Basic Troubleshooting Chart

For Marvel-Schebler® / MSA Float Carburetors

NOTES:

  • INSTALLATION: It is absolutely necessary to install this carburetor per the Engine and / or Airframe Manual for proper operation. Failure to do so may result in unsatisfactory operation.
  • REMOVAL: Before removing carburetor from engine for warranty consideration, and after verifying all other components work properly, troubleshoot the following;

PROBLEM

PROBABLE CAUSE

REMEDY

ROUGH IDLE
MIS-ADJUSTED IDLE MIXTURE RE-ADJUST IDLE MIXTURE PER ENGINE MANUAL.
FAULTY OR LEAKY PRIMER DISCONNECT AND CAP OFF TO TEST FOR PROBLEM.
CRACKED PRIMER LINES INSPECT ALL JOINTS AND CONNECTIONS.
INTAKE MANIFOLD LEAK(S) PRESSURIZE AND TEST.

POOR IDLE CUT-OFF
MIXTURE LINKAGE NOT FULL TRAVEL RE-ADJUST MIXTURE LINKAGE.
MIXTURE VALVE BEING PULLED UP BY MISALIGNED MIXTURE CABLE RE-ALIGN MIXTURE CABLE STRAIGHT WITH MIXTURE LEVER.
FAULTY OR LEAKY PRIMER DISCONNECT AND CAP OFF TO TEST FOR PROBLEM.
IDLE SPEED ADJUST TOO HIGH RE-ADJUST IDLE SPEED PER ENGINE MANUAL.

CAN'T ADJUST IDLE
FAULTY OR LEAKY PRIMER DISCONNECT AND CAP OFF TO TEST FOR PROBLEM.
CRACKED PRIMER LINES INSPECT ALL JOINTS AND CONNECTIONS. REPAIR AS NECESSARY.
INTAKE MANIFOLD LEAK(S) PRESSURIZE AND TEST.

RUNS RICH

(LEANING MIXTURE MINIMIZES PROBLEM)
FAULTY OR LEAKY PRIMER DISCONNECT AND CAP OFF TO TEST FOR PROBLEM.
MIS-ADJUSTED IDLE MIXTURE ADJUST TO OBTAIN 25-50 RPM RISE AT ICO.

RUNS LEAN

(CARB HEAT MINIMIZES PROBLEM)
CRACKED PRIMER LINES INSPECT AND REPAIR AS NECESSARY.
INTAKE MANIFOLD LEAK(S) PRESSURIZE AND TEST.
MIS-ALIGNED IDLE MIXTURE ADJUST TO OBTAIN 25-50 RPM RISE AT ICO.

STUMBLES ON ACCELERATION

(MA-3™ & MA-4™CARBS)
FAULTY OR LEAKY PRIMER DISCONNECT AND CAP OFF TO TEST FOR PROBLEM.
IDLE MIXTURE ADJUSTED TOO RICH. ADJUST TO OBTAIN 25-50 RPM RISE AT ICO.
PUMP LINKAGE MIS-ALIGNED RE-ADJUST PUMP LINKAGE.

If all the above items have been eliminated and the carburetor is under warranty, Marvel-Schebler Aircraft Carburetors LLC must be contacted prior to any warranty consideration. For additional information or other assistance, please contact MSA

at: Telephone 336-446-0002; FAX 336-446-0007;
or Email: customerservice@msacarbs.com