Hey guys. Im working on a 2005 Dodge with a Air dog. Truck keeps coming up with a low voltage code for the lift pump. Also the glowplug light is continuasly on with no code. If you clear the truck will run hard like it has a tune in it but after about 2 min in falls on its face and seems like it some type of limp mode. Also check fuel pressure from the air dog it runs around 18-19psi all the time.

 

I pulled a few schematics for you they are attached below.
Just a couple of questions, is the air dog using its own draw straw?
Is the glowplug light you are talking about the check gauges, wait to start or check engine light?
If you look at the thrid attachment down below it shows the FP circuit in and out of the ECM I would suppose that the ECM is seeing a incorrect voltage through that wire run. maybe a pump or a wire broken.
Anyways not completely sure but the ECM may use this information to curve the fuel timing or reduce performance by opening the Fuel control actuator (FCA) solenoid and dump fuel pressure back to the tank.
Check your pump and the wiring to the pump and at the ECM connector.

2005 dodge fuel system.pdf

fuel-control-actuator-2005 Dodge.pdf

engine-controls-1-of-4 2005 Dodge.pdf

engine-controls-2-of-4 2005 Dodge.pdf

engine-controls-3-of-4 2005 Dodge.pdf

engine-controls-4-of-4 2005 Dodge.pdf

 

The glow plug light is usually a leak in the fuel system detected by the ECU. You will have a DTC is that is the source. You really need a scanner to look at the codes rather than the ODO window which will not show all of them. some scanners will not show all the codes unless they the correct updates also.


Depending on how the AD is wired it could be a bad connection or a bad relay. Hopefully the LP wire form the ECU is wired to a relay that is feeding the LP. Otherwise, you could have a bad AD, they are known to have issues like this.

The only pressure monitored by the ECU is rail pressure and it uses that to modulate the FCA to get the desired RP. There is no monitoring on the low pressure side so issues there translate to high pressure side codes.

 

Yes the air dog is using its own draw straw. It is now a brand new FASS pump. The glow plug light im talking about is the coiled wire light on the dash. Like the wait to start light. Also I am using my Snap on scanner to read the code. It has the latest update.

 

OK I got the light to go out by putting the signal wire to the fass into the signal for the fuel pump relay. But now it has codes in it for the fuel level sensor voltage high and low. Wtf is going on with this thing?!?!

 

Did you accidentally unhook the fuel level sender at the tank while troubleshooting?
Is the fuel reading level correct in the tank? Is the fuel level light on.