Setting start of delivery
 

Ok I have a question regarding the drip tube method of setting start of delivery on the injection pump. I have read both the FSM and haynes and am a bit confused. So the specs say Start of Delivery should be at 24degrees before TDC. So I should have have the pointer on the harmomnic balancer set to? 24degrees? The pictures in Haynes led me to believe it was TDC but I think that is wrong. Is there a 24degree mark on the balance or do you have to guesstimate?

See if I have a pic in the below thread.
Result of me advancing the timing to 28 degrees
My Results timing advanced to 28 degrees 617.952 - PeachParts Mercedes ShopForum

There is an emissions sticker on the upper Cross Member in front of the radiator that has the Timing Specs there should be a + or Minus tolerence.

For re-timing a Fuel Injection Pump that has been on a running Engine.

Added: I for got to mention it should be 24 degrees before top dead center on the compression stroke.

Crank the Engine in the direction of rotating and stop at 24 degrees Before Top Dead Center.
Remove the #1 Fuel Injection Line and unscrew the Delivery Valve Holder being careful not to drop the Spring.
Remove the Spring and the Valve in the Center of the Delivery Valve.
Re-install the Delivery Valve Holder and install your Drip Tube.
Put a Pan on the Ground to catch any Fuel.

Start pumping on the Hand primer and observe if any the number of drips coming out of the Drip Tube. You need to check the spec. I don't remember how may drips per amount of time it should have.
It is importent to keep the pressure up with the Hand Primer.

If you have the right amount of drips you do not need to change anything. Reassemble with a New Copper Crush Washer.

For most Timing Chain and Gear Strech or Wear make the timing Late/Retarded. Remove all of the Fuel Injection Hard lines because the Fuel Injection Pump will be too hard to turn with them on.

Before you do anything else scribe a line acrossed the Fuel Injection Pump Flange and the Engine Block. If things get messed up that allows you to return the Fuel Injection Pump to the same spot.
Loosen the 3 Bolts on the Fuel Injection Pump front Flange and the one on the Bottom rear of the Pump.

Here is where people make their mistake. The Fuel Injection Pump needs to be nudged only a fraction at a time. I mean if you rotate your Fuel Injection pump even 1/16 of an inch past your scribed mark that can push you past the sweet spot.
You will nudge the top of the Fuel Injection Pump towards the Engine (this advances the timing).
Stop and carefully pump with the Hand Primer. While you are pumping good and the pressure is up count the Number of drips.
Repeat the above until you get the proper drips per amount of time.

When done snug up all Bolts/nuts that hold the pump inplace and re-check the drips. If OK Tighten the Bolts and Nut more and re-assemble the Delivery Valve and holder with New Copper Crush Washer.
Install the Fuel Injection Hard Lines but leave them a little loose on the Injectors so when you Crank the Air Will bleed out of them.
When you feel enough Air/Fuel had come out from under the Hard Line Nuts at the Injectors tighten them and attempt to start.

If you have had the Pump out of the Engine the proceedure is slighly different.

I don't want to be appearing to be teaching you to suck eggs but perhaps this will help?

1) You need to find the TDC that happens towards the end of the compression stroke - the intake valve was the last valve to close (look at the camshaft as described in the wikki)

2) When you've found the 0 degrees mark at the crankshaft (and you are standing in front of it looking at it) "history" is on the right hand side - the "future"is on the left! So the numbers on the right hand side of that zero are before TDC.

Thanks! The car smokes so I'm going to try to set this when I get back home on sunday.:D

1978 Mercedes 240D
1981 Mercedes 240D
1982 Mercedes 240D

If you still have all of the above Cars you have a chance to get plenty of practice.

I am posting this here for a PM that I got. But it might be helpful to someone else reading the thread.

These are 4 an MW type Fuel Injection Pump puc

Part #1 is the Delivery Valve Holder

Parts #2 Delivery Valve Spring and #3 the Delivery Valve Valve are removed for drip timing

Part #4 The Delivery Valve Body stays in the Pump for Drip Timing and the Delivery Valve Holder is #1 is re-installed before you install the Drip Tube.

After you are done drip timing you remove the Delivery Valve Holder #1 and carefully pull out #4 Delivery Valve Body noting which end that Ring around it is on top or bottom. That Valve Body only goes in one way.
You remove #5 the Copper Crush Washer and install a new one in the place of the old one.

And, re-install parts 4,3,2 and 1; torquing #1 to the proper torque.

The M type Fuel Injection Pumps are slightly different.

Long winded
 

I used to do a lot of acoustic work when I was in the Navy and these days when I'm doing manual camera repair, I use acoustic means to time shutters. A few years ago, I used a combination of acoustic recording and scan lines from a CRT to time a 4x5 focal plane shutter in a Speed Graphic camera. I got the speeds accurate to within 1/30 of a stop which is far more accurate than most mechanical cameras. And the camera body was produced in 1953, so age doesn't matter.

But I digress, my apologies.

Wouldn't it be a similar procedure to acoustically isolate the #1 injector line from the other lines by removing the clips that bind them together, then using a pickup, record or live-feed the acoustic signal of the #1 line and the injector popping to very accurately find out how the IP is timed? Of course there is the issue of "freezing" the motion of the crankshaft optically through use of a strobe like a gasser timing light. It can be done but I'm thinking it would take a bit of gear and a bunch of patience.

All that work-around seems easier to me using gear that I know well, vice the counting of drips. Maybe it's just me thinking around this in an odd way.

Through this last few months of owning my '78 300D I've wondered things like this and how I could get around not having spark plugs to measure signal off of. I'd just have to create my own signal somehow and I'm thinking that acoustically timing the IP would not only be extraordinarly accurate, it would be just plain neat. When I get to a place where I have a garage at my disposal (in a month or so) I'll give it a try and post the results here.

Phil Forrest

We have done a variation of this approach using equipment designed to sense the pressure drop in the injection line when the injector releases. A small pickup is attached to the line and, using a strobe, the injection timing can be determined from the marks on the damper.

The correlation on the 617 between the method that uses the electronic A-B lights (617 is capable of this in '84 and '85) is as follows:

A-B light sets timing to 15 ATDC. This is the precise correlation for the engine when it is drip timed to 24 BTDC.

The pickup and stroboscopic unit is then checked. The engine shows just about 15 BTDC.

So, if you're going to acoustically measure the #1 line, you'd be looking for 15 BTDC as the setting.

Thanks, I was wondering what the variance would be since I'd be measuring from a different point in the fuel delivery chain.

Phil Forrest

The "drip method" really is not as much about "counting drips" as it might seem. The point is to position the IP at the point just before "full flow" becomes "no flow." Much like turning a water faucet off, but not quite all the way off.

just to confirm here. you mentioned atdc first, then btdc after... which is correct? oh, I think I see. the a-b light measures to the ATDC setting, which lines up perfectly with the pulse of BTDC... I get it.

I finally found the right page in the FSM, 07_1-110.pdf. They talk about one drop a second.

They also talk about starting more advanced and start pulling the crank through until you just notice the dripping. Same idea as discussed but a bit more dynamic. Also they discuss the importance of making sure the engine is at full throttle and that the vacuum hose is disconnected. I have never done it and I am just quoting from what I read.

A-B lights use a reference point at 15 ATDC which corresponds to an actual start-of-delivery at 24 BTDC. Actual SOD at 24 BTDC will be reflected by an impulse indication occuring at 15 BTDC.

No, it doesn't. The light just flashes 39 degrees late.

Now - wow - er how?

I'm interested to hear if you've got a reference for the difference between the start of delivery and the point of delivery when the injector lets go; at engine revolutions below the interaction of the timing device.

I've been trying to find one for ages.

The FSM mentions that it is possible to do "dynamic" timing (using a sensor on cylinder #1 injector line with a bit of jiggery-pokery in the form of signal conditioning and connecting this to a strobe light) but so far I haven't found at which point BTDC this is meant to be set.

Looks like I did not remember the whole of the instructions.