Gir496

Hi all, new member here looking for advice. I've got myself a 2001 Chevrolet Suburban 2500 8.1 Vortec/4l85E. Truck has approximately 127000 miles on it and it and on cold Canadian winter days it refuses to start unless I turn the key in the ignition slowly/gently. When turning the key "normally" it will crank endlessly and never fire off. I've put both a noid light and spark tester on the motor and found no spark or injector pulse when it does this, and when I do get it started via turning the key as previously mentioned it runs totally normal and has no issue restarting unless I let it sit again in the cold. No codes stored in the computer either. I should also mention on warmer days like during the spring summer and fall it starts at the first turn of the key every time. My first thought is it's time for a new ignition switch.

Any help would be greatly appreciated

Cusser

Try turning the key to the "Run" position of 10 seconds (not he "Start" position), then return to initial position. Do this like two additional times. Then try to start. An ASE master mechanic this builds up fuel pump pressure, and if it starts essentially every time doing that, indicates weak fuel pump pressure.

repairman54

Sounds like the switch is worn by your diagnosis. Stuff shrinks in the cold. I would change the switch, they wear out and parts age out.

Gir496

Do you happen to know if the anti theft system needs reprogramming after replacing the switch?

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I've actually had this issue and dealt with it in the past, The Suburban has a fresh fuel pump, filter and pressure regulator. The truck previously wouldn't start unless I did what you described when it was cold out. I thought it might be the same issue again but it still refuses to start even after cycling the key a few times and waiting.
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repairman54

I think your switch is down on the column and not inside the key tumbler where the security system sensors are. Look it up on Rock Auto's site, they have pictures and multiple choices.