BalckBeauty

Hi Community,

I have strange problem with a 2008 Suburban 6.0.
Somehow the fuel pump does not get any signal anymore to pump the fuel.
What rellay makes no sense that neither the relais nor a fuse is in place at the fuse box. However the car was running 20.000 miles without any problem. Only now no more fuel is coming. At the moment we managed to make is running as we put constant power on the pump as soon as the igintion is on. But I really dont understand the absence of the relais and the fuse. I hope that one of you has a explanation for this.

Thank you
Christian

MDTAHOE

Fuel Pump Control Module (FPCM) - LMF

The fuel pump control module (FPCM) is a serviceable GMLAN module mounted to the underbody just forward of the spare tire. The FPCM receives the desired fuel pressure message from the engine control module (ECM) and controls the fuel pump located within the fuel tank to achieve the desired fuel pressure. The FPCM sends a 25 KHZ PWM signal to the fuel pump, and pump speed is changed by varying the duty cycle of this signal. Maximum current supplied to the fuel pump is 15 amps. A liquid fuel pressure sensor provides fuel pressure feedback to the FPCM.

Electronic Returnless Fuel System (ERFS) - LMF

The electronic returnless fuel system is a microprocessor controlled fuel delivery system which transports fuel from the tank to the fuel rails. It functions as an electronic replacement for a traditional, mechanical fuel pressure regulator. A pressure vent valve within the fuel tank provides an added measure of pump control module (FPCM). Desired fuel pressure is commanded by the engine control module (ECM), and transmitted to the FPCM via a GMLAN serial data message. A liquid fuel pressure sensor provides the feedback the FPCM requires for Closed Loop fuel pressure control.

Liquid Fuel Pressure Sensor - With FPCM

The fuel pressure sensor is a serviceable 5-volt, 3-pin device. It is located on the fuel feed line forward of the fuel tank, and receives power and ground from the FPCM through a vehicle wiring harness. The sensor provides a fuel pressure signal to the FPCM, which is used to provide Closed Loop fuel pressure control.

Fuel Tanks

The fuel tanks store the fuel supply. The front fuel tank is located on the left side of the vehicle. On dual-tank applications, the secondary fuel tank is located in the rear of the vehicle above the spare tire. The fuel tanks are each held in place by 2 metal straps that attach to the frame. The fuel tanks are molded from high density polyethylene.


Diagnostic Instructions



Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection\Initial Inspection and Diagnostic Overview\Diagnostic System Check - Vehicle
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description

When the ignition is turned ON, the engine control module (ECM) supplies power to the in-tank fuel pump, by energizing the fuel pump relay. The in-tank fuel pump remains ON as long as the engine is cranking or running and the ECM receives crankshaft reference pulses. If there are no reference pulses, the ECM turns the in-tank fuel pump OFF, 2 seconds after the ignition switch is turned ON or 2 seconds after the engine stops running. The electric fuel pump is incorporated into the modular fuel pump and sender assembly and is located inside the fuel tank. The fuel pump supplies fuel through a fuel filter, also located in the modular fuel pump and sender assembly, through the fuel feed pipes, to the fuel rail assembly. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. The fuel pressure regulator, located in the modular fuel pump and sender assembly, keeps the fuel available to the fuel injectors at a regulated pressure. When the fuel pressure rises above the pressure regulator calibration, the pressure is relieved, with excess fuel exhausted into the modular fuel pump and sender assembly reservoir


Fuel Pump Relay (Single Fuel Tank)

Left side of the engine compartment mounted to the fuse block underhood bracket assembly.

Fuel Pump Relay (Dual Tank)

Underhood Fuse Block

BalckBeauty

Dear MDTAHOE,

thank you very much for your detailed answer.... however we tried but somehow we can not solve properly... is there way to get exploded charts from the FPCM (location and connections..) ? That would be a great help.

And 2nd: Now I have a problem with the Trailblazer (2004, 4.2 LTZ)... the ABS (Antilock-braking-system). The lamp is showing but no error code is apprearing at the computer. The symponts are as follows: breaking is good as usual but sometimes when I psuh the pedal slowley I get this typical ABS noise (brrrrrrr) and the pedal is vibrating. I guess it is one of the sensors. But how can I find out, when no error code is showing up.

Thanks a lot
Christian

MDTAHOE

I can not figure out how to copy the pictures from the book and post them or email them. sorry.

As far as the ABS problem the light is not on because the computer does not know there is a problem, it thinks one of the wheels is lock up. One of the speed sensors probably drops to 0 mph before all the others. You would need a scan tool that shows ABS data so you could watch all the speed sensors at the same time.

BalckBeauty

Allright, thank you.
I will try to find exploded views in the WWW somewhere.
In regards to the ABS I guess I have to go to Chevrolet dealer, as he would be the only one to read out the ABS Data...

thanks
Christian

Blessed3

Hi. Did you ever figure out the problem with your Suburban? I have the same exact problem and today noticed the missing relay and fuse.