If you happen to have a "parts" IP lying around you can do a simulated timing by the bubble method using the IP timing "mark". Just rig up the hoses and turn the splined shaft and see where the bubbles stop. Then go try it on your car.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

... by the way my middle name is " Millsaps ", a most English family name with a shield/crest and all... so don't let my "Limey" prodding get to ya!

Thanks for your explanation about the inner workings of the IP... it together with my off-FORUM discussion with "Yellit" from this FORUM has finally pounded home just how the IP works... and I particularly liked your explanation of the final stage in the "element" section.

So after NOT getting consistent results from the method I described when I started this THREAD, well I went back to the "by the book" MBZ method and find that now IF I repeatedly try to stop where there are 3-seconds between drips, the timing marks or readings I get off the crankshaft's dial vary by ~6 degrees from the 24 deg. BTDC I believe my engine/IP are set at ... all the way up to ~30 deg. BTDC. But IF I repeadedly crank it over just a little further to where I perceive the fuel droplets to have effectively stopped altogether [ time-between-drops clearly > 15 seconds] then my results are more consistent with readings that are ~24-to-25 deg. BTDC.

So at least I have found a method that is consistent... but just not " by-the- book " per the MBZ manual.

Q - So what, IF anything, am I possibly doing wrong to cause inconsistent results when I try to use 3 seconds between droplets method?
Regards,

Personally, I very much doubt that you are doing anything 'wrong'....

What I feel may be giving you inaccurate readings at 1-3 drip per sec. maybe wear of the pumping-element. Not serious enough to cause you any issues with running etc, but at the point the plunger JUST closes the spill-port you may have some tiny amount of wear, or some minute scoring of the faces.

Ive noticed with my old 300D which has done 350K miles, a similar situation, where the timing can vary by a degree or two between setting and checking/re-checking. A OM-615 engine I recently aquired, with unknown history shows no such 'error', but the IP does not look like the original and very clean and shiny in comparison to the engine, so could have been re-built with new elements/roller followers/cam......

The 'difference' in Pump position between 1 second per drip and 15 secs per drip I would expect to be miniscule, in fact so small as not to make any difference, as the pumping-plunger is on the 'rising' part of the cam in the base of the I.P. This cam has a VERY fast 'rise-time', and in fact the 'rising' flank is actually flat, with the roller follower running on it.

I guess that if 15 secs per 'drip' gives reliable and repeatable performance, Go with that, as its indicating the plunger is Just about to start pressurising the fuel, which is exactly where you want itto be

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Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....

Hi everyone!

I just couldn't help adding my technique (at least I think its my technique ) to the fray! There are a couple things I hate about the standard MB method because they introduce uncontrollable variables.

The primary variable is Pressure. As we all know, more fuel will go through an orfice at a higher pressure than at a lower one. So my question is, "One drop per second but at what pressure? How much pressure remains in an IP when you stop pushing the plunger? I don't think it is consistant. On my 77 240D, I couldn't get any dripping without constantly pumping the plunger.

The second variable is Time. Can we really accuratly time 1 second drops with a stopwatch? We could probably get more accurate by counting 10 drops while timing that with a stopwatch, and seeing if it takes 10 seconds, but it still lacks a certain elegance, doesn't it?

The third variable is temperature. Colder fuel is more viscous, and flows through an orfice slower than hot fuel. That may not skew a drip test much, unless its 40 below out, but to say it has no effect at all wouldn't be right either.

The Compressed Air Method
This method eliminates ( IMHO) all three of the problems associated with the standard MB method. Here is how it works, and how to do it.

First, what we are trying to do is establish Exactly when the IP piston has Just closed the inlet port in the IP cylinder because this point is when fuel delivery acctually starts. The drip test is using fuel as the indicator, so it really is timing the point just barely before the piston closes the port. After the port is closed, timing is ambigious because further rotation does not give any indication of having gone too far. The same thing happens with the compressed air technique, but nuthins purrrrfict!

Now imagine that the IP is filled not with fuel, but with regulated low pressure (5 psi) compressed air? The #1 Delivery check valve is removed, and the element screwed back in just like the MB test. Air is leaking from the #1 element at a constant rate. As we rotate the crank, we put our finger over the element port to feel exactly when the piston closes the port. This gives a very precise break point. It is very easy to tell when it Just closes, and it's also easy to feel the air with your right index finger while turning the engine with a long breaker bar in your left while watching for the timing marks.

Getting the air into the IP easy too. Just take off the fuel line banjo fitting on the front end of the pump (closest to the radiator) and attach your extra banjo fitting, aquired during your last romp through the wrecking yard and thoughtfully affixed to the end of your compressor hose, in its place. Remove the fuel cap from the fuel tank. This makes sure the tank is not damaged because some of the air is going into the tank through the return fuel line. I know it's vented, but vents get plugged. Put on your safety glasses! Slide a piece of clear tubing over #1 element threads and run it to a collection vessel of some sort, then turn on the air gradually to about 5 PSI on your regulator gauge. I don't know how much pressure the outter IP housing will take, but I know its more than 5 PSI. The air will force some fuel back to the tank through the return line, and the rest out through the #1 pumping element and into your collection can. When it stops slobbering, take off the tube and proceed to set the IP timing as refered to above.

After putting everything back together, purge the air from the pump with the hand plunger. Next, I like to purge the air from the injector lines by having them tight on the IP, but loose on the injectors. Crank untill you get fuel from all the injector line fittings, then tighten the fittings on the injectors. Then start it up and see how it runs!

I hope everyone finds this valuable. I 've been setting IP timing on my 77 240D this way for about 3 years now, and it runs like a top.

Cheers, Chris

Chris,--

Guess you Are removing the 'delivery-Valve' before you do your test, as the M.B. test also requires, or you would not get any air-flow from the pump outlet union.

Having many times had to bleed out a system full of air, I personally dont relish the idea of deliberately admitting air under Pressure into the system intended only for diesel, There is also the issue of dirt ingress carried by the air into the system and its first port of call will be your precision I.P, but That is my personal take on it....

Other than that, I cannot fault the logic behind it, as you are still determining the Exact time the plunger is closing the spill-port in the I.P...

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Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....

Hi Alastair and all,
I agree with your point on the dirt. I neglected to mention I am getting the air from a filter/dryer off my air compressor, so it is dry and free of dirt. I also make very sure to blast out any debri in the hose and banjo fitting with a high pressure blast (135 PSI) of air before attaching it to the clean IP.

As far as purging the system of air, I've never had any problems doing so.
The fuel supply line from the tank, the lift pump, and the filter are never filled with air. Only the chamber surrounding the IP pistons/cylinders and the Return line to the tank are filled with air. Of course all of the injector lines are filled with air because they are all removed so we can turn the IP.

Anyway, just thought I would share this method in case anyone else wanted to try it. So far it has worked very well for me, and I think it adds precision by eliminating a lot of ambiguity.

Thanks for your comments.

Cheers, Chris

Hi Everyone, Having read many threads on this forum I feel compelled to say that there have been many interesting and helpful treatises, comments, and hands on experiments that have helped me along in the maintenance of my two Benz's. At this point I will specifically thank Bio 240D for his contribution in the start of delivery saga because in my subjective experience this process worked best for me. I realize this thread was posted quite some time ago, however, the info is current as I have just performed this process on a 1980 300D and it worked beautifully. I will be using the same procedure on an '83 300D that has been through a long and protracted resurrection. Thank you
And by the way I found a useful tool for assisting in the positioning of the IP while making these adjustments. It's a common plumber's tool and I think it's called a basket strainer wrench. I got mine at HF some time ago for a different application. Am currently unable to locate the same tool on the HF website.

It sounds wrong to me to look for when the IP starts to force fuel out of the #1 port. The factory method is to apply pressure to the IP inlet (continuously pump the hand pump is a convenient way) and you look for the point where the #1 IP cylinder's inlet port just closes which is where it goes from a steady stream to 1 drip/sec. The method described above requires that the IP's #1 piston start appreciably moving upward, which might be many crank degrees later (since a sinusoidal function).

I don't get hung up on the "1 drip/sec" spec. That might be something a tech writer felt compelled to add to quantify the step. If you do this timing, you will see a very sharp transition from "full flow" to "no flow", so counting drops seems silly. Put your effort more into carefully jogging the crank by <1 deg increments as you get close. I also use the p.s. pump pulley to turn the crank over initially, since it is "right there", then usually switch to a long-handled ratchet torque wrench on the crank bolt (32 mm?) for the finesse needed as one approaches the "1 drip" angle. I also don't fool with a goose-neck tube. I might have used one the first time, then found it is easy to just look at the fuel coming from the delivery valve port (w/ guts removed). Be real careful to photograph the orientation of the delivery valve internals since it is easy to re-assemble incorrectly.

I set both my 300D's to an earlier 27 deg timing (24 deg is spec), since that is said to increase performance and efficiency at a slight increase in idle roughness. But I can't say I noticed any difference. Thus, since people can argue over the optimal setting to +/-3 deg, 1 deg accuracy in setting it probably doesn't matter, nor does 1 drop/sec vs 5 drops/sec. But M-B owners can be fussy.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

I have mentioned this before.

My last fuel injection shop job was in about 1988. At that time most of the inline Fuel Injection Pumps were timed during rebuilding of the Pump by the Drip Method (also called flow timing).
Some other companies used a Dial Indicator or a Depth Micrometer to achieve the same thing.

In the shop I worked in we had a gravity feed setup to supply the pressure. I have seen a Pic of an old Mercedes Diesel using a similar setup.

When drip timing the pump on the Vehicle I move the Fuel Injection Pump just a hair and snug down one or more of the Nuts and then I start pumping on the Hand Primer. When you do that the Fuel Pressure Relief/Over Flow Valve holds back some pressure.

While you are pumping count the drips. By doing that the pressure should be somewhat even.

Besides the Gravity Feed Setup another way is to connect an Electric Fuel Pump to supply the pressure.

Before you start it there is no reference marks on the Block to Fuel Injection Pump Flange scribe one so that you can return to were you started and it also gives you something to look at to determine how much you rotated the Fuel Injection Pump.

If you are not getting the drips you want stop, loosen the Nuts and rotate the Fuel Injection pump another hair and repeat the previous instructions till you get your drips.

If the Fuel Injection Pump is on an running engine and you are re-timing it; it only takes tiny amount of rotation to correct that. From the threads I have read lots of people grab the IP and rotate it like 1/8 inch (when something like 1/32 was all that was needed). That puts them beyond the sweet spot.

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84 300D, 82 Volvo 244Gl Diesel

actually 27mm.

Nothing like bringing up a good old thread. Personally I am not a fan of using the power steering pump to rotate the engine.

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Jim