A few days ago you talked about finding the weak cylinder in a loping engine. I have lost the email, but I believe you tried the one-at-a-time cylinder method where you "crack the nuts" one at a time and look for a lack of change in the engine. I believe you said that it revealed nothing and I have been mulling that for a few days as I have the same thing in my TD. Every cylinder was contributing to the operation of the engine at idle and cracking the nuts one at a time actually proved that. The engine was obviously benefiting from each cylinder and every nut I cracked slowed the engine down. So here is what I came up with FOR WHAT IT'S WORTH . . .
The problem isn't a non contributing cylinder. It is one or more under-contributing cylinder(s). Probably close to each other in the injecting order. ( yeah, right, like any two cylinders could be more than two apart in the injecting order. (slaps forehead) well duhhh.) it's an issue of ballance, in other words.
Anyway, having gained a wealth of understanding dealing with my jeep engine, today I went after the fuel system on my 300TD.
I replaced every outlet check valve,
I tested every injector - 4 "popped" at about 1700 - 1800 and one was less than 1500
I replaced the weak injector with another one that popped at 1700 - 1800.
I used one of my test adapters to check each outlet under pressure for a spray pattern at cranking speed.
(this is not a rigorous test but can reveal obviously low or high flows through the injector.)
I cleaned the heat shields and seats under them on each injector hole.
I cleaned the check valves in the lift pump
I cleaned and unstuck the fuel galley return hose outlet check valve
Then I put it all together and bled it out and got only a barel noticeable difference.
Then I did the unthinkable in an attempt to balance the contribution of each cylinder - I loosened the 13mm nuts on the outlet pipes (but just barely since those shims are part of the tune of the system) and one by one I twisted the outlet with a 15mm wrench. Stress 15mm! (At this point let me just say that I haven't learned what I know by listening to those who tell me not to ever do something.) On each outlet one of two things happened - 1) either the engine changed speeds a bit or 2)the loping diminished. If the speeds changed I let the springiness of the delivery pipe return it to it's original position then helped it with the wrench find it's old position. But . . . if the loping or chugging or (insert you favorite word for imbalance here) diminished I worked it until it was as smooth as possible with that outlet pipe. In my case #2 and #5 IIRC noticeably affected the smoothness of the engine. When I got it as smooth as possible on any adjustment I tightened down one of the 13mm nuts. I kept repeating this with all cylinders that would improve the smoothness. Those that only changed engine speeds I left alone. When I got it as smooth as I could I locked down all the 13mm nuts and then cracked and tightened each 17mm nut to relieve the spring stress from twisting the delivery lines.
The result - there is still an audibly noticeable imbalance. But the engine is not shaking anywhere near as much as it did 20 minutes before the procedure. In fact it is remarkably stable. It has a very regular clatter even with the slightly audible imbalance. Perhaps a new rack damper is in order.
Anyway, this "worked for me". So I thought I would pass it along. Hope it helps.
Bogy
"Hardware eventually fails. Software eventually works" - Michael Hartung
