How to Check the Injectors on a Nissan Altima

The Nissan Altima comes equipped with a port type fuel injection system that features an individual fuel injector for each cylinder of the engine. The electronic fuel injectors are controlled by the on-board computer to provide precise fuel control and performance under most operating conditions. These injectors can fail electrically or mechanically, so two tests are done to verify proper operation or pinpoint a failure. The average home mechanic can complete the tests in a few minutes using some specialized test equipment available at most auto parts stores.
Difficulty: Challenging
Instructions
Things You'll Need
Small pick set
Digital volt/ohm meter
Fuel pressure tester set
Jumper wires
Electrical Testing.
1

Slide the retaining clip out of the electrical wiring harness connector on the injector using a small pick. Remove the electrical wiring harness connector from the suspected faulty injector by pulling it straight up by the plastic connector and not the wiring.
2

Plug a noid light into the electrical wiring connector, and start the engine. If the computer is working properly, the noid light will be flashing. If the light isn't flashing, there is a problem other than a faulty fuel injector.
3

Set your digital volt/ohm meter for "Ohms," and touch the probes of the meter leads to the two terminal pins inside the injector's electrical connector. The resistance displayed on the meter should be 8 to 15 ohms . More importantly, it should not be 0 ohms, or indicate infinite resistance. If the injector read 0 ohms, infinite, or is outside of the specified resistance, replace the injector.
Mechanical Testing
1

Loosen the two small hose clamps on the 3-inch long rubber fuel line that is found between the fuel rail and the high pressure fuel line coming from the pump to the engine on the Altima. Remove the rubber fuel line. Attach the fuel pressure gauge by installing the Nissan adapter in the fuel pressure test set in place of the short piece of fuel line that connects the fuel rail to the steel line.
2

Clip a jumper wire to each of the terminals in the injector's electrical connector. Clip the other end of one of the jumper wires to the positive battery post. The battery on the Altima is located in the front of the engine compartment on the driver's side.
3

Cycle the ignition key off and on a few times to prime the fuel system and build pressure. Turn the ignition key to the run position, and note the fuel pressure reading displayed on the gauge face.
4

Momentarily touch the loose end of the remaining jumper wire to the engine block, and observe the fuel pressure gauge. The fuel pressure should drop a few pounds indicating the injector opened. If it does not drop the injector is frozen or clogged beyond repair and should be replaced. Repeat the tests for the remaining injectors.

Tips & Warnings

Wear safety glasses and work gloves to prevent serious injuries.