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Technical Service Bulletin (TSB)

2020-01 Low Voltage:  Some Corvairs may have low voltage on switched power wire (in the engine compartment) which indicates low voltage on the ECM.  All wiring harnesses produced after Jan 15 2020 have the ECM power coming from Relay #1 and not the switched 12V.

2020-02WBO2 power source:  WBO2 needs to be wired to the fuel pump power wire and proper grounding of WBO2.  Starting Feb 2020, The WBO2 sensor has a power connector wired to the fuel pump output (Relay #2).  If your WBO2 power is connected to the main feed wire, run a new power wire to the fuel pump wire and splice.

2020-03 Alternator Diode:  We are adding an alternator diode to our kits starting Nov 2020 and should be installed to prevent a “run-on” condition when the switch is turned off.

2021-01 – Spartan2 Wideband O2 Ground:  The Spartan2 Wideband electronics ground-black wire (NOT THE Heater Ground-white wire) needs to be connected to the ECUs sensor ground.  Run the WBO2 controller black wire to the black wire on the temp sensor lead.   This will prevent a spontaneous injection of fuel with the switch on the engine not running after approx 15 seconds.  This could create a flood position or worse a hydro lock if left for a long period of time.  The fix in TSB 2020-02 (WBO2 power source) needs to be applied before applying this fix.  The use of the 6025 distributors eliminates the grounding issue.

2021-07 – Dual Fuel Tables ‘Dual O2 Sensors:    If the second O2 sensor is installed, you will need to install the dual WBO2 wire on the drivers side of the car.  After the installation the software is activated and will adjust the fuel on each bank based on O2 information.  Call for more details.

2021-08 – Lean area in fuel map during tuning:  2-TBI fuel rails can produce a fuel “pressure wave” that disrupts fuel flow to the injectors at approx. 3000 RPMs.  The use of a Fuel Pressure Dampener located between the body fuel line and engine bay will reduce those waves.  The part number is PFFD-5 and was used on the 1990 Dodge Caravan 2.5 engine.

2022-02Some EFI/Carb pump combinations may have defective NBL/Neoprene in the power stud.  We have sent a letter and Email to everyone affected and sent replacement Viton washers.  If your pump was purchased between 15 Oct 2021 and 1 Mar 2022 and suspect you have a bad washer and did not get an email, call us immediately for a replacement.  We advise everyone to check their sending unit after 6 months of use for any issues or rubber deformities.  This is another reason to make sure you have a fused pump power wire.

2022-03Engine compartment spare tire may cause the failure of the fuel line or injector housing.  Ensure the spare tire has plenty of clearance between the fuel system and or TBI to prevent breakage from the normal engine “rocking” which may contact the spare and cause failure over time.  Use a “Donut” spare or shim the full-sized spare to create clearance.

2022-04 – Injector Hat may loosen without a lock nut.  The hex head bolts that hold the injector and hat to the TBI may loosen over time and cause a fuel leak.  You should periodically check your engine for leaks, but this upgrade will prevent the loosening of the bolts over time.  Add 2 each #10-24 nuts with lock washers between the injector boss and injector holder and tighten against the boss.  (see pic).  Some 4 TBI systems injector is too wide to install the nut and a thread locker should be applied to the threads at the base of the bolt.









2023-08 – Loose Carb Shaft Brass Screws.  A Customer reported that the brass carb shaft screws had vibrated loose and entered the combustion chamber.  An unknown number of TBIs left the shop with the brass screws not pinned and may loosen as you run the engine.  You will need to remove your throttle bodies and check the screws.  You can pin with a center punch or use blue Loctite brand to prevent loosening from vibration.  The brass screws are used because they are soft so if they do enter the combustion chamber, they will only make superficial marks on the piston and cylinder head and usually blown out the exhaust.