Subject: Re: [Mgs] Fuel Issue

From: "Stephen West-Fisher" <[email-masked]>
Date: Mon, 28 Jan 2013 14:48:48 -0500

Since you didn't mention it can we assume you didn't have a strong smell of
fuel when you shut it down?

--
Stephen West-Fisher
N4IK

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Bill Snyder
Sent: Monday, January 28, 2013 2:41 PM
To: [email-masked]
Subject: [Mgs] Fuel Issue

I have a '66B that I cranked after a 6-month hiatus a few days ago. It
started but ran very rough as if on 3 cylinders. I put in fresh plugs,
checked the dizzy cap and cleaned it contacts as well as the rotor. There
was no change. After re-inspecting the plugs, it appears that the 4th
cylinder was not firing, but the plug was not gas or oil fouled. Laying the
plug out on the block, attached to the plug wire and cranking showed the
plug firing properly, so I am apparently getting no fuel to that cylinder.
Can anyone run me through the procedure to check on that issue? It has
Petronix ignition and has been converted to negative ground. Thanks in
advance.

Bill Snyder

Waynesville, NC
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From: Richard Ewald <[email-masked]>
Date: Mon, 28 Jan 2013 12:02:23 -0800

Check the piston in rear rear carb for free movement. Of that is OK, check the
needle and seat.

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On Jan 28, 2013, at 11:40, "Bill Snyder" <[email-masked]> wrote:

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From: Charley & Peggy Robinson <[email-masked]>
Date: Mon, 28 Jan 2013 17:09:36 -0600

If the valve train is working OK, it may be running on only the front 
carb.    I've run into this.

CR
On 1/28/2013 1:40 PM, Bill Snyder wrote:
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From: Jim Juhas <[email-masked]>
Date: Mon, 28 Jan 2013 19:31:21 -0500

Another possibility is a valve stuck open in #4. Check compression.

Sent via iPad
Jim Juhas

On Jan 28, 2013, at 6:09 PM, Charley & Peggy Robinson <[email-masked]>
wrote:

> If the valve train is working OK, it may be running on only the front carb.
I've run into this.
>> Petronix ignition and has been converted to negative ground. Thanks in
http://autox.team.net/mailman/options/mgs/[email-masked]
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From: Richard Ewald <[email-masked]>
Date: Mon, 28 Jan 2013 20:23:20 -0800

And the pushrod bandito might have stolen the intake pushrod for #4, but I
would put that about as likely as the #4 valve being stuck open.  Assuming
the engine was OK when parked, I doubt that a valve would get stuck open or
closed without some serious accompanying noises from the motor.  Bill made
no mention of any unusual noises.
A stuck carb on the other hand is quite common, and would not have strange
noises accompanying it.  I have seen this numerous times over the years.
Pull the air cleaners and lift the pistons by hand, do they both rise and
fall the same?  or is the rear piston stiffer to move?
I'll bet 40 quatloos on a carb issue.
Rick

On Mon, Jan 28, 2013 at 4:31 PM, Jim Juhas <[email-masked]> wrote:

> carb.

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From: "PaulHunt73" <[email-masked]>
Date: Tue, 29 Jan 2013 08:36:49 -0000

On the face of it, if only one cylinder isn't firing it can't be the rear 
carb as that would affect a pair of cylinders.  But the MGB has a large bore 
balance tube joining all four cylinders so it's possible the 3rd cylinder is 
getting just enough mixture from the front carb but the end cylinder isn't. 
If it's only firing on three then you wouldn't really know if the 3rd 
cylinder were firing fully or not.

It's a simple check to tell whether it's fuel or ignition, after running for 
a few moments remove plug 4.  If it's wet or smells strongly of fuel then 
it's ignition.  If it's dry and no fuel smell then it's fuel.

A plug can fire when laying on the block but not when in the cylinder under 
compression pressure if the cap (or other HT component) is marginal and 
breaking down under the higher HT voltage that is required to fire a plug 
under compression.

After having the ignition on for a few moments it's another moments job to 
remove the lid of the float chamber to check you have fuel in there, i.e. it 
isn't a blocked float valve.  If that's OK remove the air cleaners and blow 
gently into the float chamber overflow port you *should* see fuel bubbling 
up the jet in the intake to check the jet pipe and jet aren't blocked.

PaulH.

----- Original Message ----- 
> ... After re-inspecting the plugs, it appears that the 4th
> cylinder was not firing, but the plug was not gas or oil fouled. 

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