BMW K bikes (Bricks)

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1Back to top Go down   Fuel Pressure Regulator Question Empty Fuel Pressure Regulator Question Tue Aug 17, 2021 2:07 pm

dwnhillskater

dwnhillskater
active member
active member
I just reassembled my K1100 and I am not getting any fuel to the fuel rail. The fuel pump is pushing strong but the fuel is getting blocked at the fuel regulator. Has anyone heard of this happening before? I want to make sure I didn't just do something wrong before dropping $160 on a new one.

    

2Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 3:34 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
The regulator is not plumbed in such a way that it can block flow to the fuel rail. I would suggest that you check the connections to the spigots on the tank.

The return line fitting on the tank has a check valve that will block the flow from the pump. The return line goes to the forward spigot, it's the one with the hex where it is attached to the tank. Fuel comes from the pump on the rear spigot.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

3Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 3:46 pm

dwnhillskater

dwnhillskater
active member
active member
Point-Seven-five wrote:The regulator is not plumbed in such a way that it can block flow to the fuel rail.  I would suggest that you check the connections to the spigots on the tank.  

The return line fitting on the tank has a check valve that will block the flow from the pump.  The return line goes to the forward spigot, it's the one with the hex where it is attached to the tank.  Fuel comes from the pump on the rear spigot.

Thanks for the info! If the fuel is not even making through the rail and back up to the tank, would that check valve be doing anything?

    

4Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 4:22 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Are you sure you have the fuel lines connected to the correct spigots on the tank?  You wouldn't be the first one to connect the hoses to the tank incorrectly.

Disconnect the fuel supply hose from the tank to the rail and direct the flow into a bottle.  Hit the start button and see if anything comes out. If it flows, you may have the regulator connected backwards.

The regulator is a poppet valve and connecting it backwards will block the fuel flow through it.

If there is no fuel getting to the rail the problem is not in the regulator.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

5Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 4:55 pm

Laitch

Laitch
Life time member
Life time member
dwnhillskater wrote:
Point-Seven-five wrote:The return line fitting on the tank has a check valve that will block the flow from the pump.  
Thanks for the info! If the fuel is not even making through the rail and back up to the tank, would that check valve be doing anything?
The check valve was eliminated in Bricks after '85. Your K1100 should have a fuel return line inlets and outlets like my '95 K75: Regardless, you wouldn't be alone if the hoses had been connected incorrectly as Point-Seven five indicates. The odds are 50:50. Smile

As can be seen here, its inlet port is not threaded; it is brazed to the tank's underside. The return line outlet is mounted at the ceiling of the tank above the vapor collector and dumps fuel just forward of the fuel cap opening. In the attached photo, the forward section of the tank is at the top of the image. The red arrow indicates the fuel return line and the orange arrow indicates the approximate location where fuel cascades downward from the return line's opening.
Fuel Pressure Regulator Question Late_m10


__________________________________________________
1995 K75 81,000 miles
Fuel Pressure Regulator Question Usa-lo10
    

6Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 5:04 pm

dwnhillskater

dwnhillskater
active member
active member
Laitch wrote:
dwnhillskater wrote:
Point-Seven-five wrote:The return line fitting on the tank has a check valve that will block the flow from the pump.  
Thanks for the info! If the fuel is not even making through the rail and back up to the tank, would that check valve be doing anything?
The check valve was eliminated in Bricks after '85. Your K1100 should have a fuel return line inlets and outlets like my '95 K75: Regardless, you wouldn't be alone if the hoses had been connected incorrectly as Point-Seven five indicates. The odds are 50:50. Smile

As can be seen here, its inlet port is not threaded; it is brazed to the tank's underside. The return line outlet is mounted at the ceiling of the tank above the vapor collector and dumps fuel just forward of the fuel cap opening. In the attached photo, the forward section of the tank is at the top of the image. The red arrow indicates the fuel return line and the orange arrow indicates the approximate location where fuel cascades downward from the return line's opening.
Fuel Pressure Regulator Question Late_m10

Looks like the fuel filter was installed backward causing low flow... I swapped it and now I am getting good fuel flow. Only issue now is no fuel coming out of the injectors... Sigh...

    

7Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 6:54 pm

Laitch

Laitch
Life time member
Life time member
Was the frame of this project moto painted or powder-coated?


__________________________________________________
1995 K75 81,000 miles
Fuel Pressure Regulator Question Usa-lo10
    

8Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 7:20 pm

dwnhillskater

dwnhillskater
active member
active member
Powder coated. Why do you ask?


__________________________________________________
1993 BMW K1100RS
    

9Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Tue Aug 17, 2021 9:03 pm

Laitch

Laitch
Life time member
Life time member
dwnhillskater wrote:Powder coated. Why do you ask?
Did you clean the frame electrical ground connections down to bare metal before coupling the ground wire terminals to them or were they protected by tape? Coating will interfere with completing circuits. Intermittent electrical problems can be caused by poor grounding. Injector firing happens when the injector circuits are grounded.

Are you using all the original relays and the original Motometer cluster or do you have a new set up? Did you clean all the wiring harness connectors before coupling them? Checking the injector connectors is probably due.


__________________________________________________
1995 K75 81,000 miles
Fuel Pressure Regulator Question Usa-lo10
    

10Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Wed Aug 18, 2021 1:53 pm

dwnhillskater

dwnhillskater
active member
active member
Laitch wrote:
dwnhillskater wrote:Powder coated. Why do you ask?
Did you clean the frame electrical ground connections down to bare metal before coupling the ground wire terminals to them or were they protected by tape? Coating will interfere with completing circuits. Intermittent electrical problems can be caused by poor grounding. Injector firing happens when the injector circuits are grounded.

Are you using all the original relays and the original Motometer cluster or do you have a new set up? Did you clean all the wiring harness connectors before coupling them? Checking the injector connectors is probably due.

I will go through and check my grounds. Do you know where the ground wire is coming from for this circuit?

    

11Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Wed Aug 18, 2021 4:39 pm

Laitch

Laitch
Life time member
Life time member
downhillskater wrote:Do you know where the ground wire is coming from for this circuit?
What about my questions?  Smile

The notes I'm using indicate the ground wire is probably Pin19 of the Motronic control.

Put your moto's model and year of manufacture in the Signature section of your Profile so it will show up in every post and let readers know what you've got without needing to backtrack to find out.


__________________________________________________
1995 K75 81,000 miles
Fuel Pressure Regulator Question Usa-lo10
    

12Back to top Go down   Fuel Pressure Regulator Question Empty Re: Fuel Pressure Regulator Question Wed Aug 18, 2021 5:25 pm

dwnhillskater

dwnhillskater
active member
active member
Laitch wrote:
downhillskater wrote:Do you know where the ground wire is coming from for this circuit?
What about my questions?  Smile

The notes I'm using indicate the ground wire is probably Pin19 of the Motronic control.

Put your moto's model and year of manufacture in the Signature section of your Profile so it will show up in every post and let readers know what you've got without needing to backtrack to find out.

Haha sorry! Yes. I actually moved the grounds to the gear box instead of the frame.

I'll check my wiring to see if I got Pin19 grounded. :-)

I have the yellow/gray wire from the injectors going to the Ignition in the m.unit.


__________________________________________________
1993 BMW K1100RS
    

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