No crank no start issue

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

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?

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

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)?

Yes, that is correct. they call it many different things but in the end it is the engine control module.

Keep me updated.

Roy

Do you think I should change out the crankshaft and camshaft sensors before I replace the PCM?

Let us do the testing first to see if they are needed.

Roy

Okay.

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

Okay, I'll check the RPM gauge while cranking at lunch, report back around 1 p.m. (CST)

Sounds like a plan.

Roy

RPM needle didn't budge while cranking.. still no start.

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

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?

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

Okay, got it.. if I get 5v what's next step I could do this evening?

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

Did you respond?

I got an email but nothing came through.

Roy

I got it and I'll check the crankshaft sensor this evening. thanks

You are welcome.

Keep me updated.

Roy

Okay, I couldn't get to the crankshaft sensor because I've got to jack up the jeep, but I checked the camshaft sensor at the front of the block and it read 4.35 volts on pins 1 and 3, grounded to Pin 2 and then to the chassis. It'll be Thursday evening before I can check the crankshaft sensor.....

Okay, keep me updated.

Roy

10-4.

Actually got a chance to check the crankshaft sensor yesterday. both the crankshaft and camshaft sensors are getting 4.35 volts each with ignition key on.

You checked it exactly as I suggested? You have 2 powers? Did you check using the body ground as well as the ground for the harness?

Roy

Yes, on both sensors.

Next step? to replace sensors?

Replace the crank sensor.

Roy

Will do.. I know it will be Thursday before I can do that, so I'll let you know Friday what happens.. thanks a ton.

You are welcome.

Always glad to help.

Roy

Suggestion on best way to remove sensor. The bolt is behind the sensor and the exhaust pipe limits access.....

It is tight. Use a wrench and when you get the bolt out, twist the sensor to release the o-ring and then pull it out.

Roy

Keep us updated.

Roy

Just checking in.. I got the sensor, but I didn't have time to put it in.. probably be sometime Saturday. have a great weekend.

You as well.

Roy

Okay, attempted to remove the crankshaft sensor, wouldn't budge, so I soaked it down with penetrating oil overnight, still would not budge, started tapping it, still no budge, then tapped harder and head broke off.. I Googled the situation and seems it's common for them to be seized in by rust. some recommend chipping it out piece by piece.. what do you recommend? By the way the camshaft sensor came out very easily....

Okay, why did you replace the cam sensor? We or I did not recommend that.

Yes, you will need to chip it out. Once you get down to the seal, it will free up and come out.

Roy

Thought since while I was at it (Cam), I'd install a new one, $25.00. Okay, I'll chip away at the Crankshaft sensor this evening.....

Sounds like a plan.

Roy

Thanks.