Thread: Limp mode and low fuel pressure

Hello guys,

I am sorry for registering and directly posting a thread, but I can't seem to sleep lately, because of my L322.

Basically, I got an L322 diesel 3.6 V8 and it goes into limp mode. The codes are injectorpressure too low and fuel pressure too low. The car could not be driven at all, I mean you could, but a slight, harder press on the pedal and it entered a limp mode.

I have changed the fuel pump in the tank, fuel filter, measured 0.5 bars before the HPFP. All 8 injectors were bench tested and they are fine. The HPFP was replaced with a brand new one Siemens VDO (hard to find). Now the car can be driven, but.... When it gets warm, around 70+ degreesC if I smash it, again it goes into limp mode with the exact same errors (Fuel Pressure too low and Injector pressure too low).

There isn't a single mechanic that wants to work on these cars. Basically, I am out of options. I have some knowedge (above average) about cars, but I cant seem to think of something that could cause this.

What do you think? A fuel pressure sensor? Bubbles (air) in the system (doubt it). I just cant think of anything else. I can provide you with extensive logs, about everything that can be logged. Basically from this log:

"id": "00000381",
"title": "Fuel Rail Pressure",
"unit": "kPa",
"maximal": 169790,
"least": 21840
},


I can see that the maximum rail pressure of ~170k can be reached and indeed it happens, but when its cold (below 70degC).

Any suggestions, everything is welcomed. Please dont make me sell the car...

Wish you all the best.

Apologize for my English.

I only have the L320 WSM but in case it helps, here are the extracts for the 2 codes. The fuse number won't be correct and the reference to the 2.7 can be ignored.

P008700 Fuel rail/system pressure too low
Fuel lift pump circuit fault
Fuel lift pump relay fault
Fuel lift pump fault
Check the lift pump and circuits. Refer to the electrical
guides. Check fuse 1E of the engine compartment junction
box. Check the fuel pump relay in the engine compartment
junction box. Rectify as necessary. Clear the DTCs and test
for normal operation.

P229000 Injector Control Pressure Too Low
Fuel leak (high or low-pressure system)
Fuel filter/line fault
Air lock in injection pump
Fuel pump fault
There are different approaches to this depending on whether or not
the vehicle runs.
If the vehicle does not run: remove the lift pump
fuse (fuse 1E of the engine compartment junction box). Disconnect
the volume control valve connector from the rear of the injection
pump. Disconnect the fuel spill lines and direct into a suitable
container through a length of clear pipe. Crank the engine to at least
250 rpm for a minimum of 15 seconds. The pump spill flow should be
at least 160 ml/min. If the spill flow is greater than this, install a new
injection pump.
REFER to: Fuel Pump (303-04D Fuel Charging and Controls - TDV8
3.6L Diesel, Removal and Installation).
Clear the DTCs and test for normal operation. If the spill flow is less
than 160 ml/min, carry out the low-pressure bleeding procedure.
REFER to: Low-Pressure Fuel System Bleeding - TDV6 2.7L Diesel
(310-00 Fuel System - General Information, General Procedures).
Recheck the spill flow, if it is still less than 160 ml/min, install a new
fuel pump.
REFER to: Fuel Pump (303-04D Fuel Charging and Controls - TDV8
3.6L Diesel, Removal and Installation).
Clear the DTCs and test for normal operation.
If the vehicle does run,
install a new fuel filter and run the engine at 3,000 rpm for 3 minutes.
During this, monitor the fuel pressure using a data logger function. If
there is an airlock in the pump, the fuel pressure will be low and
unstable, but a high-speed run should clear this. If the fault does not
clear, check the low-pressure system to the injection pump. Insert a
length of clear pipe into the fuel line and check for a steady flow of
fuel with no air bubbles. If the low-pressure system checks out,
disconnect the fuel injector electrical connectors and check
connections. Direct the lines into a suitable container and crank the
engine. Compare the flow from the injectors and if there is one or
more with low flow, install a new injector to that cylinder. REFER to:
(303-04D Fuel Charging and Controls - TDV8 3.6L Diesel)
Fuel Injectors LH (Removal and Installation),
Fuel Injectors RH (Removal and Installation).
Clear the DTCs and test for normal operation. If the fault does not
clear, install a new injection pump.
REFER to: Fuel Pump (303-04D Fuel Charging and Controls - TDV8
3.6L Diesel, Removal and Installation).
Clear the DTCs and test for normal operation.