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SU HS Carb Flooding?

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jwmhelipilot

jwmhelipilot

Freshman Member
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Hi

I'm looking for advice on a flooding problem ( I think).

1969 MGB GT

My grandpa just gave me this car, it has been sitting in his driveway for the last few years. I put in some new fuel (with some stuff to help with old fuel) and changed the spark plugs. The old plugs had a lot of carbon build up on them.

This is what's happening:

It will start up real easy, and idles fine (after I adjusted the idle). But after running a while it won't start back up. The engine cranks, but no light off.

After 30mins or so it will start up again with a little hesitation. And the longer you wait the easier it is to start.

Driving it has a lack of power.
 
You probably want to take this checklist & go through it...starting an engine isn't always the best thing to do before you've checked brakes, steering, clutch, etc.

But, you probably need to rebuild the carbs, drain the tank & flush it!

https://www.theautoist.com/CHECKLIST.HTM
 
Next time it won't start, check the fuel level in the float bowls. If you're in the LA county area I can help you with that.
 
Wow that's a thorough checklist! Thanks Mr. Barnhill.

I'll have to check what's been done on it, but I know it had a lot of work a few years ago.

But it sounds fun to go through all of that anyway, to be sure.

-James
 
Steve,
Sounds like a plan. I'm at work for the next week... but when I get back into town, I'll fire her up and then see what the level is looking like.

What are we looking for?

-James

I'm up the coast from you, near San Luis Obispo.
 
jwmhelipilot said:
...it had a lot of work a few years ago.

-James
Click to expand...
Doesn't mean a thing & everything done then will probably require doing again!

Jack her up & start checking off again....now, remember, that checklist is designed to produce a daily driver so some things aren't necessary during the time you're getting her roadworthy but are necessary before you set out on your morning commute.
 
You're a little unclear on the symptoms. Are you saying that when it idles for a while it dies and then won't restart, or does it run as long as you want and it is after you've turned it off that it won't start back up again? That would make a big difference in diagnosing the problem.

If you're pretty sure it is flooding, it could be crud stuck in the needle and seat in the float bowl. Try unplugging the coil, then turning on the ignition for a while. The ticking of the fuel pump should stop. If it doesn't, and fuel is running out of the float bowl overflow (into the carbon canister if you have one) or out through the jet (remove air cleaners to see this) then you have a problem with the needle and seat.
 
Davester,

It will run as long as I like. But once I turn off the ignition, it won't fire back up.


Don't think it has a carbon canister... looks to me like the fuel goes straight from the float bowl to the jet. So I'll check the needle and seat inside...

-James
 
The carbon canister on later cars is connected to the float bowl overflow lines. If there's no canister then I believe the overflow lines on your car are simply directed towards the ground.

In any case, I don't think its at all clear that you have a flooding problem. It might even be an electrical problem. I'd suggest that next time you are trying to restart unsuccessfully you should have someone help you check to see if the plugs have any spark. Another possibility is that its a heat problem. What shape is the heat shield in that protects the carbs and float bowls from exhaust manifold heat? I've had an MGB and a Sprite where the outer part of the heat shield cracked then broke off, leaving the carbs subjected to the searing heat of the exhaust manifold, thereby boiling the fuel when I stopped the engine which then bubbled out of the jets and overflows. A long shot, but possible.

It's also possible that your carbs are running far too rich which is not too bad when starting a dead cold engine but problematic with a warm one. Do you need to use the choke when starting from cold? If not, you're mixture is probably too rich.

So many possibilities, so little time!
 
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