Solenoid, starter good but turning key does nothing... help me find the demon

[deluxe]

Stock 302 in 76.
Drove well for about a week after getting a new ground straps and bettery cables. It then just stopped turning over. I jump the solenoid and it cranks but with the key I get a strange buzzing noise that seems to come from the distributor area. I am stumped. There is some vacuum do-hickey on the driver side valve cover that seemed to be a possibility but it did the same thing when I disconnected the two wires going to it (still have no idea what that thing is) got the same result.
Though I am comfortable with electronics, I have no idea how to continue to debug this. The battery is good, the solenoid is almost brand new and everything is well grounded.
Is something grounded? Should I start going through all the wiring on the top of the manifold to see if I am grounding the ignition wire? WHAT HAVE I DONE TO MY BABY... please help.

 

[ransil]

Read this thread, it will get you started.
http://classicbroncos.com/forums/showthread.php?t=102685

 

[deluxe]

more baffled now

Thanks Ransil... I tried some of the things in that thread as well as others and I finally found where the buzzing is coming from.
Turning the key to start and the lights don't dim and there are no volts at the S terminal. Again, I can jump the solenoid on the S terminal with 12 volts and the truck turns over fine so the starter and solenoid seem good. I then started trying to localize the loud electrical buzzing sound coming from the middle of the engine compartment. I found that the distributor is the problem. Its a newer reman unit from pep boys but when I disconnect the wires going into it from the control module the buzzing stops. Since the wires from the control module also go to the S terminal from the ignition switch, could my module be bad? What to do next? I replaced the ignition switch about a year ago and the dash was just out a few weeks ago so the wiring should be straight. What is next?

 

[RRRAAAYYY2]

Do a voltage drop test down the "S" line until you find 12volts. Then replace the next thing in line that didnt have 12volts at it. Hope that makes sense.

 

[deluxe]

Continued testing

It is looking more and more like a short either in the balast resistor bypass circuit or the control module that is causing zero volts at the S terminal on the solenoid during start.
Here are the facts of the situation and the tests that I have conducted:

1) Jump a wire from the S terminal to +. Solenoid clicked over and the engine cranked completely normal. Starter, solenoid, battery appear good.

2) Turn the key to the start position. 0 volts at the S terminal. Buzzing noise inside the distributor sounds like an electrical short. Removing the three wires from the distributor that go to the control module stops the noise from occuring but still no current at the S terminal.

3) Turn the lights on during cranking to see if there is a hard draw. The lights don't noticably dim or change.

4) Ground the I terminal and retest. Same result as 1.

5) Look for damaged wires or possible locations of hard shorts. None found yet.

I have reviewed the wiring diagrams and it appears as though the 12 volt ignition start wire goes to 3 places: The S terminal, the positive side of the coil to bypass the balast resistor and also the control module. How could the coil or control module going bad cause the symptoms I am seeing?
I still have some more testing I hope to do:

1) Unplug all other paths for the start wire from the ignition except for the S terminal. This includes grounding the I terminal to the battery and unhooking the control module and the coil. This should show that the ignition circuit is intact but one of the other components has failed with a short.

2) Begin to expose the 3 paths for the start wire and see if I can find the short. This is a last resort but worth looking at since they can't lie.

Like I have already said, the distributor, coil, ignition switch and solenoid are less than a year old and have all been working well after I fixed my grounding issues lately. I don't see how adding grounds for the frame and body could cause things like this to manifest themselves but hopefully when this is all said and done it makes sense. Once I get this thing going, how to I test to ensure that the voltage regulator is not the reason the offending piece has failed?

Please please please help me make sense of all this. I really doubt I have a short in the wiring but more likely the control module or the coil... maybe even the

 

[RRRAAAYYY2]

I think I know the answer. If you put a ground on the I terminal and the truck started up fine, then the wire going from the I terminal to the coil is bad. If it didnt not start but cranked then either the wire or the coil is bad. Or atl east that is my best guess.

 

[deluxe]

mmmmmmmmm

Grounding the I terminal made no difference. Same short to the distributor. The way I am looking at it, if the coild was bad it would short when I disconnected the 3 wires from the computer to the distributor, the coil would still short inside the distributor. I'm trying to find some time to disconnect all of the ignition components and see if the starter circuit will work. Then I'll work backwards to get sparky back.
When this is all done I'm really going to wonder what caused the failure in the first place. I have been having solenoids dieing on me and had two amps die not too long ago as well. I'm starting to worry about things like alternator and voltage regulator. Gotta find the demon first though.

 

[RRRAAAYYY2]

Where in Canada are you?

 

[deluxe]

Oh I miss the north

I'm not actually in Canada. I am from southern ontario but now I am in Georgia.

I traced the problem to the neutral lockout and am now driving the truck. After reviewing the diagrams, it appears as though the ballast resistor is bypassed when the ignition is in the start position no matter what the c4 has selected. The "short" I was hearing I guess was the power to the coil with the rotor pointing at one of the distributor cap contacts. Thus I was getting a spark on one of the cylinders. Very confusing to me because I thought the neutral lockout would prevent all the start functions from working. Seems strange that they would do it that way.

Now I am moving on to check the voltage regulator and alternator and see if it is time to go through those. I have blown two speaker amps and seem to be finding electrical issues left and right since I replaced my body mounts so it is time to see if there is anything else to go through.

Thanks for everyone's help

 

[DirtDonk]

I don't think the Neutral Safety switch needs to stop power to the ignition. Keeping the starter from turning over when in gear was probably safe enough for them way back when.
Besides, if it stopped the ignition from getting power, your engine would die every time you put it in gear!

Paul

 

[RRRAAAYYY2]

Deluxe,
Do a voltage drop test on any wires you can get your hands on. How big were the amps you burned out? How big is your alternator?