How to Ensure Fuel Injectors Are Receiving the Correct Voltage

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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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Recent Fuel Injector Replacement reviews

Excellent Rating


YourMechanic Fuel Injector Replacement Service

Average Rating

4.9/5

Number of Reviews

151

Rating Summary
142
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2
1
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142
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Matthew

32 years of experience
704 reviews
Matthew
32 years of experience
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.
Dodge Avenger - Fuel Injector - Norfolk, Virginia
Matt is great! Super knowledgeable and helpful. Not pushy at all and gives you his honest advice on what'd he'd do for his own car. Definitely recommend and will be using him again!

Zachary

8 years of experience
43 reviews
Zachary
8 years of experience
GMC Yukon - Fuel Injector - Hockley, Texas
Nice guy, friendly and courteous. He did good work. While it did not fix the overall issue with the car, what he was tasked to do was done well and knocks off a possible cause of my misfire. Thanks Zachary!
Jeep Cherokee - Fuel Injector - Cypress, Texas
Zach was on time, fixed the diagnosed issue and pointed out another problem, which could have resulted in a major safety issue if not repaired. He was not scheduled to work the rest of the day, but fit me in and got my car back to good condition! Thanks Zachary.

Joseph

19 years of experience
450 reviews
Joseph
19 years of experience
Jeep Grand Cherokee - Fuel Injector - Clearfield, Utah
Joseph was very knowledgeable on what was going on and let me ask questions about anything he was doing or if he had any ideas on what to do. He did help me cut down the price because I didn’t need as much work as a shop told me I needed which of course was very helpful. Honesty is my favorite trait. I would highly recommend this service and Joseph to anyone. I even scheduled my appointment and was fit in that day. It’s very helpful having an expert come to you then you try and find an expert. Best service I have found, I’m not gonna use a shop again if I don’t have too.
Mazda Tribute - Fuel Injector - Bountiful, Utah
He was patient with all of my questions and waiting for the part to come in the mail. Did not make me feel stupid. He was very respectful. A good guy

Clarissa

26 years of experience
168 reviews
Clarissa
26 years of experience
Oldsmobile Cutlass Ciera - Fuel Injector - Wayne, Pennsylvania
Clarissa was extremely thorough in repairing my car. I am very grateful for her dedication in making sure that my car runs well and her attention to detail and insistence that all potential issues concerning the running of my car are resolved. She is always cheerful and seems to enjoy showing my mother and me what maintenance we can perform to keep the car running well.

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