Part 1 of 2
Chart A-3 (1 of 2):
Wiring Diagram For Engine No Start:
CIRCUIT DESCRIPTION:
This chart assumes that the battery condition, engine cranking speed, and fuel quantity are OK.
TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.
1. A "SERVICE ENGINE SOON" light "ON" is a basic test to determine if there is battery and ignition voltage (12 volts) to the ECM. No ALDL may be due to an ECM problem, and CHART A-2 will diagnose the ECM. If TPS is over 2.5 volts, the engine may be in the clear flood mode which will cause starting problems. A skewed or shifted Coolant Temperature Sensor (CTS) that indicates a coolant temperature less than the actual temperature may flood the engine during hot restarts. A CTS that indicates a coolant temperature greater than the actual temperature may result in a "no start" condition in cold weather.
2. No spark may be caused by one of several components related to the Ignition/EST system. Chart C-4 HEI System Check for a no spark condition.
3. Fuel spray from the injector(s) indicates that fuel is available. The engine could become severely flooded due to excessive fuel.
4. While cranking the engine, there should be no fuel spray with injector electrical connector disconnected. Replace an injector if it sprays fuel, or drips like a leaking water faucet.
5. The fuel pressure will drop after the fuel pump stops running due to a controlled bleed in the fuel system. A fuel pressure gauge will determine if the fuel system pressure is great enough for the engine to start and run. The ignition may need to be cycled more than once for an accurate reading.
6. This test will determine if there is fuel pressure at the injector and that the injector is operating. No fuel spray from the injector indicates a faulty fuel system or no ECM control of the injector.
7. This test will determine if the ignition module is not generating the reference pulse, or if the wiring or ECM is at fault. By touching and removing a test light to battery voltage on circuit 430, a reference pulse should be generated. If the injector test light blinks, the ECM and wiring are OK.
CAUTION: Not all SCAN testers are compatible with every system. A SCAN tool that produces faulty readings should NOT be used, and the problem should be reported to the tool manufacturer. Use of a faulty SCAN tool can result in improper diagnosis and unnecessary component replacement. Follow the proper instructions, located in the owners manual, for the specific SCAN tool being used.
DIAGNOSTIC AIDS:
^ Water or foreign material can cause a no start condition during freezing weather. The problem may occur during overnight parking in freezing temperatures. The engine may start after a few minutes in a heated shop.
^ An EGR valve sticking open may cause a lean air/fuel ratio during cranking.
^ Low fuel pressure can result in a lean air/fuel ratio. Related Tests, Information and Procedures.
^ A grounded 423 (EST) circuit may cause a NO-START or a START/STALL condition.