Subject: Re: [Mgs] MGB evaporative loss system

From: "PaulHunt73" <[email-masked]>
Date: Fri, 21 Aug 2020 16:27:51 +0100 ZO2jkLh4TM0xtjWfHsK7N473injLVhHJ65jXc54dpXORCVpU2OTAE8uSgvqE0E59hC9NORj8NTWyjh58rJPbLO6mUezMgveDUK0=

Fuel filling the charcoal canister is almost certainly from one or other 
float valves failing to close, and would have been accompanied by continual 
clicking of the pump with the engine not yet started.  The only other way 
would be via the fuel tank vent pipe if fuel could somehow be forced into a 
full tank, which seems unlikely.

Happening with replaced floats and valves points more to dirty fuel than 
anything else, do you have a filter before the carbs?  Standard for HIFs 
which North America got with the first 18V engines for the 1971 model year, 
and maybe earlier.

Unless you have a non-standard pump which may be overwhelming the float 
valves.

Alternatively if it only happens when driving it could be vibration causing 
the valves to open.

PaulH.

----- Original Message ----- 

> 71 mgb. A few years ago after the first startup in the Spring, I drove 
> around the neighborhood to check things out. The car bogged down and I 
> struggled to get home. Fuel had filled the charcoal canister and running 
> out the bottom. The original floats showed some wear on the pivots, but 
> not so much that I thought it would be the problem. Couldn’t find anything 
> else so replaced the floats and valves and it has been fine since. This 
> year I didn’t start up until May or June, same thing happened.
>
> Checked everything, no blockage, debris, worn parts. An internet posting 
> mentioned the pipe union (near the fuel pump) that connects the charcoal 
> canister to the “widget” in the trunk. That too was clean. Purged the 
> charcoal of gasoline (see John Twist) put it all back together. Fuel pump 
> ticks briskly and stops before starting. I’ve driven around the 
> neighborhood a couple more times and it seems fine. Not being able to find 
> a cause and fix it leaves me worried about longer drives. Any thoughts?

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From: "Hans Duinhoven" <[email-masked]>
Date: Fri, 21 Aug 2020 19:54:52 +0200

As the '71 B still is equipped with the HS4 carbs, it may be wise to verify how the top lids of the float chambers are looking. The evaporate loss pipe and the fuel inlet are located pretty near each other. Check for correct working of the floats and check  if the needles are closing the fuel inlet correctly.
Your story looks, if the pumps does not stop timely when the float chamber has reached its correct level of fuel.
When that happens, the float chamber gets overloaded and the excess fuel will be fed into the charcoal canister.

Hope this helps.

Cheers,
Hans '71 BGT NRG W/W

-----Oorspronkelijk bericht-----
Van: Mgs [mailto:[email-masked]] Namens Allen Hess
Verzonden: vrijdag 21 augustus 2020 16:17
Aan: [email-masked]
Onderwerp: [Mgs] MGB evaporative loss system

71 mgb. A few years ago after the first startup in the Spring, I drove around the neighborhood to check things out. The car bogged down and I struggled to get home. Fuel had filled the charcoal canister and running out the bottom. The original floats showed some wear on the pivots, but not so much that I thought it would be the problem. Couldn’t find anything else so replaced the floats and valves and it has been fine since. This year I didn’t start up until May or June, same thing happened. 

Checked everything, no blockage, debris, worn parts. An internet posting mentioned the pipe union (near the fuel pump) that connects the charcoal canister to the “widget” in the trunk. That too was clean. Purged the charcoal of gasoline (see John Twist) put it all back together. Fuel pump ticks briskly and stops before starting. I’ve driven around the neighborhood a couple more times and it seems fine. Not being able to find a cause and fix it leaves me worried about longer drives. Any thoughts?

Allen

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From: Robert's New iPad <[email-masked]>
Date: Fri, 21 Aug 2020 19:21:35 -0400

More than a few have made the mistake of putting hoses onto the wrong pipe.
   Allen, when you checked that pipe to the fuel separator in the boot, did you blow down it from engine space to the boot, listening for bubbling in the fuel tank? Gentle lung-power should be all you need for that. If you do not hear the bubbling and feel pressure in your cheeks, that line is not adequately cleared.  It gets a crud of stale gasoline and rust that can be an effective plug.  
   I have never thought that John Twist’s purging of the charcoal was worth the bother. I prefer to get fish aquarium charcoal at the pet department and to replace that disintegrated rubber filter with a piece of Scotchbrite.  
Bob

> On Aug 21, 2020, at 1:54 PM, Hans Duinhoven <[email-masked]> wrote:
> 
> Unsubscribe: http://autox.team.net/mailman/options/mgs/[email-masked]

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From: Allen Hess <[email-masked]>
Date: Fri, 21 Aug 2020 21:27:26 -0400

I haven’t checked the fuel separator line in the way you suggest so I’ll do that. 
Thanks 
Allen

> On Aug 21, 2020, at 7:21 PM, Robert's New iPad <[email-masked]> wrote:
> 

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From: "PaulHunt73" <[email-masked]>
Date: Sat, 22 Aug 2020 08:54:23 +0100 MMqhPkCDbMXSGmQyW1eiF1vor1VyT3vkuHbmB5DaRQy4/CqBMVzfLVd0tUIL6+nyGHFg7ASfnOE/c6tdb1CBXP67TLJOiEIqZbU=

Wouldn't you have to remove the sealed filler cap to be able to blow through 
the tank vent?

And doesn't the vent come off the top of the tank so you wouldn't hear any 
bubbling anyway?

If that pipe is blocked you get fuel starvation as air cannot replace the 
fuel used when running, it can't put fuel in the canister.

PaulH.

----- Original Message ----- 
>   Allen, when you checked that pipe to the fuel separator in the boot, did 
> you blow down it from engine space to the boot, listening for bubbling in 
> the fuel tank? Gentle lung-power should be all you need for that. If you 
> do not hear the bubbling and feel pressure in your cheeks, that line is 
> not adequately cleared.  It gets a crud of stale gasoline and rust that 
> can be an effective plug.

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