Leaking fuel injectors are a fire hazard and has the potential to cause severe and costly engine damage. It is important to identify leaking fuel injectors and take care of the problem as quick as possible. Proper fuel injector cleaning techniques can restore your injectors to function like new for a fraction of the cost on new fuel injectors.

Symptoms of leaking fuel injectors:

  • Increased Fuel Consumption
  • Rough Idle
  • Fuel odors inside and around the car
  • Hard Starting
  • Poor Emissions
  • Oil thinning, which can lead to catastrophic engine failure
  • Hydro-lock, which can lead to catastrophic engine failure

Fuel injectors leak in the following ways:

  • At the top O-ring where the fuel injector is located in the fuel rail. (Repairable – replace O-ring)
  • The fuel injector body (Not repairable – discard fuel Injector)
  • The fuel Injector pintle, ball or disc seat due to damage or corrosion (Not repairable, Discard Injector)
  • The fuel injector pintle, ball or disc seat due to dirt (Repairable – ultrasonic fuel injector cleaning)
  • Top and bottom fuel injector O-rings (Repairable – Replace O-rings)
  • The fuel injector body at the top of the fuel injector. (Not repairable – Discard fuel Injector)
  • The fuel Injector pintle, ball or disc seat due to damage or corrosion (Not repairable – Discard Injector)
  • The fuel injector pintle, ball or disc seat due to dirt (Repairable – ultrasonic fuel injector cleaning)

Fuel Injection Systems

To understand why leaking fuel injectors are troublesome and dangerous some understanding of the fuel injection system is required. There are two types of fuel injection systems, manifold fuel injection and direct fuel injection systems. The basic manifold fuel injection system consist of a fuel pump, fuel pressure regulator, fuel lines, fuel filter, fuel rail, fuel injectors and the engine control unit or engine management system. Manifold fuel injection systems operate at about 45 Psi (Pounds per square inch) Side feed and top feed fuel injectors are used in manifold fuel injection systems

When the engine is started for the first time at any given day the fuel rail which is part of the fuel injection system is pressurized by the fuel pump, under command of the engine management system to the operating pressure of the fuel injection system. This operating pressure is maintained throughout the driving or running period. Any external fuel injector leaks such as a cracked fuel injector body or bad fuel injector O-rings can cause an engine fire at any given time.

When the engine is shut down the fuel pressure should maintain at operating pressure, or just below that for a substantial period of time. Fuel injector pintle, ball or disc seat leaks as well as the bottom O-ring leak on a side feed injector will cause fuel to escape into the intake manifold where the fuel in turn will run down to the intake valves. If an intake valve is in the open position that fuel will enter the cylinder where it will leak past the rings and eventually mixed with the engine oil. This can cause severe engine oil thinning which can lead to engine bearing damage, scorched cylinder side walls and in some cases an explosion inside the engine. There has been reported cases where leaking fuel injectors caused hydro lock because so much fuel has accumulated on top of the piston that when the engine was turned over the engine locked because it could not compress the liquid in the cylinder. Hydra lock can cause bent connecting rods, broken pistons and blown head gaskets to mention a view, all very expensive repairs.

A Leaking fuel injector or injectors are normally the cause for difficult or hard to start engines especially when they are warm. This is because the fuel rail pressure has dropped and fuel has leaked into the manifold and causes the spark plugs to become flooded.

Both top feed and side fuel injectors make use of O-rings to seal between the fuel injector and fuel rail. Fuel injector O-rings can harden and become brittle over time especially those on older vehicles. This can cause both external and internal fuel leaks and should be taken care of immediately.

Any time a fuel leak is visible from any of the fuel injection components the vehicle should not be driven and the problem should be taken care of immediately. See you repair man ASAP if you suspect your engine has leaking fuel injectors.

Direct Fuel Injection Systems:

Direct fuel injection systems operate on the same principal as manifold fuel injection systems except that with direct fuel injection systems the fuel is injected directly into the combustion chamber instead of the intake manifold. Direct fuel injection systems operate at fuel pressures from 500 Psi at idle all the way up to 3000 Psi at wide open throttle.

Leaking fuel injectors is very dangerous in these systems and should be taken care of immediately. Do not drive your vehicle if you have a direct fuel injection system and suspect it of leaking at the fuel injector or any place else.

Fuel Injector Leak Testing.

Fuel injector leak testing should be done under operating pressure and because the average DIY fuel injector cleaning project or most automotive repair shops does not have the proper fuel injector testing equipment or ability to test leaking fuel injectors or clean them properly it is suggested that you have your leaking fuel injector sent to Injector RX for proper fuel injector testing and cleaning.