There have been some excellent posts on this subject (especially the tutorial from Beagle) that I have followed with great interest. I have a specific question that I am hoping someone with more experience can help me with. My injectors range from 103 to 113, all below the minimum for the 240D I have, but above the 100 minimum for used injectors per the MB shop manual. I know they need to be balanced better, but I can live with the extra vibration for now. My question is: Does the lower pop pressure affect the timing and power? It would seem that the lower pop pressure would cause the timing to be advanced somewhat, but I am wondering how significant this is?
I just got through rebuilding my injectors and putting in new Bosio nozzles (thanks to Dieselgiant for the excellent tutorial). The improvement is impressive, but the old injectors were the original equipment and 2 were obviously bad, so a comparison is not meaningful. I made a bottle jack tester from the McMasters parts list that was posted by Boneheaddoctor (who gave credit to Old300D).Thanks guys.

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Charlie
79 240D w/auto, 250K miles
89 Suburban w/250K miles

While it does affect timing (Maybe by 1 or 2 degrees at the most), the injection pump still controls base timing.

Thanks for the reply. That's good to know.
Will the pop pressure affect power if I increase it? It would seem that the higher the pressure the more fuel would get into the cylinder, but there is probably more to it than that.

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Charlie
79 240D w/auto, 250K miles
89 Suburban w/250K miles

Those new nozzles will yield the most significant improvement you will see. Next time you adjust the valves plan on pulling the injectors for balancing if you still want to. Use the mean time to make the arrangements.

The other fuel system improvement that has caught my eye is a real 2 micron fuel filter. The reports of extended component life are impressive. Run some searches here and google it.

The pop pressure does not effect the amount of fuel injected. The IP does.

Higher pop pressure *might* give the fuel better atomization, however.

Pop pressure can effect the quantity of fuel injected. During each injection cycle, the lines expand a small amount as the pressure increases, and then shrink again when the pressure from the IP is released. The volume difference causes the amount of fuel moved by the IP to be a little bit more than what goes into the cylinder. The higher the pop pressure, the more the lines expand, and the greater the disparity between the fuel volume pumped by the IP and the amount injected into the cylinder.

I don't know how much of a difference in volume that is, but I am guessing it's very little.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

The answer to your question is yes-pop pressure affects engine timing. The answers to the question you really want to know is do your injectors have much negative consequences at there current pop pressure readings. The answer is no don’t lose sleep over it. You probably could not tell the difference driving the car if I snuck over and installed 5 injectors that popped at 90 bar. Then a week later switched them with 5 117 bar injectors I did this to my son and he never noticed a difference on the same car he drove every day A 1985 EURO W123. I put injectors in the same car one, which popped at 1 bar the rest, popped around 70 bar with a solid stream of fuel. In the hour I drove it I noticed no difference however I was driving it to sell to the state of CA, so I did not get any fuel mileage data or to see if the oil was half diesel.
Dave S

Lots of good advice, and thanks. I think I will look in to installing a 2 micron filter. and leave the injectors alone until I have a lot more spare time to kill.
Again, the improvement in performance was impressive. It keeps up with other cars taking off from stoplights, and does noticeably better going uphill at freeway speeds. I only regret that I went years with aggravatingly low power before changing the nozzles. The car is now fun to drive again and is at least close to how it performed new.

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Charlie
79 240D w/auto, 250K miles
89 Suburban w/250K miles

Beagle noted that the pop pressure is relatively insignificant in terms of the overall performance of the engine. Provided that all injectors are within the M/B specs for pop pressure, there will be no performance gains for carefully matching them.

Many on this site take great care to match the injectors within a couple of psi. However, leakoff, the amount of fuel that bypasses the injection and returns to the tank, is probably far more important for balancing a set of injectors. Nobody checks the leakoff other than a proper injection shop, because the equipment is quite sophisticated.