How to Check the Electrical Part of the Fuel Injectors
Fuel injectors act like electrically controlled firing nozzles that receive a pulse signal to inject and fire a precise amount of fuel into the intake manifold. Multiport fuel injectors deliver individual shots into each cylinder. Fuel injectors can cause a variety of problems, including surging, stalling, misfiring, hesitation, flooding and no-start conditions. The ECM, or engine control module, sends an electronic signal to the fuel injector, which must read and transfer an electrical pulse to ignite the fuel. A vehicle owner can perform a few tests to determine whether the electrical part of the injector is functioning properly.
Other People Are Reading
Instructions
-
-
1
Apply the emergency brake and set the transmission selector in "Park" for an automatic and neutral for a standard transmission.
-
2
Raise the hood and locate the fuel injector rail, which might be under the raised intake manifold, at the sides of it on a longitudinally mounted engine, or on top of the throttle body.
-
-
3
Locate the fuel injectors at the manifold location; they appear as small nozzles, with a small wiring jack connected to the top side of the injector.
-
4
Start the vehicle, if it is able to run. Place a stethoscope sensor pad on top of one of the fuel injectors; you should hear a continuous clicking pulse from the injector. This means it is receiving a trigger signal and firing.
-
5
Test each injector with the stethoscope. Mark with a piece of masking tape any injector that does not emit the clicking pulse.
-
6
Remove the electrical connector from the suspect injector by prying the fastener back and pulling the connector straight out. Have an assistant turn the ignition key to the "On" position.
-
7
Hook up the black, ground lead of a multimeter to a ground source and set the meter for DC. Probe both sides (with red lead) of the electrical connector tangs inside the connector; one of them should read 12 volts. No reading will indicate no power source reaching the injector, indicating the problem lies with the ECM, which is triggered (activated by an electrical pulse) by the crank or cam sensor.
-
8
Connect the negative lead of the multimeter to the positive (+) side of the battery. Disconnect the coil wire to the coil pack or disable the ignition fuse -- refer to your owner's repair manual for these component locations.
-
9
Probe the tang on the electrical connector that did not show a 12-volt reading. Have the assistant crank the engine over. Watch the multimeter gauge; the volts should bounce or fluctuate between 0 and 12 volts. A shorted injector will show no voltage pulse bounce. Check all injectors in this fashion.
-
10
Set the multimeter for the lower ohms setting. The vehicle does not have to be running or have the ignition key turned on. Touch the black multimeter lead to one of the connector prongs and the red multimeter lead to the other tang; it makes no difference in which order.
-
11
Read the ohms, which is the resistance. The ohms reading will be model-specific, so refer to your owner's repair manual for the correct ohms reading. Check all fuel injectors in this manner. Any injector that reads "0" ohms, or reads significantly different than the others, has a short and must be replaced.
-
1
References
- Photo Credit Thinkstock Images/Comstock/Getty Images
