Electrical gremlins

[89cherokee]

So my friends jeep cherokee wagoneer 87 was having problems starting but the alternator was fine so he replaced the battery and all was good we left it for a week come back and it was completely dead turn the key nothing.  We checked the new battery it still has 12v. We replaced the starter with one from my jeep (fires everytime) and nothing. When we hookup the starter to batt positive it will spin but not engage flywheel! Nothing happens when we turn key, interior lights are on power seats work etc. anyone have any ideas?

[Moezer]

fuel pump?

[vantagetes]

fuel pump?

No.

Starter solenoid (the relay version not the one that kicks the starter gear out).

[89cherokee]

So not on the starter but up in the bay? We replaced that to. Still nothing.

[WagoneerXJ]

Here's my thoughts..... Neutral Safety Switch could be bad or out of adjustment. Try wiggling the shifter in park, while you are trying to start the jeep. You can also put the transmission in neutral and turn the key. See if that works for you.

If it does turn out to be the NSS you can clean and adjust it, or replace it. Lots of write ups on the net about it.

[WagoneerXJ]

I should say that this happened on my 98, and on a 1990 cherokee I just finished swapping the engine on. Got the new engine in, everything hooked up. Had power to everything, lights, fuel pump etc. Hit the key and nothing! Checked and re-checked everything I'd done for 2 days.
 This is what my problem was. Wiggled the shifter and it started right up!

[89cherokee]

Tried all that, i will diagnose the NSS, thanks!