An easy first step in troubleshooting a slow cranking problem.

Engage parking brakes.
Place transmission in neutral.
No not turn ignition switch on.
Take a long screwdriver and press in the starter motor switch (red arrow) for about 3 to 5 seconds.
The starter motor should run very fast (whine).
Attachments
Starter Motor Switch.jpg (49.93 KB, 269 downloads)

Last edited by buoymaker; 12/31/2022 1:43 AM.
"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."