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Old 06-06-2009, 08:11 AM   #205
brontotx
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Join Date: May 2009
Location: Space City! (TX)
Posts: 46
Re: Tbi swap build thread

RF - thanks for the latest diagram. I now realize that the your statement about "both pins measuring 12V" that I originally disagreed with was because you were measuring the voltage with the connector attached to the injector. I normally disconnect things since it can be tough to get a probe on the terminals when connected - I assumed (the old ass out of you and me adage is correct in this instance) you were probing the connector when disconnected, which would show only 12V on the red or white wires of the terminals and an open circuit across the connector terminals like I stated. So, in retrospect, your statements are correct when measuring with everything connected and mine are also correct when disconnected. BTW - all your diagrams do ROCK!

cjracing: You are correct that that the ECM requires both a starter signal and oil pressure signal to fire the injectors, however, my understanding is that the oil pressure signal is not required when starting/cranking. That is, when cranking in START, the ECM sees the signal from the starter and doesn't look at the oil pressure as it realizes that the engine's oil pressure may not have built to a sufficient pressure as yet. Once started and in RUN, the ECM requires oil pressure to continue to fire. However, getting back to the start sequence, the ignition module signal to show the engine is spinning is also required by the ECM before firing the injectors. That is, if the ECM were to fire the injectors and the engine wasn't spinning, there would be a bunch of gas being introduced into the TB and manifold that could ignite out of the firing sequence - bad news. In summary, in START, the ECM requires the starter signal to tell it to ignore the oil pressure, but also requires an ignition module signal to tell it the engine is spinning before firing the injectors. In RUN, the ECM requires both the oil pressure and ignition module signals before firing the injectors. Hopefully this is now clear (as mud, I'm sure).

Mark
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