melben & Jonas302 - The crank relay I refer to is in the ignition circuit, that is when you push the start button, that's supposed to send voltage to close the coil in the crank relay (I've checked that voltage on a button press & it seems OK), when the coil closes it allows the constant 12v on one pin of the relay to flow out the ignition wire to the starter (I've checked that voltage & it seems OK). The Denso starter has 12v constant to its main lug.
The seat switch only needs to be pressed (engaged) in order to start the power on/preheat cycle. Once that's complete, you can then press the start button, regardless of the seat switch status. The lap belt only needs to be buckled in order to press the operate button to release the brake. Of course the seat switch needs to be engaged also to have the brake release. So, both the seat switch & the lap belt are not part of the crank logic once the start button is pressed.
As I've posted previously, I've stopped trying to diagnose further until in the normal course of my intermittent usage of the machine, it fails to crank. Then I'm going to try to pull out the crank relay just enough to jump 12v around the relay into the ignition pin of the relay socket, while I observe voltage at the end of the ignition wire at the starter. If I get 12v ignition at the starter (which I expect, since I've previously ran at least 9 amps thru this wire), & the starter does NOT crank, then the problem has got to be in the starter, despite my local starter shop's determination that it's good. Remember, the main lug of the stater has 12v to it all times, which I've verified by measurement & tracing of the cable from the battery.
If the starter DOES crank, then I think I'll still be puzzled, because:
- the direct, reapplication of 12v to the ignition circuit might have been enough to "jar" the starter or it's solenoid off its dead spot,
- or the crank relay might still have failed the 1st time,
- or the start button might have failed to send the coil closing voltage to the the crank relay that 1st time.
So, I might just have to live with the intermittent problem until it becomes constant. If that turns out to be my only choice, I can't express in words how frustrated & mad I will be!!