Forksone,

First, the model you have listed is for a diesel engine and the GLP050VX normally does not come have the Vortec V6 engine. I suspect this is a GLP080VX. Without knowing the serial number or hours I would suspect the cam sensor that is mounted in the distributor. If you have over 5000 hours on lift, replace distributor assembly. The distributor is known to fail with high hours. Also, the cap and rotor are a constant annoyance. Change the cap and rotor first before anything else. Good Luck.