Welcome!
Sorry to hear of the trouble but hopefully the cause is something simple.
It think you are on the right track with troubleshooting so far. The things you mentioned checking are exactly where I would start also. Basically there are three things that could be causing this:
1) Air entered fuel system (a hose connection or the fuel filter loosened up) or a blockage occurred in the tank or something in the fuel supply caused aeration or restriction.
2) Loss of function of the fuel shutoff solenoid in the injection pump (solenoid failure or loss of voltage supply).
3) Base engine timing problem (slipped front or rear timing belt).
There could theoretically be a 4) loss of airflow due to blocked intake or exhaust, and a 5) sudden internal fuel injection pump failure, but those are both very unusual and unlikely compared to the first three.
Sounds like you will probably get the problem figured out in short order, but here are a couple of quick questions if it continues to be difficult to pinpoint:
- You said the engine was running completely normally right until it shut off. Maybe more fuel use but it might have just been the gauge. So, no other indications of trouble? Loss of power, harder starting etc?
- Did you check the fuel shutoff solenoid for voltage and clicking when actuated, as you mentioned planning to do? Something as simple as a blown fuse could deactivate that solenoid. The fact that you still saw a little dribble of fuel at the injectors doesn't necessarily mean the solenoid was opening, since a small amount of fuel still gets past it even when it's closed.
Fuel shutoff solenoid not functioning would be my first guess at the cause of the issue. On my '86 745 it used to blow fuse #13 occasionally and show this exact symptom, until I found a shorting wire to the A/C compressor that was on the same circuit.
If fuel is being delivered successfully to the injection pump but still not making it to the injectors even when that solenoid is confirmed to have +12v, you can also unscrew the solenoid and remove the plunger to determine whether the solenoid itself has failed.
Let us know what you find.
