Starter Solenoid diagnosis questions

[JefCooks]

Hey fellas, I need some help with my '92 Comanche w/ 4.0 & AW4. Last week I refurbished my parking brake which entails pulling the driver side fuse panel. Once I got everything back together I turned the truck on, it fired right up like normal and I took it around the neighborhood to make sure everything was as before. A few things were wrong, radio didn't come on, dome lights didn't work & headlights didn't work, so I turned it off and started checking into some things. The IOD fuse in engine bay had blown which caused the radio and dome to not be working unless engine was running and I had to reconnect my headlight wiring. Once I got that all squared away I went to turn the truck on again and it wouldn't crank. I checked all the fuses, relays, battery is fully charged, tried it in neutral, nothing is working. The starter will spin when I get underneath and bump it but nothing from the ignition. When turning the ignition I can hear the relay charging but nothing goes to the starter. This leads me to believe the issue is with the starter solenoid but I don't know where to start because I replaced the starter and solenoid with a Bosch unit 2 years ago and repaired the coolant leak that was dripping onto the starter causing the first one to go out. Also, before replacing the first starter I cleaned and lubed the NSS. The extremely sudden change in functionality makes me think it's electrical but since I can hear the relay working, it makes me think it's in the starter. Please help me diagnose.

[zomeizter]

Sounds like connection issues with the ones you were handling when you did your parking brake work, double check again in the areas you were working with. Once you are sure all is good there, ensure that the starter relay is getting power from the ignition switch when you crank. A test light will be handy for this...

[JefCooks]

So there's nothing on/in the interior fuse panel that would affect the starter. I put the multimeter to the engine bay relay/fuse panel today and found that the relay gets the 12V signal from the ignition but there is no high power feed to or from the relay. My battery cables don't have a ton of corrosion on them but I'll pull them off and try again. Anything else I should check? What are my next steps? Please don't tell me to pull the engine bay panel apart.

[Pete M]

if there's no 12v feed at the relay, did you track that wire back?  12v should be there.  at least I think so.  I'm far more familiar with the renix stuff.

[JefCooks]

I haven't because I was hoping it would be something else and I wouldn't have to pull the fuse box apart. I guess I'll have to do that next.

[Pete M]

does the HO have a main primary wire that feeds the entire box?  can you check that without disassembly?

[gogmorgo]

So when you’re down at the starter jumping stuff, you’re taking power from the post with the cable going to the battery, and then putting power to the small trigger post? If that doesn’t crank the engine or only spins the starter motor then you’ve got an issue with the starter/solenoid. If it does crank the engine over, then you’re not getting the start signal when you hit the key. 
Jumping between the two large terminals on the starter solenoid will spin the starter motor but won’t push the bendix out to engage the flywheel and turn the engine. 

[JefCooks]

1 hour ago, Pete M said:

does the HO have a main primary wire that feeds the entire box?  can you check that without disassembly?

Yes, it does. The + battery clamp has 2 large wires feeding directly off the clamp. One goes to starter, the other goes to PDC.

 

57 minutes ago, gogmorgo said:

So when you’re down at the starter jumping stuff, you’re taking power from the post with the cable going to the battery, and then putting power to the small trigger post? If that doesn’t crank the engine or only spins the starter motor then you’ve got an issue with the starter/solenoid. If it does crank the engine over, then you’re not getting the start signal when you hit the key. 
Jumping between the two large terminals on the starter solenoid will spin the starter motor but won’t push the bendix out to engage the flywheel and turn the engine. 

You're right. I was just reading a NAXJA page and found same info. I'm gonna try to jump the solenoid rather than just the starter motor.

 

Thanks so far everyone!

[JefCooks]

UPDATE:  I think I figured it out. I pulled apart the PDC and everything was in order. Followed all wires and they all had power when they were supposed to. So I got under the truck and tried to jump the starter again like gogmorgo mentioned. I connected power to the solenoid post and it clicked but then retracted and all power in the truck went out. I pulled battery terminals off and let it sit overnight. This morning I went  back out, reconnected the battery and everything powered up but still no crank. I got under the truck and pulled the starter off to bench start it, nothing. The starter motor still works fine when connected directly but any power through the solenoid stops dead. The starter and solenoid are a Bosch reman unit under warranty so they're sending me a new one. I'll update this thread once I get the new solenoid in.

 

TL;DR: I think it's the solenoid

[gogmorgo]

The whole truck dying when you pull a big load like the starter sounds more like a low battery or connection issue. Especially if you’re not turning the key to the start position which does shut some things down. 
I only ask this because we’ve been down the road once, but when you were bench testing you definitely had it hooked up like in the truck, with the starter housing connected to the battery negative, and power to both the b+ terminal and jumped across to trigger the starter? And did you use the truck’s battery or one that you know is good… I haven’t scrolled back up but you did verify the MJ’s battery was fully charged?

Its a strange coincidence the starter would die right then while you were doing other stuff… not saying impossible but usually when I messed around with a bunch of stuff and then something else quick working, it ends up being something I messed with and didn’t put back together correctly or forgot to plug back in.  And if a guy left the key on for a couple hours while he doing the messing it can definitely drain the battery. 

[JefCooks]

I tested the battery and it had full charge. I also did not leave the ignition on the whole time. Owning a 30 year old truck; if the engine is not running, the ignition is not on. When I pulled the starter I bench tested it with my running diesel Grand Cherokee and the negative hooked to mounting the ear. The starter spins like new but the solenoid does nothing. I'm going to the JY today to get a. 8.8 for a wrangler I have and I'm gonna get a solenoid from an XJ while I'm there to use in the interim while waiting on my warranty solenoid from Rock Auto. Once I get home I'll test it out and let you all know.

[JefCooks]

I got it working again!

And....I feel like an idiot. While waiting for the new starter I pulled the battery and set it on the trickle charger. The new starter came in, I swapped it out, hooked up the battery and still nothing. At this point I decided to start over and go from least complicated to most complicated. Having been to the JY recently I came home with an abundance of fuses and relays so I decided to replace all fuses. Still nothing. Then I decided since I was there I'd just fill all the fuse and relay locations, even the ones that don't work, so that I would have spares handy. Then the truck started. Evidently, when the IOD fuse went (see first post), so did the 40A ABS fuse. I mindlessly pulled the ABS fuse and tossed it because I don't have ABS then immediately forgot that I had done such a thing. It turns out that my ABS fuse is not for ABS, but a fuse betwixt the solenoid relay and the solenoid itself. Now the truck is running great again and all is right in the world. Thank you to all who helped and to all who may read in the future, check ALL fuses and relays, even if it doesn't seem applicable.

[Pete M]