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MG MGB Technical - SU HIF carb flooding

My orig.'73B has twin carbs and fuel floods out of the fuel vent line ports towards the exisisting Evap Loss Canister. I have replaced jet needles and seats and set up float adjustment according (approx. 1.5 mm). Checked floats, are good. With float weight and carb upside down, jets seals port and carb right side up, jets slides freely. Installed carbs in the car and verified all lines for proper connections (as when it was running good) and I still get overflow/flooding. Why??
joe

Joe,
I've had a similar issue, but don't know the answer. At least you're not alone!
David
David Steverson

Are you running the stock SU low pressure fuel pump? Is there a filter in the line going to the carbs? RAY
RAY

Joe.
Same problem mate.
I have it to the stage now where the front carb was flooding, replaced the float, float needle, and it seems fine. BUT i run the car from cold, get it warm, switch it off, and when i start it again out comes the petrol, only this time its out the back carb (line that goes to the charcoal cannister). It comes out at quite a rate. I have found that hitting round the bottom edge, gently, with a hammer makes the flow really die off, which mates me think sticking float. I have two previous posts, one on HIF woes from 1-2 weeks ago and one on the original petrol pump, i thought it was pumping to much fues at a high pressure but everybody said NO. I'm getting a new float next weekend and will let you know. Maybe check inside the bottom of the float for areas that the float could stick when fully down.
Fight the good fight, or get a webber
Gerry

Well guys, thank's for the reply(s). I think the problem on my SU-HIF flooding issues is the fuel pump. I haven't verified type of pump I got on the car as of yet but I read on a (mgb) blogs somewhere that the older-earlier mgb pumps puts out 1.5 psi and the later models at 2.5psi respectively for normal operation ( I hope some mgb guru can correct me if I'm wrong). Anyway, I verified my pump to put out 5 psi. I believe with this much pressure it'll overcome the float effect to keep the jet needle seated to shut incoming fuel.....and flows out to the fuel vent ....does this make sense?. My plan now is to get me a fuel regulator valve and reduce pressure..experiment and test....and see what happens. If someone gets ahead of me ...please, e-mail or write a follow up.....Joe
Joe

Joe;

You definitly need a pressure regulator or the proper fuel pump. You should not have any more than 2.5-3 pounds pressure. this appears to be the total cause of your problems.
Is the fuel pump you have a little rectangular box that lookes like a transformer ? if so that is definitley your problem. They make two different models of that and they look alike.
Sandy
conrad sanders

All factory MGB SU pumps put out the same pressure and don't need a regulator, it is *aftermarket* pumps that put out a higher pressure and need a pressure regulator.
Paul Hunt

Thanks Sandy and Paul. Got me a Holley pressure regulator
range adjustable 1 to 9 psi. Will install soon as I get the chance and let you guys know if it works.
J P Wyc

This thread was discussed between 15/07/2008 and 19/07/2008

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