I got this 1980 240 DL for $325, drove it nearly 6 years with no troubles.

It now runs on only 3 cylinders. It has adequate (not great) compression, it has 175 PSI in two holes and 150 PSI in other two. Has decent spark. Conclusion is it must be fuel supply. Even on only 3 cyls, the car starts easy, just a flick of the key.

To determine which cyl was bad, I pulled 1 plug wire at a time to see when engine running changed. It was so rough (at idle) I couldn't really tell. So I went the other way, and put on only one plug wire at a time. It would start and idle on 1, 3, and 4 (actually, I was surprised it really would run at all on one cyl.)

So, it looks like #2 is the culprit. The injector nozzle seemed the most obvious culprit. I went to the u-pull-it, found a similar model that was clearly there because of a crash (and therefore was likely a running car) and pulled all the injectors. Swapping in these injectors made no difference.

In retrospect, what is probably a related symptom is that over the last year or so, the car began pinging a bit. Not much, and I attributed it to crappy modern gasoline. Now I'm thinking that one hole (or maybe more) was gradually getting lean and causing the problem.

So, the problem must be deeper in the injection system. Anyone seen anything like this before? What am I looking for?

-rcf