Fuel Injector System - General Check


This is general check to help you determine if your fuel injectors are getting the power they need, and if they are, to also determine if they are operating properly.

Note: these are general instructions. Consult a repair manual written specifically for your truck, car, SUV or van for the exact procedure.

Warning: gasoline is an extremely flammable substance. Use the greatest caution when working with any part of the fuel system. Do not smoke or allow open flames of any kind in the work area, including the pilot lights in gas-type water heaters and clothes dryers. Do not allow bare electric bulbs in the work area. Fuel is carcinogenic; therefore wear latex gloves if there is a possibility of spillage on your skin. Should any fuel spill on your skin, immediately wash it off with soap and water. Do not store fuel-soaked rags where they could ignite, and mop up any spills immediately. Always wear safety glasses when working on a fuel system and have quick access to a Class B-type fire extinguisher nearby.

Poor grounding and loose connections cause issues that mimic more serious problems. Therefore, the first step is to inspect the fuel injector connections and verify that all ground wire connections are tight.

The powertrain control module (PCM), commonly know as the onboard computer; the information sensors; and the "output actuators," the valves, relays, solenoids - all of these devices depend on steady and adequate voltage for proper function.

Inspect the filter air-filter element. A partially blocked or dirty element will cause poor engine performance and efficiency. Clean or replace if necessary.

Inspect any fuses for the circuit on which you are working. If a fuse is blown, replace it. Notice if it blows again. If it does, you have a short in the circuit somewhere and need to track it down and repair it.

Inspect the throttle body, the air intake duct, and the intake manifold for leaks. Any leak will cause an excessively lean fuel mixture. Look for similar leaks in the vacuum hoses connected to the intake manifold and throttle body.

Remove the air intake duct. Inspect the throttle body for carbon, dirt, varnish or other residues inside the bore of the throttle body. Look especially around the throttle plate. Clean any dirt, grime or varnish with a shop rag and carburetor cleaner.

With engine running, place an automotive stethoscope against each injector, one at a time, and listen for a clicking sound. This indicates the injector is operating. Use a long screwdriver if you don't have a stethoscope and listen through the handle.

If you hear the injector operating, but the cylinder is misfiring, it means the electrical circuits are functioning but the injectors may be dirty or fouled with carbon deposits. Commercial cleaners may help. If not, replace the injector.

If you can't hear the injector operating, disconnect the electrical connection to the injector. Using an ohmmeter, measure the resistance across the terminal of each injector that is not operating. Compare the measurement with the value in your service manual. Replace the injector if it is not up to specification.

If the resistance is within range, the circuit between the PCM and the injector may be faulty or the injector driver may be defective. If the driver is bad, replace the PCM, after having a qualified mechanic test it.