Next up: ring job?

you have a problem with air pressure in the block. a clogged breather e.g,

does it do it when its running or sitting still?

If its when its running you have ignition system problems causing weak spark from either bad plugs, the wrong plugs, bad ignition wires, worn distributor cap and rotor, or a weak coil.

This is a bit weird for a 3yr-old engine.

Is there any performance issue, i.e. a fall-off of it compared to when it was new, please?

Whatever the correct diagnosis is, accomplish the repair before running the engine. The fuel is severely reducing the effective lubrication of the engine, and this will result in many damaged internal parts.

Ok, let me ask this for clarity,

Raw gasoline is leaking into the oil? You are finding gas in the oil pan.

I am confused because the ecm has nothing to do with the segregation of fuel, oil, or even coolant in any engine I have ever encountered.

What was the rational for changing the ecm?

GA

Good thoughts and questions, I would have asked the same but you beat ne to it.

Thought, some older engines had a mechanical fuel pump, mounted somewhere on the engine to be moved by some part of the engines innards....theoretically that could be a reason for such dilution....but I don't think so personally.

My thoughts are something that allows fuel to enter the lubricating oil from the bores.

Something like:- Sticking rings, worn rings, broken rings, damaged piston, bad injector, leaky injector, badly calibrated injector, choke on all the time, engine running too cold, engine timed wrongly (mechanical and electrical: Also I have included both petrol and diesel types of possible problems)

Sadly the OP neglected to mention (I do believe) if it was a diesel or a petrol engine, 2 or 4 stroke, water or air cooled, carburetor or injectors.......basic infos....

Yes, a Hyundai H-1 with a Sirius 2.4 litre fuel injected petrol engine.

Well,

After reading all the other posts, I now need to ask if this engine has a mechanical fuel lift pump?

Not really normal to have one on an engine so late-model, but .................

Like Rashavarek and Andy, I can't fathom why the ECM was changed.

For so much raw fuel to get into the crankcase oil via the injection system, it would be black smoking like a bushfire.

Note: Exhaust emissions ARE part of the diagnosis.

Excess petrol into the cylinders will be noticed, especially by those unfortunate to follow.

Need to know about the fuel pump to give you any kind of further sense.

Just a thought.

Fuel could get into the crankcase via a faulty or wrongly connected Carbon vent cannister.

Perhaps the tubing has been wrongly connected and all the venting, (tank etc) is dumping fuel into the cannister and then leaking into the inlet manifold via the vacuum line.

Possible. Probable???

Stu.

Possible that... The mechanic, when replacing the injectors, could have incorrectly connected the Fuel Return Line to a vacuum port.

Hello. Either the petrol is entering the oil via the injectors or not.If we assume not,then you are looking for a rerouting of the fuel through a defective part such as a perforated fuel pressure regulator diaphragm.If the petrol is entering through the injectors then you either have leaking injectors (doubtful since they have been changed) or the injectors pulse width modulation is too long or triggering at the wrong timing. You should have the technician plug a noid (test) light into one of the injectors electrical connector and look for light on at the wrong time.Example : the injectors ground circuit wire to the ECM driver has had the insulation punctured and finding ground thereby keeping the injector on. If this is not the reason for the excessive fuel then look for a sensor which plays a major role in the ECM's calculations for fuel delivery such as a coolant temperature sensor reading a continuous 40 degrees below zero. Hope this helps.

Hello. I will add a note that i assumed that the technician would follow normal procedure and have checked fuel pressure. If not check it.If above spec. this would also cause your condition.A restricted petrol return line will increase pressure. Hope this helps.

Ask a Hyundai mechanic.

Sounds like (because you wrote "but now change, the fuel goes to the oil") the new injectors/ECM appear to have caused the condition. Is this right?

Or was the "now" supposed to be "no," in which case the new ECM and injectors had no influence on the condition and you are out a very large amount of money for no result.

Before doing anything, (and especially before replacing injectors and ECM) it is essential to have the vehicle tested for emissions and fault codes. In modern engines it is almost impossible for the engine to run so rich that oil becomes diluted without codes showing up. But measure the exhaust emissions anyway. Also read the O2 sensor voltages (while leaning out/richening the mixture with a vacuum leak/propane) to see that the response is normal.

Replacing injectors and ECM on a 2010 vehicle is really unusual... unless it is in commercial service and has accumulated 500,000 km. It is also really unusual to replace both at the same time. Perhaps you need to take the vehicle to a shop where they diagnose the problem before replacing parts.

About the only place where fuel can go directly into the crankcase without first going into the cylinders (where you will see symptoms of rich mixture) is through the PCV. The PCV valve is tied into the vacuum system as is the evaporative canister.

Perhaps you are topping up the tank at fuel fillups, instead of stopping after the first auto shutoff? This can flood the evap canister.

You really need a good diagnostician with the vacuum piping diagram and fuel piping diagram in front of him.

Of course, if the engine has a lot of mileage on it, then ring leakage could be so severe that petrol could be diluting the oil. Is the compression up to factory specs?

you can buy new one ...

If you park the bus nose down hill, do you get hydraulic lock in any of the cylinders?

This is where petrol has flooded in and sits on top of the piston and because it's relatively incompressible, when you crank the engine its stops the motor turning.

Lots of times causes mechanical damage, especially bending the connecting rod of that cylinder.

Of course there is some leakage down past the rings and then you get contamination of the lube oil.

Have you had the oil analysed to find out how much fuel is getting into the oil?

Stu.

I recently remembered a problem that gave a similar effect, caused many years ago so I cannot say that its still a problem with modern engines, but very short running, with a cold engine, would/could cause fuel and water to collect in the crankcase......

It may be that with modern engine control that this does not happen anymore......

Years ago I knew of a few people that had this happen, but did not of course know till they went on a long journey and with the resulting (proper) heating of the engine, the fuel and water eventually boil off and cause the oil level to make a sudden drop!!!

I have heard several people who maintain "my car only uses oil on a long run!"........it always made me laugh, though it does cause an engine far more wear and tear......

consider a leaking intake manifold. maybe a partally clogged catalytic convertor or a dirty air cleaner or anything else that won't let the crank case [breath]. the fuel pressure is regulated on fuel injected engines. is it working correctly. has the engine been over heated taking the temper from the rings?