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1999 GMC Sierra Repair Question


Topics covered: Fuel pump, Spark, Engine.
Mileage: 107,000 miles.

Asked on October 28, 2011

Truck starts fine when cold, difficult starting after it is turned off after it is warmed up. 1999 gmc sierra 4.8l engine

Bought the truck 2 months ago. replaced plug wires, plugs tuned @ dealer. runs great. just trouble starting after it is warmed up.
Avatar Asked by gwaleyd

Answer

Replied on October 31, 2011

Hot or Cold-Do below

Next time it refuses to start don't wait for it to make up its mind-do below immediately to determine if its fuel or spark problem

Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if okay-check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor,distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing

Tiny Answered by rasmataz
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