99 e300 won't start
 

Fuel filter, pre filter and o ring changed. Car started and ran good afterward. Won't start after sitting overnight. Not leaking fuel. Recent fuel lines and shut off valve replacement. Small bubble in line next to pre filter and line feeding big fuel filter. I'm wondering how to test lift pump? Will the car run, even if it's toast. Thank you for any help

How long did it run good afterward?

Do you see the level rise in the line to the prefilter during start? If you do the lift pump is working. I suspect you have air getting in it somewhere. Did you replace the o-ring at the lift pump?

Yes, the o ring is new and from dealership. Haven't messed with car since last Thursday. Strangely, after cranking tonight for about 5 seconds, it sputtered to life and ran great all evening running errands stopping and starting at different places. After I parked it, about 30 minutes later, it had a bubble next to pre filter and when the wife turned the key, the fuel level rose up and car immediately started! Will attempt to drive to work in the a.m. and see what happens. Thanks, Eric

Sounds like it had trapped a little air in the wrong place initially and has finally worked it's way out. Not uncommon to see the level fall slightly in the clear line to the prefilter when shut down.