91 Explorer XLT

[jeffpcell]

I originally posted in the new members forum, but there seeem to be more people viewing this forum on average so sorry for making a duplication! I bought a 91 Explorer from a friend of the family. Was told it needed a fuel pump, but i've since learned otherwise. This will get a bit lengthy but i wanna put it all on the table and save everyones time in making replies. Here goes, 91 Ex XLT, 4.0L (vin X) 4WD, No check engine light while key is on, I know it works tho cuz i tested it, fuel pump doesn't prime, PCM doesn't seem to run at all. I've checked the FP & PCM relays which are good, I've cleaned up all connections between the battery and the vehicle on both ends of the cables. The fuel pump runs while the FP test lead is grounded, and i even got it to start once while i had the FP test lead grounded ( sigh of relief!!! at least the mechanical is in order, just gotta comb the fuzz out of this GD computer issue ) I've done some reaserch ( mostly on this forum, thanks ya'll ) regarding the PCM pinouts. Pins 20 40 and 60 are good grounds while the key is off, but when the key is on 40 and 60 bring back 12v+ while 20 remains grounded ( i disconnected the pcm and checked them with a DVOM ) 1, 37, & 57 are 12v+ with the key on as they should be. With the pcm connected and key on, i checked for the reference voltage from the pcm at the throttle position sensor connector, i think it should have been 5 volts, but it was actually 11.46 volts. The previous owner told me very little about it other than it doesn't run, he really isn't a "car guy" but i know this much. For the last few months that he was driving it before it stopped working, he couldn't get it to go into 4H or 4L and also said that occasionally he would have to take it out of park, run it through the gears and back to park or neutral before it would start. My guess is that both of those would be due to a bad neutral safety switch, or faulty wiring. The issues with pins 40 & 60 at the pcm could likely be due to the same sensor or wiring shorting 12v to ground..... anyone have some suggestions on what might be to blame? I tried disconnecting the NS switch to see if the pcm would start working, and sadly i got no change

 

[MrShorty]

It doesn't seem quite right, but my first thought is that someone somehow got those grounds accidentally wired into the positive battery cable (maybe while replacing battery cables). Have you followed those grounds to the "other" end to see if they are going to the right battery cable?

 

[Ryuske]

It doesn't seem quite right, but my first thought is that someone somehow got those grounds accidentally wired into the positive battery cable (maybe while replacing battery cables). Have you followed those grounds to the "other" end to see if they are going to the right battery cable?

This kind of happened on my 91 XLT. Basically the one with the black cover goes to the positive terminal, and the one with the red cable goes to the negative terminal of the battery xD I put some corrective tape cause I kept getting confused and accidently fried some jumper cables one day ><