1989 240 DL, no turbo, 155K. Owned it 4 years. Had never let me down until this week.

Am getting no spark. Problem started 3 days ago. 29 minutes into a 30 minute drive, the engine just stopped running, and dashboard lights came on-could not restart it immediately. Was able to start it later that day after replacing the coil. Twice since then engine has stopped while driving, both times within 5 minutes of starting. One time it started up again immediately, the second time it started right up when I arrived with a tow car about 1 hour later.

Before working on the car today, I checked for spark and got it. Decided to install known good power stage and RPM sensor. Here is what happened:

1) Replaced the power stage with one from our 760, so that I knew I had an operating one, and got no spark. (I put my power stage in the 760 and the 760 started, so pretty sure the power stage is good.) Put the original power stage back on-no spark. Identical part #'s on these 2.

2) Installed the RPM sensor from the 760, again a known good part-you guessed it, no spark. (Tried my RPM sensor in the 760 and it started right up).

3) Checked the 25 amp fuse on the left inner fender. Blades were slighty dirty. Sanded them and sprayed blades and fuse holder with contact cleaner, then reinstalled. Still no spark.

4) Checked the OBD codes. Now this is interesting. After pressing the button for more than 1 second and less than 3 seconds, NO CODES WERE DISPLAYED-the light did not flash. (Does no codes mean dead computer won't display codes?)

5) Got out the Bentley manual and started troubleshooting the ECU connector. First step, check for 12V with ignition on, and I have 12 V. Checked for grounds-checked good. Did not perform all of the ECU connector tests that Bentley describes (on p. 280-11 and -12) because the terminal #'s in Bentley do not match my connector.

The fuel pump relay tests fine and I hear the pump running when ignition is on.

All of this makes me think the computer is kaput. Am I fated to do the dreaded ECU replacement? Is there any other way to test the ECU besides checking that everything else works, yet the car won't spark? Recommendations on sources for ECU's? BTW, the "ECU" I'm referring to is the black box, about the size of 2 decks of cards, on the passenger firewall above the passengers right foot, and NOT the computer mounted to the side of the passenger footwell. Any comments would be appreciated. Thanks.