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Technical Support for Bonanza/Debonair System 


System Model Type: Fuel Selector Valve

Bonanza models with factory installed fuel tank combinations standard tanks and extended range tanks:

  • 20 gallon main tanks

  • 20 gallon main tanks with baggage tank

  • 20 gallon main tanks with wing aux tanks


OSBORNE Kit P/N 35668-1 models J 35 thru P35, 33 A33 B33 & C33 (aka M668)

OSBORNE Kit P/N 35668-3 models A35, thru H35, 35R (aka M668)

Brief description: OSBORNE selector valve assembly is installed (up stream) of the main tank factory selector valve.  The main tanks selector valve is equipped with a (4 position) including an aux position inlet.  This was available for extended range tanks.  (four way valve: LH main, RH main, “optional” aux and off)  The OSBORNE selector valve assembly is installed (plumbed) up stream of the factory aux inlet.

Note: The following is description of OSBORNE valve(s) assembly installed on the –1 and –3 kits only.


Probable Cause


Valve is hard to turn

Worn out/dry

Grease seat and replace shaft seal


Fuel stain at selector shaft

Worn out/dry

Grease seat and replace shaft seal

Fuel bypassing valve

Worn out, foreign debris caught in seat

Replace Valve

Handle is loose after installation of new clevis pin

Worn out handle  and or selector valve shaft  

Replace handle/valve assembly  

Valve handle is attached to selector shaft with a screw on type (handle)

Non approved valve 

Replace with approved part assembly

Valve turns with no feel or tank position detenting

Wrong selector valve body or worn out detent assembly  

Replace with approved part assembly

OSBORNE Kit P/N 35668-1(-1 kit with extended range 74 usable tanks), -5 and –6

Brief Description: The OSBORNE selector valve P/Ns 55034 and HE 763 replaces the factory selector valve, from four (4) position to a five (OSBORNE) (5) position accommodating the Tip Tanks.


Probable Cause


Stiff detents

Worn rotor plate 

Overhaul Valve

Low fuel flow on take off 

Selector valve filter   assembly improperly installed

See Beechraft model 35 parts catalog page 2-325 for other information

Low fuel flow in level  Flight

1. Loose plumbing   connection

2. Not using low boost

Check all plumbing/filter connections for tightness

See POHs/AFMs for operating  instructions


Fuel returning to both main tanks

Selector valve is internally bypassing


Valve turns hard or rough 

Internal seals dry or   worn out


Valve is hard (to turn)  from one tank selection to another  

Internal seals dry or   worn out


Weak tank position detents

Weak detent ball/spring rotor plate worn


Fuel filter area has fuel
  stain or is seeping 

Hard selector valve filter assembly seals, filter canister assembly bolt too tight

Replace seals

OSBORNE Cross Feed Valve P/N 55028  

Kit applications: 35668-1 Models N35, P35, B33, C33, C33A, E33, E33A, E33B, E33C,(with 74 gallons usable factory installed extended range tanks) –5 Models 35-C33A, E33A, F33A, S35, V35, V35A, V35B V35BTC , -6  Models 36, A36, A36TC Bonanza and Navion Kit P/N 11982 (TT2-1)  

This valve is used in level fight when Tip Tank is selected to achieve “cross feed” of both (LH and RH) Tip Tanks usage.  


Probable Cause


One Tip Tank feeds faster

1. Weak cross feed valve  

2.Plugged Tip Tank vent  line

Replace valve Clear slow feeding Tip Tank vent line

No cross feed occurring when cross feed switch is selected “open” 

1. No power to valve 

2. Valve is not engaging

Check power source to valve  

Bad coil replace valve 

Tip Tank fuel is bypassing (siphoning) to opposite Tip Tank; in static condition. “Not in flight”

Seal in valve is worn out

Replace valve  

OSBORNE Kit P/N 35668-7 Bonanza Models N35, P35, S35, 35-B33, 35-C33, 35-C33A, E33A, F33A, V35, V35A, V35B, V35BTC, –8 Bonanza Models 36, A36, A36TC, G36  

Electric Transfer System:  Fuel lines are readily routed forward of the main wing spar connecting to the Transfer Pump.  The Transfer Pump Assembly is located near the forward wing inspection cover, accommodating pump filter change and maintenance ease.  The Tip transfer outlet fuel line exits into the main tank through an existing metal inspection cover (or inlet fitting); Tip fuel is electrically transferred, shutting off automatically when Tip Tanks empty.  

Auto shutoff switch description:  

OSBORNE uses two (2) types of shut off switches.  These switches are know as (Auto shut off switch).  Switch descriptions are known as pressure and flow (alternate) switch.  

The following trouble shoot is for the “Pressure switch”.


Probable Cause


The transfer pump will not arm (stay on)

Switch is out of adjustment

Pump is weak or in-op


Replace Pump

The pressure switch
 will not shut off pump when fuel flow is interrupted or when Tip Tank empties.

Switch is out of adjustment 


Fuel flow rates are not even

1. Pump is worn out

2. Dirty pump filter 

3. Vent line clogged  

4. Loose fittings

5. Inlet orifice clogged



Clean out

Check all fittings for tightness  


The following troubleshoot is for the “Flow switch”.

Pump runs when toggle
  switch is in “On” position prior to using (Start position)

Circuit is closed  (contacted) 

Check switch for debris, clean and check for open  circuit  

Pump will not auto shut
off when fuel flow is interrupted or when tip tank empties

1. Flow switch is stuck (contacted) closed circuit

2. Contact point are shorted

Check switch for


OSBORNE transfer pump P/N 55041



Probable Cause


Pump will not start (run)

Bad pump 

Bad electrical ground to  pump

No Power to pump


Check power circuit  

Check ground continuity

Pump by-passes fuel from Tip Tank to main tank when off

1. Bad anti-siphon seal in pump

2. Pump transfer switch  was operated in the “start” position for extended amount of time

Replace pump and check
flow/pressure switch for proper operation (auto shut off)

Replace pump and
  check flow/pressure switch for proper operation (auto shut off)

Pump (is slow) has low fuel flow                  

1. Loose fitting connection 

2. Clogged inlet orifice  

3. Bad Pump

Check all fittings



OSBORNE fuel gauge P/N 55027   

Fuel gauge (single) with selector switch. 


Probable Cause


Reads empty at all times
 with fuel in Tip Tanks

1. Fuel transmitter between Tip Tank and selector switch/gauge is grounded

2. Faulty fuel transmitters

3. No power to gauge

Check fuel transmitter wire
for continuity, check power source

Reads full at all times
 with less than full Tip Tanks

Open fuel transmitter circuit.          

Check fuel transmitter wire
for continuity. Check for loose wire connection