P1585 Misfire with empty fuel tank

P1585 Misfire with empty fuel tank

The P1585 trouble code can have different meanings depending on the vehicle manufacturer, but for certain makes, it specifically refers to a misfire with an empty or very low fuel tank

. It indicates that the engine's computer has detected misfires and correlated the event with a critically low fuel level. 

Common vehicle applications for P1585

The context for this code is critical. A generic OBD-II scan may only show "P1585," but on certain vehicles, particularly some Porsche and BMW models, it indicates a specific fuel-related misfire. For other manufacturers, P1585 is completely unrelated and may refer to throttle control, transmission, or sensor issues. 

Causes of a misfire with an empty fuel tank

When your fuel level is low, a number of issues can cause the engine to misfire:

• Fuel pump sucks air: A fuel pump submerged in gasoline is cooled and lubricated by the fuel itself. When the fuel level is critically low, the pump can pull in air instead of fuel. This creates an imbalance in the air-to-fuel ratio, causing the engine to misfire or stall.
• Contaminants clog the fuel system: Over time, sediment and debris can accumulate at the bottom of your fuel tank. When the tank is nearly empty, the fuel pump is more likely to draw this gunk into the fuel filter and fuel injectors. This can lead to a clog, which restricts fuel delivery and causes a misfire.
• Fuel pump overheating: The fuel surrounding the pump helps to keep it cool. When the tank is low, the pump can overheat and malfunction, causing erratic fuel pressure and misfires. This can lead to premature fuel pump failure over time.
• Lean air-to-fuel mixture: A consistent lack of fuel delivery leads to a "lean" condition (too much air, not enough fuel). The engine's computer can detect this and trigger a P0313 code, which is the more generic version of a low-fuel misfire, but the effect is the same. 

Symptoms of a low fuel misfire

In addition to the Check Engine Light, you may notice one or more of the following symptoms if your fuel level is critically low:

• Engine hesitation or sputtering: The engine may run rough, especially during acceleration, as the fuel pump struggles to deliver a consistent supply of fuel.
• Poor engine performance: The vehicle may experience a lack of power and struggle to maintain speed.
• Difficulty starting: If the fuel pump has been damaged from repeated low-fuel operation, the vehicle may have trouble starting. 

How to diagnose and fix the issue

1. Refuel the vehicle: The simplest fix is to add fuel to the tank. If the problem is caused by a critically low fuel level, adding gas will immediately submerge the fuel pump and stabilize the fuel delivery.
2. Reset the code: After refueling, the code may clear on its own after a few drive cycles. You can also use an OBD-II scan tool to manually clear the code.
3. Check fuel system components: If the misfire persists after refueling, it indicates that a damaged component is the root cause. A mechanic should inspect the following:
   • Fuel filter: A clogged filter will need to be replaced.
   • Fuel pump: Test the fuel pressure to confirm the pump is operating correctly.
   • Fuel injectors: Clean or replace dirty or clogged injectors.
4. Inspect other components: If the fuel system is healthy, other common misfire causes should be investigated, such as faulty spark plugs, ignition coils, or oxygen sensors.