P0093: Fuel system leak detected – large leak
The engine computer has found that fuel is being lost from the fuel system: more fuel is pumped than the injectors use, or the pressure drops faster than it should. Fuel may be leaking out.
Updated
What P0093 means
On diesels with common-rail injection, and some petrol engines with direct injection, the engine computer knows how much fuel the pump delivers and how much the injectors use. If the pressure drops faster than that explains, fuel is going somewhere else.
P0093 means it has found a large loss like that. The fuel may be leaking out, for example from a high-pressure pipe, or back towards the tank through a leaking valve or injector. The code alone can’t tell which, so treat it as a leak until it’s been checked.
P0094: a small leak
P0094 is the same check finding a smaller loss. The causes are the same, and so is the advice: until it’s been checked, assume fuel may be leaking.
P0094: Fuel System Leak Detected - Small Leak
The engine computer has found a small loss of fuel from the fuel system: a little more fuel is pumped than the injectors use. Fuel may be leaking out.
Common causes: leaking high-pressure fuel pipe or loose union, injector stuck open or leaking, leaking pressure-limiting valve or rail seal, leak in the fuel supply from the tank.
Can I keep driving?
Stop and get help
Stop when it’s safe to do so, switch the engine off and don’t restart it. Fuel may be leaking, and fuel on a hot engine or exhaust can catch fire. If you smell fuel or see smoke, get everyone out and away from the car. Have it recovered and checked before driving again.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
Fuel that escapes under high pressure can spray as a fine mist, and on a hot engine, turbo or exhaust it can catch fire. Keep sparks and flames away from the car. Don’t look for the leak with the engine running: leave that to a workshop.
The engine may also lose power or cut out.
Symptoms
- A strong smell of fuel, inside or outside the car.
- Wet patches or drips under the car, or smoke from the engine bay.
- Less power, or the engine cutting out or not starting.
Common causes
- Leaking high-pressure fuel pipe or loose union. The pipes and unions between the pump, the rail and the injectors are under very high pressure.
- Injector stuck open or leaking. An injector that sticks open, or lets too much fuel back to the tank, loses fuel the engine computer didn’t plan for.
- Leaking pressure-limiting valve or rail seal. The pressure-limiting valve on the rail lets fuel back to the tank when it opens; one that leaks loses pressure.
- Leak in the fuel supply from the tank. On some engines, a leak between the tank and the high-pressure pump sets this code too.
Typical fixes
- Don’t restart the engine. Look under the car for fuel with the engine off, and have the car recovered.
- Have a workshop check the high-pressure pipes, unions, rail and injectors for leaks. Fuel under high pressure can injure skin and eyes, so it’s not a job to do by hand.
- Have the injector return flow and the pressure-limiting valve tested if no outside leak is found.
- Repair the leak, clear the code and check that it doesn’t come back.
Questions
Can I drive with P0093?
No. Stop when it’s safe to do so, switch the engine off and don’t restart it: fuel may be leaking, and fuel on a hot engine or exhaust can catch fire. Have it recovered and checked first.
What is the difference between P0093 and P0087?
P0087 means the fuel pressure is too low, often from a clogged filter or a weak pump. P0093 means fuel is being lost from the system, which may be a leak. A leak can set both.