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Help! Won't start or prime

What is the primer doing or not doing exactly? With the bleed screw open does it hiss, spit fuel, or anything?

Same as a gas engine: no fuel to carb it's not going to run. Unlike a gas engine there is no fuel pump in the system aside of the CP3 and primer. Any air leak and you are done. Did you do a visual inspection of all hoses for leaks or kinks?

@Will L. maybe time to put pressure to the tank and see where the leaks are.
 
I'm the owner of an 03 2500 HD lb7 California emissions truck. Only 107,000 MI. Had a crank with very hard start when I bought it figured it was the hand pump housing. Deleted the hand pump housing put on a FASS. Seemed to help just a bit.
Sent to my mechanic who did the fuel bypass test for the lb7 which showed injectors in spec but CP3 was out of spec so we replace the CP3 with the fuel pressure regulator. Also replaced the fuel pressure sensor fuel pressure relief valve. Replaced all the rubber lines. Getting plenty of fuel to the Schrader valve with no air visually.
Fuel rail pressure cranking is only 500 or 600 lb at about 25,000 lb running with the new CP3 which is a bit low but not much. Power good idle is good no smoke. Runs smooth as a kitten once it started. The only way it will start is with the puff of either. Cracking speed is good and in spec.
My mechanic says since the scanner says desired fuel rail pressure at cranking is 5,000, that this says that all the sensors are telling the CP3 to deliver that so the crankshaft sensor or the camshaft sensor should be good and that the wiring should be good (and connections). Remember the actual fuel rail pressure is 500 or 600 lb.
MY QUESTION IS: IS HE CORRECT on the scanner?
 
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