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77MGB will not start...different than the little engine that couldn't

To: mgs@autox.team.net
Subject: 77MGB will not start...different than the little engine that couldn't
From: Tom McLaughlin <tmcl98@yahoo.com>
Date: Mon, 22 Feb 1999 08:25:56 -0800 (PST)
I read the thread on the little engine that would not start as I had a
similar problem this weekend.  About 2 weeks ago I changed the plugs. 
They only had about 3000 miles on them, but I had some new Bosch
platinums so I put them in (gapped at 0.35").  The car ran fine all
day.  I then did not run the car for 2 weeks.  Saturday I tried to
start it and it just cranked.  I was getting fuel so I checked for a
spark, no spark.  So, I had another set of plugs that I bought at the
same time as they are cheap and replaced the plugs again.  Still no
spark.  I do have voltage at the coil with the ignition switch on.  I
checked the primary resistance of the coil, about 14 ohms.  A bit high
according to the manual and I'd never changed the coil so what the
hell, I went and bought a new one up at the parts store (AC delco that
looked exactly the same as the one I pulled out of the car that has
worked for 3 years and their computer said it would work on....what
was that again...an MG what...who makes that).  The primary resistance
of the new coil is only a couple ohms and about 6k ohms through the
secondary...both should be okay according to the manual.  I checked
the sparc plug wire resistances through the disti cap.  They range
from 5.3k to 8k depending on length.  All within spec.  I cleaned up
the contacts on the disti and the rotor (which looked fine), put it
all back together and still no spark.  With the ignition switch on I
get 13.2 volts at the coil (its hooked up to another car so not to
drain the battery during all this cranking)  Amature question.  The
maunal says that the proper way to check for a spark is to hold the
plug "with a dry rag" about 1/4" from the block and crank.  Is this
true or should the plug be touching the block...??? 

However, there is a crack in the disti cap where the clips fasten
(more like a hole, not a crack)...and it rained pretty hard a few days
in the last couple weeks, but the car was not driven so I don't see
how water could have gotten in there.  Is it possible moisture got
into the disti and it is causing my problem?  I'm getting a new disti
cap today and I'll clean the inside of the disti before installing. 
Do I have to go further than just underneath the cap...meaning, do I
have to take the rotor off and go deeper than that?

I started to suspect the electronic ignition cause I was running out
of things to test.  Here is why...it has a Piranah system that looks
pretty beat up.  It looks like it was coming apart and the PO used
silicon to put it back together.  I don't know how to test these
things.....so any suggestions would help.

In summary, new coil, new plugs, plug wires are fine, new cap today. 
Car ran fine 2 weeks ago, sat for 2 weeks and now no
spark......HELP!!!  And please, don't be shy with the details, half of
what I said above, I learned yesterday from the manual.  I saw one
post that said to take the wire from the coil to the disti off and
hook a spare plug up to that, close the points and see if you get a
spark...I don't have points though do I as it has electronic
ignition....not sure what to do next.

Tom
77B (ran great until I let it sit for 2 weeks; maybe she's just mad at
me)



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