I have a 2001 GMC Savana 3500 van that start bad but run good. My code reader is tell me PO251. Injection pump A rotor/camshaft position sensor and PO370,timing reference high resultion signal A. Can someone please tell me where the Injection pump A rotor/camshaft position sensor is.When I purchased the van they said it had water in the fuel so I changed the fuel filter.The codes will not go away.Any ideas what could be my problems.

 

Those are essentially injection pump codes that often require a new/rebuilt injection pump.

The cam sensor is internal in the injection pump and is called the optical sensor.

Sometimes after water ingestion a double dose of fuel conditioner with lubricity additive can stop those codes from returning.

Also these engines were never meant to run on ultra low sulpher diesel and require more lubrication than todays fuel provides-fuel conditioner with lubricity additive should be used in every tank and/or marine 0 ash outboard 2 cycle oil at a ration of 1 part oil to 200 parts fuel can be used.

 

Thanks for the advise. I did all that and change the fuel filter and it runs alot better. It has pickup alot of water from somewhere, I drain the filter in a pint jar and it had a 1/2" of water in it.NOT GOOD!