[Mgs] Intermittent miss

[Chad]

On mine it was the ignition switch, it had worn out enough at the contacts
just enough to be randomly disconnected.  Unfortunately no one sells just
the switch, which is detachable from the key assembly.

-----Original Message-----
From: mgs-bounces at autox.team.net [mailto:mgs-bounces at autox.team.net] On
Behalf Of PaulHunt73
Sent: Tuesday, July 31, 2012 4:47 AM
To: Peter Schauss; Mgs-Digest
Subject: Re: [Mgs] Intermittent miss

The CEI system is very good, so I'd be looking for an intermittent
connection before replacing it without doing a proper diagnosis.  You could
replace it and still have the problem, which would annoy me (having just
bought a new external disc drive which had the same problem as the old one,
then paid #50 to 'fix' a USB problem, only to discover for myself that it's
probably a faulty hub, that the external drives weren't even plugged in to).

The question is, does the tach drop because the 12v supply to it has been
lost, or because it is no longer receiving pulses from the ignition?  If the
former then it can only be the relay, ignition switch, or connections around
them.  If the latter then it could be the ballast resistance, coil,
amplifier, trigger or connections around them.  If other ignition powered
circuits are affected as well then you know it is the former, if they
continue to work normally then it is the latter.  The temp and fuel gauges
are thermal and very slow moving so the power would have to cut for a second
or more before you would see anything on those, so you need some other more
instantaneous indicator.  In the past when I've had an intermittent problem
I've hooked up a meter or test light in the cabin connected to various
points in a circuit to track down a problem.

PaulH.

----- Original Message ----- 
> My 1980 MGB has developed and intermittent miss. 
_______________________________________________

Mgs at autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation  $12.75
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe: http://autox.team.net/mailman/options/mgs/mgb72@airmail.net