89 No Crank Electrical Mystery

[barimpact]

I recently came into a 1989 Comanche 4.0L 5 speed manual 4x4 (Pioneer trim). It's rusty, lifted at least 6 inches on 31s, and doesn't run. I could get it to crank over with a battery jump starter, but of course with the dead battery, that cranks slow; however, it wasn't getting fuel. I replaced the fuel pump and tried cranking it over, but again, really slow, and low enough voltage I felt like the starter was using all the power (therefore fuel pump couldn't pump).  So I decided to grab my 2000 Cherokee and use jumper cables, but after hooking it up, the Comanche still showed low voltage on the dash, and cranked over even slower than before. I used my multimeter and checked to make sure the cables were actually transferring power from the XJ to the MJ (under the hood of the XJ is extremely muddy), and everything checked out. I still cleaned the connections anyways, but nothing helped. It was basically just clicking like it had a dead battery. So next I took the battery out of my XJ and put it into the MJ and it just clicked like the battery was dead. Multimeter showed 12.7V at the battery, but the MJ dash showed 9V. I tried cleaning connections again, but still just a click like dead battery. When I put the battery back in the XJ, it fired right up like normal, no slow cranking, so I know it wasn't the battery. So now I'm at a loss. 

 

A couple things maybe worth noting:

1) When cranking slowly with the battery jump starter, the battery cables would get really hot, like it had to draw a lot of current to slowly crank.

2) A lot of the dash is taken apart as the previous owner said he planned on chopping the whole front off and replacing everything from the doors forward with a 99 XJ (which I will not be doing). The cluster is still plugged in and seems to be working correctly.

 

Any direction would be appreciated. My first thought is that maybe the starter motor is bad, so it's taking a lot of power but cranking slowly. But before I start throwing money at a project I'm just gonna beat up off road (it's way too rusty to restore and only cost me $250), I'd like to see if anyone here has had the same issue.

[Ωhm]

2 hours ago, barimpact said:

the battery cables would get really hot

 

2 hours ago, barimpact said:

My first thought is that maybe the starter motor is bad

Suspect starter motor.

Welcome to the forum.

[jdog]

Either starter or bad cables

1988 swb 4.0 ax15 np 231 red with gray interior.

[DirtyComanche]

The engine also might be totally f'd and that starter is doing everything it can to turn it.  Turning the engine with a big ratchet will tell you if this is the case in a hurry.

 

More likely starter or bad cables.

[DirtyComanche]

Also make sure the trans and/or tcase is in neutral.  The clutch may be packed up with mud and hanging.

[Manche757]

You have checked to see that the cables are not touching the frame?  Cable to starter for example.

[barimpact]

2 minutes ago, Manche757 said:

You have checked to see that the cables are not touching the frame?  Cable to starter for example.

I did a quick glance but did not look hard. I'll have to check more closely.

 

 

2 hours ago, DirtyComanche said:

Also make sure the trans and/or tcase is in neutral.  The clutch may be packed up with mud and hanging.

Not having it in neutral got me the first time lol 

 

 

2 hours ago, DirtyComanche said:

The engine also might be totally f'd

I thought of this too, but I have heard it run on starter fluid, so it's not grinding or locking up.

 

 

4 hours ago, Ωhm said:

Welcome to the forum.

Thanks!

 

I have a friend with a rebuilt starter laying around so I will check on the wires and throw this in just to try it. The only part that still puzzles me is that the dash reads 9V with the key to run and the battery still showed 12.8V with the multimeter during the same test (before cranking over). 

 

Thanks for the input everyone.

[WahooSteeler]

10 minutes ago, Manche757 said:

You have checked to see that the cables are not touching the frame?  Cable to starter for example.

 

I was also thinking short/ground issue with the hot cables. 

[jdog]

Factory gauge are not accurate measurement for the voltage. When checking the cables make sure to ohm them from end to end.

1988 swb 4.0 ax15 np 231 red with gray interior.

[JMO413]

I would check the ground carefully. Renix are very pick about the ground.

http://www.cruiser54.com/

I would start with cruisers first 6 and go from there.

[Comanchejess]

On 7/24/2019 at 10:25 AM, Ωhm said:

On 7/24/2019 at 7:54 AM, barimpact said:

I recently came into a 1989 Comanche 4.0L 5 speed manual 4x4 (Pioneer trim). It's rusty, lifted at least 6 inches on 31s, and doesn't run. I could get it to crank over with a battery jump starter, but of course with the dead battery, that cranks slow; however, it wasn't getting fuel. I replaced the fuel pump and tried cranking it over, but again, really slow, and low enough voltage I felt like the starter was using all the power (therefore fuel pump couldn't pump).  So I decided to grab my 2000 Cherokee and use jumper cables, but after hooking it up, the Comanche still showed low voltage on the dash, and cranked over even slower than before. I used my multimeter and checked to make sure the cables were actually transferring power from the XJ to the MJ (under the hood of the XJ is extremely muddy), and everything checked out. I still cleaned the connections anyways, but nothing helped. It was basically just clicking like it had a dead battery. So next I took the battery out of my XJ and put it into the MJ and it just clicked like the battery was dead. Multimeter showed 12.7V at the battery, but the MJ dash showed 9V. I tried cleaning connections again, but still just a click like dead battery. When I put the battery back in the XJ, it fired right up like normal, no slow cranking, so I know it wasn't the battery. So now I'm at a loss. 

 

A couple things maybe worth noting:

1) When cranking slowly with the battery jump starter, the battery cables would get really hot, like it had to draw a lot of current to slowly crank.

2) A lot of the dash is taken apart as the previous owner said he planned on chopping the whole front off and replacing everything from the doors forward with a 99 XJ (which I will not be doing). The cluster is still plugged in and seems to be working correctly.

 

Any direction would be appreciated. My first thought is that maybe the starter motor is bad, so it's taking a lot of power but cranking slowly. But before I start throwing money at a project I'm just gonna beat up off road (it's way too rusty to restore and only cost me $250), I'd like to see if anyone here has had the same issue.

Suspect starter motor.

Welcome to the forum.

this might sound ridiculous, but I was having similar issues, bypassed my ignition and boom... My jeep started. currently still have the ignition bypassed. 

[cruiser54]

Swap starters with the XJ......

 

Or, take the one off the MJ and take it apart. super simple. an old oil leak can foul them badly and frequently they can be brought back to life with a good cleaning using brake cleaner. 

[Cheapamanche]

15 hours ago, cruiser54 said:

Swap starters with the XJ......

 

Or, take the one off the MJ and take it apart. super simple. an old oil leak can foul them badly and frequently they can be brought back to life with a good cleaning using brake cleaner. 

x2 on this.

I would start by swapping. If it starts then you can quit wasting time hunting down other electrical gremlins. Then clean the other one while it's off.

[Manche757]

Did you get this solved?

[barimpact]

I haven't been able to work on the truck - been moving all my mechanic stuff to a new "shop" but I should be able to get back to it soon. I'll definitely update here when I get the starter swapped with a working one and check wiring.