I have a ML 320 '00 with 125K. When it sits for more than 30 mins. the engine turns for a while then starts, less than 30 mins. it fires right up. What causes that?

Most likely fuel pressure bleed-off.

Either filter OR pump.

Connecting a gauge and watching the fuel pressure will tell you the truth on that issue.

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The filter makes the most sense to me. If the regulator (which is part of the filter) would hold pressure, it would start up again. If it were the pump, it might start for at least a few seconds (assuming the filter is OK and regulator is holding pressure), then die if the pump wasn't running.
Gilly

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Thanks for the responses, replaced fuel filter, still have problem.....what's next?

Mine did that. Replaced the crankshaft position sensor and the problem seems to be resolved (knock wood). Didn't make the check engine light come on, but due to issues with my PC I can't say whether it set a code. When the engine was warmed up and it sat for more than a few minutes it would not restart until the engine cooled completely. It seemed to be worse in hot weather.

Read this thread for instructions. The part was about $65 online or $110 at the dealer. I have an early '98; it takes an earlier version of this part than the later ones, but the dealer said they sell a lot more of the later parts so it must be a common problem. The guy who wrote the DIY rated it 3 of 5 for patience; I would say 4.9 but I'm not a patient person. Once you have the old one off it's all downhill (easier) from there. I replaced the Torx bolt that held it in with a socket head bolt; this will make it easier to replace next time. 211K miles on my ML.

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Like I first suggested....either pump or filter.

Since it wasn't the filter, it must be the pump.

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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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