Does the 172 have a Thielert (ex-Mercedes A-Class) engine with dual FADEC? Here's what's in the DA-40 TDI checklist, with regards to the engine:
Preflight:
- Engine master off
- Electric master (key) off
- ECU swap automatic
...
- Electric master (key) on
- Waterlevel light out
- Fuel quantity check
- Electric master (key) off
Front fuselage:
- Check gearbox oil level
- Check engine oil level
- Exhaust pipe
- Venting pipe
Starting engine:
- Power lever friction adjusted
- Power lever idle
- Electric master (key) on
- Annunciator panel check & press ack
- Engine instruments check
...
- Engine master on & wait till "glow" is out
- Electric master (key) start
- Check oil pressure
- Warm up idle or < 1400 rpm, at least two minutes (you can taxi with this rpm)
Before take-off:
- Engine instruments all green
- Alternate intake air check & off
- ECU test button hold
---> this checks FADEC B, then FADEC A, then A+B, cycles the prop, you name it. Takes about a minute
- ECU B; check smooth running
- ECU automatic
Shutdown:
- Power idle at least two minutes (turbo needs to cool down)
- Avionics off
- Electrics off
- Engine master off
- Electric master (key) off
In addition to this, you've got to set power in %, not with RPM as this is automatic constant speed. Need at least 30% power above 5000', cannot restart the engine if above 6500 feet (no turbo pressure).