petrol in with the oil

[Timo]

I have been noticing that my engine oil has a distinctive petrol smell about it which is quite worrying to say the least.
It’s a standard set up TV8 with strombergs and SU pump upon further investigation today I have noticed the carb overflows are leaking after a run but would this result in petrol getting into the engine? The fuel pump is putting out 2psi and no debris in the fuel bowls so I’m assuming a sticking needle valve to account for the fuel overflow issue but if servere could it get into the oil?

[barkerwilliams]

Have you pulled all plugs do they all have similar deposits? Are all eight plugs firing? One cylinder failing to fire (plug, lead whatever) will allow some fuel past the piston into the sump. Is the oil level moving up the dipstick i.e. lots of fuel in the oil or is it just a smell?

Alan

[wilf]

Yes - very excessive fueling will allow fuel to get past the piston rings and into the sump. This is a condition that needs remedying fast as you are loosing lubrication for the pistons and rings, and affecting the oil in general.

Same issue on diesels with failed DPF regens - can cause total engine destruction.

[Timo]

Thanks Alan and Wilf, I haven’t pulled the plugs lately but it does run very smooth, also noticed today when revved quite hard black smoke from exhaust so un burnt fuel I guess and yes the oil level is rising up the dip stick so will only run to diagnose from now. I guess new needles again is the Gros Jet type the way to go?

[Lemp1953]

Hi, I had the same problem and the oil level had raised on the dip stick . Cylinder 8 was not firing as the sparkplug had failed. I immediately changed the oil but not the filter.
Mike

[daverosey]

I found starting the engine for short periods obviously with choke on tended to dilute the oil

[barkerwilliams]

No point in changing the jets or anything else if it is not wrong, do not be in a rush to spend money and introduce new items and extra disturbance of settings before you have diagnosed the problem, then just fix the one problem not all of the ones you have created.

Run the car until it is hot and turn the engine off and go and have a coffee to allow the engine to cool a little. Remove and inspect the plugs ensuring all plugs are kept in order from the cylinder it came from. All the plugs business ends should look identical, clean'ish thin beige coating certainly no black furry deposits a sure sign of rich running. If there is any significant difference in any plug then that indicates an issue that needs following up.

If all the plugs are black then the carbs / air filter / choke are suspect. If one or two plugs black then suspect ignition / leads, but perhaps a compression test is in order whilst the plugs are out.

Has the ignition been serviced recently? If not fit a new set of plugs, and a new air filter, new rotor arm, if you have the original points renew them and the capacitor as well. Remove plug leads (ensure they are labelled for each plug) and distributor cap. Clean the plug leads with a degreaser (hand cleaner will be OK) rinse and dry thoroughly. Clean distributor cap inside and out with carb, or brake cleaner and carefully inspect inside and out for tracking with a bright light - small trails across the cap surface.



Alan

[wilf]

Problem with "reading plugs" these days is that unleaded fuel does not give the same plug colours as leaded, or at least not as defined a range as in the diagram above.

[022Dave]

And if all that doesn't show up a problem, don't forget to clean & lubricate the distributor base plates (I use moly grease), its springs and weights, as well as checking the vacuum advance capsule operation. Also check the conical screw that goes between the vacuum advance arm and baseplate. My original was almost 'sawn' through by years of the arm movement. This will probably improve your running, but may have a limited effect on liquid petrol getting in the sump with the oil, if something else is amiss.

Dave

[Timo]

Just a quick update, I’ve had the carbs off and one of the float heights was way out about 20mm reading instead of 16/17mm. I have also changed the plugs and have a good spark on all cylinders (lumenition) compressions are ok. Going to put it all back together with fresh oil and monitor the oil level and will report back.