What is an electric fuel pump and how does it work?
What were the requirements for an Otto cycle engine to work? Well 3: Fuel , air and spark . If any of these elements is missing, the party is over. So you will understand the importance of the electric fuel pump .

Formerly this pump was mechanical, and was driven by the combustion engine itself. It is currently electric, and usually goes inside the fuel tank. Engines gasoline direct injection , needing higher injection pressure plus the pump ele to have a mechanical pump that is usually driven by one of the camshafts. Thus, the injection pressure in that case rises to 150 or 200 bars, depending on the engine.

In addition, in the most recent models, the electric pump does not work in a constant way, but its flow varies depending on the power requested by the driver : the more the gas is stepped on, the more chicha is needed, but when it stops Not so much fuel is needed, so the gasoline pump can work at a more relaxed pace and thus saves electricity, which will eventually come out of the alternator, which in turn is moved by the combustion engine. So we will save fuel. A misery, but something is something.

Operating principle

In the case of the RFS engine , we will not go around with nonsense: we only have an electric pump (nothing mechanical) and its operation is constant. It goes inside the fuel tank and generates a pressure of 3 bar.

Later, already in the injection ramp , that constant pressure is corrected by the fuel pressure regulator (which in this engine is mechanical). Here, the pressure is regulated between 2.5 bar for idling up to 3 bar for when the engine goes full throttle. Excess fuel is returned to the tank.

This pump is activated by the tachymetric relay (also called injection relay), which I explained in this  video . The difference is that in that case we put direct power to the gasoline pump, without going through that relay.

Symptoms of a defective fuel pump

If the gas pump fails, we will have a serious problem . Not because it is difficult or expensive to fix it, but because it can leave us lying in the middle of a polygon full of chonis, yonkarras, zombies and zombies yonkarras chonis. The symptoms of a pump that has died or is giving its last blows can be several:
  • - The engine does not start
  • - The engine stalls
  • - The car strikes
  • - The car is not crap
  • - The motor throws pedets (petardea)
  • - Strange noise inside the fuel tank and they are not drug bundles that you have forgotten

As you can see, all these symptoms are related to a poor fuel supply, less noise.

Checking your status

The first step to check the pump is ... your ear. So turn up the volume of the Whisper XL. In the vast majority of cars, when giving contact, the fuel pump is activated for 2 or 3 seconds.

If we hear a strange noise, like a kind of whistle, it is most likely that the pump motor is about to move to a pine box.

If nothing is heard, it will be necessary to check if current reaches the pump . How? With a multimeter or, even better, with an oscilloscope  (and to measure its current you can use a clamp meter ).

Why better with the latter? Because as I said, the pump receives power only for 2 or 3 seconds when the contact is put on. With a multimeter we will have to look carefully at the screen and pray to show a more or less constant value during those 2 or 3 seconds. Instead, with the oscilloscope, we can see the time graph on the screen without any stress. That said, if we receive power, we must check the connector, and if it is in good condition, it is that the pump has said that see you later Lucas (as in the previous video about the two pumps of the 205 GTi). So it will be time to change it.

If the pump makes normal noise, it receives current, but the symptoms are still there, then it must be verified that it supplies the correct pressure . To do this, a pressure gauge must be placed in the fuel line , between the pump and the injection ramp. If all goes well, the pressure gauge should mark 3 bar of pressure (in this particular car, check the working pressure values indicated by the manufacturer for your pot). If it indicates less than 2.5 bar, the pump blades are screwed and, although the electric motor rotates, it is not able to provide adequate pressure. Touch change the pump.

If, on the contrary, the pump does not receive current , then we have the problem upstream. The first thing to check is that the inertia switch is not activated. This switch is activated in the event of an accident, to avoid spilling fuel on the road. In other words: deactivate the fuel pump. Although we have not had any ostia, it never hurts to check.

If the inertia switch is OK, the next upstream component is the tachometer relay . A quick check of that element is bypassing it: we put direct current into the fuel pump. If then the pump works, you know: relay to take in the ass. At least it will not be necessary to change the pump , which is worth its money. Invest that paste in other more productive things...