Noise when turning the key

[maxp]

When i turn the key just one click, i hear a 1-2 second droning noise. Is that the fuel pump? If so what exactly is it doing?

Also if it is, i thought the fuel pump was attached to/inside the tank, this sounds like its coming from the front?

[rubjonny]

yes and its priming the fuel system, the main pump is under the car just in front of the rear driver side wheel, stick your head under the car and try it

[Ben Lessani]

That's the fuel pump, I *should* hear it on mine, but my relay is lazy so it doesn't bother priming any more, lol!

I'm thinking the 555 chip inside has died, so I might swap it out and see if it puts me back on track.

[mattkh]

I'm thinking the 555 chip inside has died, so I might swap it out and see if it puts me back on track.

Hi
You wont find a 555 in the relay.
It is the ECU that stops the fuel pump running after a few seconds when the ignition is turned on.

[Ben Lessani]

You wont find a 555 in the relay.
It is the ECU that stops the fuel pump running after a few seconds when the ignition is turned on.

I almost definitely would - unless its fallen out since the last time I opened it.

A K-Jet is ECU-less, the 555 in the relay is what controls prime and pulse.

[mattkh]

A K-Jet is ECU-less, the 555 in the relay is what controls prime and pulse.

Hi
That is very interesting.
By ECU, I meant the FEI unit.
So, if there is a 555 in the fuel pump relay to stop the current after say 2 seconds, then what makes the fuel pump run continuously when the engine is running.

[jezza16v]

The pump takes about 2 secs to pressurise the fuel circuit, when 'up to pressure' it stops, it is not specifically 'time' dependant. As soon as you start the engine it takes fuel from the system and the pressure drops so the pump has to keep going to keep up the pressure in the system. If you disconnect the fuel feed into the metering unit and turn the key it will just keep on pumping rather than stopping after 2 (ish) secs.

[Ben Lessani]

So, if there is a 555 in the fuel pump relay to stop the current after say 2 seconds, then what makes the fuel pump run continuously when the engine is running.

The pulse from the coil pack is what makes the fuel pump continuously run. There's a smaller pin in the corner of the relay which takes this input.

The pump takes about 2 secs to pressurise the fuel circuit, when 'up to pressure' it stops, it is not specifically 'time' dependant. As soon as you start the engine it takes fuel from the system and the pressure drops so the pump has to keep going to keep up the pressure in the system. If you disconnect the fuel feed into the metering unit and turn the key it will just keep on pumping rather than stopping after 2 (ish) secs.

That's what I originally thought, but its not the case, it is time dependant, hence the 555 chip inside. I read a good article on K-Jet fuelling - I'll try and dig it out.

[rubjonny]

yeah on the 8v k-jet there is no ecu or fei, its exactly the same ignition system as whats on the carb models