Trun the key & the starter engages for about 1 second. That's not normal.

On the second try the starter stays engaged till the engine starts. That's normal.

What is the cause of the short engagement on the 1st try?

Sounds like a starter bendix failure in the making.

Sounds like the starter gear is not engaging the flywheel as it may not be shimmed properly, or the starter solenoid is bad, First check for a full charge and go from there.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
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87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
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