11.4.The fuel pressure at the injectors is held con- stant by the fuel pressure regulator. The amount of fuel delivered to the cylinders is controlled by the length of time that the individual fuel injectors are triggered. The length of time the injectors are triggered varies from 1.5 to 8.0 milliseconds.
11.5.Both injectors are triggered simultaneously. Each triggering causes the injector to spray half the amount of fuel required by the corresponding cylinder on the next cycle.
11.6.The injectors are “hot” as long as the key switch is on. The injection is triggered by the comple- tion of a ground path within the ECU.
11.7.The injectors make an audible “click” each time they are triggered. If this click cannot be heard or felt, there may be a problem with the injector itself, or there may be a problem in the wiring harness.
Figure 11.7
11.8.If a fuel injector is suspect, the circuit may be tested with a commonly available “noid” light, or the injector may be triggered using an electronic fuel injection pulse timer (eg. Thexton model number 139) in conjunction with a fuel pressure gauge. With the key switch off, triggering the injector should result in a measured drop in fuel pressure.
M48 Tank
11.9.The ignition coils are also controlled by the ECU. Each cylinder has its own coil. See Figure 11.9.
Figure 11.9
11.10.The
Figure 11.10
11.11.The ECU is the brain of the engine control sys- tem. It is very durable, but there are some rules to follow in order to avoid damage to the ECU:
•If you diagnose a faulty ECU, do not replace it without calling Cub cadet Technical Support for specific handling instructions.
•Previously mentioned: do not use a conventional test light to look for power in the engine control circuit.
•Previously mentioned: do not disconnect any electrical devices while the engine is running.
•Do not reverse the battery terminal connections.
27
