Just wanted to send a note to thank Barney for putting so much time & effort
to write detailed fixes such as this one instead of a quick smart-alecky
remark like some of us are likely to give. Just wanted to say that the
mechanically-challenged people like me appreciate the assistance given by
all the more knowledgeable listers out there.
Giving money and power to government is like giving whiskey and car keys
to teenage boys. -(PJ O'Rourke)
Steve Conley
Marysville, WA USA
'76 MGB Roadster
GHN5UG393585G
mailto:swconley@foxinternet.net
MGB Online = http://web3.foxinternet.net/swconley
-----Original Message-----
From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net]On
Behalf Of Barney Gaylord
Sent: Thursday, October 28, 1999 11:52 AM
To: Pleczko, Rick
Cc: mgs@autox.team.net
Subject: Re: Help - I have angered the Lucas God
Rick,
At 04:07 PM 10/28/99 -0500, Rick Pleczko wrote:
>.... MGA .... wouldn't start.
>
>- Tunrned over fine so batteries are great.
>- The fuel pump is making noise ....
>- I have no spark at the plugs
>....
Okay, start here:
http://www.ntsource.com/~barneymg/mgtech/electric/circ_i.htm
Just to double check, if the fuel pump is running continuously it may be
out of gas. If the fuel pump runs to fill the carbs then stops, then it
has gas. Some aftermarket fuel pumps will run continuously, but become
quieter when the pressure is up.
When the fuel pump runs there is power from the ignition switch to the A3
terminal on the fuse block. From there, it is just one wire (originally
white) going to the ignition coil. Turn the ignition switch on and check
for power at the coil input terminal (test light or volt meter). If no
power at the coil input, fix the feed wire.
The rest of the primary circuit just goes to ground through the contact
points in the dizzy. If you pull the small wire off the side of the dizzy
and touch it to ground (on the engine block) a few times you should get a
small spark at the small wire and a big spark(s) from the coil high tension
wire. Power in and a good ground and still no spark, replace the coil.
Next check the ground continuity through the dizzy to the engine block.
Use an ohm meter, and you should have less than 1/4 ohm with the points
closed and about 50 megaohms with the points open. When this is working
correctly it does the same thing as touching the wire (small wire coil to
dizzy) to ground.
If you have more than 1/4 ohm with the points closed, clean or replace
the points.
If you have little or no resistance with the points open, look for a
short circuit in the dizzy, particularly where the moving arm of the points
is hooked to the wire. Here there should be insulating plastic grommets so
the input wire and condenser wire are connected to the curved spring but
not to the base.
If you have an open circuit when the points are closed, look for a
grounding problem. The dizzy may not be clamped tightly against the engine
block. More commonly, the wire hidden below the moving breaker plate used
to ground the moving plate to the housing can be broken. Often you get a
break inside of the insulation where you can't see it, and that can be
intermittent, sometimes work and sometimes not. Move the advance plate or
wiggle the wire to see if the connection makes/breaks.
Last component is the capacitor (condenser) inside the dizzy. Turn engine
so the points are closed. Pull wire from side of dizzy. Touching this
wire to ground on the engine should give a weak spark at the high tension
lead, probably orange and short throw. Touching this wire to the terminal
on the side of the dizzy should give a strong sparg, probably blue and a
long throw, being an indication that the condenser is doing its job. If
you still get a weak orange spark this way, put in a new condenser. If you
have a good blue spark, leave the condenser alone, don't temp fate by
changing it, as some new condensers are bad out of the box.
Have fun Sherlock.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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