BMW E91 320d Engine Stalling? Fuel Rail Pressure Issue

Hello everyone,

I have the following problem with a 320d manufactured in July 2009, with 116,000 km mileage, an N47 engine producing 177 hp, and a manual transmission:

"Under near-static, full-throttle conditions, the engine simply stalls. However, it can be restarted afterwards. The error memory doesn't show any relevant codes. I did record some data logs including boost pressure and rail pressure, etc."

At TIME = "12156", you can observe how the rail pressure drops.
The MSG (Manifold Supply Group) is still indicating a target pressure of 1200 bar. This means, to me, that it's not an emergency mode or shutdown situation.

Explanation of "Quasi-static":
"If you drive in a straight line in gears 3 through 6 and simply run the engine at full throttle through all the gears from beginning to end, the error does NOT occur. You need a hill or extremely high speeds for the tachometer needle to barely move. The log shows that the vehicle was driven in 6th gear. If you drive with half-throttle and the vehicle slows down on a hill, nothing happens either."


Which valves/relays, etc., are responsible for the rail pressure? The pump itself is demand-controlled, but replacing it would be the last thing I'd want to do simply because of the price of €1100 + installation.

Otherwise, the engine runs completely normally. The power output and fuel consumption are also normal.

Thank you for your ideas and suggestions!

Best regards, Stefan.

Hello,

Quote:

Which valves/relays, etc., are responsible for the rail pressure?

I am not familiar with this vehicle or its typical wiring diagram. The wiring to...
a) Rail pressure sensor, typically mounted directly on the rail.
b) Pressure regulating valve.
It should definitely be checked.

Best regards, Rainer.

Fuel supply? The BMW has a two-part fuel tank. Without knowing the exact details, it appears that one half of the tank contains a fuel pump, while the other half contains a suction pump that transports the diesel to the pre-chamber of the fuel pump.
If the problem doesn't occur when the tank is full, then the issue lies there.
There is a control unit for the fuel pump located in the right rear wheel well.

Thank you for your answers.

My thought process:
The tank was/is full. Also, for example, you can drive at 240 km/h according to the speedometer without anything happening – it just has to be slightly downhill. For me, this means that the fuel supply from the pre-pump is sufficient. Otherwise, it would likely run out at higher RPMs/power levels rather than at lower ones.

I'm ruling out the rail pressure sensor because it reliably measures pressures from 350 to 2000 bar. I can't imagine why it would suddenly stop displaying any readings at a constant RPM/full load.

The 20D engine has a pressure control valve in the fuel rail and a flow regulator located before or inside the fuel pump.

My theory:
As long as the engine is experiencing a rapidly increasing RPM and an increasing target rail pressure, the fuel quantity control valve remains fully open, and the rail pressure is regulated by the rail pressure regulator on the rail. When the target value remains almost constant, for efficiency reasons, the pump's demand-based control is activated, reducing its diesel supply. If the fuel quantity control valve fails, the vehicle will always shut down if the valve throttles too much.

Would explain the strong dependence of the error on dynamics. Does anyone know if the rail pressure is actually regulated in this way?

Best regards, Stefan.

The rail injection pump and the diesel filter weren't the problem.
Does anyone else have any ideas?

I also just drove with a completely full tank.

Error: Boundary conditions.
1600 rpm, 6th gear, full throttle on an approximately 10-12% incline - only a very slow increase in engine speed.

Same route, 4th gear from 1000 to 2500 rpm, full throttle. The vehicle pulls well and reaches the target load demand (it doesn't get stuck anywhere). No errors are reported.

"When trying to restart the car after a fault, it now hesitates for about 10 seconds initially. Then, when you turn the ignition on and off, it takes another 3-4 seconds before it starts."

Sure, here is the translation of the text from German to English:

"Hello."

Can you log the power supply (operating voltage) from the engine control unit?

I once had something similar; occasionally, after starting for about 30 seconds, it would shut off or while driving – it was the pre-lift pump that wasn't working intermittently. It's quite quiet.

Okay, I'll check it out. I'll be back at the vehicle on Sunday. Is the pump connection located under the rear seat? Or does it have two connections?
Okay, I'll set up nine test rigs with inspection lamps.

Best regards and thank you in advance.