Gents
Still trying to get this '69 roadster started !
I've got the fuel supply working but when I pull the choke on full, fuel flows rapidly from the front carb air inlet (under pressure from the fuel pump)
I think it is the jet assembly but before I replace it does anyone have any suggestions ?.
Cheers
Dave
Carb flooding
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- Posts: 59
- Joined: Tue Dec 24, 2019 8:33 am
- Forename: David
- Surname: Green
- Location: Surrey / Hampshire
Carb flooding
MGB Roadster 1970
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Re: Carb flooding
Sounds as if the needle valve in the float chamber is not doing its job? This valve should close (by a float) when the chamber is full, and the pump should then stop ticking.
Check that the float is floating(!), Check the setting arm, and finally consider replacing valve seat and needle.
Ian F
Check that the float is floating(!), Check the setting arm, and finally consider replacing valve seat and needle.
Ian F
MGCC member
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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- Posts: 59
- Joined: Tue Dec 24, 2019 8:33 am
- Forename: David
- Surname: Green
- Location: Surrey / Hampshire
Re: Carb flooding
Thanks Ian
That was my first thought, so I cleaned and checked the float chamber (dry so not certain the float is floating -although it is not full of fluid- or that it is adjusted properly but the needle does block the intake)
The fuel doesn't flow out when the choke is in and the pump is on ?? Which made me suspect the jet assembly. Maybe it is still letting fuel through but much less noticeably ?
I'll recheck the float adjustment
Cheers
Dave
That was my first thought, so I cleaned and checked the float chamber (dry so not certain the float is floating -although it is not full of fluid- or that it is adjusted properly but the needle does block the intake)
The fuel doesn't flow out when the choke is in and the pump is on ?? Which made me suspect the jet assembly. Maybe it is still letting fuel through but much less noticeably ?
I'll recheck the float adjustment
Cheers
Dave
MGB Roadster 1970
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Re: Carb flooding
I think the choke just lowers the jet and opens the throttle butterfly a tad? I think I would focus on the float chamber components and adjustment if you have flooding problems. Are you using a standard fuel pump and not a high pressure aftermarket unit? You may need a pressure regulator if you have an aftermarket pump.
The valve and seat of SU carb float chambers can be quite troublesome - they may look OK but still leak a bit.. I would recommend the newer Grose Jet type - one upgraded part which seems to work and is hardly any more expensive than the standard part!
Ian F
The valve and seat of SU carb float chambers can be quite troublesome - they may look OK but still leak a bit.. I would recommend the newer Grose Jet type - one upgraded part which seems to work and is hardly any more expensive than the standard part!
Ian F
MGCC member
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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- Posts: 789
- Joined: Wed Dec 21, 2016 6:07 pm
- Forename: Vic
- Surname: Butler
- MGCC Member: Yes
- MGOC Member: Yes
- Location: North West Hampshire
Re: Carb flooding
Switch the ignition on but don't start the engine. The fuel pump will be heard ticking then the ticking should slow down and then stop. If it doesn't stop have a look around the carburettor float chambers to check for flooding.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
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- Posts: 59
- Joined: Tue Dec 24, 2019 8:33 am
- Forename: David
- Surname: Green
- Location: Surrey / Hampshire
Re: Carb flooding
Good news 👍👍
Managed to get the engine started and up to running temperature - although running rough I am chuffed as I bought it as a non runner with loads of bits missing from the engine or removed and in boxes.
Which leads me on to the embarrassing admission of not noticing one of the carbs had the wrong float chamber lid. It is the rear one and has a straight through fuel inlet as apposed to the breather inlet from the float chamber. I connected both together which meant the front chamber was being flooded from the rear via the breather - if that makes sense !
Anyway I blocked them off and no more flooding 😊😊😊
Thanks guys for pointing me in the right direction and stopping me from wasting money on a jet assembly.
Not sure where the wrong chamber lid is from but I'm thinking of keeping them both blocked until I can get a second hand replacement - how important is the breather connection I wonder ?
Cheers
Dave
Managed to get the engine started and up to running temperature - although running rough I am chuffed as I bought it as a non runner with loads of bits missing from the engine or removed and in boxes.
Which leads me on to the embarrassing admission of not noticing one of the carbs had the wrong float chamber lid. It is the rear one and has a straight through fuel inlet as apposed to the breather inlet from the float chamber. I connected both together which meant the front chamber was being flooded from the rear via the breather - if that makes sense !
Anyway I blocked them off and no more flooding 😊😊😊
Thanks guys for pointing me in the right direction and stopping me from wasting money on a jet assembly.
Not sure where the wrong chamber lid is from but I'm thinking of keeping them both blocked until I can get a second hand replacement - how important is the breather connection I wonder ?
Cheers
Dave
MGB Roadster 1970
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Re: Carb flooding
That's good!!
I think I would need at least one photo to make any sensible appraisal!!
Ian F
I think I would need at least one photo to make any sensible appraisal!!
Ian F
MGCC member
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
-
- Posts: 59
- Joined: Tue Dec 24, 2019 8:33 am
- Forename: David
- Surname: Green
- Location: Surrey / Hampshire
Re: Carb flooding
As promised photos
However with these blocked it would not start this morning . Could be due to no choke, but when I reconnected them it started 🤨. I assume the flooding was helping 🤪
Anyway I’ve sourced the correct lid now 👍
Cheers
Dave
However with these blocked it would not start this morning . Could be due to no choke, but when I reconnected them it started 🤨. I assume the flooding was helping 🤪
Anyway I’ve sourced the correct lid now 👍
Cheers
Dave
MGB Roadster 1970
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
MGF Roadster 2001
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Re: Carb flooding
Dave, thanks for the photos. What you are calling the breathers I have always thought of as emergency overflows for when the float chamber valve malfunctions. But I guess they also allow air pressure to remain constant if there are variations in the levels of fuel in the chamber. They should each have a rigid steel pipe attached which extends down well below the carbs. and is open at the end.
I will attempt to post photos of both carbs on my BGT which are as original (although with K&N filters).
Ian F
I will attempt to post photos of both carbs on my BGT which are as original (although with K&N filters).
Ian F
MGCC member
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear