When To Supercede A Fuel Injector

During its evolution, the fuel injector has moved from the intake manifold to the combustion sleeping accommodation. This has made them more precise in dispensing fuel. If this precision is thrown off by restrictions, electrical problems or fuel problems, it tin cause driveability problems. Hither are 10 signs to look for when you need to supercede a fuel injector or information technology needs service.

replace a fuel injector

1. Restrictions

A restriction of only 8% to 10% in a single fuel injector tin can lean out the fuel mixture and cause a misfire. When this occurs, unburned oxygen enters the exhaust and makes the O2 sensor read lean. On older multiport systems that fire the injectors simultaneously, the computer compensates past increasing the "on" time of all the injectors, which can create an overly rich fuel condition in the other cylinders.

Direct fuel injectors are more sensitive to restrictions because of the precise amount of fuel they inject into the combustion bedroom.

ii. Turbo Troubles

In turbocharged engines, dirty injectors can have a dangerous leaning effect that may lead to engine-damaging detonation. When the engine is under boost and at a higher rpm, it needs all the fuel the injectors can deliver. If the injectors are dirty and tin can't keep upward with the engine's demands, the fuel mixture will lean out, causing detonation to occur. The leaning out may cause higher than normal exhaust temperatures and turbo failure.

3. Heat Soak

When the engine is shut off, the injectors undergo heat soak. Fuel residue evaporates in the injector nozzles, leaving the waxy olefins behind. Because the engine is off, there is no cooling airflow moving through the ports and no fuel flowing through the injectors to wash it away, so heat bakes the olefins into hard varnish deposits. Over time, these deposits tin build upwards and clog the injectors. Even if a vehicle has low mileage, short bulldoze cycles and increased heat soaks can clog the injector.

Since the germination of these deposits is a normal consequence of engine operation, detergents are added to gasoline to help keep the injectors clean. But if a vehicle is used primarily for short-trip driving, the deposits may build up faster than the detergents can wash them abroad. On four-cylinder engines, the No. 2 and No. 3 injectors are in the hottest location and tend to clog upwards faster than the end injectors on cylinders No. 1 and No. 4. The same applies to the injectors in the middle cylinders in vi- and 8-cylinder engines. The hotter the location, the more vulnerable the injector is to bottleneck from rut soaks. Throttle body injectors are less vulnerable to heat soak because of their location loftier in a higher place the intake manifold plenum.

Estrus soak can affect straight-injection injectors due to their placement in the caput. Fifty-fifty with the higher pressures, the orifices can get clogged over fourth dimension.

direct-injection injectors

iv. Increment or Decrease in Long- and Curt-Term Fuel Trims

The fuel calibration curves in the Powertrain Control Module (PCM) are based on OEM dyno testing using a new engine. Fuel pressure level is within a specified range for that engine, and the injectors are all clean and new. The PCM'southward built-in adaptive fuel control strategies allow it to conform both short-term and long-term fuel trim to compensate for variances in fuel force per unit area and fuel commitment to maintain the correct air/fuel ratio — but simply within sure limits.

The PCM may not exist able to increment injector duration enough to get-go the deviation if:

  • An injector becomes chock-full with fuel varnish deposits and fails to deliver its normal dose of fuel when it's energized, or
  • Fuel force per unit area to the injector drops beneath specifications because of a weak fuel pump, plugged fuel filter or leaky fuel pressure regulator.

This can leave the air/fuel mixture too lean, causing the cylinder to misfire.

Powertrain Control Module

5. Not Plenty Resistance

The solenoid at the peak of the injector creates a magnetic field that pulls upward the injector pintle when the injector is energized. The magnetic field must be strong plenty to overcome the spring force per unit area and fuel pressure above the pintle, otherwise the injector may non open all the manner. Shorts, opens or excessive resistance in the injector solenoid can too cause problems.

Typically, the solenoids oftentimes short internally when injectors neglect, which causes a drop in resistance. If the specification calls for iii ohms, for example, and an injector measures only 1 ohm, it will pull more electric current than the other injectors. Too much current catamenia to an injector may cause the PCM injector commuter circuit to close down, killing any other injectors that also share that aforementioned driver circuit. One mode to check the injectors is with an ohmmeter.

6. Longer Crank Times

An injector leak will cause the track to lose pressure while the vehicle is sitting resulting in a longer than normal creepo because the rail will need extra time to pressurize.

Longer Crank Times

A normal crank time in a diesel fuel common-rail injection organization is unremarkably around three to five seconds. This is how long it will take the common-runway pump to build fuel pressure level to the "threshold." The fuel rail force per unit area threshold for cranking occurs around 5,000 psi. Normal common-track systems will operate at v,000 psi at idle and can achieve up to 30,000 psi at wide open throttle.

seven. Failed Residuum Tests

If you lot suspect that an injector is clogged or malfunctioning, an injector residue test can isolate the bad injector. Scan tools that tin can disable injectors can isolate an injector for diagnostics. Engine rpm driblet may not be an constructive diagnostic method when performing a cylinder balance test where an injector is disabled.

clogged fuel injector

A more effective method is looking at the voltage changes from the O2 sensor. Leaking injectors and some expressionless injectors can be missed even when an injector is disabled. Other problems with the ignition system and mechanical components also may not show an rpm loss when an injector is turned off. If an injector is skillful, the voltage from the O2 sensor volition drop to or below 100mV. If the problem is a airtight or dead injector, the long-term fuel trim may accept compensated enough so that the voltage doesn't change.

Another constructive exam is to measure out the force per unit area loss in the fuel rail when each injector is fired and pulses for a fix menstruation of time. Use an electronic injector pulse tester for this. As each injector is energized, a fuel pressure judge is observed to monitor the drib in fuel force per unit area. The electrical connectors to the other injectors are removed, isolating the injector existence tested. The difference between the maximum and minimum reading is the pressure level drop.

Ideally, each injector should drop the aforementioned amount when opened. A variation of one.v to 2 psi or more is cause for business organization. No pressure drop, or a very low pressure drib, is a sign the orifice or tip is restricted. A higher than normal pressure driblet indicates a rich condition that could be caused by a stuck plunger or worn pintle.

8. Misfire Codes

A lean misfire may trigger a misfire code and turn on the cheque engine light. The code ofttimes will exist a P0300 random misfire lawmaking, or y'all may find one or more than misfire codes for individual cylinders, depending on which injectors are most affected.

Misfire Codes

nine. Vehicle Won't Get-go With Total Tank

Major symptoms of contaminated fuel tin can include cranking no-start, hard starting, stalling, loss of power and poor fuel economy. Because symptoms of fuel contamination mostly appear immediately later on refueling, the fuel gauge needle pegged on full should always be a diagnostic red flag. Remember to ask if the vehicle has recently been refueled because some drivers just add fuel rather than topping off their tanks.

10. Lack of Maintenance

If an owner has neglected maintenance services like oil changes and filter replacements, chances are the fuel injectors will endure. For port fuel applications, not changing the oil tin upshot in blowby and a compromised PCV system, which builds up contaminates on the tip of the injector. Not irresolute the oil in an engine with directly fuel injection tin can event in a worn fuel pump camshaft lobe.