86 K20 No start, bat & starter good

[JensenHealey]

Good morning all:
I have a 1986 K20 that the previous owner added a 454 w/TBI from a 1987 Suburban R20 and I have been experiencing some issues with getting the truck to start. Recently I have had occasions where the starter is not being activated when I turn the key. Previously when this has happened I goof around with trying to turn the key off and on a few times and then finally it will work. However last evening when I wen to use the truck after two days of sitting this happened again and no amount of fiddling with the key did anything. I tried jumping the battery since it is very cold here but that had no effect. I pulled the battery and brought it in the house to check it and it seemed fully charged.

The lights on the dash are lighting up as normal when I turn the key to On or start positions and I can feel resistance when I turn the key to the start position. Just nothing happens with the starter.

I believe I either have a problem with the neutral safety switch or the ignition switch. I understand from the research I have done that the actual electrical part of the ignition switch sits on top of the steering column and is activated by an ignition activator rack. However I have no idea where the neutral safety switch is located.

BTW, the truck does have a tilt steering wheel.

So now I have questions. 

1. How do I diagnose if it is indeed the neutral safety switch or the ignition switch. (this question is related to the 2nd and 4th questions, since if I have a good wiring diagram to work from and knowledge of the location of the neutral safety switch as well as the pinouts of the two switches, then I can figure this out on my own).

2. where is the neutral safety switch located?

3. Is it possible to drop the steering column enough to access the ignition switch by just removing the two large nuts under the leading edge of the dash that hold the column up in place?

4. Where can I get a good wiring diagram for a 1986 K20 and a 1987 R20?

One other piece of info, it's 15°F outside so I am trying to minimize the amount of time I am lying under the truck if possible.

[VileZambonie]

You need to first go to the starter solenoid with a test light. Put the test light clamp onto a good ground. Verify the test light works with your ground connection by touching the B+ terminal on the solenoid and your test light should illuminate. Go to the S terminal on the solenoid and have an assistant turn the key to the crank position. Tell us if it lights up