Where are you located, it might be a good idea to take it to a reputable diesel shop and have them look at it

 

upstate ny area here

 

I've pulled the glow plug and bench tested it, and it was fine. I also checked the wiring and it was fine. Will a bad fuel pressure sensor located on the fuel rail not allow the truck to start. It is just really wierd that I can pull the fuel filter and replace it and the disconnect the fuel supply line to the fuel filter housing and then it will start just fine for a day. The lift pump is running just fine, and the system is staying pressurized. I can leave the truck off for 2 days and the prime pump on top of the fuel filter is hard as a rock. Has anyone had a cp3 pump go bad, or the diaphram between the suction side and high pressure side go bad? I've taken it to a couple of dealers here in Wichita, KS and they are dumbfounded....I know more about the damn truck than their diesel techs.

 

By it you mean they right it has8 glowplugs. Other than that I have no idea , when you do get it figured out let us all know

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hi there new to this site and i came across this thread, i was wondering what the outcome of your problems were i am having the exact same problem.

 

What about a leaking filter housing? Merchant auto sells a rebuild kit.
Fwiw Duramaxes don't have lift pumps

 

does it turn over slow? or turn over fast and start.

 

it turns over fast i have confirmed that the filter housing is fine, pressurized the tank found no leaks. it will start in the mornings but after a fair bit of cranking. it will not start in when hot. it will not start again even if i shut it off for one second. it will not start if the truck has been parked in the heat all day even if the engine temp is cold. it will keep cranking fast batteries are brand new. i have done all the common checks been to multiple dealers with no luck. truck has 170 km no programmer

 

when you prime the fuel filter with the hand pump ontop of the housing (bleeding air at the same time) does the plunger stay hard to push after a minute or two?

 

Time to check injector return rates. The balance rates will tell you NOTHING in this case. Get a scan tool and watch the rail pressure. If the pump cannot create at least 4500 PSI during a crank, it will not start.

If you find low pressure during a cranking condition, you NEED to do a return rate test. Just so you know, it's a fairly involved process for getting the detailed information and a few minutes for getting a general idea.