2 replies to this topic

[thegreenhornet]

I've noticed that the inline glass fuel filter going to the HS4 carb on my 998 has a lot of bubbles running through it when the engine is hot and idling.

It doesn't seem to be affected by how full the tank is, and I don't *think* there's any fuel in the oil. It's a mechanical fuel pump, so I'm hoping the diaphragm is okay. The oil level hasn't gone up and although the oil smells (it's due a change), it doesn't really smell of petrol. I also would have thought that, if it was the pump, it would just do it all the time. There's nothing leaking underneath car and, if I rev it, the bubbling gradually stops. If it has been bubbling, then it will continue for a minute after I stop the engine.

It seems more affected by heat than anything else. The fuel line runs very close indeed to the manifold, which I'm hoping to remedy soon for safety's sake. Could the fuel being heated by the manifold cause so much bubbling? I didn't think petrol could boil like that...

Any advice much appreciated :)

Glen

[Rog46]

You say you have a mechanical fuel pump, so it sucks the fuel along the line from the tank, I'd say there was a very small leak in the line letting air in! Check all the connections between the tank and the filter.

Edited by Rog46, 30 September 2013 - 09:46 AM.

[thegreenhornet]

I'll take a look when I can get underneath it then. I'm just puzzled by the fact that it doesn't do it constantly! Just when it's hot and ticking over :/