Engine oil smells of petrol!😱

[Danny172]

Hey all…..back again!!
Whilst going through the rather emotional turmoil of trying to obtain another years mot, whilst doing checks, I noticed the engine oil has a very pungent odour of fuel…reminds me of old 2 trike mix!
The oil in the car is roughly 1500 miles old and was replaced last June.
To be fair the car does only get used once a fortnight, but the runs I give it are well over 20 miles each time, mainly dual carriageway!
I do suffer with a lump idle, and my initial thought was injectors.
There is no smoke, and no fumes in the engine bay, or in the car.
I pulled the plugs (again replaced last June and 1500 miles) and they are all equal and remarkably spotless…no carbon or soot whatsoever! They weren’t wet, or smelling of fuel either.
I’ve changed the oil again, and it does smell of fuel again?
It it possible for the fuel injectors to leak whilst the car is idle, but perform without issue when running?
Again there is no trouble starting, starts instantly, and plenty of power on the go?
Any ideas greatly appreciated!

 

[NZ00Z3]

What engine do you have?

It could be a leaking injector. Fuel dripping into the cylinder while the engine is off and going past the piston and into the oil sump/pan.

Ways to check include:

• What the the total fuel trim at hot idle for each bank? Total fuel trim = STFT + LTFT. If it's negative at idle but positive above idle, then that indicate that more fuel than is required is being injected at idle.
• Do a fuel pressure test and a residual pressure test (see below). If the residual test fails, it is likely due to the leaking injector
• Pull the fuel rail and injectors. Set the rail up with the injectors correctly fitted but clear of the engine. Turn the key to position 2 to prime the fuel rail and watch for a leaking injector.

Fuel Pressure Testing
All 6 cylinder engines except the S54 and the M56. Set up the fuel pressure gauge on the Schrader Valve on the fuel rail. Key in position 2 to prime the fuel rail.

• Fuel pressure 3.5 +/- 0.2 bar or 50.76 +/- 2.9 PSI
• Residual fuel pressure after 20 minutes - Fuel pressure >3 bar or >43.51 PSI

 

[Danny172]

What engine do you have?

It could be a leaking injector. Fuel dripping into the cylinder while the engine is off and going past the piston and into the oil sump/pan.

Ways to check include:

• What the the total fuel trim at hot idle for each bank? Total fuel trim = STFT + LTFT. If it's negative at idle but positive above idle, then that indicate that more fuel than is required is being injected at idle.
• Do a fuel pressure test and a residual pressure test (see below). If the residual test fails, it is likely due to the leaking injector
• Pull the fuel rail and injectors. Set the rail up with the injectors correctly fitted but clear of the engine. Turn the key to position 2 to prime the fuel rail and watch for a leaking injector.

Fuel Pressure Testing
All 6 cylinder engines except the S54 and the M56. Set up the fuel pressure gauge on the Schrader Valve on the fuel rail. Key in position 2 to prime the fuel rail.

• Fuel pressure 3.5 +/- 0.2 bar or 50.76 +/- 2.9 PSI
• Residual fuel pressure after 20 minutes - Fuel pressure >3 bar or >43.51 PSI

Thanks for the info! I’ll give it a go

 

[Danny172]

I’ve just realised I’ve posted in the wrong category…it’s only 1.9 16v

 

[NZ00Z3]

I’ve just realised I’ve posted in the wrong category…it’s only 1.9 16v

I did wonder?

Maybe ask the admin @GazHyde to move the thread to the right place?

 

[Mike Fishwick]

I have seen this problem on BMW motorcycles, where the diaphragm of the fuel pressure regulator has become porous. Fuel consumption does not seem to suffer, or performance, but the engine oil smells of petrol. testing is difficult - except by substitution - but a check on the time the system holds pressure after the engine is stopped my show something.

 

[Danny172]

I have seen this problem on BMW motorcycles, where the diaphragm of the fuel pressure regulator has become porous. Fuel consumption does not seem to suffer, or performance, but the engine oil smells of petrol. testing is difficult - except by substitution - but a check on the time the system holds pressure after the engine is stopped my show something.

Thanks for the reply, definitely worth looking at!
Would I be right in thinking that I would smell fuel in the vacuum line to the regulator?

 

[Mike Fishwick]

Maybe - give it a try. A large hypodermic would be a good way to pull a vacuum in the regulator.

 

[Danny172]

Thanks mike
I’ve just spoken to an ex bmw tech and he says the same, as in the fuel regulator.
The worrying thing is I’ve just looked online and the are scarce and seem expensive to say the least!