i have a 2000 ML320, 140,000 miles. after it sits for a while it cranks over a long time before it starts. if i shut it off and start it right away it starts normally. i have scanned it but no codes were found. i have replaced the fuel pump and filter but it hasn't helped. i pulled the injecotrs out to see if any were bleeding off any pressure after shutoff but couldn't see any signs of a leak anywhere. i believe there is supposed to be residual pressure in the fuel system after it's turned off so it will start right up but i'm not sure. after it sits for a while i open the schrader valve on the fuel rail but there is no pressure (there is right after shutoff though). is there a check valve in the fuel line i've overlooked? about a week ago the check engine light came on and it ran rough. i turned it off and restarted and it ran fine but the engine light remained on. when i got home i did a scan and misfire on #4 came up. i reset it and since then it runs well and hasn't had any trouble except for the hard start. someone told me it could be the crank position sensor? i can't keep throwing money at this car. i really don't like it but my wife does, and for now i'm stuck with it. my car is an '86 300SDL with 300,000 miles and is a much better car quality wise.

Sounds like a fuel bleed-off issue.

Either the replacement pump OR filter is to blame!

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thanks for the reply. i guess i'll try the filter first since that's the cheapest. i understand there's a check valve in the filter but i'm not sure about the pump. this problem happened suddenly when she stopped for gas one day. the pump that we took out was a replacement, only about 6 months old. not noisy and car ran fine and still does after startup. i was able to warranty it but with the new pump and filter there's no difference.

thanks M.B. DOC. i changed the filter (no easy task) and that solved the problem. it starts right up now.