'05 intermittent won't crank - start

[axxense]

Rene - you are, at least, pretty much, if not totally, correct - the smaller terminal is the 'start' (ignition) terminal. The bottom-most large terminal is power (hot). The other large terminal goes back in through the side of the cylinder body of the starter.

That still tells me when I jump the hot to the 'start' (smaller, ignition) terminal - I should get crank if all was fine with the starter.

I am, though, a little mystified by the starter gear spinning, but no engagement, when I jump the large hot terminal to the other large terminal. Wouldn't mind a bit if someone clued me in to that one.

I removed the starter relay and jumped 30 and 87, as you said, HUMTECH, and got nothing (well, maybe a teenie spark when I poked the lead in) - no crank, no spin, nada.

I also did something like HUMTECHs test light check... ...using a voltmeter, I clipped the red (+) voltmeter lead on to the smaller start (ignition) terminal. I then clipped the black (-) voltmeter lead on to the starter housing (ground). I then placed the voltmeter on the hood of the truck (so I could see it from the drivers seat - my voltmeter has way long leads) and turned the ignition all the way to start - the voltmeter read voltage (12ish volts).

This told me two things - the starter wasn't engaging and the ignition switch was working. If it read little to nothing, I may have thought an ignition problem - a bad ignition switch or something in the ignition circuit (likely, with a HUMMER, the ignition switch, as explained in other posts).

I think this single test is the easiest and most comprehensive - it will tell you almost definitively - A) You have a starter problem (if the voltmeter reads 12v+/- and the starter doesn't crank), or, B) You have an ignition switch (or something in the circuit) problem (if the voltmeter reads little to nothing). To do it, though, you will need a voltmeter that has about 3' leads (or longer!) or someone else to turn the key for you.

I don't think I can isolate it any further.

Again, I will replace the starter this weekend and post what I believe will be the final post to this thread.

Many, many, thanks to all. I believe I have totally nailed it down to the starter and haven't spent a dime. Sure, my time is worth something, yet, all I missed was some TV and gained a TON of knowledge. Maybe I can now help others, in the future.