Electronic Fuel Injection Issue

have you checked the connections?

take the injector nozzle out of cylinder head and run the engine. is fuel coming out?

Depending upon the engine type, injectors are actuated in pairs, triples, or in just a few cases individually. Since you have already replaced the injector, the best bet now is to determine if the ECU is driving it properly. One other quite common possibility is corrosion in intermediate harness connectors used to connect injectors and sensors to the firewall connector (some cars bring the engine harness through a firewall grommet to the ECU). Just about all injection systems tie one of the injector coil terminations to battery voltage, which in many cars remains there with the engine off, since the ECU output transistors are also off.

So use an oscilloscope, ground the probe connected to the engine block or battery negative, and use the probe tip with sewing needle and long nosed pliers to pierce the injector drive lead insulation to read conductor voltage. The needle will not damage the wire, since it is stranded, and the insulation hole will close up afterwards. I've done this over some years and never had wiring problems as a result.

There are two types of injectors, saturated and non-saturated. The former use a ballast resistor, and are used in high performance cars. Coil resistance is only a few ohms. The latter are 12 to 15 ohms, used in most common engine applications, so that will serve as a guide if you want to check injector coil continuity. I've had instances where two of six injectors will go to an open circuit at differnt times, stay that way for a week or so, and then "heal", only to open circuit again months later, usually after a cold night. A set of rebuilt injectors now has one exhibiting the same problem.

When you look at the oscilloscope trace, you will see 12V on one end of the connector. The other end will pull to ground as the ECU opens the injector, and then "fly back" to maybe 30-50V for a short period as the injector closes. The flyback is from magnetic field collapse like in an ignition coil. Resistor-capacitor damping networks in the ECU control it to the voltage described.

You may have a defective ECU, assuming that you KNOW the ignition system for that cylinder to be working. If the spark plug is not firing, you will wear the piston rings and cylinder wall very quickly in that cylinder due to presence of raw fuel. You may also overheat the catalytic convertor, since its oxidation loading is driven way up by an ignition related misfire.

Hope this helps. Check spark, and fuel, in that order. You can safely pull of spark plug wires with insulated pliers with the engine idling as a diagnostic measure to find the dead cylinder, evident from a misfire. A high power zener diode protects the coil switching transistor when a lead is disconnected.

Bernie Katz

great reply i learned a lot from that short seminar.i love to listen to a man who knows what hes talking about.

Just to echo dennis that is a great reply!

Ditto.