‘91 K100 LT... now I have a fuel problem...

[Cgswssbmwk100]

trying to find my fuel problem... I now have 60+ psi fuel pressure on the out put side of the filter.  Over 50 psi checking at the outside of the gas tank (. Most likely the same 60+ I had inside, I just didn’t let the fuel pump run as long)


I have zero gas at the rear tube to the fuel injection rail


So I’m guessing I have something wrong at the fuel supply pipe.  It looks like there should be an unobstructed path from the tank thru the supply pipe, and the pressure regulator would have nothing to do with it.


I have the tank off, seat off,left lower off and currently have the injectors out of the engin and injection rail hanging from the wires.  Both fuel lines are off the fuel rail.  And of course I can’t see the the supply pipe or regulator.  It appears they must be hidden behind the air plenum.


So I’m sure some of you have actually seen this little think, so I’m looking for advice.


Should I continue to dig deeper from the left side (remove air plenum) or should I go it from the right side.


It seems this bike wants me to take it down to the bare frame!


Thanks!


Craig

[Martin]

More than likely a faulty fuel pressure regulator. Check the vacuum line on the last throttle body and make sure it is clear of fuel. It has been known to pump fuel into the cylinder and cause a hydraulic lock. unfortunately I have to now go to work.
Regards Martin.

[The Mighty Gryphon]

As I read your post, you are not getting fuel to the injector rail.  Is that correct?

Does fuel come out of the spigot on the tank where the hose to the rail connects when the pump runs?  I assume that is where you say you see pressure outside the tank.  If you measured pressure there, I would think that you should have fuel coming out.  If it is, and there is none at the rail, you may have a collapsed or obstructed hose.  It happens with brake lines so I would think it could happen with a fuel line as well.

[rbm]

Did you disconnect the fuel hoses from the tank at some point?  Did you make sure you replaced the right hose on the correct spigot?  It's easy to confuse inlet and outlet.  Fuel going back into the tank from the regulator uses the spigot nearest the front of the motorcycle; fuel going to the fuel rail comes from the spigot farthest from the front of the motorcycle.

[Cgswssbmwk100]

On the bottom of the tank there are two houses.  I assume one is the return from the regulator and the other goes to fuel supply pipe.  I have good fuel pressure at the rear tap on the tank.  The hose coming off that rear tap is full of fuel and will not let fuel flow.


I guess I am miss reading how the pressure regulator works.  The way it looks to me is that the fuel goes from the tank, thru the fuel supply pipe, and to the fuel rail.  Then it goes out the other end of the fuel rail back up to the pressure regulator.  Then I assume if the pressure is too high, the regular let’s fuel back into the tank to lower the pressure.  In other words, there is nothing to stop the fuel going from the tank to the injector rail.  Remember the fuel lines to both sids of the injector rail.disconnected.  The way I read it, there should be free fuel flow to the injector rail

[Cgswssbmwk100]

Rbm, at this point, nothing is connected.  I’m trying to find what is stopping the fuel getting to the fuel rail.  What I would like to do is find where it is being stopped.  I was hoping to get some direction on how to get to the fuel supply bar.


The way it looked to me, the fuel supply bar is really just a buffer to smooth out the pressure pulses from the fuel pump.


Craig

[The Mighty Gryphon]

On the bottom of the tank there are two houses.  I assume one is the return from the regulator and the other goes to fuel supply pipe.  I have good fuel pressure at the rear tap on the tank.  The hose coming off that rear tap is full of fuel and will not let fuel flow.

If you remove the hose on the rear spigot does fuel flow out of the spigot when the pump runs???   If that hose is full of fuel but nothing comes out, doesn't that mean the hose is blocked???

[Cgswssbmwk100]

That’s kinda what I’m trying to trace.  The hose goes to the fuel supply pipe.  Which I don’t know where it is.  Once I find where they hide it, I can take off the hose.  If I have fuel coming out of the hose, I can take off the hose going out of the fuel supply pipe and find where the blockage is.


What I was hopeing to find out is if I should keep going in from the left side , which means removing the air plenum, or if I have to go at it from the right side.

[The Mighty Gryphon]

The two fuel supply spigots are located on the bottom of the tank a couple inches from the front of the tank on the left side above the front end of the fuel rail on the cylinder head.

The spigot closest to the front is the return from the fuel pressure regulator.  The one about two inches to the rear of the return is the supply line from the fuel filter.  The supply should go to the rear end of the fuel rail.  The return from the fuel rail is at the front end of the rail.  That hose goes behind the air box to the fuel pressure regulator, with a second hose from the fuel pressure regulator going up to the front spigot returning unused fuel to the tank.

When the pump is running fuel should flow freely from the outlet spigot on the front end of the fuel rail. 

Hope this helps.

[Cgswssbmwk100]

Thanks!


I guess I screwed up on this thread.  Too much information.


I guess I should have just titled it, “ where is the fuel supply pipe, and how do you get to it”

[The Mighty Gryphon]

Did you find it?  Can you find your way around the fuel plumbing now?  Things can be a bit confusing in the beginning on these beasts.

[Cgswssbmwk100]

Ok, my bad.  I was looking at the drawing in the Manuel and the fuel rail I’d drawn up under the tank and it looks to me as if there vis a fuel line down to the injector.  Of course there is no fuel line, the injector mounts on the fuel rail.  Just me not reading the drawing right.  What really got me screwed up is that the person that worked on the bike before mre put the fuel lines on the wrong outlets.  So now I have a fuel line stright to the fuel rail and I have pressue.   Sorry for all the confusion