TORQDEX // FUEL & AIR DIAGNOSTIC
Fuel Injector Problems
Diagnose fuel injector faults by checking injector command, electrical resistance, contribution, flow balance, leakage, fuel trims, and cylinder-specific misfires.
01 // WHAT IT MEANS
Understanding the symptom
Fuel injectors can fail electrically, mechanically, or hydraulically.
A restricted injector may cause a lean cylinder, while a leaking injector can cause rich operation, hard starting, fuel fouling, or cylinder wash.
02 // QUICK CHECKS
Check these first
Start with simple observations and scan data before moving into deeper testing.
Check cylinder-specific misfires
Determine whether the same cylinder repeatedly shows weak contribution.
Listen for injector operation
A consistent mechanical clicking sound can confirm movement but does not prove proper fuel delivery.
Inspect the spark plug
A dry, lean-looking plug and a wet, fuel-fouled plug point in different directions.
Check fuel trims
Bank or global fuel correction can help identify under- or over-fueling.
03 // SYSTEMS TO CHECK
Common systems involved
Injector command circuit
Power supply, driver circuits, wiring, and connectors must operate correctly.
Injector fuel delivery
Deposits or internal damage can reduce flow even when the injector clicks normally.
Injector sealing
An injector that leaks when closed can enrich a cylinder and cause hard starting.
Fuel-system supply
Injector diagnosis must be performed with correct fuel pressure.
04 // DIAGNOSTIC ORDER
Diagnose it in this order
Identify the affected cylinder
Use misfire counters, contribution testing, or cylinder balance data.
Check injector electrical operation
Verify power, command pulse, connector condition, and resistance where appropriate.
Compare injector contribution
Use balance or disable testing to compare cylinder response.
Evaluate injector flow
Perform appropriate balance, pressure-drop, or flow testing.
Check for leakage
Observe pressure decay and inspect for fuel-fouled plugs or hot-soak hard starting.
Verify fuel pressure
Confirm a system-wide pressure problem is not being mistaken for an injector fault.
05 // TEST RESULTS
What the results may indicate
Check injector flow and mechanical cylinder condition
The injector may be restricted or the cylinder may have another combustion problem.
Injector fault is strongly supported
If a safe and appropriate component swap moves the fault, the injector deserves replacement or service.
Check for injector leakage
A leaking injector is one possible source of rapid pressure decay.
06 // COMMON MISTAKE
Don't condemn an injector just because its cylinder is misfiring
Ignition, compression, intake leakage, wiring, and fuel-pressure faults can all create a cylinder-specific misfire. Verify injector command and delivery.
07 // RELATED OBD-II CODES