[Mgs] Won't start

[Monte Jane Morris]

BTW, This 79B has a 45D distributor with points and condenser. I'm now
confused as to which coil to order. I think my last post was wrong. Since I
have not changed the wiring and the "drive resistor" is still connected, I
should order Moss coil #143-230 (for a ballasted system) and leave the
resistor and other wiring intact, correct?

Whew, back 12 years ago when I bought a 74 parts car, trashed the ZS carb
on the 79 and converted to HIF's, trashed the Opus electronic ignition and
switched to a points dizzy, used parts from the 74, bought other parts new
and used.... I can't remember what parts came from where, so the ignition
system as well as the fuel and exhaust system are HYBRIDS!!  Several times
I've mistakenly ordered parts for a 79 when I should have ordered parts for
a 74:). I suppose many MGs on the road are now hybrids.

On Thu, Apr 25, 2013 at 9:24 AM, Monte Jane Morris <montejane at gmail.com>wrote:

> Paul,
> You've probably "hit it on the head".
> Yes, I do have a points dizzy (from a 74B) that I've used for about ten
> years now when I converted to HIFs. I never changed the wiring at all when
> I did the conversion and kept the original coil. There is a "drive
> resistor" (Moss #131-560, pp. 86) still wired in.
> When I replaced the original 79 coil back in 2004,* I used a 79B
> replacement at the local parts store*.
> Therefore, I would assume that the coil is shot and that's the cause of my
> problems.  I should now replace it with one from a 74B, correct?  When I
> install the new coil (Moss#143200) do I just disconnect the drive resistor?
> Will anything in the ignition have to be adjusted with the new coil?
> I guess having the wrong coil does not affect (effect?) the performance of
> the car since it runs real well (when it runs:)?.
>
>
> On Thu, Apr 25, 2013 at 3:38 AM, PaulHunt73 <paulhunt73 at virginmedia.com>wrote:
>
>> I'm wondering whether you mean the ignition relay doesn't click when you
>> turn on the ignition.  The starter relay doesn't click until you turn the
>> key to crank, and is drowned out by the solenoid clicking if not the engine
>> cranking.  I presume the engine is cranking?  Originally the coil was
>> powered from the ignition relay, and if that isn't operating then you would
>> have no spark, but you would have no power on the second fuse up neither
>> would you have battery voltage on the coil +ve.
>>
>> You say your car has a dizzie, but they all do.  I'm assuming you mean it
>> has a replacement points dizzie of some type.  If so, then it all depends
>> on whether the coil and coil wiring was changed when that was fitted.
>> Originally your car would have had a length of resistance wire (the ballast
>> resistance) in the harness in series with the coil.  With the points
>> closed, and ignition on, if that circuit is good you should have 6v or less
>> at the coil +ve, not battery voltage.  Battery voltage there implies there
>> is no continuity through the coil, the points, and the distributor earth
>> wire, or maybe no ballast resistance.
>>
>> Late MGBs with the 45DM4 distributor may well have had a 32C5 coil, which
>> may have measured as low as 0.8 ohms on the primary.  Using one of these
>> with points ignition, or some other non-standard ignition system, could
>> well result in significant overheating and damage to the coil.  A 0.1 ohm
>> coil, if that is what you are saying you have, has either gone
>> short-circuit or is completely the wrong coil and is one intended for
>> modern electronic systems that use a very short pulse of high voltage.
>>  However you need to remove the wiring from the coil before you can measure
>> its primary resistance as there are other components on the wiring that
>> goes to it that will affect the reading.
>>
>> You are going to have to go back to first principles and determine
>> whether you have the ballast resistance in circuit or not, which will
>> determine which type of coil you should have.  If your coil doesn't measure
>> up to that it has probably failed and will need replacing with the correct
>> one.  Then you will need to check the circuit through the points and the
>> distributor earth wire, as excessive current that is enough to damage the
>> coil will likely damage these as well.
>>
>> PaulH.
>>
>>
>> ----- Original Message -----
>>
>>> Any suggestions of observations from the above?