R1100 Fuel Pressure Regulator Replacement - Questions

[Jim Moore]

I spent yesterday afternoon and evening cursing softly to myself as I rode 600 miles home with a leaking FPR. It's a minor leak, just enough for me to ponder whether the bike would burst into flames every time I stopped. Luckily it was raining the entire time so the fuel was immediately washed away by the deluge.

But now I gotta pull the FPR and rebuild or replace it. The stock answer is to lift the rear subframe and get at it that way, but I remember hearing it can be done with the subframe in place. Has anyone tried that technique?

Also, what am I dealing with here? If a line is cracked I have to replace the spider, but I assume I can use the old regulator with some new o-rings? If it's leaking at the regulator itself I just replace the o-rings?

 

[dirtrider]

On 9/17/2023 at 11:10 AM, Jim Moore said:

I spent yesterday afternoon and evening cursing softly to myself as I rode 600 miles home with a leaking FPR. It's a minor leak, just enough for me to ponder whether the bike would burst into flames every time I stopped. Luckily it was raining the entire time so the fuel was immediately washed away by the deluge.

But now I gotta pull the FPR and rebuild or replace it. The stock answer is to lift the rear subframe and get at it that way, but I remember hearing it can be done with the subframe in place. Has anyone tried that technique?

Also, what am I dealing with here? If a line is cracked I have to replace the spider, but I assume I can use the old regulator with some new o-rings? If it's leaking at the regulator itself I just replace the o-rings?

 

Afternoon Jim

 

I have seen those regulator assemblies leak from a split plastic line, from the regulator itself, from the joint between the regulator & the distributor assembly.

 

I have tried a few times to install by cheating but it never seems to work out for me as it seems to be more effort & time than just biting the bullet & lifting the frame. I know some cut the plastic lines then use rubber hose & clamps to re-splice (I won't do work like that). 

 

You might check on you-tube as there should probably be some shortcut hacks on there, then see if see something that you can live with shows up. 

 

Just keep in mind that if you bend one of those plastic lines just a little too far it will kink the plastic line & compromise it, then sooner or later (after enough pressurization events) that compromised area can crack then spray high pressure fuel out like a fuel injector. 

[Jim Moore]

OK, got that one done. The issue was this. The hard plastic line on the left side comes through a slot in the airbox. It’s protected by a small rubber grommet. My grommet had worked itself out of position so the line was rubbing against the airbox. Eventually it rubbed a small hole in the line, causing the leak.

A new spider and set of grommets and o-rings cost me about $200. I re-used the actual FPR, although I replaced the internal o-rings. It was a pretty simple repair. The trickiest part of the entire evolution was getting the big circlip that holds the FPR back into place. That was a PITA.

I decided to lift the rear subframe. By the time you remove everything else you need to remove lifting the subframe is a matter of four bolts and a few connectors. And it makes the job a snap. YMMV.

I really question the wisdom of BMW using hard plastic lines in this application. Rubber fuel lines would be a lot easier to work with. Metal lines would be harder to work with, but would be much stronger. Hard plastic lines combine “brittle” and “hard to work with” in a manner only BMW could conceive.

[dirtrider]

40 minutes ago, Jim Moore said:

OK, got that one done. The issue was this. The hard plastic line on the left side comes through a slot in the airbox. It’s protected by a small rubber grommet. My grommet had worked itself out of position so the line was rubbing against the airbox. Eventually it rubbed a small hole in the line, causing the leak.

A new spider and set of grommets and o-rings cost me about $200. I re-used the actual FPR, although I replaced the internal o-rings. It was a pretty simple repair. The trickiest part of the entire evolution was getting the big circlip that holds the FPR back into place. That was a PITA.

I decided to lift the rear subframe. By the time you remove everything else you need to remove lifting the subframe is a matter of four bolts and a few connectors. And it makes the job a snap. YMMV.

I really question the wisdom of BMW using hard plastic lines in this application. Rubber fuel lines would be a lot easier to work with. Metal lines would be harder to work with, but would be much stronger. Hard plastic lines combine “brittle” and “hard to work with” in a manner only BMW could conceive.

Morning Jim

 

Most modern manufactures are using the high pressure plastic fuel lines now (including plastic fuel filters on some), some  are using hard plastic all the way from the fuel tank to the fuel injectors. 

 

They work just fine for most, the major problems that I have seen is,  problems show up after service was done & the plastic lines were either bent & kinked. Or where a line wasn't properly routed/retained/isolated. Or, possibly like your situation, during service a gromet was knocked/pulled out of place & not caught. 

 

I have also seen some static electricity arcing issues in cold drier climates where static electricity builds up in a plastic fuel filter or plastic line then arcing to some metallic point like the engine block or frame rail. If they arc in the same place enough times it eventually puts a small pin hole in the line or filter.