Low Pressure Fuel Sensor

[CarAbuser]

Hi,

I have been struggling to read the value of the low pressure fuel sensor on my E89 via the OBD port.

After reading one thread about an owner claiming that his car does not have a LPFS I went through a few parts websites like RealOEM and PelicanParts only to find that none of them seem to stock a LPFS for the E89.

So does anyone know for sure if that Z4 actually has a low pressure fuel sensor or not?
The 335i has one. Can't imagine why the Z4 doesn't!

[Constant.S]

All n54 do.

[Asbjorn]

What software are you using? Many sensors cant be read without proper bmw specific addresses/sequences.

[Ramjet]

I have euro spec e89, I can confirm that it does NOT have a lpfs.

[Lambobimmer]

I know that you can read the LPFP psi using Cobb accessport. If there is no sensor than this data is probably read through the DME or from lpfp regulator. I know for a fact that it cannot be read through the OBD port.

You probably want to look for your answer on the 3 series board. A lot of people change out the lpfp to run E85, including myself and there are a lot of logs with this info. These pumps use a pressure of 72 psi at idle. Search SteveAZ. He is the expert on this topic.

[CarAbuser]

I know the 3 series has one, just not sure about the Z4.

I have some issues with my car that point towards the lpfp sensor. Changing it out would be my next step. But if it turns out that it doesn't exist on the Z4 then I need to investigate other avenues.

[Lambobimmer]

Originally Posted by CarAbuser

I know the 3 series has one, just not sure about the Z4.

I have some issues with my car that point towards the lpfp sensor. Changing it out would be my next step. But if it turns out that it doesn't exist on the Z4 then I need to investigate other avenues.

What are the issues?

[Lambobimmer]

It appears that you may be correct. Neither RealOEM or Penske BMW shows a part number for a low pressure fuel sensor.

I have been asking Cobb to update the software for my DME for months to read the LPFP psi because it has never worked. They tell me that they were aware of this but maybe it is not possible because there is no sensor. Seems strange that every N54 model has this sensor but the Z4 does not. Good catch. Does this mean that our fuel delivery is setup different from the other models.

[CarAbuser]

Originally Posted by Lambobimmer

What are the issues?

I'm getting intermittent long crank on startup.

Also when the car is idling i get a shake/knock.

I have had the HPFP and the LPFP replaced under warranty. The car has 35k miles and the plugs were changed at 20k.

From what i've read the remaining possibilities are injectors and the crank position sensor.

[Lambobimmer]

Originally Posted by CarAbuser

I'm getting intermittent long crank on startup.

Also when the car is idling i get a shake/knock.

I have had the HPFP and the LPFP replaced under warranty. The car has 35k miles and the plugs were changed at 20k.

From what i've read the remaining possibilities are injectors and the crank position sensor.

My guess is injectors or coils.

[CarAbuser]

Originally Posted by Lambobimmer

My guess is injectors or coils.

The car runs fine and has no misfires elsewhere. I thought if a coil was bad i would get misfires at WOT.

If i have a bad injector should i expect to see a fouled plug?

[Lambobimmer]

Originally Posted by CarAbuser

The car runs fine and has no misfires elsewhere. I thought if a coil was bad i would get misfires at WOT.

If i have a bad injector should i expect to see a fouled plug?

I don't believe that this is always the case. I had bad injectors and my car idled horribly, however I did not throw any codes and it did not misfire. I had them replaced under warranty and it fixed the problem.

I just had to change my coils because I had one that went completely bad and I did throw misfire codes. However, I believe that I had symptoms before it completely stopped working.

If the issue is mostly at idle then I bet you have a bad injector.

[CarAbuser]

With no codes it will be hard to get them to look at it under warranty.

I might pull my plugs and check if they are fouled. That should be enough to prompt an injector replacement.

[nhatnguyen14]

So has anybody been able to find the Fuel Low Pressure Sensor? My car has been throwing the low fuel pressure code for some time and I cannot find the sensor. I know on N54 engines it is located right before the input line to the High Pressure Fuel Pump, but cannot find it on my Z N54 engine.. I see the metal part where the sensor is supposed to be installed but no threads for the sensor like other N54's. Have anybody found the fuel low pressure sensor, or is there not one?

[Sachak]

Originally Posted by nhatnguyen14

So has anybody been able to find the Fuel Low Pressure Sensor? My car has been throwing the low fuel pressure code for some time and I cannot find the sensor. I know on N54 engines it is located right before the input line to the High Pressure Fuel Pump, but cannot find it on my Z N54 engine.. I see the metal part where the sensor is supposed to be installed but no threads for the sensor like other N54's. Have anybody found the fuel low pressure sensor, or is there not one?

The E89 Z4 35i/is does not have a low pressure fuel sensor. If your car is running the default INAOS software then it shouldn't throw a code regarding this sensor not being present.

However if you run a mhd back end flash and choose to run the IJEOS back end flash then you will have the low pressure fuel sensor error pop up every-time you scan for errors however it won't affect the car and it won't throw an EML.

If you would like a version of the IJEOS software that this problem has been fixed then let me know via PM and I will send the files to you.

Now if you are running a JB4 and choose to write the INAOS back end flash ("which is right for our cars") then you will have a boost ceiling of I think 13 - 14 PSI with a steep dip down to stock boost quickly. This is some issue with the Z4 standard software and I have no idea why, however you won't get a low pressure fuel pump sensor error. Even if you run MHD stage 2+ software you will see in your logs that you cannot target high boost like all other N54 models can, the car will peak for a split second to 16psi if your lucky and then quickly taper down to stock boost levels or around 10 - 11psi. This is why we all run IJEOS software which then removes this useless boost target ceiling however it does introduce the low pressure fuel pump sensor error which I have taken care of.


This low pressure fuel pump issue with our E89 causes issues with tuning and I suspect it introduces a boost ceiling as load control cannot be properly addressed as the device cannot take into account LPFP sensor values. (This is my suspicion).

Hope this helps.