How to Test Fuel Injectors with a Multimeter

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For your vehicle’s engine to run effectively and smoothly, it needs to receive the correct/right quantity mixture of fuel/air, taking into consideration its range of demand.

Carburettors were traditionally used in the control of fuel/air mixture. These instruments are not perfect because; one vehicle carburettor supplying an engine with four-cylinder cannot provide each cylinder with the same fuel/air mixture due to some cylinders being away from your vehicle’s carburettor. 

In modern days, cars have with fuel-injected engines. This means that their fuel is delivered inaccurate bursts. These types of fuel-injected engines are more powerful and efficient than the traditional ones that used carburettors. Another merit is that the fuel-injected engine is more economical and environmentally friendly than the one using carburettors.

So, where is an injector located in your vehicle?

The injector through which fuel is sprayed in your vehicle is screwed into the cylinder head or in both inlet manifolds, angled in a way that the nozzle is first in such a manner that the fuel fires to the inlet valves.

Types of the injection system

1. Mechanical injection

The traditional kind of injection systems and are mechanically controlled. They are also known as petrol injection. Mechanical regulators assembly in mechanical injection controls the fuel flow of the vehicle.

Demerits of the mechanical injection system
  • Petrol injections are prone to mechanical complex drawbacks.
  • The mechanical injection system has a low/poor response to throttle backoffs.

2. Electronic fuel injection

This electronic type of system has come to replace the mechanical system. 

Merits of the electronic fuel injection
  • The electronic injection system is more popular due to the increase in reliability in the electronic control systems.
  • The electronic injection system has a decrease cost of electronic control systems.

What are the symptoms of a faulty fuel injector?

  1. Your vehicle will have starting issues
  2. Your vehicle will have poor emission
  3. Your engine will not reach full RPM
  4. Your car will increase its fuel consumption
  5. Your vehicle will produce a lot of smoke from the tailpipe
  6. Your engine may fail
  7. Your engine can detonate leading to disastrous engine failure
  8. You will experience a poor performance from your engine
  9. Your engine may start to vibrate
  10. Your vehicle’s engine will start misfiring
  11. Your check engine light turns on
  12. Fuel leak
  13. Fuel odour
  14. Your vehicle fails the emission test 
  15. Engine surge

Testing a fuel injector with a multimeter

The process of either testing a fuel injector, throttle body injection system, or electronic fuel injection is not as hard as it may seem. Since these injectors face almost the same problem, you can troubleshoot them by use of some simple tools.

A multimeter will be an essential tool when troubleshooting your fuel injection. A multimeter is an all-out combination of different meter types that measures the electronic quantities in any of your electronic projects.

A multimeter can measure various electronic measurements like;

  • Current flow- a multimeter can measure both direct current and alternating current. Measuring current means measuring how much electricity is flowing in a circuit.
  • Voltage- this is how hard electricity in a circuit is being pushed
  • The resistance- which means the level of difficulty for electricity to flow in something.
  • Electronic circuits

Selections of voltage, current and resistance have different symbols,

  • Voltage is represented as V
  • Current is represented as A
  • Resistance is represented as (Ω)

A multimeter also has some metric prefixes commonly used,

  • (milli): m: one thousandth
  • (micro): µ: one millionth.
  • (mega): M: one million
  • (kilo) k: one thousand.

Multimeters are also of two different types, namely:

  • Analog multimeter

The Digital multimeter is of two different categories:

Note; When troubleshooting using a digital multimeter on your electronic components car, it is advisable to make sure you always use the (minimum) 10 Megohm impedance multimeter to avoid circuit damage.

In our cases, we are measuring the resistance of the fuel injector using a digital multimeter, below are a few steps to follow;

Checking the Injector Coil

  1. The first step involves unplugging electrical connectors of your injector that need testing with the engine turned off.
  2. The second step will involve setting your digital multimeter to read an appropriate value. This value should be the Ohms scale regarding the resistance specifications of your specific fuel injector 
  3. The third step involves Probing your injector electrical terminals
  4. The fourth step should be reading the measurement in your multimeter. Having a resistance reading that contrast to that specified in the service manual indicates that you are required to replace your injector. Example: 

If the meter reads in your multimeter an infinite resistance, then the coil of the injector is probably opened.

If your multimeter reading is moving/ jumping all over, then your coil is opened.

If your multimeter is reading zero resistance, then your coil probably has a short circuit.

To be sure and more accurate, after using a multimeter, you can also conduct a posttest using a stethoscope.

How to replace a fuel injector

  • The first step to take is to disconnect your electrical connector
  • Secondly, you should remove the mounting bolts of the fuel rail 
  • Thirdly you should Lift the rail from your intake manifold
  • Then you should remove the retainer clip of your fuel injector 
  • The next step should involve Working on your injector from the fuel rail 
  • Next, your new injector should be matched to your old unit
  • After that, you should insert the new injector by using (O) ring seals. It is advisable to lube using engine oil
  • The next thing should be to reinstall your fuel injector’s mounting bolts and rail
  • You should then Install the electrical connector
  • Lastly, you should check for any leaks

With this few and simple steps, you can wave goodbye to all your vehicle issues associated with the fuel injection.

With the above information, I am now certain you can be in a position to test your fuel injector with a multimer. make sure to always maintain safety precautions.

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