GM/Detroit 6.5L ENGINE CONTROLS – Engine Cranks but Does Not Run

Circuit Description
This chart assumes that battery condition and engine cranking speed is OK. The quantity and quality of fuel is OK and the glow plug system is operating properly.

Diagnostic Aids
If no trouble is found and the cause of an Engine Cranks But Will Not Run has not been found, check for the following conditions:
• Proper cranking speed, 100 RPMs cold 180 RPMs hot (a scan tool can be used to check cranking speed by pulling the FUEL SOL fuse and monitoring Engine Speed on scan tool while cranking).
• Water or foreign material in fuel system.
• Basic engine problem.

If the crankshaft position sensor and the optical/fuel temperature sensor are disconnected or malfunctioning at the same time, an Engine Cranks But Will Not Run condition will exist.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
6. This step checks for proper cranking speed (see Diagnostic Aids).
8. This step will check the ground wire on the injection pump (wire located on top of pump).
12. This step will determine if the injection pump or wiring is at fault.
13. This step will determine if the fuel injection control voltage is present by probing at the black/gray 4 wire connector jumper harness instead of at the 6 wire pump connector.


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