Car runs 30 seconds stone cold only. Maybe a short sputter, then nothing will happen.

Used volvo manual, checked all (most) engine functions, ran mode three, injectors fire, I have spark down to the last gasp. Plugs are starting to foul, but dry when it dies.

ECU wiring all checked out (all sensor checks, voltage everyware, ohms good for all componentes.

Put in spare relays on fuel pump, injector relay. No change.

Checked grounds, all good, except body ground at 2k ohms, i need to cut end off and redo connector. Injector grounds to block are 0 Ohms.

Swapped ecu into my 91 740, it ran great with the 89 ECU. SO I concluded the ECU itself is good.

fuel pump busses (main and pre) before start, during run, and 1 sec after stall.

I checked for return flow, after 3-4 runs of 30 secs, I still didnt fill 1/2" hose to get measurable discharge (got just a tad). I changed fuel pressure regulatior......No change in return flow (just a little, didn't fill hose.

So......Next I'm on to changing the fuel filter, I can't crack the connector at the fuel rail, so fitting a pressure guage may cause more problems than I want to create.

Would a clogged filter cause this symptom? Would a worn main pump cause this also ? ($$)

Are the main pumps a wear item where they need to be replaced every so many miles?? Or does a junkyard one have potential to last.