Petrol fumes from THP engine

[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.

[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.

[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.

[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.

[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.

[GiveMeABreak]

So going back to the purge canister:

(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

Reference Designation (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.

"a" Green 2-way connector Channel No. Allocation of channels of connector 1 Control by earthing 2 Supply 12V

The control of the canister discharge electrovalve is of the OCR (opening cyclic ratio) type.

[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.

[xantia_v6]

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

[GiveMeABreak]

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

[xantia_v6]

So going back to the purge canister:

(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

Reference Designation (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.

[xantia_v6]

Time for a belated update on this.

I ignored the problem for a while.

I had previously fitted an oil vapour separator and catch can to clean up the PCV crankcase fumes being fed back into the engine for combustion. I began to notice that the amount of liquid caught by the system was increasing, but it did not have the consistency of engine oil, it was more like 2-stroke petrol, oily but thin and smelling of petrol. The oil in the sump seemed to have normal cosistency and did not have a strong petrol smell. So I concluded that small amount of petrol was getting into the sump, evaporating and being purged through the PCV system.

The only 2 plausible routes for petrol to get into the sump are via a leaking injector and the piston rings, or via a leaking shaft seal on the high pressure fuel pump (more on the construction of the fuel pump later). Neither of these possibilities is easy to investigate, as injector seal kits (needed if removing the injectors for testing) and fuel pumps are very expensive for these engines.

So I ignored the problem for a little longer, just changing the engine oil every month or so.

I ordered a new high pressure fuel pump. It is a lot cheaper and easier to fit than a set of injectors, and I thought that even it it were not the cause of the problem it is a common failure on these engines and it would be a good idea to have a spare. I found that it was significantly cheaper to import a pump from the UK than to buy one locally, but due to disruption of freight transport, it took several weeks to arrive.

While waiting for the new pump to arrive the petrol smell from the engine got much worse. On inspection it was found that the top of the engine was quite oily and a split PCV hose was the cause (this was actually an original piece of hose, not one that I had added when modifying the PCV system). I then found that the crankcase was pressurising due to a blocked filter in the PCV vapour separator I had fitted. The filter element is of a type normally used as a fuel filter on diesel engines. It is not clear whether the filter element was damaged by the petrol fumes, or just not suitable for this application. So I removed the filter element from the oil vapour separator and packed the housing with fine steel wool as an interim (unblockable) filter changed the engine oil again and waited to see what happened next.

The petrol smell came back after a few days, and the PCV catch can was still filling with something looking smelling and feeling like dirty 2-stroke petrol.

To be continued...

[white exec]

Mike, is the suction (low pressure air intake) side of the PCV system working as it should - i.e. enough suction?

Some recent comment too on the small crankcase vapour in-hose heater (on a 2.0i XM), presumably there to discourage condensation of crankcase vapours, and allow them to be inducted and burnt off.

[xantia_v6]

As detailed in my blog (and in some other topics), the 1.6 THP engine (versions up to 175 BHP), were fitted with 2 independent PCV systems, one which uses positive vacuum from the manifold and operates when the engine is of-boost and one which vents to the turbo inlet which only operates when the engine is on-boost. The 200+ BHP engines only have the latter system. I have modified my engine to delete the PCV venting into the manifold, as I am convinced that it is one of the prime causes of the inlet port coking that these engines suffer from. The current system is similar to that which is fitted by PSA to the higher power versions of the engine, but with the addition of a vapour separator and catch can. After removing the blocked filter (described above),, the system is venting as expected.

The problem with petrol fumes started about 3 years after I modified the PCV system and coincided with a sudden increase in the amount of condensate found in the catch can. There have been further developments which i will write up soon.

[xantia_v6]

Note that this post is being made several months after some of the activities described.

So I ordered a replacement high pressure fuel pump from a motor factor in the UK, they had a small stock of genuine pumps which they were selling off at a substantial discount, and even after freight and tax to get one to New Zealand, it was significantly cheaper than the best price I could get here.

Unfortunately, the first UK COVID lockdown hit after I ordered the pump but before it was shipped, and in the confusion, the order was misplaced, and because I was expecting shipping delays, it was over a month before I enquired about its whereabouts, and it then took a further 2 months to arrive.

Even after the pump arrived, I still hesitated before fitting it, as the car was still running perfectly, but still producing petrol vapour in the PCV system. If I had not had the catch-can fitted fitted there would probably have been no symptoms at all.

So a few weeks ago, I finally fitted the new pump and changed the engine oil again. Since then, the PCV catch-can has only been catching (a very little) oil with an even smaller amount of water condensate. So I think it is safe to say that the fuel pump was leaking petrol into the sump.

I then came across some internet videos which purport to show how to overhaul a PSA HPFP (most of these videos made me shudder at the workmanship).
This one (with Portuguese commentary) shows the internal construction of a sectioned pump:

The key thing I learned from the videos is that the chamber behind the seal on the pump shaft is filled with oil, not petrol, so even if the seal is leaking, no petrol should enter the engine. The oil chamber in the pump is sealed, with a little spring accumulator to maintain constant pressure as the oil expands and contracts with temperature, and to allow for a little loss of oil over the life of the pump. Refilling the oil in one of these pumps is apparently quite challenging (there are several techniques shown on youtube, not of which I could recommend).

The petrol and oil chambers in the pump are (primarily) separated from each other by a pair of spring (probably stainless steel) bellows that flex at camshaft speed. It is likely that a fatique crack has occurred in one of these bellows, allowing a little fuel to be pushed into the pumps lubricating oil, which has then been pushed past the shaft seal into the engine.

There is however another twist to this. The pressure accumulator for the lubrication oil has an external hole which allows the position of the diaphragm to be measured, giving an indication of whether the oil chamber has been breached. I have measured this on my faulty pump, and the measurement is 18 mm, which is apparently exactly where it should be. This seems to be a strange coincidence.

[gwest]

On my 2013 THP155 (DS5, 82,000 km) I get 5 times as much liquid collecting in the catch can on the circuit going to the inlet manifold than in the other catch can on the line going into the turbo intake. The liquid is the colour of used oil but much less viscous, and separates out a clearer layer at the bottom. I am collecting the equivalent of about 340 ml per 10,000 km from both cans. My current thinking is that blocking off the line going to the intake manifold may not be a good thing, but I would have difficulty justifying this. What I do have in common with you is an acrid smell coming from the engine noticeable mainly in the garage after the car has been switched off, but which I can also smell at times when stationary in traffic. But it does not smell like raw petrol. I did have a problem with the O-rings becoming exposed on the ~19mm connector on the small pipe joining into the turbo intake pipe. I am assuming the other end of this pipe goes to the LHS of the intake manifold (?) - it disappears down the back of the engine. I have bodged up a solution to this problem and the smell has lessened, but I also found that my SAAS catch can on the other side, that is subject to turbo boost, appears to have leaked past the O-ring seal in its cap. If I could find a 19mm one-way valve I would fit it between the intake manifold and the catch can to stop it being pressurized. However, if fitting a new HPFP has fixed your smell problem then my situation probably has no relevance.