• In the recent weeks, occasionally the engine would crank, but would not start. Eventually engine stopped starting altogether no matter how long you crank it.
• Battery is almost new (09/2025) and charged, it cranks engine with no problem repeatedly, even without recharging in the interim.
• I narrowed it down to the fuel pump not starting.
• The pump should start for 2 seconds when the ignition switch is turned to On (II) but it did not. Followed the procedure in the Service Manual for Fuel Pump problems. Removed PGM-FI relay and shortened terminals 4 and 5, this sends battery voltage directly to the pump. The pump started. So the pump is fine.
• Next checked the PGM-FI relay: removed it and bench-tested, disassembled, resoldered all solder joints, bench-tested again, everything works as it should.
• Checked ignition with the inline spark plug tester (neon bulb which goes between the spark plug and the spark plug wire): there is a spark when the engine is cranked.
• Followed the procedure in the Service Manual for PGM-FI relay, all connections between the relay and ECM are good. The only item which was off normal was the very last one: when key is in On (II), there should be "1.0 V or less" between ECM terminals A10 and A16. In my case it was 12 V. The last step would be to "substitute a known good ECM" which in my case is impossible.
• Removed and inspected ECM, no signs of damage or corrosion, no signs of bad electrolytic capacitors. Checked all el.caps with a bridge-type capacitor tester, all show capacitance in spec and small ESR.
• Then I accidentally discovered this:
• If ignition key is turned to On (II) and left in this position, without turning it to On (III), as is done normally to start the car, then the "Check engine" light comes on (as it should), and after about 1 minute Green D4 light comes on (not blinking, but solid) and the fuel pump starts for 2 seconds (as it should) then stops (and the D4 lights goes off). If the key is then turned to On (III) to crank the engine, then the engine starts normally.
• Normally this sequence happens immediately when the key is turned to On (II) or (III): Check Engine light and D4 light come on for 2 sec. and go off, at the same time the fuel pump turns on for 2 sec. and then turns off. In my case, this sequence (D4 and fuel pump) occurs only after about 1 minute.
• Looks like ECM does some checks and only starts the pump when they are complete, so it may be just some faulty sensor. No DTC codes are stored as checked with a code reader, and the Check engine light clears after the initial sequence. It could be an ECM problem (I hope not, because I doubt I will find a replacement), but I can't see how to rule this in or out. I was going to take the car to a garage (I have a decent one nearby) but I wanted to do as much diagnostics as I can myself first.
• I would appreciate any suggestions what to check next.

 

What happens if you turn the ignition to ON and jiggle the key in the ignition switch.

 

Not sure what you mean. There are three On positions, On (I), On(II), On (III), which one do you mean?