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Tim Mohr
Tim Mohr, ASE MASTER TECH
Category: Dodge
Satisfied Customers: 15121
Experience:  30 YRS EXPERIENCE, FOREIGN AND DOMESTIC, GAS AND DEISEL
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Is there a check valve on the return line coming out of the

Customer Question

Is there a check valve on the return line coming out of the back of the cylinder head on 6.7L cummins, in an 08 ram 2500. I have 450ml/10seconds coming out of my return going to the gas tank. 150 ml of that comes from the hpfp, and the other 300ml is coming
from the injector return at the back of the cylinder head. Return line to the tank is free and clear. Low rail pressure codes are present p0087, and high delivery pressure code is present p1012 on start up every time. I have a new lift pump in the tank, and
have 14psi between the fuel filter housing and the hpfp(via inline press gage) when the key is on, as soon as the engine starts, my pressure gage goes to zero. Injectors are new, hpfp is new.
Submitted: 1 year ago.
Category: Dodge
Expert:  Tim Mohr replied 1 year ago.

Hi, my name is ***** ***** is caused by a bad injector, and is common, when they go bd, they return too much fuel and this drops the rail pressure in all of them, how many miles do you have on this?

Customer: replied 1 year ago.
Just over 200,000 miles, but all 6 injectors are new. Is there a check valve At the rear of the cylinder head, on the injector return line?
Expert:  Tim Mohr replied 1 year ago.

No, all the fuel return is done by the injectors,there is no chck valve, now you also mention the lift pump pressure is 14 lbs, but when you start it it drops to zero, is this correct?

Customer: replied 1 year ago.
drops straight to zero.
Expert:  Tim Mohr replied 1 year ago.

and its the lift pump pressure that is dropping, not the rail pressure,correct?

Expert:  Tim Mohr replied 1 year ago.

are you losing power on the orange/red wire at the fuel pump module, once it is started?

Customer: replied 1 year ago.
My pressure gage that is located between the fuel filter housing and the hpfp goes to zero as soon as the motor starts. I've verified I have voltage at the fuel pump when the motor is running. I also verified my lift pump flow, key on engine off. It is 650ml over 10 seconds.
Expert:  Tim Mohr replied 1 year ago.

if you have power to the pump and the prssure out of the pump drops to zero, then it can only be a bad pump, nothing else,Tim

Customer: replied 1 year ago.
Return volume behind the filter housing is at 450ml/10 seconds with the engine running, and supply pressure to the hpfp at zero. There can't be an over demand of fuel from the motor basically creating a vacuum on the fuel supply line?
Expert:  Tim Mohr replied 1 year ago.

No, it should not drop to zero, the only thing that can cause this is a bad lift pump, or a bad filter, but the filter is unlikely if it comes up to 14 when the key is on, then when it need the fuel pressure, the lift pump cany keep up with demand, Tim

Customer: replied 1 year ago.
Ok. The p1012(delivery pressure high), where is it detecting high delivery pressure? To the rail? I have 11ksi at idle. Can I look at demanded and actual fuel pressure with a scanner that shows live data?
Expert:  Tim Mohr replied 1 year ago.

Yes, the desired and actual pressure should be very close,Tim

Expert:  Tim Mohr replied 1 year ago.

within 500 psi of each other,Tim

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