1992 GMC C2500

Engine problem
1992 GMC C2500 V8 Four Wheel Drive Automatic 153000 miles

I have a 1992 Gmc 2500 pickup with a 5.7 4x4. I have replace the fuel pump, intake gaskets, timing chain, cam, distributor, cap, wires. Plug, map sensor, o2 sensor, temp sensor, lifters. The problem is that when the timining wire is unplugged the timing is set at 0 and when I plug it back in with the battery unhooked then start it the timing advances to 25 degress.
December 28, 2007.

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