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No crank no start issue

Tiny
MIKE QUALLS
  • MEMBER
  • 2002 JEEP LIBERTY
  • 3.7L
  • V6
  • 4WD
  • AUTOMATIC
  • 140,000 MILES
New fuel pump and filter. Good pressure, engine will sputter for second when spray starting fluid in the intake, so I assume I’m getting spark. No codes or check engine light before shut off. To clarify: it will turn over but won’t start.
Sunday, October 11th, 2020 AT 4:31 PM

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Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

I would start by checking the compression to be sure the valve timing has not changed. You should have between 140 and 160 pounds of compression.

https://www.2carpros.com/articles/how-to-test-engine-compression

You can rent a tester for this procedure. We need to be sure there is no internal issues with the motor.

https://www.2carpros.com/articles/car-cranks-but-wont-start

Roy
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Sunday, October 11th, 2020 AT 4:47 PM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
Compression good. Let me back track, I've had issues with my A/C unit all summer and I had the vehicle idling as I attempted to jump start the A/C compressor. But I (mistakenly) touched a jump wire from the battery to a different pin on the A/C connector going to the battery (instead of the connector attached to the compressor and ECM) and the vehicle would shut off. I re-cranked it three times and it started and ran until the fourth attempt. After I touched the jump wire to the A/C connector for the fourth time, the vehicle wouldn't start. It turns over, but not cranking. Fuses and relays (everyone of them) are good. Then I discovered that I wasn't getting power to fuel pump, so I wired the fuel pump to a switch and auxiliary relay and the pump is sending fuel to the fuel rail and fuel pressure is good. Still no crank. So I sprayed start fluid in the intake and vehicle will sputter, so it seems I'm getting spark. Think now the computer might be the issue. I may have shorted it out or at least the part that controls fuel and ignition. Everything (except fuel gauge) works with switch to "on" position †blower, wipers, headlights, etc. What ya thinking?
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Monday, October 12th, 2020 AT 7:52 AM
Tiny
ASEMASTER6371
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Okay, got it.

What was the compression numbers?

What was the fuel pressure number?

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If it sputtered, yes, it may have some spark. The ECM does control the operation of the injectors based on the input from the crankshaft position sensor. Once the ECM see a RPM reading, it will command the injectors to fire off.

https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works

When you crank the engine, does the tach move up a little showing RPM?

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

I do not see any indication of the ECM at this time.

Do you have a scan tool that can read live data?

Roy

The Crankshaft Position (CKP) sensor is mounted into the right rear side of the cylinder block. It is positioned and bolted into a machined hole.
1. Raise vehicle.
2. Disconnect sensor electrical connector.
3. Remove sensor mounting bolt.
4. Carefully remove sensor from cylinder block in a rocking and twisting action.
5. Check condition of sensor O-ring.

INSTALLATION
1. Clean out machined hole in engine block.
2. Apply a small amount of engine oil to sensor O-ring.
3. Install sensor into engine block with a slight rocking and twisting action.

CAUTION: Before tightening sensor mounting bolt, be sure sensor is completely flush to cylinder block. If sensor is not flush, damage to sensor mounting tang may result.

4. Install mounting bolt and tighten to 28 Nm (21 ft. lbs.) torque.
5. Connect electrical connector to sensor.
6. Lower vehicle.

ECM

The PCM is located in the engine compartment near the battery.

To avoid possible voltage spike damage to the PCM, ignition key must be OFF and negative battery cable must be disconnected before unplugging PCM connectors.
1. Disconnect negative battery cable at battery.
2. Remove cover over electrical connectors. Cover snaps onto PCM.
3. Carefully unplug the three 32-way connectors from PCM.
4. Remove three PCM mounting bolts and remove PCM from vehicle.

INSTALLATION

Use the DRB scan tool to reprogram the new powertrain control module (PCM) with the vehicles original identification number (vin) and the vehicles original mileage. If this step is not done, a diagnostic trouble code (DTC) may be set.

1. Install PCM and 3 mounting bolts to vehicle.
2. Tighten bolts. Refer to torque specifications.
3. Check pin connectors in the PCM and the three 32-way connectors for corrosion or damage. Also, the pin heights in connectors should all be same. Repair as necessary before installing connectors.
4. Install three 32-way connectors.
5. Install cover over electrical connectors. Cover snaps onto PCM.
6. Install battery cable
7. Use the DRB scan tool to reprogram new PCM with vehicles original Identification Number (VIN) and original vehicle mileage
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Monday, October 12th, 2020 AT 8:22 AM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
Compression 152. Fuel pressure 50psi. I will check at lunch to see if there is a RPM reading while cranking. I do not have a scan tool.. So the ECM and PCM are the same unit (computer)?
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Monday, October 12th, 2020 AT 8:45 AM
Tiny
ASEMASTER6371
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Yes, that is correct. They call it many different things but in the end it is the engine control module.

Keep me updated.

Roy
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Monday, October 12th, 2020 AT 8:49 AM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
Do you think I should change out the crankshaft and camshaft sensors before I replace the PCM?
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Monday, October 12th, 2020 AT 8:54 AM
Tiny
ASEMASTER6371
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Let us do the testing first to see if they are needed.

Roy
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Monday, October 12th, 2020 AT 9:02 AM
Tiny
MIKE QUALLS
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  • 55 POSTS
Okay.
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Monday, October 12th, 2020 AT 9:11 AM
Tiny
ASEMASTER6371
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Let me know the results of the cranking test.

If you had a bad cam sensor, it would code. I doubt that is the issue at all.

https://www.2carpros.com/articles/camshaft-angle-sensor-replacement

Roy
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Monday, October 12th, 2020 AT 9:13 AM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
Okay, I'll check the RPM gauge while cranking at lunch, report back around 1 p.M. (CST)
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Monday, October 12th, 2020 AT 9:23 AM
Tiny
ASEMASTER6371
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Sounds like a plan.

Roy
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Monday, October 12th, 2020 AT 9:45 AM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
RPM needle didn't budge while cranking. Still no start.
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Monday, October 12th, 2020 AT 11:14 AM
Tiny
ASEMASTER6371
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I attached a picture of the connector for the crank sensor.

Check terminals 1 and 3 for 5 volts with the key on. Those 2 signals come from the ECM.

Roy
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Monday, October 12th, 2020 AT 11:25 AM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
Will do when I get home at 5. What would be the next step if I get 5 volts. When checking do I put voltmeter positive (red) on 1 and negative (black) on 3 or positive on 1 and neg to frame, then positive to 3 and negative to frame?
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Monday, October 12th, 2020 AT 11:34 AM
Tiny
ASEMASTER6371
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Red lead into 1 and black to good body ground.

Red lead to 3 and black to a good body ground.

Then red lead to 1 black lead to 2.

Red lead to 3 and black lead to 2.

Roy
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Monday, October 12th, 2020 AT 11:42 AM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
Okay, got it. If I get 5v what's next step I could do this evening?
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Monday, October 12th, 2020 AT 12:08 PM
Tiny
ASEMASTER6371
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If all is good then we will need to replace the crank sensor and see if you have a tachometer reading when cranking.

If you do not have the results, we will need to go to the ECM and verify the voltages before we condemn the ECM.

Roy
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Monday, October 12th, 2020 AT 12:13 PM
Tiny
ASEMASTER6371
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Did you respond?

I got an email but nothing came through.

Roy
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Monday, October 12th, 2020 AT 12:38 PM
Tiny
MIKE QUALLS
  • MEMBER
  • 55 POSTS
I got it and I'll check the crankshaft sensor this evening. Thanks
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Monday, October 12th, 2020 AT 12:41 PM
Tiny
ASEMASTER6371
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You are welcome.

Keep me updated.

Roy
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Monday, October 12th, 2020 AT 12:44 PM

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