Petrol Contaminated Oil

[Grim.Badger 15]

I've been having oil problems for a while now and I've just drained the oil and it stinks of petrol . The car overfueled when I put super unleaded in, could the petrol be from this? Is there any way of stopping this other than getting the car retuned to super unleaded?

 

Cheers

[aw11_hgt 0]

What do you mean by overfuelled? Are you sure its not over fuelling due to cold start issues?

[steve@cornwall 100]

I've been having oil problems for a while now and I've just drained the oil and it stinks of petrol . The car overfueled when I put super unleaded in, could the petrol be from this? Is there any way of stopping this other than getting the car retuned to super unleaded?

 

Cheers

 

Don't have a "boost" valve by any chance?

[Grim.Badger 15]

What do you mean by overfuelled? Are you sure its not over fuelling due to cold start issues?

 

I'm not sure really, I think I mean that it runs really rich, fuel systems are a bit of a black art to me What happens is that if I put superunleaded in the car sounds c**p, gets poorer mpg and stinks of badly burnt petrol. I'm fairly certain that the previous owner, for some unknown reason, had the car tuned to 95ron unleaded

 

But the point is that for some reason the car is dumping petrol into the oil and I need to stop it as I'm sick of having to change my oil reularly because it's either gone too thin, or has leaked out of all the seals. It can't be good for the engine and it's certainly not good for my wallet

[steve@cornwall 100]

I've been having oil problems for a while now and I've just drained the oil and it stinks of petrol . The car overfueled when I put super unleaded in, could the petrol be from this? Is there any way of stopping this other than getting the car retuned to super unleaded?

 

Cheers

 

try searching "ecu temperature sender"

[Grim.Badger 15]

try searching "ecu temperature sender"

 

I don't thnik it's that as the car idles well with both fuels, either hot or cold. It's never cut out and I haven't seen it smoke at all. It just sounds very rattly with superunleaded.

The idle is slightly uneven but first two intake pipes (front to filter and filter to afm) are badly cracked and patched with gaffer tape so I think the slightly uneven idle is down to them. The car also kangaroos much more on superunleaded than 95ron.

 

I just don't understand why the car would dump fuel in the sump, my old diesel returned it to the pump

[pug309twin40s 1]

sounds like the dizzy timing has been retarded for unleaded and when your putting in super unleaded the car is pinking. adjust the dizzy timing to see if the stops the tapping noise.

[Ahl 4]

How many miles has the car done?

What happens is that if I put superunleaded in the car sounds c**p, gets poorer mpg and stinks of badly burnt petrol. I'm fairly certain that the previous owner, for some unknown reason, had the car tuned to 95ron unleaded

That sounds very strange. Super shouldn't make much noticeable difference over normal UL, even if the timing was retarded for it.

I don't thnik it's that as the car idles well with both fuels, either hot or cold. It's never cut out and I haven't seen it smoke at all. It just sounds very rattly with superunleaded.

The car can idle fine, no smoke, but still overfuel. You should try the temp sensor anyway as it probably needs replaced even if its not the cause of this problem.

The idle is slightly uneven but first two intake pipes (front to filter and filter to afm) are badly cracked and patched with gaffer tape so I think the slightly uneven idle is down to them. The car also kangaroos much more on superunleaded than 95ron.

Those cracks shouldn't make any difference to idle, only air leaks after the AFM.

Kangarooing is a common problem with a few causes, but its not normally linked to petrol rating.

sounds like the dizzy timing has been retarded for unleaded and when your putting in super unleaded the car is pinking. adjust the dizzy timing to see if the stops the tapping noise.

You should try setting the timing properly as it will overfuel slightly if its too far retarded. That advice is the wrong way round though, you get pinking when the timing is too far advanced for the lower octane petrol your using.

 

 

Overall, your petrol in the oil problem is a strange one and you should probably try to look at it seperately from any of the other problems which may not even be linked to it.

 

From my understanding you'd only get a problem with petrol in the oil if your piston rings were buggered (how many miles has the car done - is the oil pressure very high?) or if the car was chronically overfuelling, though this would normally only be acheived with the use of badly set carbs.

Even still, as a starting point you should try fitting a new ECU temp sensor and setting the timing to the optimum.

[steve@cornwall 100]

Had oil / petrol contamination really badly on three "rescue-project" cars- one was a broken wire (white one) on the afm+smoked terribly! other was wire off temp sensor- this was bad enough to make it a non-starter. Third one had the reversing light switch plug plugged into the diagnostic socket!!!!! The first two would lead me to believe that a gradual breakdown in either the temp sensor or afm would cause contamination to a lesser degree?

[Grim.Badger 15]

The car has done 107k and I have no record of any engine work, although I have no real record of anything as the service history is about as far away from full as you can get. The engine does have a W painted on the back though which suggests it's been out of the car at some point

Oil pressure is low most of the time and very low at other times, but seeing as the petrol thins the oil it's not much of a surprise. It's worst at idle when the engine is at full temp (cooling fan engaged) as the idle doesn't turn the pump fast enough to maintain oil pressure because the oil is so thin

I'll try and get a compression test, retune and new temp sensor next month to try and sort some of this.

 

Edit: I forgot, the previous owner claims to have changed the HG and water pump at around 95k.

Edited May 29, 2006 by Grim.Badger

[smckeown 1]

I had the oil changed the other day while having some other work, and there was a lot of fuel in my oil apparently. As the engine and sensors are new plus it's been setup on the RR this is worrying. I dont want to have to change the oil after every track day, was expecting after every 2, as with race oil it's rather expensive. Plus i'm sure it doesnt do the car any good.

 

I'm pretty sure the cam timing was advanced significantly by mikeanics, so wouldnt expected the above asvice regarding retarded timing to be my case

 

Sean

[hengti 2]

if you can't fix it with home tinkering, take it for a RR tune

mine used to contaminate the oil when i got it; it also used to cut out alot - was traced to an AFM fault during a RR session

 

btw, are you doing alot of short stop-start journeys?

[Dream Weaver 2]

I had the oil changed the other day while having some other work, and there was a lot of fuel in my oil apparently. As the engine and sensors are new plus it's been setup on the RR this is worrying. I dont want to have to change the oil after every track day, was expecting after every 2, as with race oil it's rather expensive. Plus i'm sure it doesnt do the car any good.

 

I'm pretty sure the cam timing was advanced significantly by mikeanics, so wouldnt expected the above asvice regarding retarded timing to be my case

 

Sean

 

Hmm, there's a worrying trend developing here with our cars Sean

 

Mine was just the same after coming back from Mikeanics, hugely advanced ignition and chucking in way too much fuel that all collected in the sump. Not to mention all the torque being up the top end.