QuestionQUESTION: Don't remember if I told you what kind of car I was trying to drive. Sorry...a 1976 MG B - just drove it over a thousand miles in the last couple months and the anti-run valve started spewing gasoline when I try to start it. In all the pictures, I see a pipe coming from the bottom of the valve, but can't find one or where they go.
What causes the gasoline to run out of the bottom of the run-on valve? I think read somewhere there's a blockage somewhere in the fuel system that causes it to back up, but I'm 69 and the memory banks are getting hard to access.
Appreciate anything you can tell me that will help out.
Wayne
ANSWER: Hi Wayne,
The "Anti Run-On Valve or anti dieseling valve as they are called. stops run on by applying manifold vacuum to the float chamber of the carburetor (if all of the hoses are connected)
When you see raw fuel coming out of the valve or any of the hoses at the charcoal canister it either means that the carburetor float is sticking and flooding or you have over filled the fuel tank and fuel is being forced through the vapor line into the canister and leaking from there into the anti dieseling valve. Either way the canister is most likely destroyed and must be replaced or disconnected.
Take the hose off of the carburetor float chamber and and shake the hose to see if any fuel is in it. If there is you need to remove the carburetor and check the needle and seat and float. If the charcoal canister has had fuel in it. It is no good and can't be used. When it gets wet with fuel for any reason it will stop up the venting of the gas tank and cause the carburetor not to operate correctly due to venting of the float chamber.
If the canister is wet, you can test run the car by removing the vent from the carb float chamber and remove the vacuum hose from the canister and plug the hose and remove the vent hose for the gas tank on the canister.
69? you youngons are all alike, blaming your age. I'm 76.
Howard
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carburator
QUESTION: Really appreciate your helping the younger generation...I just printed your answer, got my toolbox and smartly opened the 'bonnet' and discovered that was as far as I was going to get today. I don't know what kind of carburator I have. I've enclosed pictures; when you get through your laughing, please tell me what I have so I can begin. I replaced the anti-dieseling valve already and will wait your reply before I get into the carb - when I first got it, went to the MG DOC, a highly touted 'expert' in St. Louis, who removed my twin SUs and put a single one in with K&N filters. I don't know what he did and he denies ever doing it...so...it's me and you, buddy...I noticed a canister I pulled from another MG has a foam type filter on top of the plastic/aluminum filter at the bottom - is that a filter or just residue? Thanks for answering and I hope this pics are good enough...
Wayne
ANSWER: Wayne, quit tossing parts at the problem until you find out what the problem is.
The canister filter is granular activated charcoal and when saturated with gasoline it is destroyed and of no use. As I remember the charcoal is in the bottom section but not serviceable.
The picture you sent was of a windshield washer container and the anti dieseling valve, not the carburetor.
The 76 MGB never had twin SU carbs on it except in Europe. The US version had a single Stromberg carb. Many MG owners replaced the single Stromberg with the older twin SUs which was the best conversion, or some opted for the aftermarket down draft Weber conversion which was better then the Stromberg but not by much. There is nothing wrong with a Stromberg carb, but the design of the exhaust manifold was very poor and they always were cracked.
Send me a picture of the carburetor (without the windshield washer can in it) confounded youngons!
I thought you young people were sharp on this computer stuff.
Howard
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Try two
QUESTION: As I shamefully make another attempt to show you something might use, I'll let you know I worked in the computer field in IBM/McDonnell Douglas and Boeing after 20 years in the Navy as a communicator...so that means I know absolutely nothing about computer stuff - I retired!!! Let's see what I can do this time - by the way, I smelled gasoline fumes in the valve cover when I removed the valve cover cap...I suspect I have a single Stromberg...but here's nothing...
AnswerWow! that is a Type HIF SU carburetor. Not normal on a 76 "B". I like SU much more then Stromberg. The HIF SU was the type used on the early (fast) E-type Jaguars. That is a good conversion from the single Stromberg it had originally.
You still need to do the tests I told you to do. The good thing about the HIF SU is that you have a good range of jet adjustment. check for raw fuel in the float chamber vent hose and the fuel tank vent hose and open both to outside air for the tests.
If you smell fuel in the valve cover you need to check the oil to see if it is thin as though fuel is in the oil. If so don't run the engine any more until you change the oil and filter.
Howard
