Truck Trend Garage: Chevrolet Lumina APV Injector Problem
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.
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at email@example.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.
Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage -- visit Alex Steele at www.RealWorldAutomotive.com.