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Engine Cranks But Will Not Run - Chart A3 (TBI)



Circuit Description :
This chart assumes that battery condition and engine cranking speed are OK, and there is adequate fuel in the tank. This chart should be used on engines using the Model 220 throttle body.

Test Description : Numbers below refer to circled numbers on the diagnostic chart.
A "Service Engine Soon" light "ON" is a basic test to determine if there is a 12 volt supply and ignition 12 volts to 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. If coolant sensor is below -30~C, the ECM will provide fuel for this extremely cold temperature which will severely flood the engine.
Voltage at the spark plug is checked using Spark Tester tool ST 125 (J26792) or equivalent. No spark indicates a basic ignition problem.
While cranking engine there should be no fuel spray with injectors disconnected. Replace an injector if it sprays fuel or drips like a leaking water faucet.
Use an injector test light like BT8320, or equivalent, to test each injector circuit. A blinking light indicates the ECM is controlling the injectors.
This test will determine if there is fuel pressure at the injectors and that the injectors are operating.
Diagnostic Aids :
If no trouble is found in the fuel pump circuit or ignition system and the cause of a "Engine Cranks But Will Not Run" has not been found, check for:

Fouled spark plugs
EGR valve stuck open
Low fuel pressure. See CHART A-6.
Water or foreign material in the fuel system.
A grounded CKT 423 (EST) may cause a "No Start" or a "Start then Stall" condition.
Basic engine problem.


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