Does anyone know if worn engine / tranny mounts could contribute to difficult starting? I'm thinking that excessive movement could be absorbing a lot of the starter motor's torque. My engine sounds laboured when turning over and sometimes doesn't start, I've replaced the whole electrical side of the starting system with little improvement shown. I'd like to hear some opinions on this.

Thanks.

Pretty unlikely that the motor mounts would absorb the torque from the starter motor.

To me it sounds like a weak battery...

Starter solenoid is on it's way out...

Or, you're not using proper gauge wire to the starter or grounds.

You should have a minmum 4 gauge cable from 12v source and 4 gauge ground.

Rebuilt starter, brand new 2 gauge wire for power and ground, brand new AGM battery that holds 13V overnight. Every connection has been sanded and cleaned.

I've ruled out every possible "normal" cause for this so that's why I'm looking for less common causes at this point.

Did you bench test the starter to see how it reacted without a load on it? Even a new solenoid can be faulty.

My next guess would be looking at your ignition circuit. Seeing what else is drawing power away from the starter if it's not getting 12 volts when cranking. Metering that would be a good idea.

I've checked the voltage drop going to the starter during cranking and it's less than 0.1V. I also tried a brand new starter that a member was kind enough to lend me, I saw an extra 10-20 rpm with that unit but the difference was minimal and it still sounded laboured.

You got me stumped!

Sounds electrical more than mechanical but that's a shot in the dark without seeing the car.

Maybe posting a log of turning it over may help diagnose an issue...?

Yep, I've been stumped for two years now. I'll post a log of a cold start attempt, it floods very easily so I usually have to open the throttle and pray on cold mornings.

Just a suggestion.
Perhaps take your accessory belts off an see if it turns over any quicker.

Ive seen tight ac compressor and alternator bearings cause this before.

That's a very interesting theory Jamie, the alternator belt does usually squeal for a few seconds on cold starts as well. I'll definitely try that this weekend.

although LESS likely, you should check your base ignition timing make sure it is not too far advanced

Good suggestion but I have a 95 non-adjustable CAS so my base timing is locked.

For anyone interested I've started a thread on the link forums with some cold start logs from this morning.

http://www.ecmtuning.com/forums/showthread.php?t=85749