. There are other possible causes of no spark at the HV coil, but the CPS is the most common cause.
2) No fuel pressure, easy to check at the fuel port on the fuel rail, looks like an air tire valve on the side of the fuel rail.
3) Too much fuel, flooded, from a leaking fuel pressure regulator(front of the fuel rail, has a vacuum line attached), leaks fuel into the vacuum line, easy to check!!!!
4) Weak spark, bad plugs (gap worn out), wires arcing to ground (obvious at night with lights off while cranking), cap and rotor worn out and or distributor bearing worn out, or HV coil bad. Bad cap and rotor, just old, are common.
5)Gets more dificult at this point, If it is NOT the above, then you need to check the computer sensors and wires (look for damaged wires, dirty electrical connectors senors to the ECU engine computer), sensor tests reguire a volt-ohm multi meter, and the FSM specs which are posted in hundreds of old threads here. Key starting sensors are TPS, MAP, CTS and IAT. Last two are temperature sensors. The MAP reads engine vacuum.

IF the engine is flooding, try holding the gas peddle to the floor while cranking to un-flood the engine. IF it starts, look for the flooding source or cause.

What part of Texas?

Ecomike said:

What part of Texas?

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Small town named Hallettsville. About 2 hours from both San Antonio and Austin.

And Houston.

Thanks for the troubleshoot list.....my Cherokee lost it's alternator and wouldn't even turn over....after replacing have had a no-start problem....learned all about relays and fuses and was suspicious of the CPS based on many posts here.....replaced the positive battery cable and will now check it out and proceed down the list.

Ecomike said:

Most common issues for a non start are:

IF the engine is flooding, try holding the gas peddle to the floor while cranking to un-flood the engine. IF it starts, look for the flooding source or cause.

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Sorry to revive this thread, but your advice above was interesting. My 2000 has started to not start. I can get it to run if I hold the gas to the floor and I have to keep the revs up for a minute or it will stall. But the normal starting routine fails 9 times out of 10. After lots of reading of related posts my primary suspect was the CPS, but now I'm not so sure. I can smell gas at tailpipe area once it starts. Could I have an injector going bad and leaking into a cylinder? Also, can a failing CPS cause hard starts but run OK once I get it started? It seems to run fine once I get on the road. I pushed the valve in the fuel rail and was rewarded with a squirt the other day.
Devilish contraptions! One more thought, I have noticed in the last two months that while under way at speed an occasional and rare hiccup when the jeep feels like it quit for a split second. Dials are not effected or any other indicators showing. Just a "bump" so to speak and then back to normal.

Thnx,
Geoff

Shoeman said:

.....can get it to run if I hold the gas to the floor and I have to keep the revs up for a minute or it will stall.

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Common symptoms of low voltage.

For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging.



Your symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will relearn the idle settings after a short period of driving and the engine will start and idle normally.

Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem. 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 them as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body.

If the symptoms reoccur, you need to have your battery and/or the alternator load tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.

Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance.

Good to know. The battery was new in April. I'll check the Alt output as a preliminary to a load test. Cables and grounds will get an eyeball and clean up too. The volt gauge shows OK when it is running if that really indicates much.
Can you tell me where the IAC is? I'll goggle it but I'm at work today so internet time is scarce even though I'm the boss. Gotta lead by example.

Bingo! 10.3V showing at the battery on my meter, engine off. On the charger overnight. Tomorrow I'll check the alt. output. Looks like it's buried under the AC Comp and will not be much fun to swap out.

Charged it over night, showed 10.66v this morning. Hmm... It started up just fine and shows 14.4+/-V at the batt terminals when running. So maybe I have a bad cell in the almost new battery? I was surprised to see less than 12V after the charging session, but maybe my charger is partially to blame for that.
Sorry for the thread drift, but you guys are a great help all the time.

Last update, I promise. Drove over to Parts America where I had bought the battery 3 months ago and had them test it. Sure enough it was a dud. Replaced it under warranty. Now it starts like it should.
I've never had a battery go bad like that in 30 years of driving.

I almost have something similar to Shoeman, but it is not a starting issue until it dies while driving. Wife, 20 month old and I went for a drive in a 2001 XJ. Drove for 15 minutes and we were parked at a parking spot and it died. It started right back up. Drove for 5 minutes and it died while coasting to make a turn. I put it in neutral and it started back up. Drove for another 5 minutes and it died, again started right back up. Drove another 5 minutes and it died and would not start. Walked home (about 30 minute walk - it was a nice night out). Got the truck to tow it home. By the time we got back (45 minutes later) it started right up and I drove it home. Have not messed with anything other than checking the battery voltage a few minutes ago and it was 12.55. Again, it starts up but dies after the engine has warmed up. Maybe unrelated, but recently replaced all fuel injectors - had one sticking open and flooding/fouling but it never caused any issues except the check engine light would flash. Also had a short on the oil pressure sending unit a few years back, but that made the engine more jerky, and it is not laying no the block like it was that time. Any input? Thanks

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.

Have the battery and alternator tested in a machine that applies a simulated work load. Handheld testers are not very accurate and will pass borderline batteries and alternators that should be replaced.

Next, test the CPS.

The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason. 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.

Crankshaft Position Sensor Connector (CPS/CKP)
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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.
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Wow, thanks for the help!

Temp sending unit or injectors, I had a 2000 that would turn over for ever until I replaced the injectors. Most of the time in my experience a bad cps wont start at all. Fuel pump and filter are a good option also. PRO5.0 has good injectors for a good price FYI. Call them if and explain what you have and need. Bad coil seems like a legit culprit also>>>