Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
System Description
The scan tool is first used to energize the fuel pump relay. The fuel injector tester is then used to pulse each injector for a precise amount of time, allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector. See FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL EXAMPLE (TYPICAL) .
| Condition | Cylinder No. 1 | Cylinder No. 2 | Cylinder No. 3 | Cylinder No. 4 |
|---|---|---|---|---|
| 1st Reading | 55 psi (379 kPa) | 55 psi (379 kPa) | 55 psi (379 kPa) | 55 psi (379 kPa) |
| 2nd Reading | 42 psi (290 kPa) | 45 psi (310 kPa) | 48 psi (331 kPa) | 46 psi (317 kPa) |
| Amount Of Drop | 13 psi (89 kPa) | 10 psi (69 kPa) | 7 psi (48 kPa) | 9 psi (62 kPa) |
| Average Range: 8-11 psi (57-77 kPa) | Replace Fuel Injector - Too Much Fuel Pressure Drop | Injector Okay | Replace Fuel Injector - Too Little Fuel Pressure Drop | Injector Okay |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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