Intermittently engine is difficult to start

[timjet]

3 times in the last 2 months my '01 Q45 won't start. The engine turns over fine but the engine won't start, like it's out of gas - no ignition. Each time after trying several times the engine starts and won't do it again for a couple of weeks.
When this happens and the engine finally does start, it runs normally with no problems.

Any ideas guys???

[loystock]

Check condition/cleanliness of the ground wires of the main engine harness (bolted to the engine frame). Check/clean the Crankshaft sensor. Clean the MAF sensor and TB. Have you changed the fuel filter? IIRC, it's near the RH rear wheel well. Have you checked the fuel pressure?

[timjet]

Thanks loystock.
I changed the fuel filter about 2 years ago. I have not checked the fuel pressure.
I'll check the condition of the ground wire at the frame.
Please explain how to clean the MAF, TP and crankshaft sensor?

Thanks
Tim