...best guesses to follow.
1) sticky float chamber needle..constant fuel demand but supply limited
or varying on you. (related to #3 below)
2) It's not uncommon for fuel filters to look OK, but be dirty enough
to limit flow rate.
3) Engine vibration setting up standing waves in the float chamber.
The float level (fuel level ) (related to #1 above) is very important to
maintaining the fuel level around the needle in the jet orifice.
If the jet gas level is low, a constant vacuum around the needle
is not going to pull a constant gas flow up around and past the
needle so the fuel/air ratio keeps jumping around on you.
4) Check to see if you are creating a vacuum in the gas tank which
would limit fuel flow at constant cruising speed.s
When it happens next time, quickly pull over, jump out and pop off you gas cap.
If you hear a whoosh as the tank suck in air, somewhere along the lines
you have a clogged vapor return system or vent thus limiting gas delivery
to the carbs. This would show up best at higher speed (cruising) as the
vacuum would only build up enough under constant demand to the point of
limiting gas flow.
5) Check you carbon canister and make sure it's not full of gasoline.
A sticky float valve would let it overflow filling the canister and not let the
gas tank vent correctly. (related to #1 above)
...the list could go on ... and on... and on....
good luck!
Paul Tegler wizardz@toad.net http://www.teglerizer.com
OBie - '73 BGT - daily driver
http://www.teglerizer.com/mgstuff/ob_description.htm
Punkin' - '78 Spitfire - corner ripping screamer
http://www.teglerizer.com/triumphstuff/spit78.htm
Lil' Greenee - '73 RWA Midget - lady killer
http://www.teglerizer.com/midgetstuff/index.html
-----Original Message-----
From: Tony Woodruff <tonyw@mailmedia.com>
To: mgs@autox.team.net <mgs@autox.team.net>
Date: Monday, January 24, 2000 1:42 PM
Subject: Re: Freeway sputtering
Agreed, anything that delivers fuel to the engine is "suspect". Some ideas.....
Fuel Lines, fuel pump, fuel filter, etc.
Also, check for debris in the bottom of the float bowl that may be restricting
the flow of fuel to the jet. That was the cause of my BTDT.
There are lots of other potential causes that I'm not familiar with, but others
will certainly chime in!
Best Regards,
Tony Woodruff
67 MGB
>>> "Andrew B. Lundgren" <Lundgren@iname.com> 1/24/00 9:53:44 AM >>>
I have never worked on the Z-S carbs, but it sounds like your float bowls are
not being kept full. Partially plugged fuel filter?
On Mon, 24 Jan 2000, Steve Conley wrote:
> I've got a '76 Roadster w/Z-S carb that I've got a stubborn problem to fix.
> When I'm cruisin down the freeway, all of a sudden the power drops way down
> and I can't go above 40mph. There is no back-firing, rough running just no
> umph. Then I pull over to the side of the road (still running) and idle for
> a little bit and then it clears up and I'm able to drive a while longer. I
> replaced the fuel pump thinking that it was the problem, I made it 50 miles
> but the problem returned. I'm going to try to work on it tomorrow. Any
> suggestions?
>
> Steve Conley
> Marysville, WA USA
> '76 MGB Roadster
> swconley@foxinternet.net
> MGB Online = http://web3.foxinternet.net/swconley
>
>
>
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