Yes. It is a free "spice" circuit simulator. Many members here use it as it is a very useful and reliable tool. It does have a bit of a learning curve though...

Thats great! I'll definitely be downloading and trying it out today. The main reason I use easyeda is their part sourcing system makes it easy to verify stock and pricing as I go

 

The lack of a starter relay is why I need to switch such a high current for short bursts.

Did you read your second schematic? Don't know where your getting 40A for the starter, when in your second schematic it shows the starter circuit having a "5Amp fuse" in it. The starter relay is built into a GM old style starter thats why they never used one.

 

Did you read your second schematic? Don't know where your getting 40A for the starter, when in your second schematic it shows the starter circuit having a "5Amp fuse" in it. The starter relay is built into a GM old style starter thats why they never used one.

I did, that "crank" fuse is what powers the lift pump during engine cranking and once oil pressure of 5psi or higher is achieved then the Oil pressure sending switch takes over for the load of the lift pump. The PURPLE wire of the diagram is routed to the crank fuse but it also goes to the starter solenoid drawing off of the same fuse that the ignition PINK wire does.

As far as the 40a goes, I'm basing it on other owners of the same truck bypassing the ignition switch with a 40a relay and having years of trouble free operation as well as this datasheet on similar starters to the one my vehicle uses (i cant find a datasheet on the exact starter) http://www.iskra-agv.cz/us/pdf/starter_motors.pdf

The datasheet specifies <50a pull in current and and <10a hold in current for the solenoid, the current PMOS(HY19P03D) im using is rated for 30v and 90a continuous current which should provide plenty of headroom. If you add up the fuse ratings of all the PINK wires it adds up to 85a which it will never see but it doesn't hurt to have the large buffer. And just to clarify the starter and ignition will have their own separate MOSFETS

 

one thread is enough, let's keep it over there:
MOSFET or RELAY for High Current DC Switching.