Subject: [TR] Help with Ignition Hiccup

From: George Haynes <[email-masked]>
Date: Mon, 12 Nov 2012 17:52:18 -0500 (EST)

The car with the problem isn't a Triumph, but the best trouble-shooters are on
this list, so:

A 1952 MG-TD has a very random ignition miss.  Like once or twice every minute
or two.  Duration is not long enough to stall the engine, just make it lumpy,
briefly.

We have a tester connected between one ignition wire and its spark plug and
the little neon lamp skips along with the engine miss. So it's not a fuel
delivery problem, but float levels, air balance and richness are good.  As is
the fuel pump.

New: plugs, wires, rotor, cap, points, condenser and coil.  We eliminated the
ignition switch by jumping directly from the battery to the coil.  Timing set
correctly.  Mechanical advance working smoothly, as tested on distributor
machine.  Compression good in all cylinders and valves adjusted correctly.
When it's running, it runs great but...

Still, the occasional hiccup.  Someone suggested a defective generator, which
might be grounding intermittently, shorting the ignition system.  Is that
possible?
We have not disconnected the generator leads yet, but will try it.

Any other thoughts?

Many thanks.  We have already spent wayyy too much time diagnosing this
problem!

George Haynes

** [email-masked] **

Archive: http://www.team.net/archive

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From: [email-masked]
Date: Mon, 12 Nov 2012 19:54:50 -0500 (EST)

How about the little wire in the distributor?  If it is intermittently 
contacting the breaker plate bye bye spark.

Dave

In a message dated 11/12/2012 4:52:54 PM Central Standard Time, 
[email-masked] writes: 
> ignition switch by jumping directly from the battery to the coil.

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From: Randall <[email-masked]>
Date: Mon, 12 Nov 2012 20:31:20 -0500

> contacting the breaker plate bye bye spark.

I agree, but there are two little wires in the distributor, one from the points to the side terminal and another from the moving point plate to the distributor body.  Either of them can be internally intermittent (conductor broken), while looking fine.  And they both flex when the vacuum changes (the vacuum advance moves), which may close the gap.  The wires are special extra-flexible wire, but you can use ordinary stranded wire as a temporary replacement.

I won't say the generator scenario is impossible, but it strikes me as extremely unlikely.  A healthy battery will put out 1000 amps or more while still supplying enough voltage to run the ignition.  The lead to the generator simply won't carry enough to short out the battery (and will let the smoke out almost instantly if you try).

Wouldn't hurt to check the wire from the dizzy to the coil too, if you haven't already.  It is less prone to fail, but it is still possible.

Randall

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From: "TeriAnn J. Wakeman" <[email-masked]>
Date: Mon, 12 Nov 2012 19:12:54 -0700

On 11/12/12 6:31 PM, Randall wrote:
> Wouldn't hurt to check the wire from the dizzy to the coil too, if you 
> haven't already. It is less prone to fail, but it is still possible. 
> Randall
Happened to me once. The wire was evidently damaged during the crimp 
(have since got a proper crimper to replace the multiple whatever 
crimper tool). The constant engine vibrations on the wire cause the wire 
to break inside the insulation.  looked perfect but the ignition 
occasionally missed then as it got worse it missed enough to cut out the 
engine then started right up & acted fine again at an idle. I replaced a 
major part of the ignition before I accidentally bent the wire while the 
engine was running.  From the outside the wire & crimp looked perfect.   
Since then shaking that wire is done early on when troubleshooting a miss.

TeriAnn

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From: [email-masked]
Date: Tue, 13 Nov 2012 16:14:36 -0500 (EST)

Check the spade (or ring) connector at the coil to be sure it's not loose  
or missing a few strands of wire.  If that doesn't help, swap out the rotor  
for a new one....if that doesn't help, swap out the condensor.....all of my 
 "favorite thngs" for gremlin misfires:)
 
Chip Krout
Delaware Valley Triumphs, Ltd.
Skippack, PA 
1962 TR4  CT2052L

In a message dated 11/12/2012 5:53:43 P.M. Eastern Standard Time,  
[email-masked] writes:

Any  other thoughts?