Listed below are some valuable Troubleshooting Techniques for Precision Airmotive RSA Fuel Injection Systems.

Remember, the art of good troubleshooting makes a good mechanic. If you have a question, please feel free to submit feedback.

WARNING:  These Troubleshooting Techniques are not meant to replace the input of a qualified mechanic. If you are unsure of any procedure, contact your local service representative. Precision assumes no liability for any advice offered or implied here.









INSTALLATION:  It is absolutely necessary to install this fuel control per the engine and/or airframe manual for proper operation. Failure to do so could result in unsatisfactory operation. Before removing Fuel Injection Servo, Flow Divider or Nozzles for flow test or repair, troubleshoot the following:




Probable Cause


High fuel flow reading nozzles Plugged nozzle, if high fuel flow is accompanied by loss of power and roughness.

Remove and clean; check system for source of contamination.

Faulty gage

Criss-cross gages and replace if necessary.

Staggered mixture control levers If takeoff is satisfactory, don't worry.  Some misalignment is normal in twin engine aircraft. Check rigging
Poor cut-off Improper rigging of mixture control linkage Readjust rigging
Rough engine (turbo nozzles charges) & poor cut-off Nozzle airbleed hole(s) clogged Clean or replace
Engine won't accelerate past a given RPM Oil in air chamber Refer to P.A.C. SIL RS-40
Rough idle

Slight induction leaks through loose pipes or bad O-rings. (Usually able to adjust inital idle but rough in 1000-1500 RPM range)

Repair as necessary

Large induction leaks such as missing pipe plugs, etc.  (Usually unable to throttle below 800-900 RPM)

Repair as necessary

Fuel vaporizing in lines or flow divider.   Encountered only under high ambient temperature conditions or following prolonged operation at low idle RPMs.

Keep temps low by:  Avoid excessive ground run.  RPMs as high as practical.  Cowl flaps open when practical.  Upon restart of hot engine, operate at 1200-1500 RPM for several minutes to reduce residual heat in engine compartment.
Low takeoff fuel flow Faulty gage

Criss-cross gages if twin engine; change gage if single engine

Sticky flow divider

Clean flow divider

Hard starting Technique

Refer to airframe procedure


Clear engine by cranking with throttle open and mixture in ICO.

Throttle opened too far

Open throttle to position approximating 800 RPM.

Rough engine Mixture too rich or too lean

Confirm with mixture control.  Rich will be corrected and roughness decreased during lean out while lean will be aggravated and roughness increased.  Adjust idle to give a 25-50 RPM rise at 700 RPM.

Plugged nozzle(s).  Usually accompanied by high takeoff fuel flow readings.

Remove and clean nozzles for 20 min. in Hoppes #9 gun cleaning solvent, rinse with stoddard solvent and blow dry.  Check system for source of contamination.

Slight induction leak through manifold drain check valve. (Usually able to adjust initial idle but rough in 1000-1500 RPM range)

Confirm by temporarily plugging drain line.  Replace check valve if necessary.

Air leak in fuel line from tank to servo

Confirm by connecting clear tubing between servo and flow divider and watch for air bubbles.  Locate and correct source of leakage.  May include boost pump or main pump seal leakage. 


If you have exhausted all troubleshooting leads, now is the time to have your Servo, Flow Divider and/or nozzles removed for flow test to verify proper operation. This should be done by a qualified A&P mechanic, IA or factory authorized Repair Center.



Return to RSA Support Page

Copyright 1997-2015, Precision Airmotive LLC, All Rights Reserved

17716 48th Drive NE Arlington, WA 98223         (360) 651-8282