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  #1  
Old 03-28-2001, 09:50 PM
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Location: Tucson, Arizona
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Greetings all,


Don't seem to be a pain, and yes I did read the manual and followed the directions I think to a tee but still confused.
I am trying to adjust the start of delivery on this beast which I imagine has a '79 engine in it, the number on the side rear of the IP is RW375/2200MW19 Trying to adjust the start of fuel delivery on cyl. 1 has been a venture. I would say this pump is the MW style as stated in the serial number. I pump the primer pump after getting to the general start of delivery location on the dampner wheel, maybe 1 degree off if that. After pumping the manual pump to rid system of air, and fuel is flowing from the test tube, it just quits and maybe one drop may follow that, no dripping at one drop per second ect. What am I doing wrong? If I leave it sit for a few minutes, I see air bubbles form in the return line from the injection pump to the tank/filter fitting, then the prime seems to be lost all together.

Help with any info to get this set up right or replace perhaps a part that has gone bad. Have a feeling the primer pump is leaking fuel back to the tank in reverse flow, via a bad check valve perhaps. Let me know what you all think.


Charles
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  #2  
Old 03-29-2001, 11:20 PM
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Help Me Out Here Guys

Reposting, hoping for help from one of you that have viewed the post.


Charles
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  #3  
Old 03-30-2001, 12:39 AM
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Okay, Charles, I'll give it a go.

As you know, I have the MB manuals for 1979. In the Checking for Start of Delivery instructions, step #8 reads as follows:

"Rotate crankshaft in direction of rotation until fuel at overflow pipe just stops dripping. One drop should follow after about 3 seconds."

In appears that after you turn the crankshaft to turnoff, 3 seconds later one drop should appear and then nothing more (It is not supposed to keep dripping). If these things happen, then you can take the reading on the balancer. If something else happens, you should go on around with the crankshaft and do it again because you haven't stopped at the proper point.

Hope this helps.


[Edited by Ted2222 on 03-29-2001 at 11:44 PM]
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1979 240D
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  #4  
Old 03-31-2001, 02:59 AM
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AWE, come on guys, give me some help

Please! Need more details as to what should be happening when I am preparing and actually doing this drip timing.


Charles
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  #5  
Old 03-31-2001, 01:14 PM
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You do not mention whether you removed the pump element check valve to allow fuel to flow.

We quit drip timimg MB diesels when the mechanical pumps started coming around in the late 70's. We use the high pressure method now which is exactly the same idea only a high pressure pump pumps the fuel through the valve. We bought this tool when we started having trouble getting flow with the mechanical pumps.

The concept to drip timing goes like this: The pump plunger goes down, uncovering the fuel feed hole, the plunger/piston goes up and closes the feed hole. At that time the fuel starts being pushed through the line and out the injector. This point is called "beginning of delivery. In the early pumps where the pump element check valve was removed, gravity caused the fuel to flow through the pump into the pump piston chamber and out via the missing check valve through the drip tube. As long as the piston was down and there was fuel in the filter the fuel flowed. As the pump was turned the piston eventually rose and when the inlet hole started to be closed the stream of fuel through the drip tube slowed untill no flow was attained with the hole totally closed. The one drip per time interval was the measure of how closed you were. If you were "no flow" there wasn't an exact position as no flow would continue till the piston again came that far down.

The point to all this is that we have always had problems getting flow from the pumps with non removable check valves. Your flow has to be distinct or you won't get the measurement you are looking for.
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Continental Imports
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  #6  
Old 03-31-2001, 01:43 PM
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Steve,

After reading your post, can't help wondering if my interpretation of the manual instructions was wrong. In doing this job, should there be a continuing drip of one drop every three seconds?

When I did mine (many years ago), I got one drop after about
the three second interval and that was all. Thought that was the way it was supposed to be. Following that adjustment, the car ran so much better that my wife asked what in the world I had done to it. The engine has started and run fine ever since. Now I am wondering if I did it wrong?

Thanks for sharing your expertise.
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  #7  
Old 03-31-2001, 02:21 PM
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Location: Tucson, Arizona
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By The Book

Greetings All,

Steve I tried it by the book, MB diesel engine manual, and I did remove the pressure valve and spring as directed to do. I primed the system and got flow from the drip tube then if came to a slow flow within two seconds, and one drop of fuel followed after that, no more flow after that. I was pretty close to the 24 degrees BTDC at that time. Was looking at other posts concerning drip timing and found this method listed at the following site. http://hsb.baylor.edu/html/easley/autofaqs/iptiming.htm

Would you consider this to be a better way of timing the pump? I have a question, and most likely it's obvious but I'll ask it anyway for myself and others that want too but didn't. Let's assume the pump timing is off, what indications would let the owner know that? Does the engine miss and hit, lack performance at particular throttle positions, slow to accelerate or what?

Thanks,

Charles

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  #8  
Old 03-31-2001, 03:45 PM
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I again must preface my remarks with the knowledge that I haven't drip timed a diesel in over 15 years.

The real key to good drip timing was geeting good flow when more than a few degrees before "beginning of delivery". When all restrictions (I don't think the later pumps can be put in this condition) are removed (spring and valve on pneumatic pumps)the fuel flows continuously when more than a few degrees before this position. The flow stops totally within one to two degrees of crank rotation. This is the reason for one drip per time constant, if you go too far then you must go around again.

As to the alternative method provided on cando's link, It seems a good alternative to the problems I have seen on the mechanical governed pumps. I would add a degree or two as the 24 degree position is for "beginning of delivery" and is measured just before the point (by the drip method). This method is measuring after the fact as it is looking for the actual fuel being pushed.

Engines not timed properly may start poorly, smoke blue or white, and lack in power.
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