How to Ensure Fuel Injectors Are Receiving the Correct Voltage

If your engine is running rough, there may be an issue with the vehicle’s fuel delivery system. Having a faulty injector can cause one of your cylinders to not ignite fully, which will throw the balance of the engine off at all speeds. This ruins fuel economy since all of the fuel may not be combusting, and you have to press harder on the gas pedal to get the car to move.

Fuel injectors are a particular type of solenoid that are made to actuate their pistons very quickly. This allows the injector to deliver precise amounts of fuel into the cylinder, even while the engine is spinning at higher RPMs. Over the life of the car, the injectors fire millions of times and eventually can wear out or clog up, preventing the engine from operating correctly.

This guide will focus on making sure the injectors are receiving the correct amount of power and that the injector itself doesn’t have too much resistance. It is possible for the injector to cause issues even if it is receiving the correct voltage. They can clog up, which will decrease the spray inside the cylinder. This, in turn, causes the fuel to not burn completely and will create a misfire.

Part 1 of 2: Testing injector resistance

Material Needed

  • Digital Volt-Ohmmeter (DVOM) or multimeter with ohms setting

  • Note: Some engines have plastic panels that need to be removed before you can access the injectors. They are typically secured by bolts and can be removed with a basic socket set including an extension.

Step 1: Make sure the key is off. You don’t need power for this test.

location of injectors

Step 2: Remove injector wiring harness. There may be a slide lock that you need to move before you can press down on the tabs to remove the wiring harness.

DVOM set to measure ohms

Step 3: Set DVOM to measure ohms. Set the multimeter to measure ohms. Set it to the lowest range if the meter doesn’t autorange.

close up of injector prongs

Step 4: Test resistance with DVOM. Place the meter leads on the prongs inside the connector, making sure that they are not touching each other.

  • High impedance injectors are the most common found on cars these days. They will range from 12 to 17 ohms.

  • Low impedance injectors are found on high performance and larger injectors. They have much lower resistance, typically around 2-5 ohms.

Step 5: Repeat with all injectors. They should all have a resistance within half of an ohm from each other.

Any major difference and that injector should be inspected to make sure that it is firing correctly.

  • Tip: You can find the correct resistance for your injectors by searching online or in your vehicle’s repair guide.

Part 2 of 2: Testing injector wiring

key in second position

Step 1: Turn the car on. Turn the key to the second (ON) position for this test. You want battery power flowing, but don’t want the engine running.

DVOM on DC voltage

Step 2: Set up DVOM to measure DC voltage. Use the lowest range possible if the meter doesn’t auto range.

negative lead touching metal

Step 3: Touch the negative lead of the DVOM to a ground source. The car’s frame is connected to ground, so look for an unpainted piece of the frame under the hood.

  • Tip: Some DVOMs have alligator clips so that you don’t have to hold the lead. This frees up your hands to focus on getting the positive lead in the correct spot.

positive lead on wiring terminal

Step 4: Place positive lead on the wiring harness terminal. The wiring harness will have two terminals that the prongs on the injector insert into.

One will be connected to ground and will read 0 volts. The other should read around 12 volts.

Step 5: Repeat with all injector wiring harnesses. Leave the ground lead in position and test all of your injector wiring harnesses.

They should all be around 12 volts. A lower reading means there is excess resistance in the wire somewhere.

Hopefully, these tests have allowed you to find the issue with your fuel injectors; but, as mentioned before, it may not be an electrical problem that is causing the injector to malfunction. The next step if the injector resistance is normal would be to remove the injector and test the spray pattern it produces on an injector tester. If you are experiencing any difficulty with testing your injectors, our certified technicians here at YourMechanic would be able to assist you with diagnosing the problem and replacing any bad fuel injectors.


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Robert

31 years of experience
641 reviews
Robert
31 years of experience
BMW 328i L6-3.0L - Fuel Injector - Mountain View, California
Robert brought the whole mechanic shop with his amazing knowledge/experience into my garage, and he was very flexible. He paid attention to every details during the repair process and didn’t bother to explain on my questions. Most importantly, Robert is a very honest man whom you can count on...^^
GMC K1500 Suburban - Fuel Injector - San Jose, California
I cannot begin to describe how great of a mechanic Robert is not only did he constantly keep me updated , was very straightforward , extremely professional and did absolutely excellent work we'll probably never use another mechanic other than him ever again I would recommend him to absolutely anybody

William

34 years of experience
517 reviews
William
34 years of experience
Cadillac STS V8-4.6L - Fuel Injector - Phoenix, Arizona
He came to the first appointment explained what was happening he was able fix and get me a quote for the issue I had and scheduled me quick for the other issue I had was able to explain with my certain items were not needed even though online portal stated was needed. Only paid for the services required to fix the issue. He kept in contact with me to advise on the repair status and the final result. Nice to have the mechanic come to you. Would recommend William very courteous.
Mercedes-Benz 380SL - Fuel Injector - Sun City, Arizona
William was wonderful. Very knowledgeable and hardworking. Absolutely the best of the best mechanic.

Matthew

33 years of experience
1210 reviews
Matthew
33 years of experience
Chevrolet Corvette V8-5.7L - Fuel Injector - Newport News, Virginia
Matthew was awesome professional patient with my questions very knowledgeable and insightful I'm so grateful for his help and I will definitely request his services in the future I thank you!
Mitsubishi Raider - Fuel Injector - Newport News, Virginia
Great Mechanic!!! Work was complete in a very timely manner. Much easier than having go through the gymnastics of having a dealership perform the work.

Torrieanto

12 years of experience
632 reviews
Torrieanto
12 years of experience
Chrysler Town & Country V6-4.0L - Fuel Injector - Saint Petersburg, Florida
Torreanto replaced all 6 injectors on my 2008 Town and Country for an extremely reasonable cost. He is a very competent mechanic with excellent experience. His troubleshooting and analytical skills were very apparent during our discussion of the work at hand. I really enjoyed talking with him on an engineer to engineer level. The job was completed in a timely manner with careful attention to detail. My car is running smoothly again with excellent power. He was also helpful in discussing other issues that were identified that may need addressing in the future. I will definitely look for him to do any necessary work on my van in the future.
Volkswagen Jetta - Fuel Injector - Riverview, Florida
Torrieantos arrived on time to complete the repairs. He was courteous, knowledgeable and got the car back up and running like new.

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