Kent Bergsma has a whole series of YouTube videos on a car named Digby that he brought back to life, including detailed troubleshooting steps for an old, sick diesel Mercedes.
I decided to follow this process. The first steps are to get the engine running and then crack each fuel injector line individually to see whether the tone of the engine changes. If you get one for which the tone does *not* change, that strongly points to an issue with that injector.
Well, I did all five, and each one made the engine tone change noticeably. This makes me think there isn’t anything horribly wrong with any of the injectors.
It’s kind of bad news because it means I need to dig further into the engine to figure out why it’s idling rough.
Since I needed to replace the fuel filters anyway, and I had bought a couple of cans of Diesel Purge, I decided to go ahead and do that treatment this afternoon. I had already used about half a can of DP to fill up the F-250’s fuel filter when I replaced it, so I poured the remaining 1.5 cans into a 2-liter soda bottle and connected the fuel supply and return lines to the bottle. I left the old fuel filters in place, figuring I would replace them after doing the treatment.
Well, I can’t say I noticed anything very dramatic. I did run the engine at all kinds of different RPMs, high and low. The DP in the bottle did not turn a filthy dark color like some people say it does if your fuel system is really dirty. And while I think it may have smoothed the engine out a little, it’s really not very noticeable.
So I used up the Diesel Purge, then replaced both fuel filters.
Next steps for troubleshooting how the engine is running are a compression test on each cylinder and a valve adjustment. I also want to pop test the injectors on the bench.
Rancho Zoidberg 