Question: I have a Chevrolet Lumina APV van with the 3.1-liter V-6. There's no spray from the injectors. I think they're not receiving the signal to spray the fuel. I've replaced the injectors, fuel pump, oil-sending sensor, fuel-pressure regulator, and even the ECM. All fuses are good. I can put direct current to the injector and it sprays fine. Help!

Answer: I'm a little confused. If you had the knowledge to hotwire the fuel injectors and produce a fuel spray, why didn't you first check for power and a ground pulse to the injectors before replacing all those parts? The first thing to do is check for spark. An rpm signal is necessary for the electronic control module to produce a spark or the electronic pulse to the fuel injectors to determine if the engine is rotating and, if so, at what speed. If it's missing spark and pulse, I'd go straight to the crankshaft position sensor and test it accordingly. That's the source of the rpm signal to the ECM. Does it have spark, but no pulse? Test one of the wires at the injector for 12 volts and the other for the pulsating ground signal from the ECM. That will direct you to which circuits to trace for a broken wire, poor connection, or bad ground. Again, if there's no spark or pulse, check the crankshaft position sensor and all related circuits. Spark but no pulse, check for power at the injector. No power, get a schematic and trace back to its source of 12 volts. No ground pulse, check the circuits to the injectors from the ECM, along with power and ground circuits to the ECM. Gnawing rats can work wonders on wiring harnesses.




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