Engine Performance
Work Example 13

WorkKey Level: 5
NATEF Automotive Tasks: VIII.D.5, VIII.D.8

You are testing the injectors on a 4-cylinder engine, the base pressure is 36 psi in the fuel rail.  When each injector is energized, the fuel rail pressure drops down to the following readings.

Fuel Injector	Reading
1	25
2	27
3	35
4	25

 

According to the specs, these reading should not vary by more than 10% of the highest reading. Do these end of test readings after tests fall within specs? Please explain your answer. Predict which injector(s) are bad.

Solution:

10% of Highest Reading = (.10)(35) = 3.5
35 psi – 3.5 psi = 31.5 psi
Readings need to be greater than or equal to 31.5 or r > 31.5
no, not all of the readings are acceptable and they do not fall within the 10% range.