Brand: Keeping fuel injectors healthy

Q: A few weeks back I read about the car owner whose fuel injectors went bad. Two of my sons had the same problem recently, and the repairs were expensive. Both cars had relatively low mileage -- 55,000 and 68,000 miles.

What preventive maintenance should car owners start with as soon as we buy a fuel-injected vehicle? What can we do to keep them running for at least 100,000 miles? This could be more important than changing oil every 3,000 miles.

A: Changing oil frequently will always be my No. 1 maintenance priority, but your concern over the life expectancy of fuel injectors is valid.

First, what specifically is the fuel injector's job? A port fuel injector is basically an electrical solenoid that opens and closes a spring-loaded fuel valve for a specific period of time based on a precise voltage signal from the engine management computer. Fuel under pressure is supplied to the valve through the body of the injector. As the valve opens for a fixed period of time, a precise quantity of fuel is atomized as it is delivered in a uniform spray pattern from the injector nozzle or tip. When working properly, the injector stays open for a precise pulse width, measured in milliseconds, and delivers a very precise, finely atomized spray of fuel that is vaporized and carried into the combustion chamber by the incoming flow of air.

Fuel injectors suffer from two basic types of problems: deposits or corrosion, and shorted or open windings. Deposits from the fuel can build up on the pintle, tip, filter or spray housing, partially blocking the flow of fuel and disrupting the spray pattern. This, in effect, causes a lean condition in the cylinder serviced by that injector.

Contaminants or corrosives in the fuel can also create this type of problem. If the spray pattern is disrupted and the droplet size increases, it's much more difficult for the incoming flow of air to vaporize the fuel so that it can be burned in the combustion chamber. Remember, liquid fuel cannot burn. The fuel must be vaporized into a gas before it will mix with the incoming air and burn.

Deposits and corrosion can also prevent the injector tip from fully closing or sealing, leading to leakage from the injector with the resultant hard starting, poor idle and other driveability problems.

Heat can be a factor in this type of failure. As the windings overheat, the varnish-like insulation begins to melt. This starts the process of shorting the windings together, reducing the resistance across the windings. Because the winding is fundamentally a continuous coil of wire, its resistance is quite low to start with, under 2 ohms in most cases. Thus, it doesn't take much of a short in the windings to bring resistance down toward zero -- a dead short.

Many automotive professionals point to fuel quality as a primary suspect in premature injector failure. John McGinity at the GM Training Center in Golden Valley spoke frankly about this issue. He blames excess alcohol (isopropyl or ethanol) and fuel additives for many injector problems, particularly with the early GM Multec injectors. McGinity described how alcohol can permeate the bobbin for the winding on the injector coil, leading to shorted windings, lower resistance and eventual fuel delivery problems.

He confirms that GM and AC Delco don't recommend fuel additives or injector cleaning for Multec injectors. He also said the updated Multec Top Feed Port Injector has been redesigned to deal with alcohol and additives in today's fuels.

Gerald Barnes, GM's environmental and energy staff manager, also believes some of today's fuels are a problem. Speaking at the Renewable Fuels Association National Conference on Ethanol Policy, Barnes identified a strong acid in some 10 percent ethanol fuels as the suspect in reduced durability of injectors, fuel pressure regulators and fuel pumps.

So where do these concerns leave you, the car owner? Stuck between a rock and a hard place. The Twin Cities metrowide ethanol mandate, which becomes a statewide reality in October, leaves you with virtually no choice of fuels at the service station.

Personally, I'm inclined to add a fuel system cleaner such as SeaFoam, Wynn's Power Charge or GM's Top Engine Cleaner periodically in the hope of keeping the fuel moisture-free and the fuel system components, including injectors, as clean as possible.