New Engine, no start with ignition switch

[Incredible Hulk]

Replaced the Hulks 312,000 mile engine after it started knocking... drove it in the shop with the knock... installed new GM crate engine. Engine won’t start with the ignition switch, will start if switch is on run and I touch a test light to the crank fuse or yellow ignition switch wire... along with that the brake lights stay on in the run position so I think they may be related issues. I have replaced the brake switch with GM part.
it’s an automatic transmission K1500

thanks for any feedback

 

[Erik the Awful]

You don't state what year it is, but if it's a Vortec, did you hook up the ground terminal on the front passenger side of the motor? It's stupidly placed in the middle of the harness that runs next to the timing chain cover.

 

[Incredible Hulk]

It is a 97 and Vortec... I was pretty sure I hooked all the grounds back up but I’m going to look for that one

thanks for the information

 

[east302]

So if you put voltage onto the yellow (5) it starts? To me, that rules out anything downstream of the ignition switch (starter relay, transmission position switch) leaving just a bad ignition switch?

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You could maybe try backprobing pin D1 on connector C266 and see if you get voltage when turning the key to start, but I think it’s a safe bet that you don’t.

Or, disconnect C266, turn the key to start and see if you have continuity between D1 and D5 on the ignition switch side of the connector.

The brake lights run through the turn signal switch which is also connected through C266. It probably wouldn’t hurt to separate that connector and make sure the pins look good, that everything is seated tight and that the closure bolt is in good.

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[Incredible Hulk]

East 302, Thanks for the schematic and pin outs..
I did not see any voltage at Yellow 5 with a multimeter when I turned to start... so I was using a test light probing the ignition switch contacts and when I probed Yellow 5 it started the engine.. also when I probed the Crank fuse it started the engine too. So when a test light contacts Yellow 5 or the Crank fuse the starter relay energizes. The Brake light relay is energized when the switch is in run
Also my gear indicator lights go out in run and start and that is when my brake lights activate too.

 

[east302]

The PRNDL indicator would be hot in run and start, so to me it sounds like the ignition switch isn’t completely making the circuit to the transmission range switch (which looks to provide the grounds for the PRNDL indicator). Did you check for continuity with ignition held in start at the D5 and D1 pins on the ignition switch side of connector C266?

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[Erik the Awful]

You have your ground clamp on your test light clamped on to a hot source, and not a ground, and it tries to start when you hit Yellow 5? If any of the other ignition switch positions work, it's your ignition switch.

Do your dash lights come on like normal when you put the ignition switch to "Run"? Does the "Acc" position work?