c32jet

My next stop is the dealership. Need to get the truck back on the road as I've been tinkering with it for a few weeks now. Wife unhappy as this is her primary car and she is not as keen to drive my C32.
If you have some insights, please share... Hoping it does not turn out to be the CPS (Crankshaft Position Sensor).

2003 - ML 55 - ~60K miles.

Intermittent 'crank - no start'
No CEL.
Codes showing p0400 - this is due to a vacuum leak on the brake booster - been there forever - not worried about it.
also showing p0110 - this is due to me disconnecting the MAF sensor during trouble shooting...
no other codes..

Pulled Fuel Pump RELAY - put it back in... start
Thinking the relay may be going bad... I got a spare
Wife drives 10 min to post office - no Start. Calls me to see if I can come fix.
I bring the spare fuel pump relay - pop it in - starts fine.
Works fine for a few days... then 'cranks, no start' again.
Ordered more fuel pump relays - swapped them in - no luck.
Installed new fuel pump, fuel filter and two new lines connecting them. All EOM / Mercedes parts. Still 'cranks - no start'.
Removed and visual inspection of Crankshaft Position Sensor... reinstalled same one after inspection.

Seems the fuel pump is not doing the 2 second 'pressurize the fuel line' action. No sound from fuel pump either before or after new fuel pump.

There is no fuel pressure at the rail in the engine bay. Not sure if Fuel Pump is getting power. Sounds like the relay is clicking... still... cranks, no start.

Thoughts? Thanks for your insights.

c32jet

Turns out it was the Crankshaft Position Sensor (CPS). Dealer wanted $800+ dollars to fix. So, lesson is check this part first. I did the fuel pump first... mistake. And btw... the $20 CPS on ebay was just slightly different enough with the guide pins it did not work. Had to buy the OEM CPS from the deal for $133. The work is not terribly hard to do. Take off the front driver wheel well (6 or so little plastic bolts). Remove a small heat shield (3 screws) and then its tricky to guild a long extension down to undo the bolt holding it in. Then you'll need some small hands to unclip it. Will take you an hour the first time... 30 min the next. Hope this is helpful.