Fuel in Oil - Help

[Brownbetty]

We have a 1982 2.0 Aircooled which was running just fine until a week ago. She started misfiring and backfiring when started and using a lot of fuel. Compression check showed low compression on one cylinder(4). Checking the oil showed that it is now an oil / petrol mix so I now know where the extra petrol was going. Al joking aside, the sump was full of petrol so it appears to be going straight through the engine into the oil. My assumption is that un-burnt fuel from the misfiring is somehow managing to get past the piston rings in the low compression cylinder.

It's going to be an engine out job to sort out the compression but has anyone got suggestions on what caused it in the first place. It would be a shame to do all that work just to have the same problem again.

Original carbs have been replaced by twin webers and the fuel pump is now an electric fuel pump. Engine is standard apart from that.

Any suggestions will be greatly appreciated

[tonytech]

Ouch.
I seem to remember reading that the mechanical fuel pumps can fail, allowing petrol to run down the pushrod and into the sump.

T

[itchyfeet]

This^^

[what2do]

Got to be the pump as unburned fuel would simply be thrown out the exhaust. Sounds like your lucky day, only a new pump required.

[marlinowner]

But OP states electric fuel pump...

[ELVIS]

Has is only just started since you put the leccy pump on?

Are you running a FPR? If so have you tested it to make sure it hasnt failed?

[what2do]

Oh, jumping the gun - again!

[marlinowner]

Yes, don't know about webers on the t25, but the sidedraught ones on my kitcar drip petrol out of the trumpets when the pump pressure is unregulated.

[itchyfeet]

But OP states electric fuel pump...

Ahh yes

[Brownbetty]

The electric pump has been fitted for about 2 years with no previous problems. I am using a fuel pressure regulator but have no idea how to check if it has failed. Any suggestions?