1995 GMC Jimmy No Start When Cranking

1995 GMC JIMMY
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RONALDJ
  • MEMBER
  • 1 POST
'95 Jimmy.4.3vortec CMFI Fuel Injection unit.

It will not start when cranking[intermittent], it has fuel pressure[60 lbs.] at injector, has spark, will start only when spraying Carb Cleaner into throttle plate, and then vehicle runs on its own.Ignition module and crank sensor have both been replaced

My theory is the Fuel isnt being delivered to cylinders in crank mode but will in run mode.
Jan 6, 2007 at 12:54 AM
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JDL
  • ✓Experienced Mechanic
  • 16,098 POSTS
Sorry for the late reply.

Usually with koeo, the fuel pressure is 60--66 psi. After it is running, it will run with less pressure. That spider fuel system is noted for problems. There have been some service bulletins about the fuel poppet valves sticking. Usually on first start-up of the day, the rest of the day, it may run fine. The cleaning procedure I've seen is a shop procedure.

Also, during cranking, your systems are getting battery voltage. Engine running, the systems get alternator voltage, there can be several volt difference.
Mar 15, 2015 at 4:15 AM

Suggested Repair

Have the CMFI spider injector poppet valves inspected and cleaned with the shop procedure; they are a known sticking problem, often worst on the first start of the day. Also compare battery voltage while cranking with alternator voltage while running, since a several-volt difference can affect fuel delivery.

Conversation Summary

A 1995 GMC Jimmy with 4.3 Vortec CMFI has intermittent no-start while cranking despite about 60 psi fuel pressure and spark. It starts only after carb cleaner is sprayed into the throttle plate, then runs on its own. The ignition module and crank sensor were already replaced. The expert said 60-66 psi key-on is normal and that this spider system is known for sticking fuel poppet valves, often on the first start of the day, with a shop cleaning procedure and related service bulletins. The expert also noted that cranking uses battery voltage while running uses higher alternator voltage.

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