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.
What should fuel rail pressure be on Duramax at idle?
For starting a Duramax, you’ll need a minimum of 1,500 psi fuel pressure at the rail while cranking and at idle a
minimum of 5,000 psi
.
How much fuel rail pressure does a Duramax have?
Use common sense safety practices when servicing any diesel system: While maximum control oil pressure on a Power Stroke can reach nearly 4,000 psi, the Duramax fuel system is pressure-relieved at a blistering
27,550 psi
.
What should my fuel rail pressure be?
The rail pressure during normal idle should be
5,600 – 6,500 PSI (386 – 448 bar)
.
What causes low fuel rail pressure on Duramax?
It could be
a restriction or a leak on the supply line between the fuel tank and the injection pump
. It could be a weak injection pump not able to increase fuel pressure up to the maximum under load. It also could be one or more injectors have high return rate.
How do you check the fuel rail pressure on a Duramax?
High Pressure Testing (LB7 Example)
Start by
first stroking the hand pump
. If the hand pump is soft and then becomes hard, recheck cranking fuel rail pressure. If pressure is now okay, you have a fuel supply issue. Testing the high side with a supply side fault will definitely lead to an incorrect diagnosis.
Where is the fuel pressure relief valve on a Duramax?
This valve often referred to as FPRV is located
in the rear of the driver’s side fuel rail on the LLY, LBZ, and LMM
, and is buried in the valley on the LB7 and functions much like the Temp and Pressure valve on your water heater.
What causes low fuel rail pressure?
Typical causes for low fuel pressure include a
dirty fuel filter, weak pump
, incorrect tank venting, restricted fuel lines, a clogged pump inlet strainer and faulty electrical control.
How do you fix a low fuel rail pressure on a LBZ Duramax?
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.
How do I know if my fuel rail pressure sensor is bad?
- Hard starting. One of the first symptoms of a potential problem with the fuel rail sensor is hard starting. …
- Decrease in power, acceleration and fuel efficiency. …
- Check Engine Light comes on.
What happens if my fuel pressure is too high?
The Importance of Correct Fuel Pressure
If fuel pressure is too high, your vehicle’s engine could be over fueled, leading to many of the symptoms listed below. Some of these symptoms include your
engine running rough, poor fuel economy and black smoke from the exhaust
.
How do you fix high fuel pressure?
Start the engine; the fuel pressure should remain the same. Snap the throttle and make sure it increases; this an indication of a good fuel pump. Test a vacuum-operated fuel pressure
regulator
by removing the vacuum line while monitoring fuel pressure. The pressure should increase (5-15 psi.).
What causes Duramax limp mode?
Duramax Allison Transmission Limp Mode
In some cases such as a heavy load, towing, down shifting to pass, etc, and is especially common in performance tuned trucks can cause enough
transmission slippage
to trigger limp mode.
What causes P0087 Duramax?
DTC P1093, P0087 causing
limp mode
is common with this issue. Low rail pressure may or may not cause an MIL (check engine light). This is a very common problem that we hear about from our Duramax customers. Actual fuel rail pressure is not keeping up with desired fuel rail pressure.
What is CP3 on Duramax?
The Fleece Performance CP3K is a
modified Duramax LBZ CP3 designed to eliminate the factory fuel flow restriction
that begins at 3,000 RPM. If you have a stock CP3 pump you are losing fuel flow and rail pressure after 3000 RPM, which correlates to lost horsepower when you need it most.
