20 replies to this topic

[JCmini]

Hello.

Was changing my air filter and noticed these two pipes going to my carburetor. One appears to be just pushed on and almost falling off and the other is off completely .

 

Can some one tell me what they are and should they be held on much tighter with clamps or jubliee clips. 

https://imgur.com/F0dcSKG

 

 

My car is  a 998cc 1986 automatic 

 

The previous owner said he fitted a new su carburetor. Is that the right carburetor ?

Thanks. 

Edited by JCmini, 16 December 2017 - 11:35 AM.

[Mike L]

The little one is the vapor return line that goes back to the fuel tank. The big one should be the crankcase purge pipe. These are parts of the emission control system. The vapor return line sends any fuel vapor that builds up in the fuel bowl back to the fuel tank rather than releasing it into the air. The crankcase purge keeps the crankcase from becoming pressurized from the movement of the crankshaft and pistons. It's vented into the carburetor so that any small amount of oil vapor will be burned rather than simply released into the air.

Someone please correct me if I am not accurate here but I believe this is correct.

[JCmini]

Ah yes I believe your right. I know it as crankcase breather pipe. 

 

Well I've connected it back together however due to the angle of the vapor return line i wasn't able to get a clamp around it. Its almost as if the lid assembly is fitted incorrectly and the line should be pointed away. 

 

I've seen other carburetors that don't have a vapor line

Edited by JCmini, 16 December 2017 - 12:41 PM.

[cal844]

Buy a new float bowl lid with the two pipes pointing to the outside of the lid(where fuel pipe is)

[sledgehammer]

normally UK carburettor cars only have a float chamber to atmosphere vent

 

they don't go back to tank - that said , other country's may have a different set up - US , Canada , etc

 

& OP is correct some carbs don't have a pipe attached , they have a small hole with a tin cover over it -

 

if fuel is overflowing from float bowl , it can get onto exhaust this way

 

I would check that fumes are getting out of the crankcase vent , as I can't see much oil in that area

 

you may need to re-tune the engine after fitting the pipe

[JCmini]

Hi sledgehammmer. You are right. I refitted both pipes and now the car runs like a pig. Really rough idle and cuts out when i apply throttle. The engine sounds like a horse trotting. 

 

Also i'm getting a lot of fumes from somewhere under the carb. Not sure exactly where.  

[Spider]

It sounds like the vapor return line is blocked somewhere, or plumbed wrong. It should go to a Charcoal Canister then, on a separate line, back to the tank from that.

 

It also sounds like you have an exhaust leak, most likely from the pipe to manifold joint.

[sledgehammer]

It sounds like the vapor return line is blocked somewhere, or plumbed wrong. It should go to a Charcoal Canister then, on a separate line, back to the tank from that.

 

It also sounds like you have an exhaust leak, most likely from the pipe to manifold joint.

 

Its a 1986 carb version , so in the UK , they don't usually have a charcoal canister - but there could always be a few UK ones that were different ?

 

I expect a Aussie version would need it - being driven upside down & in the hot all the time ;o)

 

on a serious note - I expect they did have some kind of vapour / vent system down under back in the 80's , like California spec etc

 

would be interesting to know 

Edited by sledgehammer, 16 December 2017 - 06:30 PM.

[Spider]

 

It sounds like the vapor return line is blocked somewhere, or plumbed wrong. It should go to a Charcoal Canister then, on a separate line, back to the tank from that.

 

It also sounds like you have an exhaust leak, most likely from the pipe to manifold joint.

 

Its a 1986 carb version , so in the UK , they don't usually have a charcoal canister - but there could always be a few UK ones that were different ?

 

I expect a Aussie version would need it - being driven upside down & in the hot all the time ;o)

 

on a serious note - I expect they did have some kind of vapour / vent system down under back in the 80's , like California spec etc

 

would be interesting to know 

 

 

Ah OK, cheers.

 

Yeah, we did have a Charcoal Canister from about 76, but since they changed over to unleaded fuels, they are no longer needed. I don't know what keeps our fuel from pouring out the filler (hehehehe),,,,,,

 

In that case, check too that the fuel tank vents are clear.

[Rorf]

That small pipe on the carb fuel bowl is only a petrol overflow pipe should the needle and float get stuck - nothing to do with petrol vapour.

 

Originally this was connected to  a steel pipe which was routed away from the exhaust and attached to some of the clutch wok bolts with pipe clips. You can re-position the float bowl top to get that pipe to better fit.

 

It would appear that the crankcase oil breather canister is blocked thus the engine performance poor when connected. Lastly you will need to set up/adjust the carb. 

 

Note set up in this pic

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Edited by Rorf, 17 December 2017 - 05:32 AM.

[Rorf]

Note the correct method of connecting the fuel line to the mechanical pump

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[Mike L]

Rover Mini Repair Manual 1976-1989

 

 

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•  Evap Control.png   73.41K   5 downloads

[sledgehammer]

That small pipe on the carb fuel bowl is only a petrol overflow pipe should the needle and float get stuck - nothing to do with petrol vapour.

 

 

that is one use for it - but the main use is a vent to atmosphere

 

it is to allow the engine to draw fuel into the inlet manifold where a vacuum is created across the carb bridge

 

atmospheric pressure (outside pressure) pushes down on the fuel in the float chamber ,

 

pushes fuel thru jet pipe up jet tube into the jet / bridge area to be atomised

 

the metal pipe does flow excess fuel when float valve fails - but it also has other purposes

[JCmini]

I took the lid off and that allowed me to refit the fuel hose better and then put the breather hose on. They kind of both wedge against each other. I also adjusted the screw on the rocker for the choke to give me slightly higher revs. 

This seems to have sorted my rough engine running.

 

As Moke spider suggested tho I do have some sort of leak around the manifold. So that will need sorting just need to find time to get the car up in the air. Is there a common place for leaks?

Edited by JCmini, 17 December 2017 - 03:24 PM.

[Spider]

 Is there a common place for leaks?

 

Between the pipe and the manifold joint.

 

I usually clean them up, and re-assemble with some muffler putty between them, and use the jack to hold the pipe up while getting the clamp back on.

 

Before doing this though, check your engine steady rubbers and engine mounts. A common cause to make these leak in the fist place is worn steady rubbers.