MGB Wont stay runing

[Carlbanan56]

Hi,
I have just got my car that has been sitting for 25 years to start! That's a very big achievement for me. Unfourtenetly the car will not stay running. When first starting the car it will start and run for 5 to 10 seconds and then die. When I then try to start again, the car will not start. If I let the car sit for a few minutes and try to start it, it will run again but still for only 5 to 10 seconds. I have taken a look at my brand new sparkplugs and there is a little soot on them. I am there for guessing that the fuel-air mixer is rich. But can the mixture be so rich the car won't start? I have completely renovated my carbs with a kit with new parts. My fuel tank is pretty rusty so I have removed the pump and temporarily placed it in the engine bay with a small gas container hooked up, so I am pretty sure the carbs are geting fuel from the pump. Should I just turn the adjuster screw to make the mixture leaner or do you guys might think there is something else?

Young and inexperienced

Thank you beforehand

 

[NutmegCT]

Hi Carl - some questions for you:

1. Which MG model and year?
2. Which carburetors?
3. How did the engine start and run *before* you rebuilt the carburetors?
4. If you disconnect spark plug wire, and try to start the car, are all the plugs wet with gasoline?
5. Is each carburetor fuel bowl filling to the proper height?
6. Are you using choke to start?

Every one of us here started as "young and inexperienced".

Thanks.
Tom M.

 

[Carlbanan56]

1. It's a 1975 mgb
2. HIF4
3. I renovated my cabs before I ever got the car to run, in hindsight this was maybe the smartest move.
4. I will try this tomorrow and come back with an answer.
5. I am not sure how I can check this now that the carbs are installed but during the assembly, I set the float bowl level.
6. I have tried using both with and without, and don't notice any difference. But have mostly tried with the choke.

 

[JPSmit]

5-10 seconds is pretty much exactly the amount of gas in the float chamber. Simple things first. does the glass gas container have a vent hole in it to keep the fuel flowing?

after that, it is likely either the float or the float needle? (Don't assume the needle is good because it is new - the viton tipped ones can be defective)

another possibility is that the pivot pin for the float lever isn't dropping and opening the float needle as the fuel goes into the carb.

I do feel like it is your area of focus though - good luck!

 

[YakkoWarner]

I'd start with the simplest old-school solution (which also works right nicely on Seagull outboard motors that have a carb with external float chamber) - give the float chambers a couple nice thwacks with the plastic handle of a screwdriver. Float could be stuck UP (closed) and over time enough seems thru to get it to run again for a couple seconds. Another way to test is bottle-feed a small amount of fuel (not carb cleaner or starting spray or any kind of solvent - I like to use 40:1 chainsaw gas because it has a little oil in it) into the carbs and see if it'll stay running on that. This is tricky on the side-draft SU's but can be done with one of those squeeze bottles.