So I have a 1980 300GD with a European OM617 naturally aspirated engine.
Living in Colorado, this truck has to pass emissions every year, just a simple opacity test at a couple load points. The first few years I had it, it passed without issue, something like 13% opacity max with 45% being the max allowed.
Then all of the sudden it was very hard to pass, jumped up to over 50% opacity!
So I did the usual, adjusted the valves, replaced the injectors, new air filter... Nothing helped.
I then took it to a shop figuring it would need the fuel injection pump timed. However, the shop I took it to used a pizo sensor on the #1 cyl fuel to measuring the timing. He said it was basically dead on, no issues.
So I am currently trying to use the drip test to verify his results (I am a little skeptical of the pizo results). After hooking everything up and rolling it over a few times I notice some odd behavior. Basically, it appears to drip (flow actually) multiple times per revolution of the engine. There appears to be the expected flow, from ~65 degrees BTDC to 24DBTC. However, it quickly begins flowing again after it stops.
Below is a link to a video where I am rolling the engine over by hand and the video is looking at the drip pipe. I start at 24 degrees before TDC on a compression stroke of the #1 cyl. I rotate it over and you can see it start flowing again, a bit later I say I am about 180 degrees (crank degrees) away from where I started at 24 degrees.
My issue is that I would not expect fuel to start flowing again here. I would expect it to flow once for every 2 revolutions of the crank (~65 to 24 degrees during compression), then be off the reset of the time.
So, is my injection pump trashed? I also noticed the other valves in the IP for the other cylinders slightly leak fuel while I am rolling the engine over, which I would not expect...
https://www.youtube.com/watch?v=IqRXjEZm66M
Thanks for any help,
Jim