Thanks for posting an update. If you can find the time to post updates from time to time on what you are doing. Plus the results of what you have done and any other observations. I really think it helps the common cause.

You have already opened up some new avenues to think about.

I am not trying to be negative but since the Glow Plugs were not made to read an accurate temp each Glow Plug will have a different electrical potential when heated to the same temp.

Picking one Glow Plug and moving that one from Cylinder to Cylinder would be more accurate.

But, even that is only going to give you an idea which Cylinder is running at a different temp from the others.
It will not tell you what is causing the difference in the temp.

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84 300D, 82 Volvo 244Gl Diesel

Disclaimer: I have not read all of this thread.

That said, I get the idea from the first few posts that there are folks who are trying to split this into a hair breadth that is too small.

Pump the hand primer enough to get a drip and that's enough fuel pressure. The point of drip is quite small. If you get too far to either side of it, you will either get nothing or a stream. Time it to a drip and be happy.

If you want it any more accurate than this, get a piezo sensor and timing light. I personally have never seen the need for this expense.

My $0.02,

Just to add my two bits to the fuel pressure part of this:

With a two tank D/WVO system pulling through both filters and a newish pressure relief valve, my diesel pressure runs 12-14 psi. Last summer it was dropping to about 5 with no apparent difference in how the engine was running. Changing filters got it back up to the normal, for me, 12-14, so I'm a firm believer in the value of a fuel gauge in monitoring fuel system health.

On WVO, I have a boost pump set at 4 psi to help send the WVO forward. It runs about 20-22 psi. I don't notice any difference in how the two fuels and pressures perform. Its a looped system and I think you gain a bit of pressure from the loop in addition to the added pressure from the boost pump.

I've never set up a fuel gauge on the stock "pushing through filter" configuration and am curious if this is why the diesel pressure is suboptimum. Lots of folks don't like the pulling through filter setup. Most of my driving is on WVO, so I don't worry over it much.

I'm not sure it was addressed in this long thread, but the pulsation problem can be dealt with by a restriction orifice, in my case a barely open needle valve between gauge and the pressure line.

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1983 CD
1958 Studebaker Packard (being resuscitated)

I mentioned the same in post #8 but did not actually make a restricted orifice to verify that; So it is nice to know that a restriction will work.

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84 300D, 82 Volvo 244Gl Diesel

Yeah the Cummins people discuss fuel gauges and restriction orifices and such a lot. Its where I got a lot of my information. Good info on: http://www.cumminsforum.com/
Particularly the 94-98 second gen engine, which uses the same IP and LP designs as 61X Mercedes and maybe others. Lots of parallel discussions.

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1983 CD
1958 Studebaker Packard (being resuscitated)

Five pounds to fourteen pounds fuel pressure might not make any seeming difference on wvo. It should on diesel.

Another part of the equation is you are probably better off overall fuel consumption wise especially at 14 over 5 pounds with wvo. It was also nice to see you mention that the gauge was an accurate indicator of fuel filter obstruction building as well. This to me anyways is an important function of the gauge.

Because of the higher viscosity of wvo I tend reciently to visualise 19 pounds as the minumin fuel pressure in the injection pump. A member running wvo at twenty eight pounds currently seems to have gained a lot.

I only know at this point that 19 pounds is better than 14 pounds on wvo.Simular on diesel fuel. I think the gentlemans primary improvement on wvo might be the fuel milage with a little more power and better smoother idle.

There may be no downside at all with his pressure on wvo either I suspect. Just not sure.

I didn't present it clearly, the drop from 12-14 to 5 I reported was all on diesel. Psi on WVO has consistently been in the 20-22 range. The filters are separate and I've never actually had a clogged WVO filter, only on diesel.

Not sure about the effect of viscosity of hot WVO on fuel pressure, but I assume you would get a higher reading for even a slightly thicker medium...correct? If the relief valve opens at 22 psi as it's intended, then I should be right on target with WVO.

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1983 CD
1958 Studebaker Packard (being resuscitated)

Your post is more complex than confusing to me. Higher pressure on wvo may be desirable to help with thicker viscosities fuels than diesel. Nineteen pounds base pressure apears to me as optimum at this time on diesel fuel.

Depending on the viscosity of the alternate fuel in comparison will have some bearing on the ideal feed pressure in the base of the injection pump.

As I visualise it fuels with higher viscosities may not fill elements as fast. Higher pressure may get the filling portion of the higher viscosities to near the speed or quantity or both of filling with diesel fuel.

Less than designed filling or loading pressure seems to cause issues. The first being the equal filling of all elements and the consistancy of that seems impacted. I also want to always see a relief valve overflowing present. Not because of only the cooling effect of the pump core it enables.

I think the cigar hose reduces severere turbulance or the ability of it to occur to some degree when the relief valve is open as by design. Otherwise disrupting the element loading out of the intended profile of the calibration of the injection pump somewhat if severe turbulance is present.

The difference in my opinion with the european injection pump and ours is that it is calibrated without a cigar hose. Yet still with an open relief valve during calibration.

The loss of milage on winter diesel may also not be only the lack of btus available when thinned in the fuel. A portion of the loss may be the increased viscosity of the diesel fuel when colder.

A fuel pre heater may increase the fuel milage at least a little in the winter. Someone should scan the temperature of the injector feed lines in summer and winter on 616 and 617 engines. There is a chance the heat of fluid compression in the pump is not enough to preheat the fuel in the lines to summer temperatures. Or the loss of temperature while in the lines is a factor.The time for all the fuel to transit the injector lines may be much more than thought depending on the injectors rate of fuel return.

Now if the two temperature readings are far apart there may be a lost milage component here of some magnatude. Volkswagon seems to have felt it an issue by eventually designing the fuel filter to recycle a portion of the fuel to preheat the incoming fuel in winter. Also some of the newer mercedes diesels with simular in line injection pumps have thermostatically controlled fuel heaters.

A lot of proper function seems tied to fuel viscosity. I wonder if those engines with fuel pre heaters suffer percentagewise as much fuel milage loss in proportion as the 616 and 617 engines do? Or perhaps mercedes just tried to stop a gelling of fuel effect.

Once again just a few of my opinions and not to be taken to the bank.what is becoming obvious to me is that the further we look into these areas the more there is to consider.

The optiimum function of the injection pump will only occur if fuel of whatever viscosity is loaded in a simular rate and fashion that it was during the injection pumps original calibration. Heavier viscosity fuels should require higher base injection pump base pressure to do this. Or attempt to get close to the feeding patterns of diesel fuel by increasing them has reciently raised it's ugly head.