EFI Component Testing

This week completed the EFI off car component testing I tested the MAF sensor, Diesel Injector Spray, glow plug testing and Ignition coil testing.

MAP Sensor Testing

MAP sensor that was tested

The test Involved using a Multimeter, a power source, and a vacuum pump. 

The sensor was required to be connected to a 5V reference voltage which was obtained by setting the power source to 5V and connecting sensor to it via jumper wires, to the red and black wires and then connecting voltmeter + probe to the white wire and - probe to earth.

after this was done the vacuum pump was attached  to sensor pipe and then readings were taken at various pressures caused by pump ranging from 100mmHg  to 500mmHg.

Testing. connected to MAP Sensor, Voltmeter, Vacuum pump and 5V power source

The readings I got from the meter indicated that the sensor was working correctly because as vacuum pressure went up voltage dropped: 100mmHg with 4.26V and at maximum vacuum 500mmHg, 1.47V was shown. 

If the readings were reversed this would indicate that the sensor was causing incorrect voltage drops making the engine run rich at incorrect times. As vacuum preasure increases (under load) voltage drop decreases and when vacuum pressure decreases (at Idle) Voltage increases.

Diesel Injector Spray Testing


This was tested using the hartridge spray tester. Which is used to check spray patterns of diesel Injectors while the are off the car. This was done by screwing the injector into the tester, which uses a type of oil to show how the injector is spraying and how much pressure is needed to make it spray. As long as its within manufactures specifications.

Spray Tester with injector screwed into it (Left) pressure reading is on screen to right

The tested injectors spray patterns were not the best only 1 of the 4 tested was spraying correctly as it was much finer than the rest.
If injectors are malfunctioning this would cause the engine to be inefficient, as more fuel is needed, and engine power would also be lost because the injector cannot keep up with the demand for fuel as well.


Glow Plugs


I also tested 4 glow plugs to see if the correct resistance and current flow was being used by them. 3 of the 4 plugs were working correctly because they first showed a reading of around 10A and then dropped to around 6A because the current was being used to make the plug glow. 

Plugs that were tested.

They were attached to a 10V power source and readings were taken by a ohm meter and current flow was measure amps on the power source.plugs were left to run for a maximum of 10 seconds to prevent damage to them. 

The plug that was not working did not cause the current to drop and did not glow in the length of time that it was tested. So this plug would not heat up the combustion chamber in time and would cause the vehicle to have difficulty starting when cold, because it was not heating up the compressed air to allow ease of combustion while cold.

ECU Inputs and Outputs with Oscilloscope 

The O2 Sensor was also tested with the Oscilloscope to check the input and output signals to examine what it is doing while the engine is Idling.

Oscilloscope in action. O2 was tested using the signal board of the 4G-FE engine

The scope showed a wave like form which shows when the engine is on a lean or rich cycle depending on the voltage of the signal.

Example of O2 sensors wave form. The peaks are when engine
 is running rich and the troughs are when engine is running lean

Ignition Coil Testing 

The ignition coil was also tested this involved the use of a Vacuum pump like used in the MAP testing and a Multimeter. 


The vacuum was used to test 3 coil diaphragms for any leakage and correct movement of the linkage. The tested diaphragms were in good order as vacuum held and linkage moved correctly with a vacuum pressure of 400mmHg. If the pressure was being lost or linkage was not moving this would effect fuel economy as the vacuum will not have the correct pressure from the manifold and it would control the spark advancing incorrectly causing the engine to run rich when it shouldn't be.


The coil was also tested for the correct voltage supply to the spark plugs. This was tested using a voltmeter and checking the resistance at the primary terminal and the secondary winding terminal.
The coils I tested both had problems with the amount of resistance at different terminals one had the incorrect resistance at the primary winding with 1.5Ω when it should be 1.3Ω or less and the other at the secondary winding with 8.1KΩ when it should be 7KΩ or less.
These faults would cause a weak spark at the spark plugs or no spark at all. Effecting engine performance and could cause missing, the engine to cease running when coil heats up, or it not  to start at all, and would need replacing.