I would like to check fuel pressure on my 300SD ('84, W126, OM617) to see if pressure relief valve on the IP is doing its job properly.

I read that the best place to get a fuel pressure reading is between main fuel filter housing and injection pump input. There's a hollow bolt/screw on the fuel filter housing (#164 on the diagram attached) which I need to get drilled and tapped, so I can install a pressure gauge on it.

I don't really want to do this to my original hollow bolt, so wanted to get another one and take it to the shop to get it drilled and tapped.

Could someone please look up the part number for bolt #164 on the diagram? I don't have access to Mercedes part database.

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84 300SD - bought in April '06 with 237,000 mi

Part # N 915011 006104.

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83 SD

84 CD

Thank you, kind sir!!

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84 300SD - bought in April '06 with 237,000 mi

Just called the dealer with this part number, and it's been superceded with a new part number:

000000-00-6772

They traced it from the diagram to the parts catalog. This new part number is a correct one, even though it doesn't come up as a part for the cars of our era - it now comes up for new G-series cars. I think they repurposed that hollow screw and forgot to update it on the parts catalog for our older cars.

But anyhow, I got the same result by calling two Mercedes parts counters, and they agreed on the final number they gave me.

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84 300SD - bought in April '06 with 237,000 mi

You're welcome.

The epc (free to American credit card holders) has been, um, difficult the past few, well, I forget how long.

That's where I got the number.

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83 SD

84 CD

It was the right starting point, though :-)

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84 300SD - bought in April '06 with 237,000 mi

I went to the dealership and measured this bolt. They wanted $21 for it, and I really didn't want to shell out this kinda money for a bolt that would be used as a pressure-gauge experiment.

Here are the measurements:

M12 X 1.50 (M12 hollow bolt with 1.50 mm thread pitch)

Length: 24.5 mm
Diameter: 11.8 mm
Head: 17 mm
Thread pitch: 1.50 mm

The original bolt on my car has 3 holes. The new one from MB has 4 holes.

I found that Volvo is selling the same bolt for much cheaper, however. Volvo part number is 973950, and it costs around $8. Quite a difference!

I am attaching a picture of the Volvo bolt. The only real difference from the Mercedes bolt is that the Volvo one has 2 holes, and the bolt head is a bit thinner. But when I go to the shop to drill and tap it for 1/8" NPT, I will have them drill another (smaller) hole or two in it.

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84 300SD - bought in April '06 with 237,000 mi