Fuel Dilution issue- how to analyze??

[Russell]

I just had Blackstone labs do an oil analysis on my 95 BMW 525I using Mobil 1 0w40, changed at 3,700 miles, 104,000 miles on the car. I was worried because the oil was getting dark very quickly.

The analysis was fine except in two areas. 23 PPM lead (considered high) and one percent of the oil was composed of fuel. The analysis indicated that my engine is running a bit rich and diluting the oil causing oil shearing. The shearing then placed stress when I really punched the engine, thus wearing the main and crank bearings.

My question for the experts revolves around the fuel issue. What is causing fuel in the oil? I was advised to look at several items. Replace the air filter (last replaced 17,000 miles ago), check fuel injectors for leaking and coils for malfunction. Both the injectors and coils are believed to be original. Oxygen sensor is another possibility. It was replaced 49,000 miles ago. Plugs have been in for 24,000 miles.

What do you think? Are there other items I should check/replace?

TIA

[Russell]

Anyone? :)

[Bill R.]

1 incomplete combustion or too rich mixture... You would notice this in the performance most likely. This would be related to the ignition coil, spark plugs wires, dist cap, crank pos. sensor or dme controlled dwell and spark.
2 . Leaking injectors, to me one of the more likely causes, but there are usually signs that thats happening , such as hard starting on a hot soak sometimes. Where you have to crank awhile to clear it out before it starts. You can check the injectors for leakage to confirm this.
3 Your crankcase ventilation system is blocked or is not working for some other reason.
4 Vapor canister, or valve is bad pulling too much vapor into the engine.
5 Temp sensor or O2 sensor giving the dme faulty info making it run too rich
6. Maf sensor giving a faulty reading.
Or have you run some injector cleaner through the engine or any other type of cleaner and not changed the oil, this will raise the level also

[Russell]

I suspect #2 I think I have had this situation especially if I start the car, run briefly and turn off and then start it a few minutes later. The car will crank awhile and run rough. Is this waht you mean? Perhaps related, occasionally upon a cold start it will "cough" and then start when I crank again.

I also suspect 3 or 4. I do know I had a ventilation hose go bad and it was replaced. How do I check? Also the vapor canister and valve are original. How do I test?

BTW, No injector cleaner etc was used on this oil change. However, I have used Techron additive in the past and generally use Chevron Surpreme 93 gas.

Thanks Bill, Your help is outstanding.



1 incomplete combustion or too rich mixture... You would notice this in the performance most likely. This would be related to the ignition coil, spark plugs wires, dist cap, crank pos. sensor or dme controlled dwell and spark.
2 . Leaking injectors, to me one of the more likely causes, but there are usually signs that thats happening , such as hard starting on a hot soak sometimes. Where you have to crank awhile to clear it out before it starts. You can check the injectors for leakage to confirm this.
3 Your crankcase ventilation system is blocked or is not working for some other reason.
4 Vapor canister, or valve is bad pulling too much vapor into the engine.
5 Temp sensor or O2 sensor giving the dme faulty info making it run too rich
6. Maf sensor giving a faulty reading.
Or have you run some injector cleaner through the engine or any other type of cleaner and not changed the oil, this will raise the level also

[Bill R.]

would have done it right there. The crankcase ventilation system depends on a vacum to pull all the vapors out of the crankcase, if there's a break or any vacum leaks such as a loose oil filler cap or bad gasket then the crankcase system can't scavenge the ways its designed to.
To check the injectors for leakage bmw shows the test procedure in the tis If i recall correctly. Their test is to pull the fuel rail and all the injectors as one unit and block off the return line on the fuel rail and attach a air line to the supply line, then immerse the rail an injectors in a bucket or trough of water. Apply shop air to about 35psi and observe the injectors for any bubbles They say that anything over 2 bubbles in 20 seconds should be replaced. You can have them cleaned too and check them after that.






I suspect #2 I think I have had this situation especially if I start the car, run briefly and turn off and then start it a few minutes later. The car will crank awhile and run rough. Is this waht you mean? Perhaps related, occasionally upon a cold start it will "cough" and then start when I crank again.

I also suspect 3 or 4. I do know I had a ventilation hose go bad and it was replaced. How do I check? Also the vapor canister and valve are original. How do I test?

BTW, No injector cleaner etc was used on this oil change. However, I have used Techron additive in the past and generally use Chevron Surpreme 93 gas.

Thanks Bill, Your help is outstanding.

[Russell]

Not sure this is the problem, as I believe I get a vacum leak when I pu;l the dipstick or open the oil filler cap as the engine runs rougher.

Looks like I will need my indy to do a fuel Injector test.

Back to the crankcase vent system. Is there a way to test the canster and valve? Want to sure since they are about $70-$90 for both.

Thanks again.


would have done it right there. The crankcase ventilation system depends on a vacum to pull all the vapors out of the crankcase, if there's a break or any vacum leaks such as a loose oil filler cap or bad gasket then the crankcase system can't scavenge the ways its designed to.
To check the injectors for leakage bmw shows the test procedure in the tis If i recall correctly. Their test is to pull the fuel rail and all the injectors as one unit and block off the return line on the fuel rail and attach a air line to the supply line, then immerse the rail an injectors in a bucket or trough of water. Apply shop air to about 35psi and observe the injectors for any bubbles They say that anything over 2 bubbles in 20 seconds should be replaced. You can have them cleaned too and check them after that.

[Russell]

The vacuum at the oil filler cap seems higher (better pull/suction on thin plastic) after replacing the large crankcase hose.

Is there a simple way to test the vapor canster and valve? Want to be sure since they are about $70-$90 for both parts,

TIA

[Derek A.]

BMW's ( particularly the M50) run very rich at startup. Its no uncommon for one to not restart after its run for a short period of time on a cold morning. There is so much fuel flowing into that engine that it washes the oil away from the rings and reduces engine compression. If you are doing a lot of short haul driving in the winter time and are running an oil as thin as 0w40 you are probably going to see more fuel in the oil. Unless you are having a driveabilty or starting problem I would leave the motor as is, maybe run some injector cleaner through it as Bill suggested.

[Russell]

I use the car for my daily commute of about 30 miles each way on two lane fairly open roads. Very few short trips. However I have noticed if I, for example, start the car and back out of garage, turn off and then start it a few minutes later, it starts harder and runs rough for a minute or so. Has done this as long as I have owned it. 2 years and about 35,000 miles.

By the way, I am starting to run Fuel Power, 1 oz per 5 gallons, by Lube control in every tank of gas. I swear the car runs smoother. It was recommended by Blackstone labs/Terry Dyson to help ensure clean injectors without impacting the oil like an additive like Techron can. Just a FYI.


BMW's ( particularly the M50) run very rich at startup. Its no uncommon for one to not restart after its run for a short period of time on a cold morning. There is so much fuel flowing into that engine that it washes the oil away from the rings and reduces engine compression. If you are doing a lot of short haul driving in the winter time and are running an oil as thin as 0w40 you are probably going to see more fuel in the oil. Unless you are having a driveabilty or starting problem I would leave the motor as is, maybe run some injector cleaner through it as Bill suggested.