Starting problems

[railroad sam]

Hello Jeep Folks,

I have a 1996 Jeep Cherokee. 4.0L. 2wd, automatic. 

Sometimes the Jeep starts right up. Take a drive. Turn engine off. An hour later will not start. Stranded again. I'm thinking it's in the ignition switch itself. Unlike my 87 Comanche I don't think the Cherokee has a actuator rod going from key cylinder to actual ignition switch on steering column.

In a no start situation with the Cherokee. I thought about leaving key in the on position and with vehicle secure from moving crawling under and try hot wiring to see if it will start. Kind of forgot how to do that too.

Any input would be appreciated. 

Thanks,

Railroad Sam

[JYau]

Have you checked the starter relay? See this thread: 

 

[railroad sam]

Yes I've checked the starter relay in the under hood fuse box. Even switched it with same size relay. Didn't help. Thanks

[gogmorgo]

Absolutely nothing when you hit the key? Have you tried starting in neutral? Running the shifter back and forth a few times? If that changes anything, this is classic dirty neutral safety switch (nss) behaviour. Bonus points if your reverse lights are also intermittent. If that sounds accurate, pop it off, pull it apart, clean it, coat the copper bits in dielectric grease (or don’t, I’m not your mom) and run a bead of RTV around the gasket before you put it back on. If you really want to test first, see if you’ve got power to the trigger on the starter solenoid or to pin 86 (and ground to 85) of the starter relay socket when you turn the key. You can also test a couple pins on the trans connector (near the trans dipstick) to for sure isolate the issue  but I don’t remember which ones. 
 

Of course it could also be a tired starter, or any other number of things. 
To test the starter itself, or just get it started, make damn sure the thing won’t move on you if the engine starts then take a screwdriver you don’t care about and short from the b+ terminal on the starter solenoid (the one the positive battery cable runs to) across to the small terminal on the solenoid (the starter trigger). Will be sparks, but it should engage the starter, and start if the key is on. If that doesn’t engage the starter then strong chances the starter’s shot. 

[railroad sam]

Thanks for your suggestions. Yes I've tried starting it in neutral. Checked starter relay too. It's off and on starting. Works for days then nada. Let it sit awhile or overnight then might start or not. 

Next time no start. I'm going to leave key on, transmission in park and emergency brake on, crawl under with a screw driver and spark up the starter. My 87 MJ i used to have to do that. It was bad solenoid on engine wall.

As far as the pins 85 and 86 that's over my head. I did pull relay, moved another one to starter slot and nothing, no start.

 

Thanks again,

Sam

[gogmorgo]

Standard relay diagram:

 

A relay is just an electric switch. It uses a small current to control a larger current. If you send power through pins 85 and 86, the relay connects pins 30 and 87 together. 
Pin 85 should have continuity to ground. 
Pin 86 should get 12V when you hit the starter. 
Because all you’re doing with those two is energizing a coil, you can get away with having pins 85 and 86 reversed in some cases, so even though it’s not “proper” sometimes a manufacturer will set it up backwards. 
Pin 30 should have constant 12V

Pin 87 is the load side, so will have some continuity to ground, and if you put power to it, in this case it should crank the starter. If you’ve got power at pin 30, the easiest way to get power to pin 87 is to jump across the two. 
 

If you have a good relay in the socket but there’s a wiring issue, it will not start. The start signal wiring passes through the neutral safety switch between the ignition switch and pin 86, so if it’s not starting and you pull out the relay and have power at pin 86 when you turn the key to start, and you have ground at pin 85, and it still won’t start if you put the relay back in, it’s probably related to the starter itself and not the neutral safety switch. 
 

Also because the diagram references it, 87a is a terminal that gets used for the load if you want the relay to switch off when you put power to it, or switch from one load to another.