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Does anybody know or understand the relationship between the EGR vacuum solenoid switch and the fuel pump relay in the electrical sense ? The switch is also on carby EA82's

The EGR solenoid is fed power by the fuel pump realy, but it is grouned by the ecu, so is not always on when the fuel pump is running.

My understanding is that the EGR operates when you are cruising, so i assume when the ecu is in closed loop/ o2 sensor feedback mode.

I have got to stop thinking wipers are the only thing in a car that is earth switched. Now it is subie headlights and MOST ecu controlled things.

I have borrowed a vacuum/boost gauge so now watching vacuum hoses as they work. The egr does not get vacuum at idle from the electrically ecu controlled switch. in fact found a test that asks to give egr independent vacuum at an idle of 2000rpm to see if engine dies or falters, if it does egr is working.

The easiest way to test the valve itselt is to gently push down on the inner part of the exposed diaphram - dont use a sharp probe . If the engine falters (as it should) the valve is capable of opening , when you release the probe the valve should shut and the engine run normally .
This is an old mechanics trick to make shure the bloody thing hasn't siezed open .
Also for the record exhaust gas recirculation was used to drop combustion temps which if high enough increase NOx emissions . I can also be used to supress detonation without increasing air fuel ratio or retarding ignition timing .

Cheers .

And i am hearing the knock for an instance, then i guess it is being controlled by the knock control unit. I will eventually hook up the egr again as Fuji intended. It may have been slightly stuck open, but the control valve was not working. Might have had the egr gasket leaking ??