02 Liberty 3.7 - New Crank Sensor now No Start

[alecmesa96]

Happy Monday folks, first time poster here. Got this jeep for free about a year ago and wanted to share a few questions I had regarding a recent repair. As always, I'll start with the story...

Was in my back yard hooking up my boat one night so that I could have everything ready to go out in the morning. Just as I was getting the trailer connected, the engine sputtered and shut off pretty quick. I hopped back in and tried starting it, as expected it just cranked and cranked. After about 15 minutes of waiting, I cranked it again while having my foot all the way to the floor and it just barely caught but it did start up and run on its own. When it started, it ran just fine. While I was cranking, I saw the tach needle go crazy, not all over the place but between 500 and 1500rpm pretty randomly, and it threw a code for the crank sensor. I figured I'd go get a new crank sensor in the morning as I didn't want it to leave me stranded in the middle of some road with my boat attached. I parked it in my driveway and shut it off.

Next morning got up early went to NAPA and got a crank sensor. I know I should have gone Mopar for this sensor but I was in a rush and didn't have time to wait since I was selling the boat that day and planned to meet someone. Got home and tried starting the truck to get it in the garage, wouldn't even crank. Had plenty of power but the starter would not engage so I just pushed it into the garage. Jacked up the truck, disconnected the sensor and removed the bolt. Found that it was stuck pretty good, so I got a vise grips on it with some PB blaster however it still snapped off in the block. I said screw it and it has been sitting all winter as I haven't really had the time to get it out due to my college class schedule.

Yesterday was a pretty nice day for us in southeastern Wisconsin (53 degrees) so I decided to go out and start hacking away. I pulled the passenger side cat converter so I had plenty of room, then drilled a hole in the old sensor. I put a big screw in it along with a washer, got a crowbar and gave it hell, came right out with the help of more PB blaster.

After installing the new sensor but before installing the passenger side cat and connecting the O2 sensors, I put the battery in and decided to give it a go to see if anything had changed. Still would not crank via the key. I got it to crank by removing the starter relay and jumping the terminals. It cranked just fine, saw the tach creep up a little when cranking so I'm guessing the new sensor is working, but still no start. Won't even try to fire and I don't smell any fuel whatsoever so I'm assuming that the injectors are not firing. Plenty of fuel pressure at the rail. I have not gotten the chance to test for spark as I figured it was pointless since it was pretty obvious that I have no fuel.

My question is...what now? Should I just get a Mopar sensor and replace it again? I'm thinking the no-crank problem may be related. I don't know anything about Chrysler products as I mainly work on heavy equipment. Any guidance here would be greatly appreciated.

 

[LibertyTC]

Welcome. How many miles on your Jeep?
A lot going on there. I would like to say swap out the Napa Crank sensor for a Mopar one !
Did you charge your battery up before installation? Take the battery in for a load test if possible.

 

[Billwill]

The fact that the engine only turns over when you jumper the Starter Relay usually means that the Actuator Pin Assembly has broken. Jumping the Starter Relay overrides the Ignition Switch, the Actuator Pin Assembly, the Park Sensor and the Neutral Sensor.
So first check if it turns over in Neutral instead of Park.

The Actuator Pin Assembly is a hollow rectangular rod that rotates when you turn the ignition key. The end of this rod starts to crumble...at first it has enough strength to turn the ignition ON but bends when trying to go that last bit to activate the Starter Relay. This is a very common problem!

Remove the plastic covers covering the steering column....two Female Torx screws.

Remove the smaller Female Torx screw that holds the ignition switch onto the column. Newer KJs have a "security" Torx screw there which requires a Male Torx driver with a hole drilled down its center...your 02 KJ probably has a standard Torx screw.

When you pull the ignition switch off you will probably see some debris falling down which indicates a broken Actuator Pin Assembly.

You can put the ignition key into its normal slot to activate SKIS Anti Theft and disable steering wheel lock.

While in Park or Neutral turn the Ignition switch with a small flat screwdriver....engine should turn over and start normally unless you have another issue.

Obtain a new Actuator Pin Assembly from Dorman...the Agents do not stock it.

You definitely need to use Mopar Cam and Crank Sensors.

Once you get to this stage if it is not running you need to pull codes out with your Code Reader.

If you do not have the Service Manual download the 2002 Jeep KJ Service Manual here:

www.colorado4wheel.com/manuals/Jeep/KJ/

 

[LibertyTC]

Thanks Bill once again for your help!

 

[alecmesa96]

Welcome. How many miles on your Jeep?
A lot going on there. I would like to say swap out the Napa Crank sensor for a Mopar one !
Did you charge your battery up before installation? Take the battery in for a load test if possible.

Good morning, 189,*** miles on the truck. The battery is 2 years old now and I did have it fully charged right before cranking.

While in Park or Neutral turn the Ignition switch with a small flat screwdriver....engine should turn over and start normally unless you have another issue.

You definitely need to use Mopar Cam and Crank Sensors.

Thanks for the information. I will take some time this weekend and check for this broken pin you speak of. I also forgot to mention that when I pulled the fuse that says starter, it was pretty heavily corroded, so perhaps a new fuse box will be in order. I did not have a meter at the time to start probing stuff for power but I will make sure to have one next time I go out there. I will also make sure to pick up a Mopar sensor since I made sure to leave everything off in case I had to do it again. At least it will be easy to pull out now!

I'll post results.

 

[Billwill]

Fuse #8 40A carries the high current through to the starter motor when the Starter Relay is energized or when you jumper the Starter Relay out. That obviously has a clean enough connection to carry the current so the Starter Motor is able to turn over.

But there could be other fuses that are not making good connection so it is always worth while pulling fuses out and putting them back in a few times to clean the contacts a little bit.
Do this for the internal fuse panel as well!

You need to check fuses with a volt meter where if you get +12 volts on the one side of the fuse then you expect +12 volts on the other side...also pull the fuse out and measure it with an Ohm Meter...fuses often visually look OK but have actually blown somewhere out of sight!

There are also lots of connectors around the Jeep carrying the voltages around...if these are exposed to water, snow, salt etc. the contacts can also get damaged....this you generally have to find by tracing with a Volt Meter.

 

[alecmesa96]

Just a minor update with this one,

I called a few of my local Mopar dealers and was told by all of them that they stopped making the crank sensors 3 years ago...poop.

I'm going to hope that someone somewhere has one lying around somewhere under a pile of parts or in a warehouse somewhere.

 

[LibertyTC]

Did you try mopar wholesale parts online?

 

[alecmesa96]

I did, and I was only able to find the sensor for 2007+ (part number 56044180AC). It looks completely identical but I don't want to be throwing any more money away unless I know it will work.

 

[alecmesa96]

Alright, time for an update!

Just spent some time on the truck poking around and hooked a scanner to it. Only code that was being thrown was from the TCM saying the battery was disconnected. Then I bought up a live graph of engine RPM. Cranked the engine, absolutely nothing. Replaced the cam sensor with another NAPA sensor since they are part of the same circuit (just to test), still 0 RPM while cranking. I have +5vdc to both the crank and cam sensor, good ground, and the signal wires going to the computer are intact. I didn't get to tearing away at the steering column yet but I plan to do that soon. I guess I'm gonna keep working on finding a Mopar sensor. I have had several people recommend I just go to a junkyard and yet one, however it's pretty likely that I won't be able to get a junkyard sensor out in one piece anyway. If it was that easy, I'd have done it already.

 

[alecmesa96]

Last update, got the truck running! I took the time to probe all the wiring from the sensor to the PCM, it was all good. Then went through voltage tests to see if the sensor was putting out a signal while cranking, it was. I was about to condemn the computer until I thought to check the resistance across the fuses. Whoa, they were reading up to 46 megaohms. Replaced them all, tried turning the key, it cranked with the key and started right up. I don't know why I didn't check something so simple like that sooner. Amazing how easily the simple things can be overlooked. Thanks everyone for the help.

 

[Billwill]

Glad you got it fixed!
The Jeep fuses are not always water proof and can get rust inside.

You could have a fuse that looks OK, has +12 volts on the one end and if there is no load on the other side also shows +12 volts.

However this particular fuse may have an internal resistance of several thousand Kilo Ohms! Because there is no current going through it there is no voltage drop so you will still see +12 volts on the other side!

Only when current starts going through the fuse will you see a voltage drop...easy to measure if the Jeep is running but if Jeep is dead then a bit of a quandary!

So you either need to pull each fuse out at a time and measure its resistance...should be zero Ohms. Better to replace them with new ones.

In the Mainframe Computer industry we used to replace certain Critical Fuses on a time-based rotational basis. These were large solid sealed fuses but they can spit off metal over time and become vulnerable!

 

[Michael Wolfe]

Glad you got it fixed!
The Jeep fuses are not always water proof and can get rust inside.

You could have a fuse that looks OK, has +12 volts on the one end and if there is no load on the other side also shows +12 volts.

However this particular fuse may have an internal resistance of several thousand Kilo Ohms! Because there is no current going through it there is no voltage drop so you will still see +12 volts on the other side!

Only when current starts going through the fuse will you see a voltage drop...easy to measure if the Jeep is running but if Jeep is dead then a bit of a quandary!

So you either need to pull each fuse out at a time and measure its resistance...should be zero Ohms. Better to replace them with new ones.

In the Mainframe Computer industry we used to replace certain Critical Fuses on a time-based rotational basis. These were large solid sealed fuses but they can spit off metal over time and become vulnerable!

I used to do the same with control relays. Every time one opens up, you get some amount of arcing, which damages the contacts, especially with DC. Sometimes it's minimal, other times its pretty substantial, depending on how much amperage is being controlled. In certain situations, we would schedule replacement to prevent unscheduled downtime and service calls. Good point about voltage vs load. It may look ok static, but may not be able to support the designed load. Similar to having a wire conductor too thin to work properly.