Diagnostic Aids

1986 Pontiac 6000 Base, 2D Coupe, 2.5 RSECTION Diagnostic Aids

An EGR valve sticking open can cause a low air/fuel ratio during cranking. Unless engine enters "Clear Flood" at the first indication of a flooding condition, it can result in a no start.

Check for fouled plugs. A defective cold start circuit or water in fuel line can cause a no start condition in cold weather. See CHART A9. A defective MAF sensor may cause a no start or a stall after start. To determine if the sensor is causing the problem, disconnect it. The ECM will then use a default value for the sensor, and if the condition is corrected and the connections are okay, replace the sensor.

Also check that injectors on both sides of engine will cause a test light to blink. If not okay, check injector fuses. If above checks are all okay, see the CEC TESTS W/O CODES article in this section.

Fig 1: Flow Chart A3, (1 of 2) Engine Cranks/Won't Run (5.0/5.7L)
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.