Is 0.9v supposed to be enough to activate the relay?
Where does the R7 or R8 get power from, and how much power should it get?
High amp power goes from the battery to the INJ fuse then to the INPUT side (R9) of the main relay where it waits for the control circuit (R7 & R8) to activate the relay and send power from R9 to R10.
Power then goes from R10 (high power output) to the fuel pump relay high power INPUT side where it waits again for the ECU to call for power on the signal terminals of the fuel pump relay to send power to the fuel pump.
So, power goes directly from the INJ fuse to the R9 terminal and ALSO goes directly to the white/green wire where it goes to the ECU to power it.
The white/green wire is fed B+ directly from the INJ fuse. It isn't switched on and off through the relay.
There should be B+ going from the INJ fuse, to the white/green wire then over to ECU where it powers the ECU.
My car was idling like crap yesterday and I thought my IAC was dirty or something, but then I realized I had pulled out my INJ fuse to test for voltage on the terminals which killed the power to my ECU and I lost my memory so my IAC had to relearn how to idle the car.
If you don't have B+ going from the INJ fuse then over to the ECU, then you will never have the relays switched on by the ECU.
I'm calling R7 and R8 the control circuit side of the relay and R9 the input and R10 the output.
You need to find out if there is power going down the white/green, with everything connected.
You could poke your test lead through the plastic casing on the wire (maybe sharpen the point a bit) or test for B+ at the ECU on pin #4 and pin #55.
Both #4 and #55 are white/green as well, right at the the ECU. You can unplug the ECU connector to test for B+.
If you've got B+ at the ECU, then either power isn't getting from the ECU to the R7 and R8 of the main relay or your ECU is fried.
Are these 2 statements correct?
1) High-amp power goes from battery to 30 amp INJ fuse, then to R9 Output side of Main Green Relay then to Output side of Fuel Pump Relay, then to fuel pump and car runs.
That is correct except power goes in on the R9 terminal then out on the R10 terminal where it goes to the fuel pump relay then to the fuel pump and runs the car.
R10 also goes to the injectors, purge solenoid valve and vehicle speed sensors.
2) ECU sends low-amp power to R7/R8 Input side of Main Green Relay (is this the role of white/green?)
Yes, indirectly, the ECU needs power coming into it on the white/green wire before it will send power to R8 and R9.
and to Input side of Fuel Pump relay.
No,.. The control signal and the high power input come from R10 of the main relay.
(Well,.. Half the control signal,.. The other half comes from the ECU where it continuously switches the power on and off while driving to keep the pressure where it needs to be.)
This means there are conditions where the ECU will not send Input power, the relays will not close and no high-amp power goes to fuel pump so car cannot run.
As soon as you turn your ignition on, the main relay should switch on, sending power to the fuel pump relay and fuel injectors.
That leads me to wonder about your ignition switch again,.. If power isn't getting through it when you turn the key on, then the ECU doesn't know your key is in run or start position spit doesn't power up the main relay.
After a merry trip through the garden chasing wild gooses, I think we got it !!