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  #1  
Old 01-11-2021, 05:29 PM
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Start of Injection Timing

So I have heard this irregular noise coming from the engine for the past couple years. Generally at lower speeds accelerating or uphill but sort of all the time. To me, it sounded like some sort of "knock" like pre-ignition or misfire or something. I never felt a lack of power when it made these noises. If I have the radio on, I can just forget about the noise so I often did. It recently got worse, so I decided to do something about it by checking the start of ignition timing.


Checked the timing and it was a couple degrees retarded. It seemed to fix the problem but over the course of 1000 miles, it came back worse if anything. Just did it again and it sounds good again.


The only thing I can figure is that I didn't tighten the nuts on the pump enough and gradually rotated back to the old spot being pushed by the fuel cam. I got the nuts tighter than a nuns **** this time so hopefully it stays adjusted.

Has anyone else experienced anything like this?


Will post if it continues to **** up

This is an 81 240D


Last edited by KxFred; 01-12-2021 at 08:11 AM.
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  #2  
Old 01-11-2021, 09:49 PM
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I have experienced the fuel knock both when the timing was retarded and also when I experimented with advancing the timing further then normal. I have not had the timing change except over a long period of time.

What condition are the Injectors in and maybe is it possible the valves need adjusting?
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  #3  
Old 01-12-2021, 08:22 AM
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I checked valve lash before I did the fuel timing. Some of the valves were actually too tight, which I did not expect but this had no effect on the noise I'm chasing. Valve noise is usually pretty rhythmic but this noise is as I said irregular. There will be a couple pops every few seconds when it does it. The only time I don't hear it is at idle.

Running that diesel purge is something I have considered because I don't know how my injectors are.
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Old 01-18-2021, 02:16 PM
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The noise has begun to return after about 200 miles of total absence
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Old 01-19-2021, 03:02 PM
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My 1985 300D engine made a loud rattling sound, like something was bouncing around inside a cylinder. That was at 325K miles. I popped the hood, didn't see anything and it went away. Maybe a year later, it happened again, very noticeable. I recall it got quieter, but continued. I drove another 3 miles, going home, but the engine seemed to need more accelerator, then as I lifted going downhill, the engine died. Couldn't even crank it over. Had to leave it on-plant and tow it home with my minivan a day later. Took the engine apart and found chunks missing around the rings from several pistons and marks in #1 cyl of something hard bouncing around, leaving some small round depressions in the cylinder head, like a small ball-bearing. The only ones I can think of are in the vacuum pump. Wonder if one could be pulled to the top by the camshaft and sucked into the PCV, then thru the turbo-charger. Seems unlikely. Installed a used engine and started on rebuilding that engine (changed cylinder liners, have set of used pistons, needs machine work next).
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  #6  
Old 01-19-2021, 03:15 PM
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Maybe you can just adjust it. Here is a short guide:

In case of a mechanical injection pump, you have to adjust the position of the pump cam in relation to the engine crankshaft: relative rotation against the engine rotating direction means earlier injection, and vice versa. Please be carefully, the adjustment should be within a low number of degrees.

Depending on the type of engine, you have different possibilities to act: In some engines, there is a flange with screws between the engine crankshaft (or camshaft or a driving gear) and the driving shaft of the injection pump. You can lose the screws a little and rotate the shaft. Before doing this, make a mark on both sides of the flange, so that you can find the original position again. If there is no adjustable flange, you could try to modify the flange with slots.
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Old 01-19-2021, 05:32 PM
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I have twice adjusted the position of the injection pump by rotating it with the drip spout tool to one drop per second when pumping the priming pump (per haynes manual). When I checked it 1000 miles after the first adjustment, it was in need of adjustment again. I suspect I will find the same thing if I do the procedure a third time.
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  #8  
Old 01-20-2021, 03:50 PM
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Did you check the timing chain wear (stretch) when you had the valve cover off? A stretched chain will retard pump timing.

Have the injectors been tested / cleaned / adjusted in the past 100k miles or less?

Typically the timing of the injection pump is good for the life of the engine, once it is set correctly, so I suspect you've got some other problem going on, related to fuel delivery.
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  #9  
Old 01-20-2021, 06:50 PM
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Thanks for the input. I have not checked the chain wear the shoe that it rides on did not look too worn and the engine has only 123k miles on it so I didn't think to check that. The haynes manual says to check the injection timing every 30k miles so I did that. I just need to check the injectors I think but I don't get why it seems to get better for a while when I adjust the timing.

Last edited by KxFred; 01-21-2021 at 06:48 PM.
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  #10  
Old 01-20-2021, 07:51 PM
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Quote:
Originally Posted by KxFred View Post
Thanks for the input. I have not checked the chain wear the shoe that it rides on did not look too work and the engine has only 123k miles on it so I didn't think to check that. The haynes manual says to check the injection timing every 30k miles so I did that. I just need to check the injectors I think but I don't get why it seems to get better for a while when I adjust the timing.
The timing chain stretch thing changes the Valve Timing and Changes he Fuel Injection Pump timing. However, re-timing the Fuel Injection Pump fixes the Fuel Injection Pump timing.
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Old 01-21-2021, 06:51 PM
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If it is timing chain wear, then it seems to be wearing very quickly all of a sudden.
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  #12  
Old 01-21-2021, 09:33 PM
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Quote:
Originally Posted by KxFred View Post
If it is timing chain wear, then it seems to be wearing very quickly all of a sudden.
I was not commenting on timing chain wear/stretch verses the noise you are hearing. I was commenting on what timing chain wear/stretch has an effect on which is valve timing and fuel injection timing.
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  #13  
Old 02-09-2021, 01:53 AM
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So if anyone was curious, I think the noise I was hearing was some **** rattling in the dash or in the engine compartment. Totally gone now. Feel pretty dumb but at least I got some experience with the fuel timing.

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