Help with a 2000 GMC C3500

[TheSkycrane]

Hello. I have a 2000 GMC C3500 cab and chassis with 5.7. A couple of weeks back it needed a cap, rotor and plugs, plug wires. I replaced and the truck would start and run fine. I completed a compression check and all cylinders were within specifications and within 10%of each other. I now have a no crank issue that is described as follows. The engine will spin over and sometimes catch but the firing is only helped by the starter. If it does fire it idles extremely rough. I was able to get the engine up to 2500 rpms and held it there to see if it would improve. Timing on my scan tool showed 36degrees advanced engine would run but off smell in the exhaust. Not the rotten egg smell of a bad converter. Bumping the throttle causes the engine to stumble and it sounds to me like the timing is off. It runs ok at 2500 with a slight miss. I pulled plugs they are wet with fuel. Fuel pump comes on with key, runs when key is turned off. I have pressure at the fuel line. I have spark at the plugs. I have the following codes. P0108, P0125, P0141, P0157, P0161,P0338, P0462, P0463, P1106, P0108, Pending was P0157.  I used a ohm meter to check the crank sensor ohm values and found that I had 7.62ohms between the yellow and blue( middle) wire when homing the sensor out. I had 12volts going to the sensor as well. Thoughts? 

[Sharpz]

first thought, you said you needed a cap, rotor and plugs.................. how did you know you needed these?  Try putting back your old cap and rotor, and see if your issue is solved. Plugs......... make sure they are gapped right and they will last a very long time.

 

[TheSkycrane]

Plugs were gapped to the specifications in the manual. How is I know I needed plugs because they were worn out electrodes were gone. Cap was shot and rotor was worn out as well. Plug wires ohmed out to high of resistance. So these were replaced and the truck drove fine four the last three months. Just started having issues and drained and refilled with fresh gas. Still not running right. 

[TheSkycrane]

I could still use help with this truck. I replaced the MAF sensor as the sensor didn’t test out. The truck started and ran about 15 seconds perfectly. It then began to idle lower and rough I jumped behind the well and hit the throttle engine was sluggish to respond but eventually climbed to about 2500 rpm and I tried to keep it there. It stayed running as long as my foot was in the gas, it sounds like it’s fighting itself though while running. I then let it try to idle it just died. Cranking it over it Carl’s like it wants to start but not enough to keep running unless the starter is spinning it. Pulled plug after this incident and the plug is black. Ckp sensor?

[MikeS0905]

Have you checked for cross-firing inside the cap? If you went aftermarket,  sometimes the cheaper caps will cross fire pins inside the cap which will cause several of the symptoms your experiencing.  Also fuel pressure at rail?? Definitely find out what the pump is actually pushing...