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Justin, Nu-uh maaaan! Posted by Cmyles [Email] ![]() ![]() In Reply to: Re: ECU = Electronic Control Unit, Justin VanAbrahams ![]() |
Justin,
Your "1-7" description contains an error. Your #6 says that the fuel pump relay powers the pump and injectors. The injectors are powered from the same output terminal on the main (aka "system") relay that powers the pump relay coil. So the injectors are powered up by the main relay as soon as it closes and then actuated (grounded) by their connection to the ECU. Of course the closing of either relay is dependent on the ECU grounding their respective coils through different ECU terminal pins. That means that your "B" conclusion is also in error in that if the ECU doesn't get a tach signal it's the ground (from the ECU), not the power (from the main relay), to the fuel pump relay coil that goes missing. Your "C" conclusion is essentially correct except it should say that the ECU can't ground the pump relay instead of saying it can't "power up" the pump relay.
Not trying to pick nits, these details could be important in circuit testing to find the problem.
Possibly I'm confusing the previous details in this thread but I think that at this point we have determined that the pump will deliver pressurized fuel to the rail and does so for the few seconds that the car runs before it dies. That tells us that initially both relays are closing but after a few seconds something goes dead. I suspect that it's either a bad ECU that isn't acknowledging a tach signal or the tach signal to the ECU is missing or weak so after a few seconds the ECU cuts off the injection system. Can't remember if both relays have been "proven" yet but in my experience a bad relay (main or pump) won't allow any startup at all. Wish I had this car here to troubleshoot.
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