2004 4.0 auto, crank no start

[Larry L TJ]

A little history here. Bought the jeep in May. a friend suggested I become a member here. That was good advice. Had issues starting occasionally. So, I read everything I could on the issues. Since then, I have replaced the Crank Position sensor Twice. (Currently a Mopar from Ebay). The Cam position sensor and OPDA (Crown). The TPS, IAC, Fuel pump, (Delphi) and occasionally just out of the blue it will not start. I have replaced all relays and tested all relays with a load and only found 1 bad so I took it out of the occasion. So, Thursday evening went out to eat filled up with gas and jeep would not start. Checked all fuses, Swapped fuel relay, I thought I boosted fuel pump from battery, did not hear it come on., could have been my hearing. So cranked the battery down. Had it hauled home. Unhooked the batter and did an 8-hour charge while doing other things. Let it sit until this morning. went out made jumper wires to fit fuel pump plug hooked to battery and pump came on. Tried starting from switch it would attempt to start but not. Sprayed starting fluid in it sever times and it picked up and ran. Let it idle until it reached normal temp and went on a 12-mile test ride. came back shut it off went into the house for a few minutes came back started no issues. Drove 4 mile to car wash cleaned jeep started no issues. came back home shut it off and it started. no issues. This jeep has never died unless I cut the key off. When it starts it idles and runs great. It has never lost power or sputtered while driving. Does anyone have any ideal why it will start 30 times and just out of the blue does not start. no CEL lights this time at all. Wrangler Fix tested the PCM and found no issues. Anyone have any ideal of why?

 

[Chris]

A little history here. Bought the jeep in May. a friend suggested I become a member here. That was good advice. Had issues starting occasionally. So, I read everything I could on the issues. Since then, I have replaced the Crank Position sensor Twice. (Currently a Mopar from Ebay). The Cam position sensor and OPDA (Crown). The TPS, IAC, Fuel pump, (Delphi) and occasionally just out of the blue it will not start. I have replaced all relays and tested all relays with a load and only found 1 bad so I took it out of the occasion. So, Thursday evening went out to eat filled up with gas and jeep would not start. Checked all fuses, Swapped fuel relay, I thought I boosted fuel pump from battery, did not hear it come on., could have been my hearing. So cranked the battery down. Had it hauled home. Unhooked the batter and did an 8-hour charge while doing other things. Let it sit until this morning. went out made jumper wires to fit fuel pump plug hooked to battery and pump came on. Tried starting from switch it would attempt to start but not. Sprayed starting fluid in it sever times and it picked up and ran. Let it idle until it reached normal temp and went on a 12-mile test ride. came back shut it off went into the house for a few minutes came back started no issues. Drove 4 mile to car wash cleaned jeep started no issues. came back home shut it off and it started. no issues. This jeep has never died unless I cut the key off. When it starts it idles and runs great. It has never lost power or sputtered while driving. Does anyone have any ideal why it will start 30 times and just out of the blue does not start. no CEL lights this time at all. Wrangler Fix tested the PCM and found no issues. Anyone have any ideal of why?

Since your TJ runs great when it starts and there are no CEL lights, it might be worth considering the following:

Fuel Pump Relay or Wiring Issues: Even though you've replaced relays, wiring issues between the ignition switch and the fuel pump relay can sometimes cause intermittent problems. Make sure you check for any corroded connectors or damaged wires.

Ignition Switch: If the ignition switch is worn or faulty, it might not be consistently completing the circuit for the fuel pump or other critical components. This could explain why it sometimes starts and sometimes doesn’t.

Connection Issues at the Fuel Pump: You mentioned testing the fuel pump directly and it worked. Make sure the connections at the pump and the wiring harness are solid. Sometimes a poor connection can cause intermittent failures.

Camshaft Position Sensor: Even though you've already replaced it, it could still be a factor. If the new sensor is faulty or there’s an issue with its wiring, it might not always send the correct signal for starting.

PCM Grounds: Sometimes a bad ground can cause erratic behavior with the PCM. Check the grounds associated with the PCM and ensure there are no loose or corroded connections.

Temperature Sensitivity: Since you were able to start it after letting it sit for a while, it might be temperature-related, potentially with the PCM or other sensors behaving differently when warm.

Since it seems to start when you spray starting fluid, that points towards a fuel delivery issue. Given that it doesn't sputter when running, it could be a problem that only occurs during initial crank. Keep monitoring any changes in how it behaves and those diagnostic paths might be telling.

 

[Larry L TJ]

Since your TJ runs great when it starts and there are no CEL lights, it might be worth considering the following:

Fuel Pump Relay or Wiring Issues: Even though you've replaced relays, wiring issues between the ignition switch and the fuel pump relay can sometimes cause intermittent problems. Make sure you check for any corroded connectors or damaged wires.

Ignition Switch: If the ignition switch is worn or faulty, it might not be consistently completing the circuit for the fuel pump or other critical components. This could explain why it sometimes starts and sometimes doesn’t.

Connection Issues at the Fuel Pump: You mentioned testing the fuel pump directly and it worked. Make sure the connections at the pump and the wiring harness are solid. Sometimes a poor connection can cause intermittent failures.

Camshaft Position Sensor: Even though you've already replaced it, it could still be a factor. If the new sensor is faulty or there’s an issue with its wiring, it might not always send the correct signal for starting.

PCM Grounds: Sometimes a bad ground can cause erratic behavior with the PCM. Check the grounds associated with the PCM and ensure there are no loose or corroded connections.

Temperature Sensitivity: Since you were able to start it after letting it sit for a while, it might be temperature-related, potentially with the PCM or other sensors behaving differently when warm.

Since it seems to start when you spray starting fluid, that points towards a fuel delivery issue. Given that it doesn't sputter when running, it could be a problem that only occurs during initial crank. Keep monitoring any changes in how it behaves and those diagnostic paths might be telling.

Some other things I have done when I was chasing a No bus message in August before replacing the PCM. I physically inspected every connector module except the lights on the jeep. (All points in the starting circuit from PCM/TCM &transmission & under the dash). I had to replace heater and AC core, so I did all of this at the same time. Used FSM on connection ports and ground locations. (learned a lot). I have also cleaned ever ground connection on the jeep. Added a ground block on the TCM side and physically grounded TCM/PCM and motor to firewall on passenger side. Though it may be vapor locking so I reinsulated the fuel rail, injectors and manifold valley back in June. I have cleaned all relay & fuse sockets & inspected the bottom side of the PDC under the hood. Inspected wiring and replaced all Loom under the hood from PCM to TCM.

 

[tr21triton]

sounds like ignition switch. Mine started acting like that a month ago. sometimes it started fine other times I had to turn the switch to start 10-12 times until it would come alive and start.