N47 320d low fuel supply pressure

[Rossco196x]

My Alpina D3 Biturbo has had a fault with the boost pressure for a few months now and hence i decided to scan it with Bimmer link rather than pay a garage to keep changing parts at my expense.

I've got the following codes

4CAO oil pressure plausibility (i replaced the sensor yonks back)

4530 Boost pressure Control deviation ( probably occurring as the LP turbo pressure control has been disabled by the DME as a precaution ?)

4BDC Fuel Priming Pressure Control

4BDA Fuel Pre Feed Pressure Control.

I've monitored the supply fuel pressure and this reads 3.8 Bar (1,876 mV) which i think should be 5.0 Bar. If i rev the engine the pressure remains at 3.8 Bar. I've ordered a new Fuel Filter which i will fit as i did see this as a possible cause. I assume the sensor is working so i'm thinking this could either be the Fuel Pressure regulator or worse stil the fuel pump.

Any advice, the car runs fine but performance is well down due to the Bi Turbo control being disabled ?

Thanks

RossCo

[AlexGSi2000]

Never seen this specific fault before but have worked on a few N47s - chains, rebuilds.etc

I would begin with the in tank fuel pump and work forward.

On two occasions I have had an issue with the fuel pressure regulator on the side of the high pressure pump which has lead to an unsteady / hunting idle and performance issues.

[Rossco196x]

Thanks Alex

I'm going to change the filter first and see if the fuel pressure increases to 5 Bar but as i say the car runs well enough to do a 300 mile round trip all be it at a reduced power output.

[Rossco196x]

Thanks Alex

I'm going to change the filter first and see if the fuel pressure increases to 5 Bar but as i say the car runs well enough to do a 300 mile round trip all be it at a reduced power output.

[sunbeam alpine]

Please ignore me if I'm wrong, but isn't this the model where the fuel pump fails and fills the whole system with swarf, making for an extremely expensive repair?

Just to clarify - I'm not a mechanic, but I've recovered several BMW's with the same (fuel pump failure) problem.

[I-am-the-reverend]

sunbeam alpine said:

Please ignore me if I'm wrong, but isn't this the model where the fuel pump fails and fills the whole system with swarf, making for an extremely expensive repair?

Just to clarify - I'm not a mechanic, but I've recovered several BMW's with the same (fuel pump failure) problem.

Oh yes......

The dreaded CP4 pump fitted to BMW's, Audis etc.

[I-am-the-reverend]

It's in an Eastern European dialect but gives you the general idea: the roller on the plungeer is supposed to sit across the width of the cam lobe but there is nothing to stop it turning through 90 degrees. The pump will still work but not for long as the roller eats a groove into the cam and all the swarf ends up in the tank and is drawn through the injectors.

https://www.youtube.com/watch?app=desktop&v=w3...

[Rossco196x]

Many thanks for the update about the CP4 HP pump failure. At present the car still runs and drives some 2k plus miles after the boost pressure controller was disabled.

I will take a look at the fuel filter when i change it to see if there are any signs of metallic debris then i will get the pump stripped if replacing the filter doesn't resolve the issue.

Unfortunately there is very little info available on what causes the LP turbo boost pressure to be disabled as i had this problem before and a software / firmware update resolved the issue.

If any one knows of a good BMW indy in the Hampshire area please let me know.

Thanks

[helix402]

Try Lee Shannon. I think he’s in Bentley.

[Rossco196x]

cheers Helix. Will give him a call tomorrow

Unfortunately its hard to find a decent garage that won't fleece you or has enough technical knowledge to establish to route cause of the problem as opposed to simply changing parts until they find a cure £000's later.

I did read on Baby Bimmer one guy being charged £7500 to have the full system cleaned and new injectors and pump which is about the same as what my car is actually worth.

Will see what happens once the fuel filter is changed and inspected.

If that doesn't resolve the issue and clear the codes then i will get the pressure regulator on the pump removed and inspected for metallic debris.

[Rossco196x]

Well finally as an update. One of the turbo pressure control circuits (LP) was disabled in the ECU when i got the car and hence an update fixed that thanks to Auto Dynamics in Barnstable. the car was fine for about 18 months

Next it was leaking hose to the low pressure turbo actuator and then some fault codes with the fuel pressure which cleared after the main filter was replaced so hopefully no CP4 pump issue just yet. After that i did a regen forced on the DPF which didn't work previously due to a faulty glow plug control relay and all seems good again.

I'm going to do a DPF delete after the next MOT also but yes you really can chase your arse trying to sort out issues on these cars.

Whilst road testing the car with my Bimmer app set up to monitor boost pressure i'm only getting about 2.7 bar compared to the set point of 3.2 bar on full throttle so any suggestions ? could it be the actuators have gone soft due to age ?