5 replies to this topic

[Curare]

Hey all, a merry christmas first of all.

 

I have been fighting a bit of a problem with my 88' mayfair, and recently put a carb rebuild it into the HS4.

 

When I unplugged the fuel line to the carb it gushed fuel, like it was under pressure. I've been having issues with the car stinking of fuel/exhaust, which lead me to the tank, where I noticed there's a one way valve in the system right near the tank.

 

Blowing through it, it opens but not without being at a reasonable pressure.

I checked through minispares and I couldn't find a replacement part, alll the vent lines they sell appear to have no valve! Is this something the previous owner fitted in? Is it a good idea?

 

 

[Spider]

I'm pretty sure these had a mechanical fuel pump, regardless, the outlet of the fuel pump (be it mechanical or electric) have non-return valves in them, so any pressure in the line between the pump and the fuel bowl can remain there for quite a while if the non return valve and needle & seat in the float bowl are in good order, which it sounds like yours is. I'm not 100% up to speed with these later (for us at least!) cars, but I'm quite sure that there were no other non return valves fitted to the fuel system.  Some people do fit fuel filters though and what you have maybe one of these. Some of these flow better in one dorection than the other.

 

<edit: I've just looked in the parts book, according to that, the models for the Japaise Market did have a non return valve, P/N CAC310A, however it does appear to be only for that market, those for the UK and elsewhere simply had a fuel line direct from the tank to the mechanical pump (on the back of the engine), so no reason, if it is there and you suspect it maybe faulty, why it can't be by-passed>

Edited by Moke Spider, 25 December 2014 - 08:52 AM.

[Ethel]

Does the Op mean the valve is in the tank vent line? The tank needs to vent 2 ways. Air in to replace fuel used and fumes out if there's any heat expansion. Since an SU runs at only 2-3psi above atmospheric, it won't take much to mess it up.

[Curare]

Ethel, you're correct, I'm talking about the tank breather. It's got a one way valve in it.

[Curare]

To wit:

Attached Files

•  image.jpg   23.34K   23 downloads

Edited by Curare, 25 December 2014 - 09:19 AM.

[Lincsminbin]

Hi Passed Test, merry Christmas to you too.

I have a 1990 / 998 Mayfair, I've got the tank out at the moment as I've got the subframe off to paint. There is no valve on my breather, it goes straight from the top of the tank and extends about 5 inches through the floor. The rest of the car is original, so I've no reason to believe this bit isn't.

As 'is not a girl says' the breather line let's air in when fuel is being pumped and fumes out as the petrol evaporates, especially on warm days. I'd personally say a one way valve is not an original fitment and probably a bad idea.

Attached is a picture of mine for info.
 1419506133325-1753337522.jpg   33.92K   13 downloads