Lb7 Fuel System Diagram (2024)

FAQs

How much fuel pressure does a LB7 need to start? ›

At zero volts the FCA defaults to wide open, which gives almost 26,000 psi of fuel pressure and the truck should fire right up.

The fuel injectors in the LB7 engine have a design flaw that causes them to fail. Signs you're truck is suffering from this flaw include a misfiring engine, rough idling, acceleration and performance issues, and error codes that indicate the fuel mixture is too rich or too lean.

0 986 435 502 Duramax (LB7)

Fuel return Banjo bolt to head: 12 lb-ft.

Note that the fuel rail pressure is at 24,053 psi. As stated previously, the fuel pressure with the Ignition relay unplugged needs to be a minimum of 2500 to 3500 psi during cranking for the return rate test results to be valid.

Oil psi on this motor should on a hot day be between 20 to lbs normally. Really 26 ain't that bad but a touch low.

The symptoms of a bad regulator usually manifest as a surge when idling, though sometimes the surge can happen at speed while driving. Other symptoms include power loss on acceleration or hard starting.

Quick Answer: Avoid Duramax Year Models 2001-2010

The Duramax has a long history. We recommend avoiding any GM vehicle equipped with the 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, and 2010 Duramax engines. In short, the newer model years show improved performance.

If your vehicle cranks upon starting or refuses to start, drives worse, or emits larger-than-normal puffs of smoke, it is likely that a bad FICM is to blame.

What goes bad on LB7 injectors? Typical LB7 injector failure is dripping at the nozzle, causing white exhaust smoke, especially noticeable at idle. Another common failure is body leakage, which adds diesel fuel to the engine oil, causing the level to rise.

Stock boost pressures typically run anywhere from the high teens to low twenties. Some of this depends on the air filter or intake system in use - lower with the stock air box and paper filter, higher with a performance air filter and/or air box.

How much torque does a stock LB7 have? ›

It's a 6.6-liter, common-rail injected, 32-valve, V8 turbodiesel which put out 235hp and 500 pounds of torque in its first year, and for the final year of '04 the LB7's output had grown to 300hp and 520 pounds of torque.

If the 8th digit of your VIN number is a 1, then it is a LB7 Duramax (the early engine). If the 8th digit is a 2, then it is a LLY. In mid 2004, GM switched to this newer LLY engine.

Inspect fuel lines from fuel filter to injection pump and from CP3 to fuel rails for any leaks or damage. Change your fuel pressure relieve valve to a Race Fuel Valve (solid valve replacement) The spring in the factory valve often wears out and can relieve pressure at a much lower pressure than it should.

Locate the fuel pressure sensor on the fuel rail. It's found below the boost tube pipe near the center of the engine. Removing large plastic intake resonator can make it easier gaining access.

It is supposed to build 1500psi before the ecm fires the injectors and the idle at around 5000psi.

Required fuel pressure can vary depending on your vehicle's engine and fuel system. Carbureted engines may require as little as 28 kPa (4 PSI), while modern multipoint fuel injected high-performance engines can require as much as 414 kPa (60 PSI).

The pressure to deliver fuel from the high pressure pump to the rail/injectors at cranking is around 200 bars, at idle the pressure should be around 300 bars. When the vehicle is running the pressure ranges from 1200 bar to 2000 bar.

Air at about 30 bar is used to start the diesel engine. The starting air pressure at 30 bar provides enough speed to the piston thereby compressing the charge air & on reaching the required temperature, fuel is injected into the cylinder to initiate combustion.

Injectors Buy Bosch Injectors For 6.6 Duramax

It takes about 2500 PSI rail pressure for the injectors to deliver fuel and the engine to start.