We receive many inquiries regarding the best procedure to hot start the Cessna R172K with our 210 horsepower conversion. Continental has a recommendation that works very well.
First, understanding why a hot engine is hard to start may help. On a hot day, with the airplane engine shut down, the fuel lines and fuel components get heat soaked. This causes the fuel in the system to vaporize. Until liquid cooler fuel reaches the fuel injectors the engine will not start.
Here are the steps:
Mixture lean (full off) allows fuel to bypass back to the fuel tank.
Throttle full open.
Turn on electric boost fuel pump. Let it run about 15 or 20 seconds.
After 20 seconds, move throttle to slightly cracked and mixture to full rich, activate starter.
This should allow the engine to start normally because liquid fuel has been pumped through the lines and components and eliminated the vapor in the fuel lines.