Fuel pump stopped working without warning while on the road, engine stopped.

Now, no initial 1 1/2 second whir at ignition (and no operation at crank).

No power at pump lead at initial ignition turn on or while cranking. Good ground but noticed that the power lead shows continuity to ground with tester (with or without fuel pump relay in slot).

Pump will work with 12 volts applied across terminals.

Engine will start and idle briefly after fuel system pressurized in this manner, but pump does not come to life and engine stops (seems like major electronics would be ok).

I assumed fuel pump relay was defective, installed new one and no change. Pump contacts do click when ignition switched on. Opened old one and appears to be ok
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Injection noise suppression & fan relays recently replaced but switchted around to check and no change. Don't think failure of this relay prevented pump action in past at previous failure of suppression relay.

Cleaned contacts at mass meter, O2 connectors, both suppression relays. No fuses blown, changed main and booster pump fuses anyway.

What function or signal from what device (LH control unit, ignition control unit, sensors) must be satisfied so as to allow pump start when the ignition is first turned on?

Would appreciate any insights.

Greg.