The car has 307xxx and runs like a champ, but is dripping fuel somewhere on the pump. I figure if I'm going to replace all the fuel lines (not leaking yet) and do the fuel delivery valve o-rings and crush washers, even though they aren't leaking yet, it may be a smart idea to just replace the entire shutoff valve instead of just replacing the o-ring. Anyone care to throw in their .02?

The valve can develop internal leakage out the connector.

If your connector is wet, make sure the fuel hasn’t migrated by capillary action through the wiring harness back to the control box in the right rear corner.

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2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

The O-ring needs to be changed often, you can do it with the intake manifold on if needed so it's up to how much money you want to spend. Make sure you replace the rubber line between the car and engine with one from the dealer along with the proper clamps, and don't miss the intake bolt that you have to get from under the car.

Is there a pictorial guide that points out and labels all these frequently (with growing age/milage) replaced fuel lines, o-rings, washers, valves, and so forth on the 606? Asking for a noob.

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I took apart the fuel shutoff valve (filter bolt) and was able to the right size internal o-ring from a garden sprayer rebuild kit. Those o-rings were better quality than straight rubber (can't remember which exact material).

You have to drive out a pin that holds the internal seat/stem, then you can access the leaky o-ring.

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'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter