pluriel starts and idles, but cuts out from throttle

My C3 pluriel broke down the other day. It just died on the motorway. The rac bloke said there were no codes stored. It starts, splutters for a bit, then sits in idle. The moment you rev it, the engine seems to be misfiring and it stalls.
Anyone have an idea of what that might be?

ShirleyM wrote: ↑Mon Aug 17, 2020 6:41 pm My C3 pluriel broke down the other day. It just died on the motorway. The rac bloke said there were no codes stored. It starts, splutters for a bit, then sits in idle. The moment you rev it, the engine seems to be misfiring and it stalls.
Anyone have an idea of what that might be?

Hi

Did you add fuel just before, or some time before the motorway run?

It was fuelled before motorway run and drove from full to 1/3 tank

ShirleyM wrote: ↑Tue Aug 18, 2020 7:04 am It was fuelled before motorway run and drove from full to 1/3 tank

So unlikely to be contaminated fuel.

It is surprising there are no codes stored. Even a good runner may have some codes in there.

If you release the fuel filler cap, as if you were going to refuel, do you get any unusual sounds?

I am thinking of air rushing in as the fuel filter cap is removed.

Air rushes out when fuel filler cap opened.

ShirleyM wrote: ↑Tue Aug 18, 2020 10:11 am Air rushes out when fuel filler cap opened.

Thanks. I think you have found a symptom that would cause the engine to behave as you describe.

I think it is air rushing in
If it was coming out, then it would contain a lot of fuel and would smell like a lot of petrol.


Now you have released the pressure, the engine will run ok. But the fault will return when the pressure is too great for the pump to overcome.

The fuel injectors take fuel from the fuel tank. The fuel removed should be replaced with air from the atmosphere.

What is probably happening is that fuel is being removed but not replaced by air. The fuel tank can only compress so much and at that point no more (not much more) fuel can be removed from the tank for the injectors. So it idles with minimal fuel and won't run when more fuel is needed.

It's going to be a blocked fuel tank breather. It's more that just a breather hole because the petrol evapourants need be recovered back to the tank for the environment. There are valves and charcoal canisters. I would suspect the return purge valve as a suspect to test or change.

Fuel evap system may be your problem causing a negative pressure in the fuel tank, starving the engine of fuel.

Number 2 is an electrovalve and this may be the problem, but really, it needs investigating properly and safely.

Thank you. After releasing pressure the problem remained.

There are a number of components dotted about the engine that the engine ECU can use to detect faults with the engine and not much escapes it's view.
However I agree with Arfur on this one, the fuel system has no monitoring systems on it and so if it fails the engine ECU will not detect a fault.
The first place I would start would be a fuel line pressure test but that requires specialized test equipment.
You could remove the rear lower seat cushion and then the fuel pump cover and listen to see if the pump is running.