The fuel distributor commonly referred to as the "Spider" distributes fuel to each cylinder. The iStart T fitting allows fuel from either the Primary fuel system or the iStart system to reach the cylinders
A description of the system in action:
When the pilot is ready to start he turns on the iStart power switch.
The system samples the engine temperature, starts the boost pump and injects the proper amount of fuel to prime.
The aircraft mixture control is still in Cutoff therefore no fuel is passing through the Throttle and Control Assembly.
iStart then flashes the Status light to alert the pilot that priming is complete and the engine is ready to go.
When the pilot engages the starter a number of things happen. iStart sees the starter operating and samples the cranking rpm. Depending on conditions, additional fuel may be injected now.
When the engine starts and runs, iStart is still supplying all the fuel to keep it idling. After about 15 seconds,while iStart confirms that the engine is stabilized, the system will again flash the Status light alerting the pilot that it's time to advance the mixture control.
When this happens, iStart recognizes that the mixture is Rich and it shuts completely down. As a safety feature, it's not possible to power up iStart while the engine is running.
iStart has no function during any taxi or flight operations. It just makes starting your engine like starting your car!
This is the fuel routing and the injector assembly for the iStart system.
This is the iStart T fitting which allows the boost pump to supply fuel under pressure to the iStart system.
This the primary fuel supply from the fuel tank through the electric boost pump to the Throttle and Control(mixture) Assembly and then to the Distributor (Spider) and out to each cylinder.
The Controller is the brains of the operation. It takes inputs from sensors and calculates the best fuel delivery for starting in different ambient conditions.
Its primary function is to control the injector assembly to provide the proper amount and rate of fuel delivery for priming, cranking and idling.
"Hot starting problems are just about always caused by an improper stochiometric mixture... or bad Karma"
Prof Eustis P. Dimdle UAV, DUME, ASPCA