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.

CLICK TO PLAY VIDEO!


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.

CLICK TO PLAY VIDEO!


Have not taken it for a drive yet.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

You should see a noticeable difference on a drive. I would close off the fuel return to see what pressure is present. Should be quite a reserve or you should further troubleshoot the overall supply system. If basically no differance is observed while driving pressure may be sagging under load.

Basically at cruise under load fuel pressure may drop off too much Also a great way to see when filters need attention after a baseline is established. A healthy full pressure fuel supply system should also be a more reliable system.


I have noticed Roy has not posted in awhile as someone else mentioned. Hope all is well with him.

Manual pdf. One Bar equals about 14.5 psi

Attached Files

07_1-145 Checking Fuel Lift Pump and Bypass Pressure Valve.pdf (357.6 KB, 155 views)

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84 300D, 82 Volvo 244Gl Diesel

What purpose would closing off the fuel return serve? Wouldn't that be dead heading the lift pump? Isn't the lift pump some type of positive displacement pump (using an o-ring?) and if dead headed, could it potentially blow out something?

yeah have not seen much activity from Roy on DD in a while. Hope he's doing ok.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thanks for posting the PDF. Took it for a drive, engine feels more responsive and peppier, but I am noticing a slightly more thumping idle. Not real objectionable. My fuel pressure is on the high side per spec. I am going to adjust it lower and see thumping idle improves. Before doing so, I am going to modify my pressure test set to include a Schraeder valve (like a compression tester) to get rid of the needle bounce and read peak fuel pressure.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Lift pump design just basically idles once maximum output pressure has been obtained. So no damage to the lift pump will result. Test basically is to see if lift pump is still putting out a reasonable high pressure.

I did not look carefully at your gauge but assume it is liquid filled type. You are not looking for a peak pressure but as stable an average reading as possible.

A real restriction in the gauge feed line may moderate the reading average. Or needle bounce if you will. A gauge not liquid dampened is almost useless without some work.

Anyways closing off the return line will not damage the lift pump. It is the only way I can think of to see if the valves etc in the lift pump are still pretty good. Weak return lines on the injectors may leak though has been mentioned a few times during this test.

With a closed off return I personally think 25 pounds or more should be present then on the turbo lift pump. Much higher have been mentioned by some.

Idle is usually improved at higher pressure than existed. The reason is the power balance of the engine is improved. That is why the seat of the pants feeling of it is there.

A power balanced engine produces more power has to be a given. I have no ideal without thinking about it of why your idle is different. Other than better fuel pressure tends to on average put the timing forward a little I believe. The usual effect is a smoother idle and a quieter engine on the highway. I have always visualized 19 pounds as the sensible upper limit for fuel pressure. Those pressures in the manual are the absolute lowest allowable in my opinion. Still good information.

Your injection pump has the tang . Did you verify your electronic timing with that as well? Quick and easy to double check.

Thought about your idle issue overnight it should have been better not worse.

If you goto a hydralic shop you could pick up a snubber they are basically a variable orfice to pamper the pulsation.