I have encountered a situation with 2 late model GM engines with an intermittent situation of prolonged cranking time before engine fires and starts. Situation is similar with both vehicles. One vehicle is a 2002 Chevy Avalanche with 5.3 V8. Vehicle has 93,000 miles on the odometer. Some times you can turn the ignition switch to START position, the starter spins the engine 1 - 2 seconds and the engine starts immediately. Other times it take 5 - 7 seconds of cranking time before the engine starts. This situation occurs randomly and without any pattern; ie it can be cold (ambient temperature) or warm and recently driven. Sometimes immediate start; other times extended crank time before start. Fuel pump pressure has been checked and within specification. No diagnostic trouble codes. Battery and battery cables in good condition. I suggested to the owner to cycle the ignition switch between OFF and RUN several times to repeatedly prime and pressurize the fuel system before turning the switch to START. Idea was that maybe a fuel pressure bleed-down in the pump might be causing the problem. That exercise has not overcome the issue. Second vehicle is a 2007 Chevy Silverado 1500 with 4.3 V6 engine. Odometer mileage is at 100,000. Owner is starting to experience the same situation described above with the Avalanche. Sometimes turning ignition to START and engine cranks and starts immediately. Other times extended crank time of 5 - 7 seconds before engine starts. No other engine performance issues present. No diagnostic trouble codes present. Fuel pressure has not been checked. GM uses a MAF (mass air flow sensor) in the intake to provide data to the ECM (engine control module) so that the ECM can calculate the proper fuel delivery pulse. Can a dirty / contaminated MAF cause this intermittent, prolonged starting engine?