Mark Cason wrote: > > Modern fuel injectors, are basically mini electric fuel pumps, and > run non-stop. They run off of a PWM signal, which is altered, based on > what the Oxygen (O2) sensors, and the Mass AirFlow sensor (MAF), are > telling it. On every 4 cylinder engine that I've worked on (Esp. from > the 90's), all the fuel injector operated off of the same PWM signal, > which simplified things considerably. The main proponent for doing it > that way, is that O2 sensors can only tell that the exhaust stream is > running either lean, or rich. They can't really tell WHICH cylinder is > causing the problem. > I ran the full internal diagnostic scan on a Ford 6-cyl engine some years ago, and was amazed at the built-in diagnositcs of the system. That car had separate injection for each cylinder, and so they cut off one cylinder at a time to check injector balance (reading RPM dip and oxygen sensor changes), and then cut off one bank at a time to check variations between the Oxygen sensors. It was quite cool! Yes, a number of 4-cyl engines do things a bit simpler to save ECU hardware.
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