Hello I am the proud new owner of a 2011 GL-350 with a 100,000 miles
First assessment it seems to be in excellent condition ,Drives nice and starts well in cold climate .
I now have a" Cranks over but no start " situation
Here is what I know
the last two times I toped off with fuel the reading did not register above 3/4 tank ?
There was several times I went to start and it tuned over with no start after a recycle it started
it ran fine but I might of noticed hesitation once or twice but not enough to get nervous

I was told the fuel filter was changed when I bought it ( I am going to put an OEM one in myself for piece of mind )
I replaced the Crank shaft position sensor But that is not it
checked fuel pump fuses and I am now going to check fuel pump relay

my questions :
1_ if the in tank boost pump is faulty would that make sense with my symptoms ?
2_ is there a way to trouble shoot and then bench test ?
3_if they are known to be faulty is changing it good insurance ( I noticed a new part# does that mean upgraded unit ) ?
4_ would the high pressure pump fail suddenly our does it fail over time
5_ best diagnostic computer for the GL-350 ?


thanks Herb