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TR6 ZS carb issue

Moss Motors
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tirebiter Jeff Garber
Dighton, MA, USA   USA
If you have a pressure gauge I would check to see how much pressure the needle and seat assembly can take before it is defeated and allows pressure through. Now measure the pressure in the fuel line to the carb. Once you see that there is too much pressure or not too much pressure, you can continue. Other than that it's a guessing game to determine which part to replace next.

If too much pressure in the fuel line is defeating the needle/seat assemblies, it could be because the gas tank vapor recovery system is not working properly. Have you tried opening up the gas tank filler cap to see if the fuel stops gushing out of the mainjets ?

If the pressure in the fuel line is not above what the needle/seat assemblies can take, then you need to take closer look at the floats and the functioning of the needle/seat assemblies.

If the floats are the white plastic ones take them out and dry them off. Give each one a shake. If any gasoline is inside, you'll hear it splash around. It could be the floats float but they float too low.

If the floats are the solid (plastic cork) type you need to weigh each one and get the specification for what they should weigh. They may still float but if waterlogged somewhat will be heavier and not float high enough to close the needle/seat. Maybe close it partially, but not well enough to block the (whatever it is) pressure.

It is hard to imagine but maybe there is somehow positive pressure being applied to the float chamber as has been mentioned already. Only way I know that could happen is if the float vent lines are connected to the exhaust somehow. Via the EGR system maybe or the PVC system and the engine is pushing a huge amount of blowby out the valve cover. Each is just a guess without knowing what the fuel pressure is.

Once you determine if there is too much pressure/not too much pressure, then you can ignore certain items. Concentrate on the possibilities. Ignore things that cannot contribute to the flooding. If there is not too much pressure then it can have nothing to do with the gas tank, fuel pump or vapor recovery system.

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poolboy Ken D
Sandy Hook, MS, USA   USA
In reply to # 1599529 by jacko241 Car has been driven regularly, chokes are not being used, but appear to be functioning properly.
Have you removed them and verified that the discs are properly oriented (left) AND still have enough spring pressure to keep the disc pressed firmly against the carb body openings ?



ZS carb repairs
kencorsaw@aol.com


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jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
In reply to # 1599838 by poolboy
In reply to # 1599529 by jacko241 Car has been driven regularly, chokes are not being used, but appear to be functioning properly.
Have you removed them and verified that the discs are properly oriented (left) AND still have enough spring pressure to keep the disc pressed firmly against the carb body openings ?

We did remove them, and seemed to be correct, but I have no experience with ZS carbs. Thanks for the photo, I will remove them and recheck the orientation.


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Jacalone & Sons has over 40 years experience servicing MG, Triumph, and Austin-Healey. Moss Motors dealer.
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POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
In reply to # 1599714 by ckilmer
....making sure the tab on the float is parallel to the carb base when the valve is closed and making sure the gasket between the valve and carb body is in good shape and not letting fuel leak by.

The gasket ckilmer is talking about is actually an alloy sealing washer, as I'm sure you know having replaced the needle and seat assembly once already. Most carb kits and gasket sets come with an assortment of them in various thicknesses. The correct one is close to a mm thick and it's use will assure the float tab is parallel or close enough so the tab pressure on the valve is straight on. A too thin washer would mean the float tab would have to be unnaturally bent in order to achieve the correct height. This would cause it to exert uneven pressure on the float valve's tiny stem and maybe cause it to jam some and not seat. Have you tapped on the carb bowls when the engine starts to get ragged?

This is pure speculation on my part and certainly not something I have experienced. - Pete

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jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
In reply to # 1599860 by POW
In reply to # 1599714 by ckilmer
....making sure the tab on the float is parallel to the carb base when the valve is closed and making sure the gasket between the valve and carb body is in good shape and not letting fuel leak by.

The gasket ckilmer is talking about is actually an alloy sealing washer, as I'm sure you know having replaced the needle and seat assembly once already. Most carb kits and gasket sets come with an assortment of them in various thicknesses. The correct one is close to a mm thick and it's use will assure the float tab is parallel or close enough so the tab pressure on the valve is straight on. A too thin washer would mean the float tab would have to be unnaturally bent in order to achieve the correct height. This would cause it to exert uneven pressure on the float valve's tiny stem and maybe cause it to jam some and not seat. Have you tapped on the carb bowls when the engine starts to get ragged?

This is pure speculation on my part and certainly not something I have experienced. - Pete

Thanks, I will double check this as well. The tapping part is a good idea.


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jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
Andrew & Brent, you both nailed it! The "friend" who rebuilt these carbs for my customer some time back removed all the emissions equipment, and put caps in the bowl vents!!
Thanks to all!


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poolboy Ken D
Sandy Hook, MS, USA   USA
The 'red nipples' ?



ZS carb repairs
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jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
In reply to # 1600336 by poolboy The 'red nipples' ?

How did you know!!


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LFMTR4 Lou Mijares
Scottsboro, AL, USA   USA
If something as basic as that is botched, I wonder what else is wrong from the rebuild?

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poolboy Ken D
Sandy Hook, MS, USA   USA
In reply to # 1600381 by jacko241
In reply to # 1600336 by poolboy The 'red nipples' ?

How did you know!!

Because that's what you said, Joe.
On the 73 and later carbs because of the Anti Run-on Valve (ARV)there needed to be an access port and that's it. It also functions as the float chamber vent when the throttle is in idle position...At other times, the float chamber vents like all the other years prior to 73, thru the brass line hole in the carbs' air box mounting flange..also seen in that picture.
And BTW, the reason I had that "red nipple" picture and why the nipple is 'red' was to post on the 6-Pack forum, warning not to cap it if the ARV feature was disabled.
The 'red nipple' picture got to be pretty well known over on 6-Pack....maybe it'll gain some notoriety over here now.



ZS carb repairs
kencorsaw@aol.com

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jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
That is too funny. As I told the owner, I have no experience with ZS carbs, but he said not to worry, his friend had rebuilt several so he know he did his right, lol.
I had originally assumed those were a vacuum takeoff port, but then after further inspection found that the bowl did vent thru there. My TR6 has DGVs.



Edited 1 time(s). Last edit at 2019-03-06 08:10 AM by jacko241.


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poolboy Ken D
Sandy Hook, MS, USA   USA
A picture of the carbs in question would have shown the violation right away, but to be honest, it never occurred to me to ask, Joe.
Usually when those red nipples are capped the idle suffers, but at other speeds because the float chamber vent has transitioned to the other location, there's no ill effect.
However, that assumes the transition valve is working properly and properly adjusted.
That valve is frequently messed up either on it's own or by the owner thinking it does something else...I've found it's adjustment screw has been used to set the idle speed..and it will, but in doing so messes up something else.



ZS carb repairs
kencorsaw@aol.com

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jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
Yes, you really only noticed the flooding at idle, once you were driving it was not that apparent.


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Darth V8R Vance Navarrette
Beaverton, OR, USA   USA
1980 Triumph TR7 Drophead "The Great Pumpkin"
1980 Triumph TR8 "Wedgie"
In reply to # 1599525 by jacko241 I am having trouble with a TR6 flooding. Car will start and run fine for the first 5 minutes or so, then it begins to load up and stall. When I lifted the damper, fuel was flowing freely out of both jets. I pulled both carbs, and checked the floats,and they float fine, and no liquid inside. I replaced the needle and seats, which were Grose-Jets, with standard units. No good, same thing. I then lowered the float level from 17mm to 20mm. The front carb seemed better, but rear still flooded. I then raised the rear another mm, no change. Also installed inline press. regulator, to reduce pressure, no change. Any ideas?

Joe:

A picture of your carbs and their emissions plumbing would be helpful, as our cars have passed through many hands and the various hoses have often been "creatively" rerouted, which causes a bizarre array of problems.

1. Are the carburetor float bowl vents properly connected to hoses that connect to the carbon canister?
2. Are the float bowl vent valves properly adjusted?
3. If the emissions plumbing has been removed (as is often the case) are the float bowl vents open to atmosphere?

I ask these questions because it sounds like your float bowls are pressurizing from gas vapor, which will push the fuel out of the bowls through the jets if the bowls are not properly vented.

Vance

ADDENDUM: I read the rest of the thread and see that this is exactly what was going on. So NEVER MIND!



1980 Platinum Metallic TR8, frame off restoration, complete.
1980 Vermilion TR7 Sprint replica, in progress.



Edited 1 time(s). Last edit at 2019-03-08 01:25 PM by Darth V8R.

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jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
smileys with beer


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