ICON A5 MM : Fuel System : Troubleshooting : Fuel Pressure Diagnostic
Fuel Pressure Diagnostic
100192-01
Use Table 9 to diagnose the fuel system when the pressure is outside the normal limits (40.5-46.5 psi) or when FUEL PRESS illuminates on the annunciator panel. Annunciator Panel Diagnostic
Table 9. Fuel Pressure Diagnostic Table
Symptom
Possible Cause
Remedy
Low fuel pressure (below 40.5 psi)
Low fuel level.
Check fuel level sensor connection. Inspect fuel tank for damage and leaks. Replace fuel tank if necessary. Add fuel. (Fuel Bladder)(Fuel Tank Assembly)
Clogged coarse fuel filter.
Vapor Lock
A Fuel Pressure warning light in hot, and/or high altitude environments may be poor fuel quality or a winter blend of automotive fuel. Using a mixture of automotive (MOGAS) and AVGAS will allow higher altitudes and operating conditions, as shown in (Figure 146). The graph indicates ranges where to the right of the plotted lines, fuel pressure warning lights may be due to vapor lock, depending on the blend of fuel. To the left of the plotted lines, especially near freezing temperatures, a fuel pressure light may be due to high fuel pressure.
Fuel leak.
Check for leaks. See Maintenance Manual: (Line Maintenance) for Rotax Engine Type 912 i Series leak tests section from Rotax®. Tighten fitting or replace damaged lines as necessary. Inspect tank for damage and leaks. (Fuel Bladder)(Fuel Tank Assembly)
Fuel pressure regulator malfunction.
Inspect fuel pressure regulator. Replace fuel pressure regulator as necessary. See the Maintenance Manual: (Line Maintenance) for Rotax Engine Type 912 i Series fuel system section from Rotax®.
Fuel pump malfunction.
Secure electrical connector. Inspect electrical wiring. Replace if necessary. During engine lane changes, fuel pump malfunction should have been identified. See the Maintenance Manual: (Line Maintenance) for Rotax Engine Type 912 i Series fuel system section from Rotax®.
Plugged fuel tank vent line.
Clear fuel tank vent line. (Clear Fuel Tank Vent Line)
High fuel pressure (above 46.5 psi)
Clogged fine fuel filter.
Replace clogged fine fuel filter. (Fine Fuel Filter)
New fine fuel filter.
It’s acceptable if FUEL PRESS lights up after the fine fuel filter has been replaced but goes away with power or after engine warms up. If problem persists, check and replace fuel pressure regulator as necessary. See the Maintenance Manual: (Line Maintenance) for Rotax Engine Type 912 i Series from Rotax®.
Blockage between regulator and fuel tank.
Inspect flow between fuel pressure regulator and fuel tank. Check for kinks. Refer to the Maintenance Manual: (Line Maintenance) for Rotax Engine Type 912 i Series from Rotax®.
Note:
Figure 146 shows MOGAS with 15psi Reid Vapor Pressure (RVP), AVGAS with 7.1psi RVP, and blends of the two. This gives the worst-case scenario for commercially available MOGAS, generally found in extremely cold climates. Check local regulations or test the Reid Vapor Pressure of locally available MOGAS to understand what RVP MOGAS is available.
Figure 146. Vapor Lock Risks for Varying Fuel Mixtures