[Tallicia]

Hi all,
I recently had some non optimal readings for low fuel pressure, while the high pressure reading was ok. ie first start up of day the LP showed below 10 and under load might go up to 30 and after warming up would go to 70. Mid day startup and it would be 65 and go to 75 under load.

So I replaced the fuel pump ( F90000267 ) .

Values are still low for the low pressure readings. High pressure readings range between 5 and 20.

I have a regulator that should arrive soon to swap. I hope this takes care of it, but I am wondering would temps affect the regulator this way?

Or is the low pressure fuel sensor? And if so, what is the part number for this? Real OEM shows on the N55 that it is no more?! http://www.realoem.com/bmw/enUS/showparts?id=UN73-USA-10-2010-E88-BMW-135i&diagId=13_1355

Parts 6,7,8,16 are grey and not listed. with a feed line ( 17 PN 13537605020 ) that no longer has the sensor?!

I am finding two two low pressure fuel sensors that seem mostly interchangeable.
Sensor for low pressure (N55). Up To 09/2011 PN 13537614317 $89.67
Sensor for low pressure From 09/2011 Up To 03/2012 PN 13537622231 $133.03

Tech specs on the sensors to be able to test them would be ideal.

So my questions are,
1. what's the difference in the low pressure sensors. Is one more friendly with fuel additives like winter/summer blends with differing ethanol %s?
2. Is it more likely the sensor is out of whack because the HP reading is good, while 0 low pressure would not likely be able to create a high pressure reading of 15 - 20.
3. Or is it more likely that the regulator is in fact creating some real zonked out pressures?

[Weehe]

Pretty sure all E series n55s do not have a low pressure fuel sensor. I think they brought it back for some F series. So not sure what you are actually reading.

[Tallicia]

Thanks Weehe. Where is the low fuel pressure read from? Is that the plug on the back of the HPFP?

[Weehe]

If you look at the hard line feeding the HPFP you will see a spot that a sensor could be tapped into. That is where the N54s have it.

[Tallicia]

Thanks. That's probably why when I was looking, I kept thinking it was hidden. Where does fp_l get a value? If fp_h is good, ignore fp_l. What about startup with code 2bee?

[Weehe]

2BEE is for HPFP pressure too low on startup. Probably your HPFP is getting weak.

[Terry @ BMS]

Keep in mind LFP in the JB4 interface is not low fuel pressure, on the N55, since the vehicle does not have a low fuel pressure sensor. Although Fuel-IT is coming out with a low pressure sensor kit to integrate with the JB4 for port injection purposes.

FPH is actual high pressure though. If it's falling below 5 during cranking then at least you know something is going on with the fuel system, but you'd have to diagnose the low pressure system manually, using an external gauge.

[Tallicia]

Thanks! That is good to know there is a sensor coming!

After the new regulator it starts right away now and idles too well. It's so smooth. Smooth criminal smooth... Annie, are you ok? But... It is misfiring and shutting down when not in map 0 or 4.

I thought maybe air was purging from the fuel line, but it's ok in the two low normal setting maps ( 0, 4 ). It's weird that the IGN1 and trims go high and HP_F low immediately under little boost like 4-5 psi when not in those maps. 9psi in map 0 is fine. Is there some signal issue going on here?

[Terry @ BMS]

JB4 fuel pressure connector is installed right? That is required to log high pressure.

[Tallicia]

Yes, they are. Tonight heading home I ran logs the whole way checking each map. I did get misfires in 0 and 4. That pointed to the regulator change. When I got home I took a little time after a couple glasses of wine and swapped back to the original regulator. She's happy again and no more misfires in any map.

[keyap]

Definitely no LPFP sensor on the E's so pre any other mods, e.g. the FuelIt option, you can't monitor it :-(

There are other indicators though to help you diagnose pump issues, assuming there's no other problems - As Terry said, HPFP ~5 at idle with no crank issues and 11 or above under load (this can vary from 11 to mid teens depending on whether a BEF is being run and the subsequent load seen by the DME) usually means both the LPFP and HPFP are happy.

If there are no idle issues and/or long cranks and the HPFP drops under 11 when WOT, it usually means the LPFP.

Idles issues and long cranks with the HPFP possibly under 11 when WOT usually means the HPFP.

[inevitab1e]

Originally Posted by keyap

Definitely no LPFP sensor on the E's so pre any other mods, e.g. the FuelIt option, you can't monitor it :-(

There are other indicators though to help you diagnose pump issues, assuming there's no other problems - As Terry said, HPFP ~5 at idle with no crank issues and 11 or above under load (this can vary from 11 to mid teens depending on whether a BEF is being run and the subsequent load seen by the DME) usually means both the LPFP and HPFP are happy.

If there are no idle issues and/or long cranks and the HPFP drops under 11 when WOT, it usually means the LPFP.

Idles issues and long cranks with the HPFP possibly under 11 when WOT usually means the HPFP.

My HPFP is crashing on WOT. Idle, starts fine. Upgraded LPFP, HPFP still crashing. New filter/regulator, still crashing. Any other opinions on this issue? Could fuel line from tank to HPFP be culprit?

[Weehe]

Originally Posted by inevitab1e

My HPFP is crashing on WOT. Idle, starts fine. Upgraded LPFP, HPFP still crashing. New filter/regulator, still crashing. Any other opinions on this issue? Could fuel line from tank to HPFP be culprit?

If you have a 2013 your HPFP is a different design and is likely the issue.