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  #1  
Old 06-18-2011, 01:05 AM
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W115 240D Injection Pump Timing | Destroyer of Glow Plugs

Hey Everyone-

I have a 74 240D that has had a long a sordid history with the injection pump. I stupidly took it to a general diesel shop to get the diaphragm replaced--they then sold me on a full rebuild--which they boogered pretty good. A local MB shop then put in a used pump that was supposedly running fine in another W115 240D and:

* new timing chain
* injectors
* Removed and cleaned prechambers
* "Advanced the timing as far as they dared"
* Adjusted valves

Problems:
* incredibly difficult to start (even needs a glow when hot),
* way down on power (I know, it's a 240D at 7000', but I've driven it for years)
* Eats glow plugs with gusto. I have the new fast pencil plugs and I'm only glowing them for 10-15 seconds at a time--the ends seem to get blown off. I've chewed through 6 already--could detonation be doing this?
* Is incredibly loud (need ear protection working around the running engine--not sure if it's nailing??). It's never been this loud.

The MB shop then told me compression was too low (250s when cold and came up with oil) and that was the problem... I feel like I bought ocean front property in Arizona (and probably could have before the shop fee).

I really love the car and am hoping to get it back to normal. I'm thinking the timing is way too far advanced (in the shop's attempt to get more power). So, I have tried drip timing it. Here are the questions:

1) With crank at 24 BTDC (valve lobes up) and pump loose, it delivers about 1 drop/sec. With crank at 27 or 30 BTDC it delivers about 1 drop/sec at the same pump position. Is this normal? I would have expected a change.

2) If I move the pump away from the engine, the drips stop completely. Is this advancing or retarding the timing?

3) If I move the crank to about 40 BTDC and I prime the pump, no fuel comes out at all. Could I be timing the end of injection instead of the beginning? Could the shop have advanced it that far? I thought he mentioned having to move it a spline or so.

I'd greatly appreciate any advice and thoughts on this. I'm not sure where to go next.

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  #2  
Old 06-18-2011, 01:16 AM
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Have you rechecked the Camshaft Timing since the Timing Chain installed?
After that is done recheck the Valve Adjustment.

On the later model Fuel Injectin Pumps the throttle lever is supposed to be in the Full Throttle position when you Drip Time. Being that you have an Pneumatic Governor I am not sure how you would do that on yours.
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  #3  
Old 06-18-2011, 01:23 AM
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No, I haven't verified the camshaft timing--I will do that (check that the dots line up on the cam at TDC?) Not sure how to adjust that if it's off. I have checked the valves twice since--a couple were a little tighter than I would have set them, but not really out of spec.

I have the throttle wired WOT, but I believe the default position is WOT unless vacuum is applied to the diaphragm?

Thanks for the response!
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  #4  
Old 06-18-2011, 02:02 AM
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TDC on the Compression Stroke.

I do not know if they have offset Woodruff Keys to correct the Camshaft Timing if it was off for your Engine. They have them for mine.

Also I have not read of the New Style adapter Glow Plugs having the issues you say. In the Manual it does have that timing will have an effect on the Glow Plugs.
If the Injector Spray pattern is not right and Fuel is either sprayed or dribbled on the Glow Plugs that will burn them.
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  #5  
Old 06-18-2011, 02:20 PM
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Cam timing looks good, lines up with the mark on the tower. What concerns me is that with the crank set at 26 BTDC rotating the pump away from the engine slows the fuel flow to drips and then stops it. Moving the pump towards the engine increases the rate of flow.

If moving the pump away from the motor retards injection (makes it "late" in reference to the approach of TDC) does this mean I'm looking at the end of the injection? I would expect to stop the flow by moving the pump towards the engine which would advance the timing if I was truly at the start of injection? Or, do I have it backwards?
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Old 06-18-2011, 03:00 PM
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As you move the injection pump away from the block it is retarding the timing.Are you smoking a lot or anything unusual?

It is possible to get the pump installed on the wrong stroke and you will have no power. To check this when at you are at the drip position have a quick look to verify the valve lobes on the first cylinder are both pointing up at near a 45 degree angle. If they are pointing down the injection pump is going to have to be installed again correctly.

I only threw this in because of your complaint of extremely hard starting and no power. Smoking would tend to reinforce this remote possibility.
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Old 06-18-2011, 03:09 PM
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Look at the thread I keep in my signature... about the cam marks...
You need to start at the very basics and be sure everything is where it is supposed to be in relation to everything else...
This ' advanced as far as the dared '... really does not sound proper...something else is askew which they did not bother to find ...
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Old 06-18-2011, 03:16 PM
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Turning the Plunger in the Element changes the amount of Fuel the comes out.

Depending on where the Plunger is turned it should eventually stop/reduce dripping turning it towards the Engine or away from the Engine.
It is kind of difficult to describe why because it has to do with how the cuts/grooves (helix) on the Plunger is made and what that does.
I will try to give a brief explanation.
Before you get to begin Injection the Feed port in the Barrel of the Element is open so Fuel (with the Delivery Valve and Delivery Valve Spring removed) flows out the Drip Tube.
As you rotate the Fuel Injection Pump the Element Plunger rises and blocks off the Feed Hole in the Element and injection begins (as you approach begin of injection the amount of drips should decrease but you have to turn the Fuel Injection Pump really slow or you go right past the point you want).
Fuel is injected as long as the Feed Hole in the Element is blocked off.

You reach end injection when the Element Plunger rises high enough that due to the Helix (grooves in the Plunger) the Feed hole is again opened. If the Delivery Valve and Delivery Valve Spring were installed Injection would stop and the excess Fuel in the Element gets pushed out of the Feed Hole in the Element.
But, with the Drip Tube Installed and the Delivery Valve Spring and Delivery Valve removed Fuel goes into the Element Feed Hole and will start to come out of the Drip Tube.
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Old 06-18-2011, 03:35 PM
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Thanks for the explanation, that helps. So, the duration of injection when no fuel comes out would be very brief (ie, only a couple of crankshaft degrees?)

I went ahead and pulled the fan so I could move the crank and get the start of injection now. What I see is this (with the valves #1 both at about 45 Degrees): at just about 40 BTDC (where there's a red mark put on by the shop) the stream of fuel stops, then it seems to pick back up again right around 26 BTDC--where I can push the pump away from the engine to make it stop again.

Aren't the W123 240Ds' IP timing supposed to be around 40 BTDC? I'm starting to think that the shop accidentally set this to a W123 spec instead of a W115's 26 BTDC? I'm a little hesitant to pull the pump and try to remount it for fear of making it worse.

Thanks for all the help.
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Old 06-18-2011, 03:39 PM
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Is it reasonable to expect the duration of the fuel flow "cut off" by the element plunger that Diesel911 described above to last about 14 degrees of crank angle? If so, I'm strongly suspecting that I've been incorrectly "fine tuning" the end of injection to be 26 BTDC.
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  #11  
Old 06-18-2011, 03:42 PM
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Just to be certain, there's no other reason that the fuel flow from the drip tube would cut at at that point--like from an injection on one of the other cylinders (but, those should only happen at another 360 degrees of crank rotation for #3 and opposite for #s 2&4, right?)
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  #12  
Old 06-18-2011, 03:56 PM
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Quote:
Originally Posted by MrWendell View Post
Cam timing looks good, lines up with the mark on the tower.
Look at the thread in my signature about that cam mark...
When you are having trouble especially... it can not be counted on for what you are counting on it for....
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Old 06-18-2011, 04:07 PM
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leathermang, the timing chain was just replaced at the same time the shop replaced the IP. Based on that thread you referred me to, are you suspecting the timing chain was installed incorrectly? I have that mark darn close on the tower.
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  #14  
Old 06-18-2011, 05:20 PM
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I guess I need to go look at that thread again..
but to the bottom line...
the only way the FSM says to check for setting the timing is to use the 2mm movement of the intake valve on the number one cylinder.. as the cam mark is only for the initial BUILDING of the ENGINE ( read ballpark or correct quadrant.... )... not accurate for later measurements .... particularly when youb are having a problem having used that as a reference point....
If it was installed wrong... that would be how you check it... many a good mechanic has installed new chains and found ( most probably by not keeping constant tension on the chain the whole process ) that the injection pump was off by too many degrees to set by just moving the IP body in the normal way.....
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  #15  
Old 06-18-2011, 08:21 PM
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The car is FIXED! I took the plunge and pulled the IP with the crank set to 24 BTDC. Sure enough, the notch in the gear (looking straight at the front of the pump) was about 3 teeth to the left of the dot on the pump. Using a 19mm wrench, I moved the notched gear back in line with the dot on the pump and reinstalled it.

This time I was able to push the pump towards the engine and actually get the 1 drip/sec rate at 24 BTDC! I turned the engine over by hand and verified it two more times. Starting at 80 BTDC I get a constant stream from the drip tube until about 27 BTDC where it starts slowing to the 1 drip/sec at 24 BTDC.

I put everything back together and, after purging air from the injection lines it fired right up! Power is back to normal, it's quiet and it refires when warm with absolutely no glow--just like before all this drama.

It looks like the mechanic set the timing to ~45 BTDC--probably assuming it was the same as the fintails. Hopefully, no long term damage was done. Thank you all for your help--getting this fixed has been a year and half project!

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