86 MJ no crank

[Dillithium]

Hey all,

 

It's been a while since I've posted anything here. Mostly because my Jeep has been (mostly) problem free for years now. Been daily driving it for a long time now, so haven't done much in the sense of upgrades.

 

Anyway, that's not why I'm posting. For the past year or so, it's been cranking slowly. Slower and slower, until it stopped entirely last Saturday. It simply did not crank at all, it just clicked and nothing more. I knew that the starter was going out, (there was a hole in it, it was super cruddy and old) so I replaced it. However, that did not resolve my issue.

 

I've been doing some research but I can't seem to nail down what may be causing this. When cranking, this happens:

 

- Fuel pump comes on

- Starter relay clicks ( verified by noise and touch)

- Starter solenoid clicks, though not every single time I turn the key.

- My dashboard clock turns off, but none of the lights dim when attempting to start. Not the interior lights, nor the headlights.

 

My current suspects are the starter relay and the ignition switch. However, for everything else the ignition switch seems to be working just fine. The fuel pump comes on, I can operate all electronics in its secondary position and so on. So it doesn't seem likely that it's the ignition switch. It also seems like a PITA to replace, so I'm hoping it's something else. The starter relay seems to click, but I don't know if it's actually carrying current to the starter solenoid.

 

Other things I've tested:

 

- Battery has good voltage. Haven't load tested it, but I did try jumping it with another battery, made no difference.

- Battery terminals aren't pristine, but they're not dirty either. I can't imagine them being solely responsible.

 

There's a large red wire running to the starter and a smaller green wire. Could it be possible to hook up the green wire to a wrong terminal? My new starter came with 2 tab connectors, but they were different sizes so I don't think it's that. 

 

Any tips on what to test next for the obvious fault?

 

[Ωhm]

Battery Cables????

[Dillithium]

I think I'm going to try scrubbing/cleaning all connections and test the relay tomorrow. Visually everything looked good, but you never know right?

 

[Ωhm]

Need voltage drop test for cables.

[Dillithium]

From the battery to the relay? I'll clean everything up and post back tomorrow. Thanks for thinking with me.

[Ωhm]

Connect DVOM as follows:

B+ Cable
Battery positive post to Starter Motor post.
Looking for 0vdc on the DVOM during engine CRANK.

 

B+ Cable
Battery positive post to Starter Relay post.
Looking for 0vdc on the DVOM during engine CRANK.

 

B- Cable
Battery negative post to Starter Motor Case.
Looking for 0vdc on the DVOM during engine CRANK.
 

[Dillithium]

Fixed it!

 

Turns out, it was a wiring issue which was somewhat my fault.

 

The old starter had a post terminal and one spade connector. The new starter has 1 post terminal and 2 spade connectors, a small one and a large one.

I wired the exciter wire to the same size (large) spade connector as the previous starter. Apparently this was just an auxiliary ground connection. I had to connect the exciter wire to the smaller spade connector. So I crimped on a new connector and she fired right up.

 

I figured this out by connecting the exciter wire ( the small gauge wire leading to the starter) with a jumper to the + battery post. Nothing happened, so that meant the starter was dead or I wired it wrong.

 

KISS right?

[silvertwinkiehobo]

Yeah, you have to be careful about that. When installing a replacement anything (especially on AMC vehicles, where 'mix and match' was the parts department motto), you need to set old and new side-by-side and compare them. You might've caught the error before installation, and had the new terminal crimped on, because electricity is weird--it does what it wants to, when not contained. That could've resulted in damage to your electrical system. Years ago, I worked on a Wrangler that the owner put the wrong group battery in (he was trying to save money), and even though the battery was the same size physically, the posts were reversed, and when he hooked it up, he fried a few things, namely the SBEC, because he didn't notice the reversed terminals (they are, after all, different sizes). So you were very fortunate you didn't cause any damage, and I'm glad your rig is back up and running. But please, compare and pay attention when dealing with your electricals.