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zulu_warrior1976
 Post subject: Irregular spark
PostPosted: Tue Aug 22, 2017 9:05 pm 
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998cc
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Joined: Fri Jan 28, 2011 1:19 pm
Posts: 533
Location: Adelaide
Hi All,
My 1275 is miss firing badly and I'm having difficulty determining the problem.
Fuel is 98 and is fresh
Carbies are set up correctly
New plugs
New leads
New points
Dizzy has been checked and looks fine
Coil has been replaced
No evidence in dizzy cap of tracing
The only thing left to replace is the rotor....

Is there anything else I might have missed??? :?

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Zulu...

1967 mini Cooper S
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A-7 850
 Post subject: Re: Irregular spark
PostPosted: Tue Aug 22, 2017 9:59 pm 
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848cc
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Joined: Thu Jul 19, 2007 9:05 pm
Posts: 212
Location: CASTE HILL NSW
maybe vacuum leak in brake booster or faulty pcv valve ?
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zulu_warrior1976
 Post subject: Re: Irregular spark
PostPosted: Tue Aug 22, 2017 10:24 pm 
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Joined: Fri Jan 28, 2011 1:19 pm
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Location: Adelaide
It seemed to develop slowly over the course of 2 weeks with a minor miss every now and then. Then one day just started runnin like a wooly goat.

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Zulu...

1967 mini Cooper S
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9YaTaH
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 11:25 am 
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Joined: Sun Apr 11, 2004 11:32 am
Posts: 12390
Location: Sthrn HiLoLands, NSW, Australia
zulu_warrior1976 wrote:
It seemed to develop slowly over the course of 2 weeks with a minor miss every now and then. Then one day just started runnin like a wooly goat.


There's the problem...it should run like a Morris Bull :D

Take off the vac pipe to the booster and see if there is fluid sitting there...when boosters fail it is usually shown as white smoke out the back...

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sitnlo62
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 11:46 am 
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998cc
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Joined: Tue Apr 11, 2006 8:15 am
Posts: 722
Location: Brisbane
Do a compression test, Might be a valve!

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timmy201
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 11:47 am 
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Posts: 4501
Location: Wollongong, NSW
If you have any loose connections to the coil it'll give you irregular sparking. I have had dodgy spade connectors, and dodgy wire crimping which caused me issues

Have you got the dwell set correctly?

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zulu_warrior1976
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 12:00 pm 
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998cc
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Joined: Fri Jan 28, 2011 1:19 pm
Posts: 533
Location: Adelaide
Hi all, should be able to provide an update tonight and will investigate the excellent suggestions that have been made. Thank you all so much.
Z

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Zulu...

1967 mini Cooper S
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ausdino
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 1:23 pm 
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Joined: Tue Sep 27, 2016 12:43 pm
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Location: Brisbane north
Cracked distributor cap ? I've been caught with this one before.

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zulu_warrior1976
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 1:29 pm 
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998cc
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ausdino wrote:
Cracked distributor cap ? I've been caught with this one before.


It looks ok. Will have to double check that.


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Zulu...

1967 mini Cooper S
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zulu_warrior1976
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 2:17 pm 
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998cc
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Joined: Fri Jan 28, 2011 1:19 pm
Posts: 533
Location: Adelaide
Hi All,
Just spoke to the mechanic.... He's checked everything and changed everything that has been mentioned in this post so far. Still backfires like a mofo.
I ran through everything that the kind mini forumites have suggested and they've all been checked.
Both he and I are at our wits end....

Is there anything else it could be?

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Zulu...

1967 mini Cooper S
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timmy201
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 2:20 pm 
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Joined: Sun Apr 29, 2012 1:19 pm
Posts: 4501
Location: Wollongong, NSW
Blocked fuel filter?

Empty float bowl?

Do you have a tacho? Is the needle affected by the misfire?

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zulu_warrior1976
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 2:25 pm 
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998cc
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Joined: Fri Jan 28, 2011 1:19 pm
Posts: 533
Location: Adelaide
timmy201 wrote:
Blocked fuel filter?

Empty float bowl?

Do you have a tacho? Is the needle affected by the misfire?


No tachometer.

Bowl levels look fine.

Blocked fuel filter... will check that. Thanks Timmy


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Zulu...

1967 mini Cooper S
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timmy201
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 2:33 pm 
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Joined: Sun Apr 29, 2012 1:19 pm
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Location: Wollongong, NSW
It might be worth checking the tappet clearances, and compression just to be sure.

A cheap tacho only needs 3 wires - ground, neg coil, pos coil so it's very easy to wire in temporarily. Otherwise a good timing light with a tacho will tell you if it's jumping around. If the dwell is too short the coil won't be charging up fully.

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zulu_warrior1976
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 3:08 pm 
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998cc
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Joined: Fri Jan 28, 2011 1:19 pm
Posts: 533
Location: Adelaide
timmy201 wrote:
It might be worth checking the tappet clearances, and compression just to be sure.

A cheap tacho only needs 3 wires - ground, neg coil, pos coil so it's very easy to wire in temporarily. Otherwise a good timing light with a tacho will tell you if it's jumping around. If the dwell is too short the coil won't be charging up fully.

Compression is 180 consistent across all 4.
Will check the other suggestions
Thanks Timmy


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Zulu...

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whiteysi8876
 Post subject: Re: Irregular spark
PostPosted: Wed Aug 23, 2017 3:56 pm 
replace the condenser in the distributor
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