What causes no injector pulse [Tips and Tricks]

Can’t the vehicle start? Having poor idle stability? Bad performance and increased fuel consumption?

All engines need three things to start and work properly spark, fuel and compression if one of these three factors have a defect then you’ll never have a smooth running for your engine, so if you have your engine unable to start you have to check some points such as security system, fuel level, spark plugs status, cylinder compression is good enough to compress the fuel, crankshaft angle and finally injector pulse, so let’s assume that all the above checklist is in a very good state except having an injector pulse so in this guide I’m going to show you what it means by injector how they work and what causes no injector pulse.

It’s important to learn some basics about the fuel injector to understand better today’s topic is what causes no injector pulse. So let’s start

What causes no injector pulse
Fuel Injection System

Fuel Injection History

Older cars used to supply the engine with fuel using carburetors which are a mechanical device that used to mix air and fuel, and because of the mechanical injection systems have a low adjustment that suits the different working conditions of the engines such as various temperatures, working loads altitude, and ignition timing.

The idea of electronic fuel injection systems was developed to solve the old mechanical injection systems problems so relying on the reading of a different sensor feed into a control unit analyze this data and give back the exact amount of fuel needed to meet better engine performance and at the same time best fuel consumption, these modern EFI systems usually consist of some basic components such as fuel pump, fuel rail, fuel injector.

We have seen two types of fuel system, fuel injection system in diesel engine and petrol or octane run the engine. We have a focus on the Spark Ignition engine (SI Engine), which is run by Octane or Petrol.

What is Fuel Injector?

The injector in a basic picture is an electronically controlled valve that is supplied with pressurized fuel from the fuel pump at a certain pressure level injector can be electromagnetically opened and closed at very high speed—this speed controlled by the electronic control unit using.

PWM (Pulse Width Modulation) technique, so when the injector gets a signal from the control unit to open an electromagnet moves a plunger allowing the pressurized fuel coming out in a picture of very fine droplets, and this happens when the fuel passes through a very highly engineered nozzle that atomizes the fuel to make it easy to burn, the amount of the fuel determined by the amount of time the nozzle is opened (Pulse Width). You can learn more How Fuel Injection Systems Work

Electronic Fuel injection system variation

MPI, GDI, and SPI all this are injectors’ profiles, SPI (single point injection) this is the earliest setting that has a single injector on the throttle body regardless of how many cylinders in the engine there is always one port for fuel feeding this setting used in the transition period from using carburetors to using EFI systems also they have many drawbacks such as uneven shape and bad distribution of fuel to cylinders MPI (Multipoint Injection).

The difference in this system that each cylinder has its own injector and the injectors are placed as close as possible to the intake valve this allows the ECU to give the desired air/fuel ratio to any of the possible cylinders in addition to the homogenous distribution of fuel on each cylinder, the most modern Setting of the injectors is GDI (Gasoline Direct Injection) In this setting the injectors are located right above the cylinder next to the spark plug, so the fuel is injected directly to the combustion chamber this idea increase the engine performance as well as reduce exhaust emissions.

Fuel Injectors Control

After knowing the injector and how it works so here is the question what makes a bad injector and what causes no injector pulse to answer this question we have to go deeper on what controls the injector what makes the accurate synchronization between each pulse done by the ECU, the ECU control this process by switching the ground circuit of the injector ON and OFF depending on what is required by the engine this means that if the injector ground circuit is turned on, so the fuel is sprayed on the intake valve.what causes fuel injector fuse to blow

What causes no injector pulse?

When the fuel is sprayed and make a mixture with the air inside the intake manifold, and due to low pressure in the intake manifold the air/fuel mixture vaporizes that where the fuel injection ECU sensor works and send a signal to ECU to provide the right air/fuel mixture ratio, the volume of the fuel to be drawn from the fuel pump determined by the volume of the air taken by the engine and engine RPM, there are also sensors that provide ECU with the needed data including workload, exhaust gas composition the engines ambient temperatures all this gathered data to the ECU determines the amount of fuel needed to be injected in order to ensure a smooth-running

The most important signals that determine the accuracy of a signal coming out of ECU to injectors are crankshaft position sensor and camshaft position sensor, so to test a bad injector, you have to check the voltage on the injector when the ignition key is turned on: NO VOLTAGE? , so what causes no power to fuel injectors?

“So the problem could be: a blown injector fuse, a bad injector power relay or bad wiring harness”

fuel injector relay location

In this case, you have to check and troubleshoot where the problem, the injector fuse is and relay usually located in the relay box in the engine compartment; Fuses are used to protect all electrical circuits and components while supplying power to them, fuses help the fuel pump, fuel injectors, and electronic circuits from suffering a short circuit. When these fuses blow, the system they support stops working, and the engine stops running. As a result, there is no injector pulse while craking.

To check a blown a fuse you have to pull the fuse out of its place and check it by seeing the internal wire to see its continuity if you see it cut you have to change it with a new one with the same value, also try to swap the relay with another same value relay and try.

If after all this you got the same result, so it’s time to check the injectors itself if there is no injector pulse on one cylinder, by try to unplug injectors one at a time, if the engine starts when a particular injector is unplugged so that it is the defected one that needs to be replaced

Another way to test the injector is to measure the resistance of every injector between the two terminals and compare it with the highest and lowest values stated in the injector datasheet; if the result outside the allowable boundaries, then change this injector.

In case of that, there is no injector pulse or spark, this means that is your ECU has failed in operating in this case you have to get your ECU changed or visit an expert.

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Related FAQs

Question: What controls the fuel injector pulse?

Ans: The engine control unit is the electronic brain that used to control the fuel injector pulse by gathering data from various sensors along the fuel line

Question: What causes no power to fuel injectors?

Ans: The problem may be a blown injector circuit fuse or a fault in the wiring harness to the injector or a bad fuel injector power relay.

Question: How do I know if my injectors are pulsing?

Ans: By using a simple diagnostic tool called NOID light, this tool detects a digital signal coming from the ECU and flashes an LED light, so if there is no LED flashing during cranking, this means that there are no pulses coming out of the ECU.

Question: How do you test a fuel injector?

Ans: By using an ohmmeter to measure the resistance between the injector’s terminals and compare it with the rated value of a good injector, usually when the solenoids shorten internally causes a drop in resistance causes pulling much more current which leads to a blown driver circuit

Question: How do you fix a stuck injector?

Ans: Having a stuck or clogged injector is a very wide known problem that happens because of the accumulation of carbon build-ups that coming out from using a low-grade fuel, so regularly using a fuel system cleaner can help you in this mission.

 Final Words

In general fuel injectors may cause your engine many problems and with a little care can last the life of the engine, and like any other parts of your car it needs to be maintained regularly so if you plan on running your car for a high mileages and prevent the sudden stuck, you have to regularly inspect and clean your fuel injector from carbon build ups on them. Also, a great way to keep your injector always in a good state is using fuel additives this will give your injectors the cleanliness and increase engine performance.

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Tito

Hi There, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanics (Both Heavy Commercial and Private Cars). I have been working as a mechanic for over fifteen years. I worked for a long time at Global Rebound Automotive companies (Toyota, TATA, BMW, Nissan, TVs, and Others ) as a Mechanic and Mechanics Supervisor.

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