Engine Maintenance for Spring: Assessing the Condition of Diesel Fuel Injectors

common rail diesel injection system

Chances are you have been cooped up all winter and can’t wait for spring and your first road trip. Before you take that Memorial Day trip to the beach or start using your truck to haul your boat around on summer weekends, make sure your vehicle is in tip-top condition.

In addition to checking the oil and tires, you’ll also want to ensure your diesel fuel injectors are in good shape.

Follow these tips to determine the condition of your fuel injectors before seeking the help of a mechanic.

Why Injectors Fail

There are five primary reasons a diesel fuel injector will fail: high internal leakage or return flow, no injection, excessive injection, incorrect injection rate and incorrect injection timing and duration.

The reasons for each type of failure vary, but there are steps you can take to prevent each failure from occurring.

Assessing a High Internal Leak or Return Flow

If your car or truck is hard to start or takes more cranking time than normal, you may have a return flow problem. You will also get a low common-rail pressure code reading when this problem develops.

Most of the time, this problem means you have a blown internal high-pressure seal or leaking cross feed tubes. It is also possible you have a worn injector ball seat or perhaps a cracked injector.

You can prevent this if you always use OEM injection components, keep your fuel system clean and purchase your fuel from reliable sources.

Assessing No Injection

black ford f150 parked

You may not have injection if you see high balance rates. This indicates your cylinder is getting fuel because the computer tells it the injector is not flowing enough.

This is often caused by rust or dirt inside the nozzle, or a nozzle needle is stuck. It could also be a mechanical problem such as loss of cylinder compression.

By changing filters regularly, you can avoid this problem.

Assessing Excessive Injection

You know you have excessive injection if you get a lot of smoke coming out of the exhaust when idling or if a banging noise comes from the engine.

You can verify the problem if you find the cylinder contribution test is high or if you have excessive exhaust gas temperatures.

One of the primary causes is a worn ball seat or nozzle needle. There could also be debris in the control system or nozzle needle, which will keep the needle open.

Ensuring you regularly replace your fuel injectors will eliminate this issue.

Assessing an Incorrect Injection Rate

A rough running engine or poor cylinder balance indicates the wrong injection rate. Most of the time, this means you have a partially plugged nozzle or poor nozzle flow balance.

Cleaning injectors with a wire brush can cause a problem with injection rates, too.

Avoid this by keeping the fuel system clean and inspecting your replacement parts to ensure they have no metallic burrs.

Assessing Incorrect Injection Timing and Duration

Check the timing and duration of your injectors when you’re getting ready for the spring and summer seasons.

If you hear a lot of knocking, notice piston damage or have large cylinder-to-cylinder exhaust temperatures, then you may have an incorrect timing issue.

Like return flow issues, it could be ball seat wear. You also may have missing or mixed parts.

The easiest way to avoid this problem is to replace worn injectors and then replace your injectors regularly.

Assessing Your Injectors at Home

You don’t need to take your vehicle to a mechanic to check on your injectors. You can do it in your own garage. You’ll need a voltmeter, screw drivers, wrench and socket set, protective eye wear and gloves.

Here are the steps:

  1. Start the engine and let it idle. Touch the end of your screwdriver to the end of the injector and listen. You want to hear an audible clicking sound. If you don’t, then the injector might be bad. Repeat this for each injector.
  2. Turn the ignition key to the “on” position but don’t start the engine. Take your test voltmeter and connect it to the negative side of your battery, then probe the injector wires until one of them causes the meter to jump from zero to twelve. If no wires cause this jump, you may have an injector problem.
  3. Connect the voltmeter to the positive side of the battery and probe the injector connector wires. Have someone else turn the engine over. The meter should jump quickly when starting up and ease back when the engine idles. If there is no signal, you may have a shorted injector.
  4. Connect your voltmeter to the injector and take a reading. This gives you a baseline ohm reading. If the injector tests show high resistance or an open circuit, it’s bad.

The injectors should each read between eleven and twenty-four ohms.

Final Word

group fuel injectors

Why take a chance on your injectors failing you when you want to enjoy the beautiful weather during your time off?

Doing a little preparation and assessment of your injectors each spring helps prevent surprises at the worst possible moment.

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