Ignition woes - switch needed?

[GMCNUT]

I don't know why, but when its cold or started for the first time, my 72 blazer ignition has started hanging when I hit the key and the starter will turn over and over and over a thousand times unless the motor starts or I disco the battery. When hot, its started deciding not to crank at all - flip the switch and nothing happens like its totally disconnected from power. After it cools down, seems to start fine. Assumed at first this was a starter solenoid issue, so I replaced that with a brand new one only to see it act the very same. So turned my attention to the ignition switch and replaced it with a same switch spare I had laying around from a junk yard truck, and it is still doing the same thing. So I assume the junkyard ignition switch was as bad as the one I swapped it out with? New solenoid? Can't be the starter itself I would't think because it waits for the ignition to be turned on to make the solenoid jump out - the solenoid would work regardless of the starter working and thats not occurring so it has to be the switch itself - right?
So, assuming all of you agree the switch must be as bad as the one I removed, Ebay shows about 10 different ignition switches and each seller claims their switch is correct for 67-72 - part numbers I see are:
1116695, 1116704, 1116688, 1116711 and on and on. Does anyone really know what GM part # the ignition switch is supposed to be for a 72 Blazer w/ normal 350 V8 / Automatic / CST / etc?

[LockDoc]

Originally Posted by GMCNUT

I don't know why, but when its cold or started for the first time, my 72 blazer ignition has started hanging when I hit the key and the starter will turn over and over and over a thousand times unless the motor starts or I disco the battery. When hot, its started deciding not to crank at all - flip the switch and nothing happens like its totally disconnected from power. After it cools down, seems to start fine. Assumed at first this was a starter solenoid issue, so I replaced that with a brand new one only to see it act the very same. So turned my attention to the ignition switch and replaced it with a same switch spare I had laying around from a junk yard truck, and it is still doing the same thing. So I assume the junkyard ignition switch was as bad as the one I swapped it out with? New solenoid? Can't be the starter itself I would't think because it waits for the ignition to be turned on to make the solenoid jump out - the solenoid would work regardless of the starter working and thats not occurring so it has to be the switch itself - right?
So, assuming all of you agree the switch must be as bad as the one I removed, Ebay shows about 10 different ignition switches and each seller claims their switch is correct for 67-72 - part numbers I see are:
1116695, 1116704, 1116688, 1116711 and on and on. Does anyone really know what GM part # the ignition switch is supposed to be for a 72 Blazer w/ normal 350 V8 / Automatic / CST / etc?

I don't know about the switch numbers but did you check the back of the plastic ignition plug when you had it disconnected, to see if any of the individual connectors or wires were melted? I may be wrong but it sounds like a wiring or NSS problem to me. As far as the switch itself, to the best of my knowledge there are only two different switches, one with an accessory position (late '68-'72) and one without ('67 & early '68)

LockDoc

[rpmerf]

I would be sure to test it before you go replacing parts. I really don't like throwing parts at something not knowing if that part is the cause of the failure.

Make sure your battery connections are clean and tight enough you can't wiggle them. Make sure your ground is going to a clean part of the block

Check for power at the coil when it doesn't want to start. Check for power at the starter signal when it doesn't want to crank.

If you DO have power, look at grounds. Make sure your ground is good at the body of the distributor and the body of the starter.

If you DON'T have power, follow it back through the ignition switch, fuse block, battery junctions. Look for any dirty connections, or broken wires.

Schematics:
http://outintheshop.com/faq/wiring/w...s/image002.jpg
http://outintheshop.com/faq/wiring/w...s/image003.jpg

[GMCNUT]

Originally Posted by LockDoc

I don't know about the switch numbers but did you check the back of the plastic ignition plug when you had it disconnected, to see if any of the individual connectors or wires were melted? I may be wrong but it sounds like a wiring or NSS problem to me. As far as the switch itself, to the best of my knowledge there are only two different switches, one with an accessory position (late '68-'72) and one without ('67 & early '68)

LockDoc

Thank you Leon - the idea of checking the plug or NSS had not occurred to me so I do indeed wonder if the NSS is to blame for the intermittent non-start part of the problem for sure.

[LockDoc]

Originally Posted by GMCNUT

Thank you Leon - the idea of checking the plug or NSS had not occurred to me so I do indeed wonder if the NSS is to blame for the intermittent non-start part of the problem for sure.

Let us know how it goes.

LockDoc