[Healeys] Austin Healey 100 Misfire Diagnosis.

[john harper]

Alan

Coils can fail with heat and then recover when cooled. I had one that had
these symptoms and when looking closely I saw that the insulating oil had
run out through a very small crack in the bottom of the case.

On Thu, 29 Sept 2022 at 10:34, Alan Seigrist <healey.nut at gmail.com> wrote:

> Michael -
>
> Just as a follow up to my email since the symptoms seem to manifest
> themself  ...
>
>    - whether the car is warmed up or not - this typically will exclude
>    anything related to fuel or the coil
>    - whether the car is under load or not - this typically will exclude
>    anything related to fuel
>    - whether the choke is pulled or not - this typically will exclude
>    anything related to fuel
>    - somewhat intermittent but systematically under all conditions -
>    suggests to me wiring / ground issues
>
> Given this I'd check (as a priority):
>
>    - Battery Master (when these fail they will ground the coil)
>    - primary ignition wire (white) from the switch to coil (cycle the
>    connections)
>    - motor ground straps (cycle the connections)
>    - loose wires in the dizzy
>    - loose ignition wires into the dizzy or spark plug
>
> Other things to possibly do (as secondary):
>
>    - replace rotor
>    - replace dizzy cap
>
> I don't think it would be contacts or condensor simply because this would
> either be very regular all the time, or maybe sensitive to temp.
>
> Best,
>
> Alan
>
>
> On Thu, Sep 29, 2022 at 4:46 PM Bob Spidell <bspidell at comcast.net> wrote:
>
>> re: "... I don’t recall if that wire is separate from the distributor
>> wire ..."
>>
>> It is (or should be). If the battery switch is in the 'OFF' position it
>> grounds the coil primary so no spark.
>>
>>
>> On 9/28/2022 8:34 PM, Alan Seigrist wrote:
>>
>> Hi Michael -
>>
>> Have you tried cycling the connections on the white wire from the
>> ignition switch to the coil, and also from the coil to the distributor.
>>
>> You might also want to try disconnecting the black and white wire at the
>> coil from the battery master switch - if it’s failing you’ll get weird
>> symptoms like this.  If that wire is disconnected the car should run no
>> problem.  I don’t recall if that wire is separate from the distributor
>> wire, if it isn’t you’ll have to disconnect it from underneath the master
>> switch itself.
>>
>> Best,
>>
>> Alan
>>
>>
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