Fuel contamination

[JerzyGeorge]

I would like to share fuel contamination problem I did learn about yesterday.

 

One diligent pilot noticed oil level going up !!

 

And it was real no imagination.

 

Subsequent investigation pointed it out to fuel contamination by diesel fuel.

 

The same was observed in petrol driven cars using fuel from the same bowser.

 

So not only low oil level is a problem .

 

 

[SDQDI]

Jerzy my brain isn't working particularly sharp tonight so I was wondering if you could elaborate a little for me.

 

Was the diesel in the oil? Or did the petrol have diesel in it?

 

As a side note we had a small engine stop on us the other day and when I drained the carby all I got was water, so I drained the tank and got over a cupful of water out of it as well. I couldn't work it out for ages but it finally clicked when I drained the jerry can into a clear jug and had 4 litres of fuel and 1 litre of water, I had been using that jerry can for the mower at home and I always leave the lids a little loose to prevent the build up of pressure and it just so happened that the kids had been playing with the garden hose so after a gentle questioning session it was revealed they helped daddy by filling up his fuel container with water:doh: so anyway they got their first introduction to small engine maintenance (gently of course!) and they now understand that water isn't quite the same as fuel:thumb up: so hopefully that won't be a repeated problem.

 

 

[Yenn]

Now you can see why part of the preflight is to sample the fuel. then smell the sample to ensure it is fuel, not all water. If you don't like smelling it, just tip it out and make sure it evaporates, if it is supposed to be petrol.

 

 

[kgwilson]

The same thing happened to me years ago when the refueller put diesel in the petrol tank at our company garage by mistake. I checked the dipstick a few days after filling up with what I thought was petrol & the oil level was over the full mark. The car was still running OK but I was concerned & told our maintenance guy & a few days later all was revealed

 

 

[JerzyGeorge]

Jerzy my brain isn't working particularly sharp tonight so I was wondering if you could elaborate a little for me.Was the diesel in the oil? Or did the petrol have diesel in it?

 

As a side note we had a small engine stop on us the other day and when I drained the carby all I got was water, so I drained the tank and got over a cupful of water out of it as well. I couldn't work it out for ages but it finally clicked when I drained the jerry can into a clear jug and had 4 litres of fuel and 1 litre of water, I had been using that jerry can for the mower at home and I always leave the lids a little loose to prevent the build up of pressure and it just so happened that the kids had been playing with the garden hose so after a gentle questioning session it was revealed they helped daddy by filling up his fuel container with water:doh: so anyway they got their first introduction to small engine maintenance (gently of course!) and they now understand that water isn't quite the same as fuel:thumb up: so hopefully that won't be a repeated problem.

Yes the diesel was mixed with petrol . Looking at it you could not notice. We did a simple test: poured 200 ml of suspect fuel on the clean concrete and clean fuel close to it ( the same volume) . The suspect sample evaporated slower and left oily residue while clean sample evaporated quicker with no stain.

The fuel came from local service station and owner sent sample for testing. The results should be available next week , for a time being this particular tank is locked out.

 

 

[JerzyGeorge]

Thanks guys for valuable comments, specially the one pointing out a chance of having test tube full of water without any petrol in it.

 

I avoid refuelling in wet or foggy weather, try to do it only when is dry and sunny, sometimes a bit of mission in Tasmania.

 

 

[RichTee]

Hey JerzyGeorge,

 

You did not mention where this was.....I ask as ours syndicate (in Zim) is going through this exact issue at the moment....our 912ULS making oil in our Savannah S.

 

Is this another case...or are we the ones you are referring to ?

 

I will share our story shortly once we know a little more as our AMO (who is a v good!) is working on her at this very minute.

 

Fuel assay results indicated 3% diesel contamination in our fuel.

 

As part of our pre-flight we always pull a sample from the gascolater...check color, look for water and sniff....with this level of contamination it is /was impossible to see/smell.

 

Have a look at this thread:-

 

http://www.manualslib.com/manual/846518/Rotax-914-Series.html?page=105

 

Regards,

 

Rich

 

 

[JerzyGeorge]

Hi Rich,

 

This has happened in Tasmania, it looks to me like slopy tanker driver left a bit of diesel in the "empty" tank or in the fuel lines.

 

Some people do not appreciate how important is to keep fuel clean. Disapointing that it happened to expensive 98.

 

you are right such a small contamination is not possible to detect visually.

 

Regards

 

George

 

 

[facthunter]

Quite a serious problem. It will totally ruin the larger turbo charged engines and probably a jabiru . Buy fuel from a trusted high volume source only or use avgas where appropriate. Nev

 

 

[rhtrudder]

So does the diesel somehow get past the rings not being burnt during combustion

 

 

[facthunter]

It has a very high flashpoint. Diesels often have oil level rise due DILUTION of the lube oil by the fuel. probably running cooler than optimal may worsen the effect. Nev

 

 

[Farley]

Hi all. Compliments of the season to you.

 

Re the rising oil level..... In my motor biking days I always looked at the gearbox level before riding. The small round glass window on the clutch cover had a top and bottom line marked. If the oil level rose from center to upper line I knew that the needle and seat in the carb was leaking and petrol was flowing down the carb rubbers past the rings in to the sump. Bikes to day have a vacuum petrol tap so you cannot rotate the tap to the off position.

 

I also fill up with petrol before the pre-flight, my thinking is by the time I get to the fuel check which is usually the last thing I check, I'm guessing that any water by then would have had time to settle to the drain.

 

 

[RichTee]

Hi Farley,

 

You are 100% right....there are (from my research) 3 possible reasons....which may be interlinked...for instance problem #2 could lead to a deterioration of the carb components such that problem #3 becomes the "issue". Like-wise the thinning of the oil could CAUSE excessive wear leading to problem #1.

 

1. Rings are shot (compression tests will reveal this)

 

2. Diesel (or other non combustible contaminants) in the fuel

 

3. Snag with the carb(s) leaking fuel...at rest..through the manifold. Then...if the engine stopped with the intake value open on the 1st cylinder after the carb with an issue one could see fuel leaking into the cylinder...past the rings and into the oil.

 

In the high wing Savannah where the POH stipulates leaving the fuel tap ON...this means the needle is effectively working as the fuel shut-off....something the ROTAX manual says is not standard.

 

Anyway the jury is still out for us as the AMO has not managed to check her out this week. His plan is to bore-scope and see whats going on...then inspect the carbs etc.

 

Interestingly we KNOW our fuel has 3% diesel contamination. So option #2 jumps to the top suspect...However we note that since the oil was changed (when we 1st noticed this)....she did 4 hrs (that is 80 odd ltrs = 2.4lts of diesel) and there was NO CHANGE to the oil level. Then a 5th hr was done...and 3 days later the oil was up by an estimated 500 to 750ml. This would then support suspect #3 being the issue....since if it was contamination one would have seen a linear increase. Considering the same fuel source has been used for all 5 hrs.

 

Will update you all once we know more.

 

Cheers,

 

Rich

 

 

[planesmaker]

You will find that a carb leaking will not fill a cylinder while standing, reason being gravity, yes the 912 intake manifolds rise up quite significantly after the carbs, fuel would run out the filters first or the bowl breather/overflow. Probably find broken rings due to old or poor quality fuel. How does the compression feel when turning it by hand?

 

 

[RichTee]

Hi,

 

Yes....we have been arguing that point here too...but looking at the picture below I recon fuel CAN flow into the manifolds then into the cylinders through an open valve...have a look at the level of the over-flow pipe and the level of the manifold:-

 

 

 

[planesmaker]

Yes exactly as I said, pull the airbox off and look thru the Carby it can't flow into the engine.

 

 

[rhtrudder]

We had it happen on a savannah and it ran back into the air box

 

 

[RichTee]

Hi rhtrudder,

 

Funny you should mention that but we noted evidence of fuel having been in the air box too.....I had omitted that from my posting ...sorry it was a critical point.

 

When this is all said & done I'm quite keen to open a debate on the wisdom of having the fuel tap locked on.

 

Cheers,

 

Rich

 

 

[Blueadventures]

Hi rhtrudder,Funny you should mention that but we noted evidence of fuel having been in the air box too.....I had omitted that from my posting ...sorry it was a critical point.

When this is all said & done I'm quite keen to open a debate on the wisdom of having the fuel tap locked on.

 

Cheers,

 

Rich

Hi Rich and others

 

Maybe the fuel tap is on to allow for expansion of fuel in the collector tank. I have the savannah 6 litre collector / surge tank in my Nynja. Its fed from wing tanks and I turn the fuel valves off after each flight. I have the inline glass filters fitted on the engine side of the fuel tank valves and a couple of times they have been leaking when I turn on the fuel valves. A cause for this may be that fuel is pressurizing somewhat in the mostly closed fuel system during the heat of the day. I'm still working on this issue; its not a big problem at present as I just tighten the fuel filter ends so they firm up on the end seals.

 

Cheers

 

Mike

 

 

[rankamateur]

it was revealed they helped daddy by filling up his fuel container with water:doh:.

At about the same age I used to help my Daddy by turning the little knobs on his rifle scope, and listen to the clicks.

 

 

[RichTee]

Dear All,

 

Right....the AMO had noted a slight drop of compression on #3 cylinder (still within limits)...and suspected that the fuel was coming through the right hand carb and into that cylinder...washing off the oil and resulting in lower compression. He used the bore-scope and was able to SEE the fuel (at rest)

 

Hi Rich and othersMaybe the fuel tap is on to allow for expansion of fuel in the collector tank. I have the savannah 6 litre collector / surge tank in my Nynja. Its fed from wing tanks and I turn the fuel valves off after each flight. I have the inline glass filters fitted on the engine side of the fuel tank valves and a couple of times they have been leaking when I turn on the fuel valves. A cause for this may be that fuel is pressurizing somewhat in the mostly closed fuel system during the heat of the day. I'm still working on this issue; its not a big problem at present as I just tighten the fuel filter ends so they firm up on the end seals.

Cheers

 

Mike

Hi Mike,

 

Thanks for that...just wondering...would the fuel in the 6ltr collector tank not expand back up the pipe to the inner tanks (which are vented) ?

 

Considering that the Savannah main fuel tap is between the 6ltr tank and the carbs...and its an open system between the 6lt tank and the inner wing tanks.

 

Regards,

 

Richard

 

 

[planesmaker]

I would think the fuel collector/header tank should have a breather back to the tank system

 

 

[planesmaker]

How much did your oil level rise by? Got to be coming from somewhere. I would be pulling #3 cylinder to check for ring damage. Like I said it can't run uphill from the Carby , the airbox is lower the the inlet manifold.

 

Sent you a PM

 

Tom

 

 

[Blueadventures]

I would think the fuel collector/header tank should have a breather back to the tank system

Hi have two 10mm feeds (one from each wing tank) into collector and any air escapes up these delivery lines; one to each tank. Working fine past 35 hours. Regards

Mike

 

 

[rhtrudder]

Hi rhtrudder,Funny you should mention that but we noted evidence of fuel having been in the air box too.....I had omitted that from my posting ...sorry it was a critical point.

When this is all said & done I'm quite keen to open a debate on the wisdom of having the fuel tap locked on.

 

Cheers,

 

Rich

I once had the fuel drain from one tank across to the other then out the breather on the cap because I parked it on the side of a hill I just landed on,drained the whole tank, wasn't on much of a lean either this was on a Savannah , but still warey of leaving the taps off