2nd last cylinder doesn't receive spark

P

peer oliver schmidt

New member
Feb 10, 2014
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My '73 isn't running happily.

Replaced spark plugs, didn't change things.
Replaced distributor cap, didn't change things.

Went ahead, and took each of the plug wires, plug an external spark plug
into it. 6 of 8 cylinders produce a spark. The 2nd last on both sides do
not, i.e. 5 and 6 if you count from the left top.

Changed distributor caps. Issue remains in 5 (and 6).

Switched cables between 5 and 7, the issue remains in 5.

I am out of ideas, and appreciate feedback from the combined GMCnet
wisdom :-)

Thanks
--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II 26', VA
'73 Sequoia 23', Germany, SH
 
strange. Perhaps you're missing a tooth on the reluctor?

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Johnny Bridges via Gmclist schrieb/wrote
> Perhaps you're missing a tooth on the reluctor?

How can I verify this?

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II 26', VA
'73 Sequoia 23', Germany, SH
 
Check those wires since messing with them changed the scenario...substitute some others that are known good instead of playing musical wires as that
can lead you astray :)
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
Most of the time, those wires are NOT wire, but nylon strands that have
been turned into carbon traces by running huge current through them. They
are extremely delicate, particularly if one pulls on them. The only thing
that they are GOOD at, is TVRS suppression. (Electronic static and radio
noise ). I remember the days of Packard 440 ignition wires. Spark got where
it was supposed to get, every time. But drive it down the street and every
analog receiver nearby had some interference from it. Anyway, I have had
enough new suppression wires not work out of the box to make me suspicious
of any new set. I think they are supposed to have 5k ohms per foot of cable
length when new. Check them with a good ohm meter. Similar length wires
should have nearly the same resistance. Jwik.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

Check those wires since messing with them changed the scenario...substitute
some others that are known good instead of playing musical wires as that
can lead you astray :)
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.

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> My '73 isn't running happily.
>
> Replaced spark plugs, didn't change things.
> Replaced distributor cap, didn't change things.
>
> Went ahead, and took each of the plug wires, plug an external spark plug into it. 6 of 8 cylinders produce a spark. The 2nd last on both sides do
> not, i.e. 5 and 6 if you count from the left top.
>
> Changed distributor caps. Issue remains in 5 (and 6).
>
> Switched cables between 5 and 7, the issue remains in 5.
>
> I am out of ideas, and appreciate feedback from the combined GMCnet wisdom :)
>
> Thanks
> --
> Best regards
>
> Peer Oliver Schmidt

Peer,

Ready for a Way Out test??
When you have the cap off you can see the ring that was added with the install of the Pertronix 1181. Take a small steel something, (I used a small
screwdriver) and run it around the under surface of that ring. It should try to stick to 8 places on the way around. If it does not, there is your
problem.

While I have never had a Pertronix module fail, I did discover a missing magnet in a ring/rotor just once.

We started that diagnostic by pulling the wire out of the cap and cranking and one in the party noticed a missing spark. (Unfortunately, I can't
claim that one.) I was looking and thought it looked good. The above test found the issue.

Other than that, I would be testing wires. That takes a VOM that can read megohms.

Please let us know when you find it.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Pertronix now have the one s that sense the lobe off the shaft, not as
efficient in timing as the 8 magnets, but we do not run into those problems.

> > My '73 isn't running happily.
> >
> > Replaced spark plugs, didn't change things.
> > Replaced distributor cap, didn't change things.
> >
> > Went ahead, and took each of the plug wires, plug an external spark plug
> into it. 6 of 8 cylinders produce a spark. The 2nd last on both sides do
> > not, i.e. 5 and 6 if you count from the left top.
> >
> > Changed distributor caps. Issue remains in 5 (and 6).
> >
> > Switched cables between 5 and 7, the issue remains in 5.
> >
> > I am out of ideas, and appreciate feedback from the combined GMCnet
> wisdom :)
> >
> > Thanks
> > --
> > Best regards
> >
> > Peer Oliver Schmidt
>
> Peer,
>
> Ready for a Way Out test??
> When you have the cap off you can see the ring that was added with the
> install of the Pertronix 1181. Take a small steel something, (I used a
> small
> screwdriver) and run it around the under surface of that ring. It should
> try to stick to 8 places on the way around. If it does not, there is your
> problem.
>
> While I have never had a Pertronix module fail, I did discover a missing
> magnet in a ring/rotor just once.
>
> We started that diagnostic by pulling the wire out of the cap and cranking
> and one in the party noticed a missing spark. (Unfortunately, I can't
> claim that one.) I was looking and thought it looked good. The above test
> found the issue.
>
> Other than that, I would be testing wires. That takes a VOM that can read
> megohms.
>
> Please let us know when you find it.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
Peer,

If I were you I'd order a set of plug wires from:

Dick Paterson's Springfield Performance Ignition: Recurved Distributors, Spark Plug Wire Sets, Rebuilt Carburetors, Engines,
Transmissions

http://www.springfield-ignition.com/

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Peer Oliver Schmidt GMC
Sent: Friday, October 13, 2017 10:13 PM
To: gmclist
Subject: [GMCnet] 2nd last cylinder doesn't receive spark

My '73 isn't running happily.

Replaced spark plugs, didn't change things.
Replaced distributor cap, didn't change things.

Went ahead, and took each of the plug wires, plug an external spark plug
into it. 6 of 8 cylinders produce a spark. The 2nd last on both sides do
not, i.e. 5 and 6 if you count from the left top.

Changed distributor caps. Issue remains in 5 (and 6).

Switched cables between 5 and 7, the issue remains in 5.

I am out of ideas, and appreciate feedback from the combined GMCnet
wisdom :-)

Thanks
--
Best regards

Peer Oliver Schmidt
 
I rescind my comments - I'm totally unfamiliar with the Pertronix product.

Although my current coah has one on it - "Flamethrower"

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Uh Opps. MSD Flamethrower. I'm not familiar with Pertronix atall.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Appears you narrowed it down to a problem with the distributor itself. I would replace the distributor. My personal choice is an HEI as parts are
available every ware but that is your decision.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Glad you found it. This happened to my friend on his Buick GS Pertronix conversion. I installed a newer type with the cam lobe reader. Hope you
changed the oil and filter to get rid of all the fuel wash.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
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