2788 - Fuel pressure too low

[KingofKingz]

Hi all,

I need you help again.

Car details:
MJ 6.2012
80tkm
supercharged

I am getting this fault (unfortunately directly after installing the psw):

2788- fuel pressure setpoint actual valve comparison at max pressure
Fuel pressure too low
It should be at 6,1 bar but was only at 5,5 bar at 6906 rpm

It occured the first time in 5. gear at 7trpm going WOT. I have to admit that the tank was almost empty at that time and I also got the "27C1 - Info: Tank empty on fault entry" code.

I filled up the car afterwards and tried to reproduce the fault code, with success. Allthough it took me several tries to get it again (every time going WOT from frist to at least fifth gear). The error occured this time only in 6. gear at around 7trpm. In gears one to five it doesnt came back.

It is really strange that i am getting this code just after having the battery unplugged for the psw installation. Could this be due to missing adaptions. G-Power says that one have to do an adaptions drive for at least 100km. I was just going full throttle after installing the psw.

I also tried to check the fuel system with Rheingold. But the test always stopped at the fule pump test due to missing conditions. But i met all these conditions statet before the test. I think it stopped due to the supercharger but idk.
With INPA i could test the fuel pump and it holds pressure at 100% for the 15 seconds test period just fine. During crank I am also getting the 5,5 to 6,5 bar fuel pressure and during idle it stays at 3 bar. Under WOT i also get the 6,3 bar pressure.

So whats wrong now?

1. Adaptionens
2. low fuel pressure sensor (but i am just getting the 2788, nothing else…)
3. fuel pump
4. fuel pump filter (inside tank)
5. EKP module

I do not think that this is related to the software as i am driving this sw for over a half a year now without any faults.

Anyone with any kind of advice or ideas what could be wrong?

Thanks in advance!

EDIT: I forgot to mention that i read out the fuel systems pressure adaptions. This might be helpful for some of you.
Offset: -4,9%
Factor: 1,1

[KingofKingz]

No one any clue?

[jvictormp]

Hi. Did you figure it out?

I'm facing same problem. 2788 fault code when WOT.

[KingofKingz]

It was an missing adaptions fault. Had to drive till the MSS60 was fully adapted and the error never came back.

[Davisca455]

This is not an exact apples to apples comparison, but I recently experienced something similar, although the code was P2290 "Injector Control Pressure Too Low".

The first time the symptom appeared (last January)was on track when shifting at redline through 3rd, 4th, 5th gears.
The car went into limp mode, I cruised back to the paddock, connected the scanner, cleared the code, went for a test drive and the code didn't return.
But I decided to shift under 7000rpm the next session and all went well the rest of the day.

I have an early release G-Power supercharger kit, and it turns out it's a bit of a "Frankenstein" kit at that, as there was still some development going on when it was installed.
(Months after the installation, G-Power requested that the DME be sent back to Germany for a retune, when the DME came back a smaller pulley was also in the box)

I replaced the bypass valves last week and went for a test drive.
Hard on the throttle, shifting at redline through the first 4 gears, as I shifted into 5th gear the car went into limp mode,
Got home, cleared the code and the car is running fine.

Since my kit was installed, G-Power added a larger fuel pump for this level of power kit, but looking at the original invoice, my kit doesn't appear to have the larger pump.
I think I need to purchase and install the higher capacity fuel pump…ugh.

[amrazM]

@davisca455, your car doesn’t have a Bosch 044 in parallel of the stock fuel system? It’s not hard to add it after the fact, you can probably get it from gp infinitas or you can build it yourself using an original 044 pump and source components online to a higher standard than what g power originally intended by replacing some of the rubber hosing with AN. It’s pretty simple the way the gp second fuel pump is installed.

[amrazM]

Assuming you have 123 Bosch injectors the oem pump might not be what it used to be and is unable to maintain fuel pressure at high rpms. You can Frankenstein your own secondary pump with an 044 under the car, add a pickup to the fuel pump hat, run some lines to the 044 under the car and add a T fitting on the line going into the rail.

[Davisca455]

Originally Posted by amrazM

Assuming you have 123 Bosch injectors the oem pump might not be what it used to be and is unable to maintain fuel pressure at high rpms. You can Frankenstein your own secondary pump with an 044 under the car, add a pickup to the fuel pump hat, run some lines to the 044 under the car and add a T fitting on the line going into the rail.

I've never noticed a 2nd pump clagged onto the car anywhere.
But this is my first BMW, and I'm only familiar with the areas that have needed attention so far, and up till recently the fuel system hasn't been of any interest.

Do you know if the GP-Infinitas pump gets added to the OEM fuel system, or is it a pump that replaces the OEM pump?

No idea what the size of the injectors are, only that they are not the stock ones.

[amrazM]

Originally Posted by Davisca455

I've never noticed a 2nd pump clagged onto the car anywhere.
But this is my first BMW, and I'm only familiar with the areas that have needed attention so far, and up till recently the fuel system hasn't been of any interest.

Do you know if the GP-Infinitas pump gets added to the OEM fuel system, or is it a pump that replaces the OEM pump?

No idea what the size of the injectors are, only that they are not the stock ones.

early sk2cs kits use the BOSCH 000 injectors but being how early your kit is im not sure.

The g power fuel pump is under the car under the area of the driver seat, an easy way to check for it is to look at the fuel hose going to the fuel rail, with the g power pump there should be a T fitting on the fuel hose which is the fuel supply from the second pump.

[Davisca455]

Originally Posted by amrazM

early sk2cs kits use the BOSCH 000 injectors but being how early your kit is im not sure.

The g power fuel pump is under the car under the area of the driver seat, an easy way to check for it is to look at the fuel hose going to the fuel rail, with the g power pump there should be a T fitting on the fuel hose which is the fuel supply from the second pump.

I don't see anything, under the hood, that looks like it's tee'd into the factory fuel line?

[amrazM]

Originally Posted by Davisca455

I don't see anything, under the hood, that looks like it's tee'd into the factory fuel line?

yeah so you dont have the additional fuel pump, send me your email I can send you the documents outlining the g power fuel pump system.

[Davisca455]

Originally Posted by amrazM

yeah so you dont have the additional fuel pump, send me your email I can send you the documents outlining the g power fuel pump system.

amrazM,
Thanks for the Aux fuel pump installation instructions!
Before I dive in and buy the pump kit, I'm going to see if a new fuel pressure sensor might cure the symptom.

This kit has been bulletproof from 2009 until recently, so I feel like there is a case to be made, to suspect the sensor, or even the OEM fuel pump.

Like, what would explain why the car was rock solid for 11+ years, and only recently has thrown fuel system codes (P2290, 27CE)?
It seems like if the fuel delivery was marginal from the beginning, then I feel I would have seen a code before now?

[Davisca455]

Installed the Bosch version of the sensor Friday afternoon, then went out for a test drive.
Drove around town for a half hour and then a did a couple of pulls, no codes reappeared.

Saturday morning, dove the 2-1/2 hours to Laguna Seca to crew for a friend, then drove the 2-1/2 hours back home, no issues so far.

[amrazM]

That’s good, that updated sensor seems to cure a lot of the issues on this car.

[buldogge]

Originally Posted by Davisca455

Installed the Bosch version of the sensor Friday afternoon, then went out for a test drive.
Drove around town for a half hour and then a did a couple of pulls, no codes reappeared.

Saturday morning, dove the 2-1/2 hours to Laguna Seca to crew for a friend, then drove the 2-1/2 hours back home, no issues so far.

Quick question...Did you use the adapter, or just fit an o-ring to the new-style sensor? Seems several people claim you can just straight swap them, but, obviously, there is an adapter sold for the purpose.

Just wondering for future reference.

Thanks,
-Mark in St. Louis

[jvictormp]

Originally Posted by Davisca455

Installed the Bosch version of the sensor Friday afternoon, then went out for a test drive.
Drove around town for a half hour and then a did a couple of pulls, no codes reappeared.

Saturday morning, dove the 2-1/2 hours to Laguna Seca to crew for a friend, then drove the 2-1/2 hours back home, no issues so far.

I'm about to replace mine too, but in that last picture there seems to be two different sensors in the same place, is that right? How do you distinguish them? And would you know what is the other sensor?

[Davisca455]

Originally Posted by buldogge

Quick question...Did you use the adapter, or just fit an o-ring to the new-style sensor? Seems several people claim you can just straight swap them, but, obviously, there is an adapter sold for the purpose.

Just wondering for future reference.

Thanks,
-Mark in St. Louis

Hi Mark,

I did not use the adapter.

I first removed the o-ring from the old BMW sensor and measured the diameter of the O-Ring grove.
Next I measured the diameter of the groove of the replacement Bosch sensor.
The groove diameters were within .003" of each other, so I judged that to be within manufacturing tolerances.

What worried me the most was the difference in length of the threaded feature between the two parts, so I measured the depth of the receiving fitting of the fuel line and compared it to the length of the Bosch fitting.
There was a theoretical interference of .060", meaning that the new Bosch fitting would not be able to seat properly.
But what I hoped for, was that since the Bosch fitting was tapered at the tip, that maybe the tapered bit might fit into the diameter of the hole at the bottom of the receiving fitting and allow the fitting to close up the gap at the o-ring?

So, with no o-ring I installed the Bosch fitting by hand (no force) to see if it would fully seat, which it did.

I lubed the o-ring, installed it onto the Bosch fitting and very carefully and gently installed it onto the fuel line fitting.

(You can feel the increase in torque as the o-ring tries to bunch up, so reverse the rotation a 1/2 turn when it starts getting tighter and using that method continue until you feel a nice hard mechanical stop.)

I used a small mirror to inspect the interface between the sensor and the fuel line, insuring that the o-ring hadn't "pooped" out of its groove.
I started the car, and again using the small mirror, looked for any leaks.

[Davisca455]

Originally Posted by jvictormp

I'm about to replace mine too, but in that last picture there seems to be two different sensors in the same place, is that right? How do you distinguish them? And would you know what is the other sensor?

Hahaha!!
Sorry for the confusion.

Look closely, the side view of that "sensor" you see at the top of the picture is actually a reflection in a small mirror of the underside of the actual sensor in the bottom of the picture.
I was just inspecting that the o-ring wasn't caught between the sensor and the fuel line fitting, and that the fitting was fully seated and not leaking.

[buldogge]

Originally Posted by Davisca455

Hi Mark,

I did not use the adapter.

What worried me the most was the difference in length of the threaded feature between the two parts, so I measured the depth of the receiving fitting of the fuel line and compared it to the length of the Bosch fitting.
There was a theoretical interference of .060", meaning that the new Bosch fitting would not be able to seat properly.
But what I hoped for, was that since the Bosch fitting was tapered at the tip, that maybe the tapered bit might fit into the diameter of the hole in receiving fitting and allow the fitting to close up the gap at the o-ring?

Yeah...It's really just the tapered design difference...I suppose one could also simply (carefully) turn the taper off of the new-style.

Thanks for the confirmation.

-Mark

[Davisca455]

Originally Posted by buldogge

Yeah...It's really just the tapered design difference...I suppose one could also simply (carefully) turn the taper off of the new-style.

Thanks for the confirmation.

-Mark

Ya, I thought I might run it over to the Lathe real quick and shorten it up, but it looked like some part of the sensor extended all the way to the tip, so I had to nix that plan.