In this article I show you how to make a simple injectors tester that you can do in your workshop or at home.
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In this article we discuss how to assemble a small tester and pulse generator for high impedance injectors that are common in gasoline cars. In this case we are going to take advantage of the Alternating Current and as always of few economic components that we can get from an old radio or buy them in the electronics store on the corner.
- A transformer 110 V / 9V to 12 V that does not exceed 1 Ampere.
- Two commonly used rectifier diodes of the 1N4007 series.
- Four alligator clamps.
- A suiche for 1 A.
- A Led Diode
- A Resistance of 680 Ohms
Arming the circuit is very easy as you can see in the previous figure, basically connect to the transformer so that it generates pulses of 8 ms duration on and 8 ms off and this is achieved thanks to the two rectifier diodes connected in Both lines of the transformer, the pulsating output we enter the injector by means of the alligators and we manage to make the injector work constantly and at medium speed (8 ms opening) taking into consideration that the vehicle at minimum the opening time of the injector is in approximately 3ms.
If you do not know anything about electricity, I do not recommend that you ride the circuit.
As you will work with 110VAC, always work safely, that is, whenever you are going to touch the transformer on the high voltage side (110VAC) verify that it is disconnected from the outlet. "THERE IS ELECTRICAL RISK".
The transformer is important that no more than 1 ampere, so that if there is a short circuit in the injector or it has very low resistance does not generate heating in the cables or explode the rectifier diodes and ensure that the diode test led will be effective.
The rectifier diodes have polarity, see the figure so that you place the diodes in the correct way. Remember that the side of the line is negative and the side without line is positive.
Well, the Alternating Current (AC) is a sine wave that oscillates in the case of Venezuela at 60 times per second (60 Hz). Now, although this sine wave is pulsating, you can not enter the injector directly due to the nature of its regular and progressive positive / negative cycle, it would only turn off the injector a fraction of time where the wave is close to zero and since the injector at the end is a coil that tends to store the current we would have the injector practically always open.
Now, why not rectify one of the lines? Remember that in the AC, both lines alternate between positive and negative alike and vice versa, so if we only rectify one of the lines what we will do is shorten the cycles as seen in the following figure.
So finally what we do with the two rectifier diodes is to choose only one half of the two that the CA has. And with this the opening and closing times are practically equal to 8ms each, and therefore we find the wave of the following figure
With our pulse generator assembled, we assemble the circuit of the previous figure, which has a LED diode operating with its resistance of 680 ohm to limit the current and a suiche.
Then with this led diode, we will know if energy is coming to the injector and if the impedance is less than 4 ohm (the normal is 15 ohms) the LED will turn off indicating the fault of the same. Why does this happen when the LED is off? Simple, the current always chooses to go where there is less resistance and in this case as the resistance is low in the injector and the transformer does not give more than 1Amp will drop the system voltage to less than 3 V necessary for the led to turn on.
With this we have a simple but effective tester to test and clean injectors.
Ahh remember that the Led also has polarity, so you must place it correctly otherwise it will not light. The longest leg is positive and the short leg is negative. You can see in the figure of the circuit.
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