In my quest to improve fuel economy, I have already checked timing which is spot on at 15 deg ATDC using the Xenon timing light that I built. See this thread for more info: http://www.peachparts.com/shopforum/diesel-discussion/354973-free-injection-pump-timing-checks-till-may-31-2014-a.html

I have a set of Monark nozzles and also just received a set of injector bodies from Charmalu but have yet to install/ pop test them. Before doing so I wanted to check the internal IP fuel pressure. A few years ago, I made a bunch of these adjustable fuel pressure regulators and sold them all except one and it came in handy today. I also made a fuel pressure test adapter banjo bolt which makes it easy to check pressure.

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Pressure is around 7 psi at idle which is very low. You can see the pressure test adapter banjo bolt with the white nylon line on the banjo of the IP inlet from secondary fuel filter. You can also see the fuel pressure regulator banjo bolt at the rear face of the IP (facing the block). The spring inside the fuel regulating banjo bolt has lost it's strength from age and work hardening and the fuel pressure drops. It happens to all of them after 30 years. New ones are NLA afaik that's why I built my own adjustable fuel pressure regulator.


Fuel pressure went up to 17 psi at idle after installing the adjustable fuel pressure regulator. The white tissue paper is to look for signs of leaks which would be difficult to see w/o it. I could raise or lower fuel pressure easily with 2 open end wrenches.

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Have not taken it for a drive yet.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked