Petrol fumes from THP engine

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xantia_v6
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Re: Petrol fumes from THP engine

Post by xantia_v6 »

I learned something today...

Engine oil (often?) has florescent dye in it when you buy it. The dye that I was seeing in the induction system was the same beige as the dye in the container that the oil came from, which fortunately is a bit different from the orange in the dye that I put in the petrol tank. The oil that I have bought for the next change has a bright blue florescent dye in it.

I did pull the top cover off of the engine and checked for traces of orange dye around the fuel pump seal, but did not detect any.

So overall, I am no closer to finding the leak. The next task (after cleaning and reassembling the top end of the engine) is to get underneath and drop the exhaust so that I can see the bottom of the injectors and fuel rail.

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Re: Petrol fumes from THP engine

Post by GiveMeABreak »

Having had a quick look at the handbook and instrument info for your car Mike, with the exception of TPMS which you don't have as you said, the only other internal warning lamp that would display a 'pressure' warning / message with the word 'pressure' is the 'Engine oil pressure' warning lamp and message. So maybe not a coincidence.....

Just supplementary, the Fuse F5 in the Engine Fuse Box controls the Purge canister, turbine discharge and Turbo pressure regulation electrovalves (1.6L THP), oil vapour heater (1.6 litre THP) for your vehicle.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

I jacked the car up and tried to look from below for dye on the injectors or fuel rail, but it is impossible to see anything without an endoscope (which I don't have here). There is no sign of general splatter of dye, which I expected to see if there was a leak from the high pressure fuel system.

It also occurred to me that there would probably be no dye released if the leak is from the vapour recovery system, as the dye would not be evaporating. So my current test is to disconnect the pipe from the carbon canister to the vapour purge valve, and run a temporary hose to discharge the vapour underneath the car. I have taken the car for a short drive, and it seems to have improved matters. I will drive it further tomorrow to verify.

Does anyone know more about the vapour purge valve? It is a 2-way valve that connects the carbon cannister either to the intake manifold or the turbo inlet, presumably switching to the latter when there is a positive pressure in the manifold. I presume also that the valve closes both ports when the engine is stopped, but don't know how to test it.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

I bought a few parts on ebay to eliminate some things, but due to disruptions in the shipping chain they took a couple of months to arrive.

So I have now changed:
  • The feed pipe to the high pressure pump (this was the pipe with the apparent cut or split in it)
  • The vapour purge valve (including the hose to the manifold and to the turbo air inlet)
The fuel smell is still there... sometimes...

When driving the car from cold, there is no fuel smell until the car has been driven about 5 km, and then it seems to appear when accelerating from low speed.
After stopping the car for 5 minutes and restarting, the smell is often very strong, but perhaps only after the first such stop in the day.

Neither of these symptoms seems to make sense given the design of this system.

Does anyone here have experience of removing the fuel rail on one of these BMW/PSA direct injection engines? Can the fuel rail be removed without disturbing the injectors? Replacing the injector to head seals is a job I would rather avoid.

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Re: Petrol fumes from THP engine

Post by GiveMeABreak »

Hadn’t seen your previous to last post Mike, otherwise I would of had a look for you.

I’ll now look at both the questions and put something up for you as soon as.

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Re: Petrol fumes from THP engine

Post by GiveMeABreak »

So going back to the purge canister:
Mike Cannister A.PNG
Mike Cannister B.PNG
(1) canister discharge electrovalve.
"a" Green 2-way connector.
"b" Inlet for petrol vapours.
"c" Outlet of the petrol vapours towards the inlet manifold.
"d" Outlet of the petrol vapours towards the turbocharger air inlet.
Supplier: FREUDENBERG.
(2) Magnetic core.
(3) Return spring.
(4) Magnetic winding.
(5) Valve.
When the canister discharge electrovalve is supplied, the magnetic coil (4) attracts the magnetic core (2) which pushes on the valve (5).
The fuel contained in the canister can then be drawn into the inlet manifold.
When the canister discharge electrovalve is no longer supplied, the return spring (3) pushes back the valve (5), which stops the discharging of the canister.

Operation
Mike Cannister D.PNG
ReferenceDesignation
(1)turbocharger
(2)Motorised throttle
(3)Purge canister solenoid valve
(4)Fuel vapour absorber
(5)Canister
(6)Engine ECU
Key

"A" Electrical links
"B" Air inlet
"C" Fuel vapours
"D" Fuel
When the engine is switched off, the canister discharge electrovalve is closed: The canister absorbs the petrol vapours coming from the tank.

When the engine is running, the engine management ECU estimates the load in the canister by progressively opening the canister discharge electrovalve in order to measure the change in the richness of the air/fuel mixture admitted into the engine.

As the engine management ECU knows the output of the canister discharge electrovalve, it uses this to deduce the load in the canister.

The engine management ECU reduces the injector flow and controls the canister discharge electrovalve to obtain the overall quantity of fuel to be injected into the engine.

The control of the canister discharge electrovalve corresponds to a percentage discharging of the canister which varies in accordance with the engine speed and the engine load.

The engine control ECU controls the motorised throttle unit to obtain a vacuum in the inlet manifold.

When the canister discharge electrovalve is open, the vacuum in the inlet manifold permits the drawing in of the vapours stored in the canister.

The use of a second take-off upstream of the turbocharger permits bleeding during the turbocharging phase. The upstream take-off is ineffective when the overpressure is created.
Mike Cannister C.PNG
"a" Green 2-way connector
Channel No.Allocation of channels of connector
1Control by earthing
2Supply 12V
The control of the canister discharge electrovalve is of the OCR (opening cyclic ratio) type.

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Re: Petrol fumes from THP engine

Post by GiveMeABreak »

As far as the fuel rail is concerned, the operation for replacing the injectors would indicate that they come off with the rail initially, and are then removed afterwards.

If you want the removal process let me know.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

I have the removal process, just not the special tools required to size the teflon seals...

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Re: Petrol fumes from THP engine

Post by GiveMeABreak »

Yes I think it's part of the larger engine tool kit for these engines.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

GiveMeABreak wrote:
30 May 2020, 23:56
So going back to the purge canister:
ImageImage
(1) canister discharge electrovalve.
"a" Green 2-way connector.
"b" Inlet for petrol vapours.
"c" Outlet of the petrol vapours towards the inlet manifold.
"d" Outlet of the petrol vapours towards the turbocharger air inlet.
Supplier: FREUDENBERG.
(2) Magnetic core.
(3) Return spring.
(4) Magnetic winding.
(5) Valve.
When the canister discharge electrovalve is supplied, the magnetic coil (4) attracts the magnetic core (2) which pushes on the valve (5).
The fuel contained in the canister can then be drawn into the inlet manifold.
When the canister discharge electrovalve is no longer supplied, the return spring (3) pushes back the valve (5), which stops the discharging of the canister.

Operation
Image
ReferenceDesignation
(1)turbocharger
(2)Motorised throttle
(3)Purge canister solenoid valve
(4)Fuel vapour absorber
(5)Canister
(6)Engine ECU
Key

"A" Electrical links
"B" Air inlet
"C" Fuel vapours
"D" Fuel
When the engine is switched off, the canister discharge electrovalve is closed: The canister absorbs the petrol vapours coming from the tank.

When the engine is running, the engine management ECU estimates the load in the canister by progressively opening the canister discharge electrovalve in order to measure the change in the richness of the air/fuel mixture admitted into the engine.

As the engine management ECU knows the output of the canister discharge electrovalve, it uses this to deduce the load in the canister.

The engine management ECU reduces the injector flow and controls the canister discharge electrovalve to obtain the overall quantity of fuel to be injected into the engine.

The control of the canister discharge electrovalve corresponds to a percentage discharging of the canister which varies in accordance with the engine speed and the engine load.

The engine control ECU controls the motorised throttle unit to obtain a vacuum in the inlet manifold.

When the canister discharge electrovalve is open, the vacuum in the inlet manifold permits the drawing in of the vapours stored in the canister.

The use of a second take-off upstream of the turbocharger permits bleeding during the turbocharging phase. The upstream take-off is ineffective when the overpressure is created.
I had a play with the purge valve that I removed (now presumed to be OK), and it has an interesting characteristic, with the valve not energised, it blocks all airflow (in either direction) at port 'b' (the canister port), but allows some airflow between ports 'c' and 'd'. If you blow or suck hard on ports 'c' or 'd' the valve either closes or oscillates like a squeaky toy. Even with the explanation highlighted in red above, it is not easy to understand the intended operation.