I am trying to figure out how an excellent running TPI 305/350 is supposed to start. Do they "bump" start or do you have to crank them over a little before they actually start? Odd, question but I am having problems with mine in another thread.

 

Short version
The ECM runs the pump for 2 sec ( through pump relay ) when the key turned on to prime the rails , then turns it off
When cranking over ,when the ECM sees the dist ref pulses from the dist indicating the engine is turning over , it pulses the injectors
It also turns the pump relay back on
If the 2 sec prime pressurizes the system correctly ( and the pressure holds ) the engine should start with little / no cranking.

If needing longer cranking to start ,is a indication the pressure is not holding and you are relying on the OP switch to come online ( @ 4psi cranking oil pressure )
to run the pump directly and pressurize the system

 

Thanks for a most thorough response! My '89 K1500 5.7 always required a little bit of cranking and my understanding is that is how they are with those low pressire TBI systems. My now newer '99 is just a bump of the switch.

Can you put the ESC into context for me?

 

Mine has always been a bump start.