Background:

I am second owner of 1990 240DL I puchased from private owner when it had 42K miles, dealer maintained. I have driven and cared for the car for the past 6 yrs. It now has a gentle 86K miles. I replaced timing belt at 53K.

Over the past few weeks the orange "check engine" light has been coming on intermittently at low rpm, and the car occasionally stalled at traffic lights or while turning corners. No big deal, just re-start and keep rolling. As a precaution, I replaced the spark plugs, air filter, and flame trap a couple weeks ago. The other morning I had to key the car a couple of times before it started, but off to work I went.

Problem:

Yesterday morning I got in the car and it will not start. It cranks but does not fire. Fortunately, it's sitting in my garage and not somewhere out in a parking lot.

Symptoms:

With key in "on" position, all dash lights come on. However, I do not hear the fuel pump initialize the system. When I turn the key off, I do not hear the "click" from the ECU (electronic control unit)behind the pass side kick panel.

Diagnosis:

Replaced fuse 4 & 6. Used a wire to jump the two together and heard the fuel pump run.

Located the fuel pump relay next to the ECU. Replaced it with one I had in inventory with same result. Tried a second spare relay; same result, no change in condition. Used a wire to jump terminals 30 and 87/2 on the fuel relay and heard the fuel pump run.

Checked self diagnostics for Jetronic (plug 2) and ignition system (plug 6) and only 1-1-1 "clear" codes were displayed.

Questions:

Is it an electrical problem or something else (ie: blocked fuel filter)?Are there other tests I can perform to isolate the problem? Are there other relays in the system to check? What was the "check engine" light trying to tell me while it still ran? Is it (perish the thought) the ECU that's the problem or am I missing something?

Any suggestions to diagnose and repair are appreciated.