there is no pump to push the fuel to the injection pump, the injection pump sucks its own fuel. the schrader valve is used to diagnose if the fuel filter is bad if it pulls enough vacuum.

make sure the filter is on tight and the bleeder screw is as tight as you can get it with your fingers. any tighter you run the risk of stripping it.

 

well the thing is it wouldnt start before the filter was put on as i am told, the filter was put on as an after thought. shouldnt there be pressure on the shrade vale as to tell me the fuel presure of the turck? i found when the hand pump is pumped a few times the fuel come out of the shrade valve and if i pump it several time it will start and run then die as it is out of fuel, aslo while it was running checked with the fuel pres reg to see iif it was wroking and it is, is the only pump on the duramas the cp3 injector pump? and it sucks and presurizes the rail ? im used to some of the fords (im sorry) they have a rail pusher pump or a high and low prsure pump,,,, im not ever really had to do much to the duramax

 

wait the fuel comes out the schrader valve when you prime the system?
thats not supposed to happen.

the way they use the schrader valve for diagnostics is that they hook up a vacuum gauge to it and see how many inches it pulls.

the injection pump sucks its own fuel from the tank, though the filter, past the schrader valve into the pump.

is there any check engine lights? or any blown fuses

 

with the shrade valve open and i hand pump the primer on top of the fule flieter and water checker yes fule dribbles out of the shrade valve yes yes

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so on this unit the shcrade valev is used for vacume only on the sucction side then? and not used like the other systems where i can run and test fuelk presure on it?

 

if your shrader valve is leaking you could be sucking air into it causing issues.

i mean the shrader valve as in the one next to the alternator, not the bleeder in the top of the fuel filter housing.


you could get a pair of very small vice grip pliers and pinch shut the hose that goes to the shrader valve cause it tees off from the main supply line that goes from the fuel filter to the injection pump.

 

yes.

 

well the reason there was fuel ablt to come out of the shcrade valev was because i had it open to see if i had any presure , but if it is for vacume daaaa silly me , i thought it was a presure port , ok well here is the deal then if i under stand this m the fule from the tank (no pump in the tank or in the line) is fed through the line to the cp3 pump , (sucked) by the pumpe and fed into the rail , the srade valve is on the suction side of the syatem so i should have a small amount of vacume at cranking then?

 

yup

 

i think they change filters at 15in vac. iirc

 

what really aggrivated me is that even giving gm and the local parts stores both, the vin number both gm and the locals said oh there is a fuel pump module in the tank, and inspecting the wires to the unit there are two wires to it and im sure they are for a sending unit and no pump , even gm said they could send me a pump unit that went into the tank , how silly this is sorry but im a virgin with a duramax

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is there any service port or any way to test to see if i am getting any presure on the rail side ? and also is the cp3 pump a mechanical driven pump? or is there a way to check it?