WS1

Petrol Fuel Injector Testing :

Checking the voltage at the injectors and the battery

Make : Toyota Model : 4AFE (Grouped injection)

- After turning the engine on we can listen to the injectors opening and closing which sounds more like ticking than any thing else . I put the end of the screw driver on the body of the injectors and the plastic handle of screw driver on my ear and could hear ticking from the injectors . This shows each injector is opening and closing and as long as there is fuel available to the injectors , it also means that they are injecting fuel into the cylinders and they are opening and closing . All injectors OK and could hear ticking from all 4 .

- Bychecking the voltage at the injectors we can also make sure they are getting the right voltage which is the battery volatge ( 13.50 Volts) and this will show if there is high resistance in the circuit and no poor connections. These results are within the manufactorer spec which is good under 0.1 volts from the battery supply .

- Another way of checking to see if injectors are working properly is to back probe each injector and hook up a LED tester to it ... as the ECU grounds each injector so those the LED tester and it consequently turns the LED on ... this happens so quickly that makes it look like the LED is always on especially when we rev the engine up . This can show if the injector is repetetive is in order and is getting a good PWM.

- By using the multimeter set to duty cycle we back probe the injectors and connect our multimeter to the injectors . we can see how much of the time they are staying open at idle . shows that the injectors are staying opened roughly around 2.2-2.4% of the time to spray petrol in the engine . which shows that the engine is running lean at idle.

- Having the multimeter on the same setting and back probed to the injectors we rev the engine up to see if the duty cycle changes and by how much . This results show that when we rev the engine up our injectors are staying open longer to spray more petrol as we need more to be able to increase the RPM , ECU does this to comply with the driver intend which picks up from TPS , MAF ... My results show when we accelerate the engine with a short fast throttle , the injectors are staying open 34-37 % of the time which shows more of a richer mixture than idle .

- Now by setting the multimeter to Hz and still having it hooked up to the back of the injectors
we can see the frequency of how many times per second our injectors are opening and closing . we first do this at idle . Our results show that the injectors are opening and closing 47.5-48.2 Hz times they are opening and closing per second . This shows a lean mixture.

- We now repeat the steps above but reving the engine for a short time to see if the frequency of the injectors are changing or not and by how much . Our results show that the frequency has more than doubled and that also tells us the injectors are opening and closing 112.7-116.1 Hz times per second . this tells us that we have richer mixture since the frequency of the injectors opening and closing has more than doubled .

- Now using this formula " Pulse width ms = (% duty cycle x 100)/frequency"
would show us how long in ms the injectors are staying opened .

since we have grouped injection I am doing cylinder 1&3 and 2&4 together .

At idle :

Cylinder 1 & 3 :

Pulse width ms = (2.2 x 100) / 47.5
= 4.63 ms

Cylinder 2 & 4 :

Pulse width ms = (2.4 x 100) /48.2
= 4.98 ms

Reving up :

Cylinder 1 & 3 :

Pulse width ms = (37 x 100) / 112.7

= 32.83 ms

Cylinder 2 & 4 :

Pulse width ms = (28 x 100) / 116.1

= 24.11 ms

Conclusion :

This is a very good way to check how good they are working . Easy and faster way to check injectors with out pulling them all out and if we dont have pattern tester or flow rate tester then there is actually no other way to test weather they are working and how long they are being opened for in realtion with RPM .