Petrol pump energizing while car is locked?

Questions specifically about a Petrol powered Citroen C3 (usually engine or fuel related problems).
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My Name: Fordey1982

Member
Posts: 3
Joined: Sun Aug 29, 2021 12:50 pm
Model: C3 2013-2017 Facelift A51
Year: 2016 (16)
Engine Size: 1.2
Fuel Type: Petrol
Mileage: 10000
Trim Level: NA
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)

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Hi all my mother has got a 2016 C3 1.0 3 cylinder. When the car is locked or keys out of the ignition the pump kicks on and energized, as if you’ve just put the keys in the on position.
The car drives fine with no issues and no lights on the dash. The only thing is it runs the battery down due to the fault.
Would anybody have come across the same issues?

Thanks Paul
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My Name: C3driver52

Guru
Posts: 1877
Joined: Sat Apr 30, 2011 7:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.4 i
Fuel Type: Petrol
Mileage: 79984
Trim Level: VTR+
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)
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Been thanked: 66 times

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Hello Paul

Did this just happen out of the blue?

Or has it always done this?

Or maybe after some work was done on the car, like a crash repair?
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My Name: Ozvtr

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Posts: 957
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
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Hi Paul,

Now they might seem like dumb questions but please bare with me.

How do you know it's the fuel pump running? What happens if you don't remove the key from the lock? Is there any circumstance under which the pump stays off?

I am not familiar with the later C3's electrics but (typically) the fuel pump is controlled by the fuse box in the engine bay, HOWEVER the engine ECU needs to "tell" the fuse box that the engine is running or else the fuse box cuts the power to the fuel pump. So if the pump turns on and off, at all, it is being controlled by some thing, either the engine ECU or the fuse box. If the engine ECU is not talking to the fuse box (power off) the pump should be off. I cant think of a way that the fuse box just decides, all by itself, to turn the pump on and off. There is something missing.
For the engine to run correctly, the fuel pump needs to be feeding it fuel. For the fuel pump to run the engine ECU must "communicate" over a communication line (not just power from a wire), actually talk to the fuse box and say "turn on the fuel pump the engine is running". This is a safety device, if the car is involved in an accident and the engine stops running, power is cut to the fuel pump because the engine ECU stops "talking" or it tells the fuse box the engine is not running anymore (depending on what has happened to the car).

So for the car to do what you are saying it is doing, a very complicated process is being subverted and I don't know how. If the pump was to run all the time or not at all, perhaps a relay or something. But if the pump is deliberately being turned on and off (by something) I cant tell you why.

Do you have any other clues for us? Any work done to the car lately? Modifications to the electrics? How long has this been going on?
My Name: Fordey1982

Member
Posts: 3
Joined: Sun Aug 29, 2021 12:50 pm
Model: C3 2013-2017 Facelift A51
Year: 2016 (16)
Engine Size: 1.2
Fuel Type: Petrol
Mileage: 10000
Trim Level: NA
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)

Post

Afternoon all thanks for the replies, the car has no work done to it or had a crash. It happened last Christmas and then it went! It’s back now I’ve tried a few things but nothing. If the keys are left in after ignition off it’s starts again. Energized then off for a few seconds then back on again - just repeats 24/7? Like you say it’s got to be the PLC or control module that is send the go command to do this.
User avatar
My Name: Ozvtr

Moderator
Posts: 957
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
Has thanked: 37 times
Been thanked: 257 times

Post

Are you doing anything to stop the fuel pump from running, like pulling the fuse in the fuse box under the bonnet?

When you turn the key to ignition the fuel pump should run for a second or so and then stop. Is it doing that or switching on and off?

When the engine is running does the fuel pump run all the time or switch on and off?
My Name: Fordey1982

Member
Posts: 3
Joined: Sun Aug 29, 2021 12:50 pm
Model: C3 2013-2017 Facelift A51
Year: 2016 (16)
Engine Size: 1.2
Fuel Type: Petrol
Mileage: 10000
Trim Level: NA
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)

Post

Hi there the pump runs for a couple of seconds when ignition is turned on as should be to prime then goes off before starting. Obviously running constantly while running.
This will do a self prime for a few seconds while the car is locked and off. On for a few seconds and then off. This is constant until battery goes dead.
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