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1Back to top Go down   Fuel Pressure Regulator FPR Empty Fuel Pressure Regulator FPR Wed Apr 03, 2024 11:17 pm

davemadsen

davemadsen
Silver member
Silver member
1987 K100RT
How do I test/troubleshoot the FPR? I’m on this quest to resolve a bit of rough acceleration and sub-par fuel consumption (35-38 mpg US driving like the old man I am). Thus far:
Temperature sensor tests good (2.5k ohms at 66°F)
FPR holds vacuum (ie vacuum line and FPR diaphragm function as expected)
No visible fuel leaks at FRP
Fuel filter good, no restrictions
Fuel pressure: 32 psi (low)
Fuel pressure with fuel hose between FPR and fuel rail (return line?) clamped: 80 psi

What else should I be checking before throwing money at the problem?

Dave


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Dave
    

2Back to top Go down   Fuel Pressure Regulator FPR Empty Re: Fuel Pressure Regulator FPR Thu Apr 04, 2024 4:11 am

charlie99

charlie99
VIP
VIP
with guage connected , t piece, in line with fuel rail 
observe if pressure holds after turning off the motor .

if it dissipates quickly ie in under a minute to near zero then one would have to consider the seat - valve in the fpr is worn or injectors actually leaking  .

pressure should be around 2.1 - 2.5 bar   although i have seen lower , but under 2 bar is dodgy 

if this is all ok ...one would have to consider 3 things 

atomisation at injectors ...ie dirty 

airflow meter bypass may need resetting  after doing injectors and valve clearances 

air leaks through induction path ....(zpipe cracked ?) 

just some thoughts


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

3Back to top Go down   Fuel Pressure Regulator FPR Empty Re: Fuel Pressure Regulator FPR Thu Apr 04, 2024 5:00 am

davemadsen

davemadsen
Silver member
Silver member
charlie99 wrote:with guage connected , t piece, in line with fuel rail 
observe if pressure holds after turning off the motor .

if it dissipates quickly ie in under a minute to near zero then one would have to consider the seat - valve in the fpr is worn or injectors actually leaking  .

pressure should be around 2.1 - 2.5 bar   although i have seen lower , but under 2 bar is dodgy 

if this is all ok ...one would have to consider 3 things 

atomisation at injectors ...ie dirty 

airflow meter bypass may need resetting  after doing injectors and valve clearances 

air leaks through induction path ....(zpipe cracked ?) 

just some thoughts
Many thanks for your comments. I cannot determine if the fuel pressure bleeds off over some period of time since the tester holds the max pressure. For example I just checked the tester and it still reads 32 psi and I had done the test four hours ago.

I have not checked the atomized pattern of the injectors given they would be working with below specified operating pressure. No injector is leaking.

I am clueless on the AFM bypass and how one would go about resetting it. Please forward me info on this process.

I used starting fluid and found no air leaks. FWIW, z-pipe was replaced maybe a year ago.

Dave


__________________________________________________
Dave
    

4Back to top Go down   Fuel Pressure Regulator FPR Empty Re: Fuel Pressure Regulator FPR Thu Apr 04, 2024 10:59 am

Dai

Dai
Life time member
Life time member
davemadsen wrote:(...) I cannot determine if the fuel pressure bleeds off over some period of time since the tester holds the max pressure (...)
Use a cabletie to hold the pressure release button down? Just as long as it's not a white one Fuel Pressure Regulator FPR 652573


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

5Back to top Go down   Fuel Pressure Regulator FPR Empty Re: Fuel Pressure Regulator FPR Thu Apr 04, 2024 9:45 pm

davemadsen

davemadsen
Silver member
Silver member
Fuel pressure goes nowhere with the pressure relief button pressed, the fuel just sprays out the relief valve.


__________________________________________________
Dave
    

6Back to top Go down   Fuel Pressure Regulator FPR Empty Re: Fuel Pressure Regulator FPR Thu Apr 04, 2024 11:57 pm

Dai

Dai
Life time member
Life time member
Oh well. I thought it might be similar to a cylinder pressure gauge where you can hold the relief button down. It doesn't give you a good reading like that mind Very Happy


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

7Back to top Go down   Fuel Pressure Regulator FPR Empty Re: Fuel Pressure Regulator FPR Sun Apr 07, 2024 2:46 am

davemadsen

davemadsen
Silver member
Silver member
I replaced the FPR (with a Standard PR134 - OEM substitute I read about on the forum) and the old girl was back to idling, accelerating, and cruising like the old days.


__________________________________________________
Dave
    

8Back to top Go down   Fuel Pressure Regulator FPR Empty Re: Fuel Pressure Regulator FPR Sun Apr 07, 2024 1:35 pm

charlie99

charlie99
VIP
VIP
good result ..
ride on !!


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

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