Started a new post as the original started to get a little long.
Rodd, per your suggestion I am recapping the equip in my ignition system.
'71 280 SL
Unsure of dist #
Pervious owner had installed a Crane XR3000 high energy ignition, but left original Bosch coil. This was not hot enough for system. Called Crane and was told to buy a Bosch high energy coil and did so from Ray at SL Classics. This is a silver coil. Then purchased a 8mm set of Magneton performance wires. These made a big improvement in idle and acceleration.
After all these improvements, I still noted a hesitation and miss for a few seconds when leaving a stoplight. Once rpms picked up, it was gone. Sweet exhaust note, smooth on highway, and shifted well. (translated means typical MB "decisive" shift) Also noted that it burned rich at idle and when slowly driving around neighborhood.
Thought that I should bring to shop for timing check and mixture adjustment. Nothing major in my mind. Shop kept for 6 days. Said that they started by completely "resetting rods and linkage to factory specs and now it ran terribly." They changed the new plug I had put in for Bosch 7's? (or maybe 9's- I had one or the other in there) They tried to set dwell, but could not get adjusted to spec. Perhaps due to pecularities of Crane system? Does anyone here have any experience with this? Finally, after 5 days, they try to set the timing to spec printed on door pillar, but got very poor results. He finally set to TDC (Thanks, Joe!), which resulted in adequete performance, and 30 degrees at 3000 rpm.
Went by the shop again this morning to check on the car. The mech./owner was just taking it out for a test drive so I joined him. From a stop, it now accelerated smoothly and had good mid-range power, but did not shift into 4th as it used to. Originally, if I accelerated and then leveled off the gas it crisply shifted into 4th. Now I had to completely release the pedal, and as we decelerated it would shift into 4th. He stated that 2-3 shift was by the electric microswitch, but 3-4 shift was done by a vacuum.
Anyway, as we approached the speed limit I would level off, not decelerate the gas to maintain speed. As I did the car had a very rough, raspy, gasp-like tone. It was too lean, he said. So we pulled over, turned off the car and he adjusted the idle screw in the back of the injection pump. This time the hestation was back, mid-range power was gone, and the smoothness gone on take-off. Under full power it ran like a scalded cat, but would NOT shift unless you let off the gas- then sluggishness reappeared. I questioned whether the idle adjustment would help the mixture at load. He showed me in the book (BBB) where the adjustments were. It showed 3 adjustment screws:
The external screw = idle
behind the plate were two other screws
black screw = partial load adj.
white screw = upper range adj. screw
He said that if he adjusted the external idle screw it would move the entire rack up and down and this would adjust the mixture problem. Also said to adjust the internal screws would take something the Germans called a "beer machine?" A device that measures flow rates? However, he could find no middle ground when it was adjusted through the idle screw.
End result is that I had to leave it there with the promise that he would figure it out and fix the problem.
Again the shop has a good rep, and he appears to be very professional and very meticulous. But like you guys said, this is a very finicky fuel system, and you have to be familiar with all it's subtle nuances. The injection pump looks to have been rebuilt very recently I was told, but he says that it may have problems and have to be rebuilt again. I am NOT anxious or enthused about that possibilty since it ran fine except for the hesitation/miss when I brought it in.
Thanks for any and all suggestions,
David
'71 280SL
