Any place after the lift pump will show system pressure.

Perhaps but pressure may start to rise as filters obstruct if installed before the primary and secondary fuel filters. Installed after the secondary filter will reflect what pressure is remaining as the filters obstruct.

Perhaps being more accurate at indicating the time to change fuel filters or locate why the pressure is sagging as time goes forward. Also we are watching for ideally 19 pounds pressure in the injection pumps base fuel supply. The filters between may tweak that pressure reading even if new a little. Still a gauge feed back there is better than no gauge at all and I might be splitting hairs.

Did anyone come up with an replacement part for the OM606 overflow valve? I am in need of two.

Use a valve from a 123 or 126.

I have 3 of these adjustable fuel pressure relief valves left. Send me a PM if interested.

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The adjustable ones look a little short. I measure the OM606 Overflow Relief valve at M12x1.5 and 33mm long. I took mine apart. It consists of four parts:

The body, a plastic valve element, a spring and a BB to seal the back. Just plain junk.

The actual valve opening diameter is 3.5mm or 9,6sqmm.

I think the pump is supposed to operate at 15PSI. 15PSI equals .023lbs/sqmm, so the spring ought to have 9.6x0.023 = 0.223lbs of push. I can hardly hold the spring without it collapsing.

In summary: this is not a pressure valve, but rather a one-way valve. Mine didn't even do that. I had my suspicions when I was able to drive with pump inlet line clamped (fuel drawn backwards from the return line).

(edit): The plastic bit is backwards. The actual sealing face is the part shown nearest the spring in the picture. I think the plastic part was probably not so twisted up before the traumatic dis-assembly process.

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