Bad coil?

Yesterday, my '75 RHD std beetle wouldn't start (It might be easier if
you think of it as a '74 since it has a 34PICT-3 carb and the dizzy is
the same as a US-spec '74). It cranks but won't start. Not even a
hint that any of the cylinders are firing. This is odd since it was
running yesterday, though it did seem to be missing a little.
At first, I thought I was out of gas (fuel gauge reads near the top of
the reserve area), but today I took the air cleaner off and moved the
throttle and there was definitely fuel squirting from the accelerator
pump tube into the venturis.
So, I started to look for an ignition problem. I'm running the stock
coil and distributor but have replaced the points w/ the Empi
electronic ignition unit (looks just like Comp-U-Fire). All
distributor parts are less than a month old (plugs, cap, rotor, wires,
electronic point unit). I just set the timing to 7.5BTDC yesterday.
Prior to this it was mistakenly set at 5ATDC.
Because it's running an electronic ignition, I'm hesitant to leave the
ignition on w/o the engine running for any significant time (more than
a few seconds). The instructions say leaving the ignition on w/o the
engine running could damage the unit.

Here's my troubleshooting so far:
I first looked for voltage at the "+" terminal on the coil w/ the
ignition on. My digital multimeter reads 11.8v. For comparison, the
large terminal on the alternator (with the thick red wire) reads 12.3v.
Both seem a bit low to me, but I have been cranking the engine a lot
in an attempt to start the car. The car still cranks strong w/o any
hint that the battery is getting weak.

To test the coil, I disconnected the electronic ignition from both the
coil connections (+/-). With the ignition "on" I connected a length of
wire to the "-" side of the coil. This would act as my manually
operated points. I pulled the coil wire from the dizzy and held it
close to ground (intake manifold heat riser). I then grounded the "-"
wire for a second and removed it from ground. This should cause the
primary circuit to energize and colapse, sending a nice charge out the
HT wire to ground... I didn't see anything (this was done in the
evening). I was holding the HT wire about 2mm from the manifold. I
saw nothing until I let the HT wire touch the manifold. Then there was
a small arc.
To try and improve the lenth of the arc I wired the "+" side straight
to the alternator post to get the best "quality" voltage I could. No
change in the results.

I pulled the coil from the car with it still wired to the alternator
connector and used the alternator case as my ground. Again, I could
only get a consistent arc when the HT wire was touching the alt
housing. I was able to occasionally get an arc to jump the smallest of
gaps (0.5mm), but 1/8" or 1/4" was out of the question.

Does this sound like my coil has gone bad? Was the above test
acceptable for testing coil output? Could my problem be the battery is
too weak at 12.3v? Could the electronic ignition have been too much
for my old coil (my meter showed almost 70-deg dwell w/ the electronic
unit) and killed it?

One last question, if I pick up a new coil that doesn't measure more
than 3ohms across the primary circuit, can I add (or make) an external
ballast resistor so it won't burn out my electronic ignition?



AshMan

AshMan wrote:

> Yesterday, my '75 RHD std beetle wouldn't start (It might be easier if
> you think of it as a '74 since it has a 34PICT-3 carb and the dizzy is
> the same as a US-spec '74). It cranks but won't start. Not even a
> hint that any of the cylinders are firing. This is odd since it was
> running yesterday, though it did seem to be missing a little.
> At first, I thought I was out of gas (fuel gauge reads near the top of
> the reserve area), but today I took the air cleaner off and moved the
> throttle and there was definitely fuel squirting from the accelerator
> pump tube into the venturis.
> So, I started to look for an ignition problem. I'm running the stock
> coil and distributor but have replaced the points w/ the Empi
> electronic ignition unit (looks just like Comp-U-Fire). All
> distributor parts are less than a month old (plugs, cap, rotor, wires,
> electronic point unit). I just set the timing to 7.5BTDC yesterday.
> Prior to this it was mistakenly set at 5ATDC.
> Because it's running an electronic ignition, I'm hesitant to leave the
> ignition on w/o the engine running for any significant time (more than
> a few seconds). The instructions say leaving the ignition on w/o the
> engine running could damage the unit.
>
> Here's my troubleshooting so far:
> I first looked for voltage at the "+" terminal on the coil w/ the
> ignition on. My digital multimeter reads 11.8v. For comparison, the
> large terminal on the alternator (with the thick red wire) reads 12.3v.
> Both seem a bit low to me, but I have been cranking the engine a lot
> in an attempt to start the car. The car still cranks strong w/o any
> hint that the battery is getting weak.
>
> To test the coil, I disconnected the electronic ignition from both the
> coil connections (+/-). With the ignition "on" I connected a length of
> wire to the "-" side of the coil. This would act as my manually
> operated points. I pulled the coil wire from the dizzy and held it
> close to ground (intake manifold heat riser). I then grounded the "-"
> wire for a second and removed it from ground. This should cause the
> primary circuit to energize and colapse, sending a nice charge out the
> HT wire to ground... I didn't see anything (this was done in the
> evening). I was holding the HT wire about 2mm from the manifold. I
> saw nothing until I let the HT wire touch the manifold. Then there was
> a small arc.
> To try and improve the lenth of the arc I wired the "+" side straight
> to the alternator post to get the best "quality" voltage I could. No
> change in the results.
>
> I pulled the coil from the car with it still wired to the alternator
> connector and used the alternator case as my ground. Again, I could
> only get a consistent arc when the HT wire was touching the alt
> housing. I was able to occasionally get an arc to jump the smallest of
> gaps (0.5mm), but 1/8" or 1/4" was out of the question.
>
> Does this sound like my coil has gone bad? Was the above test
> acceptable for testing coil output? Could my problem be the battery is
> too weak at 12.3v? Could the electronic ignition have been too much
> for my old coil (my meter showed almost 70-deg dwell w/ the electronic
> unit) and killed it?
>
> One last question, if I pick up a new coil that doesn't measure more
> than 3ohms across the primary circuit, can I add (or make) an external
> ballast resistor so it won't burn out my electronic ignition?
>
>
>
> AshMan
>

The Coil could still be good. Without the condensor
in the circuit, the spark will be quite tiny.

Any coil you buy should state if it needs a ballast.
The stock VW coil does not need one.

Speedy Jim
http://www.nls.net/mp/volks/

Speedy Jim wrote:
>
> The Coil could still be good. Without the condensor
> in the circuit, the spark will be quite tiny.
>
> Any coil you buy should state if it needs a ballast.
> The stock VW coil does not need one.
>
> Speedy Jim
> http://www.nls.net/mp/volks/

Thanks Jim. BTW, you have a great website! I've been following a lot
of your tech articles to keep my beetle running.

I still have the old points/condenser in the glove box. I'll wire it
to the coil and give it another go.

Will the normal (one person) testing procedures for testing the
ignition w/ points work when you have an electronic iginition? This is
where you turn the engine manually and see that the coil wire throws a
spark at TDC for each cylinder. Will this damage the electronic
module? If it will, I may need to reinstall my points just for the
test.



AshMan

Speedy Jim wrote:
>
> The Coil could still be good. Without the condensor
> in the circuit, the spark will be quite tiny.
>
> Any coil you buy should state if it needs a ballast.
> The stock VW coil does not need one.
>
> Speedy Jim
> http://www.nls.net/mp/volks/

Thanks Jim, you were correct. I wired in the condensor and the spark
output was noticeably higher. Easily getting 1/8" sparks to ground
from the coil wire. So, the coil isn't my problem.

I tried to get the electronic ignition to fire the coil as I manually
moved the crank thru the timing mark... no luck. Not sure if the
electronic module can be tested this way, but as you will see below, it
probably didn't matter.

I took apart the dizzy and found that the electronic module had been
scuffed deep by the magnetic ring. It was on the opposite end from the
hold down hex nut. The gouge was pretty deep and appeared to have gone
thru the epoxy and into the underlying circuits.

Well, time to break out the old points. My old points were pitted so
it was difficult to get the .45mm gap. When I stuck the feeler gauge
in there, the raised portion where the contacts were pitted would
increase the actual gap. I had to sort of "eyeball it". But
apparently it was good enough. I set the static timing at TDC and
fired her up. Vroom!

That's all I had the time to do tonight. Tomorrow I'll set the dwell
angle and readjust the timing. That should hold me until I can get
some new points and/or a new electronic ignition kit.

Thanks again Jim!


AshMan

AshMan wrote:

> Speedy Jim wrote:
>
>> The Coil could still be good. Without the condensor
>>in the circuit, the spark will be quite tiny.
>>
>> Any coil you buy should state if it needs a ballast.
>>The stock VW coil does not need one.
>>
>>Speedy Jim
>>http://www.nls.net/mp/volks/
>
>
> Thanks Jim, you were correct. I wired in the condensor and the spark
> output was noticeably higher. Easily getting 1/8" sparks to ground
> from the coil wire. So, the coil isn't my problem.
>
> I tried to get the electronic ignition to fire the coil as I manually
> moved the crank thru the timing mark... no luck. Not sure if the
> electronic module can be tested this way, but as you will see below, it
> probably didn't matter.
>
> I took apart the dizzy and found that the electronic module had been
> scuffed deep by the magnetic ring. It was on the opposite end from the
> hold down hex nut. The gouge was pretty deep and appeared to have gone
> thru the epoxy and into the underlying circuits.
>
> Well, time to break out the old points. My old points were pitted so
> it was difficult to get the .45mm gap. When I stuck the feeler gauge
> in there, the raised portion where the contacts were pitted would
> increase the actual gap. I had to sort of "eyeball it". But
> apparently it was good enough. I set the static timing at TDC and
> fired her up. Vroom!
>
> That's all I had the time to do tonight. Tomorrow I'll set the dwell
> angle and readjust the timing. That should hold me until I can get
> some new points and/or a new electronic ignition kit.
>
> Thanks again Jim!
>
>
> AshMan
>
Aha!! Good job.

IMHO, simpler is better. Stick with points.
(Or at least carry a set of everything needed to
convert back if something fails on a dark night
on the highway...)

Jim

> Aha!! Good job.
>
> IMHO, simpler is better. Stick with points.
> (Or at least carry a set of everything needed to
> convert back if something fails on a dark night
> on the highway...)
>

I keep my points and such in the box the pertronix came in. Stick that
in the glove box and you'll never be stranded if the pertronix module
goes south.

Chris

wrote:
>> Aha!! Good job.
>>
>> IMHO, simpler is better. Stick with points.
>> (Or at least carry a set of everything needed to
>> convert back if something fails on a dark night
>> on the highway...)
>>
>
> I keep my points and such in the box the pertronix came in. Stick that
> in the glove box and you'll never be stranded if the pertronix module
> goes south.
>
> Chris
>

Even easier in the dark:
Keep a spare dizzy with holddown clamp properly timed, properly gapped
points and a fresh condenser.
This way you only need to remove the 13mm nut for the holddown clamp,
and then swap the whole dizzy, connect the wire from the points and you
are good to go!

J.

Berg wrote:

> Even easier in the dark:
> Keep a spare dizzy with holddown clamp properly timed, properly gapped
> points and a fresh condenser.
> This way you only need to remove the 13mm nut for the holddown clamp,
> and then swap the whole dizzy, connect the wire from the points and you
> are good to go!
>
> J.

Just when I was getting ready to toss that 009 dizzy, there's now a good
reason to keep it. Whatever gets you home, is worth packing under the
back seat... )

Tony

The question that I have is why did the magnetic ring eat the points
module?

Anton

Anthony W wrote:
> Berg wrote:
>
> > Even easier in the dark:
> > Keep a spare dizzy with holddown clamp properly timed, properly gapped
> > points and a fresh condenser.
> > This way you only need to remove the 13mm nut for the holddown clamp,
> > and then swap the whole dizzy, connect the wire from the points and you
> > are good to go!
> >
> > J.
>
> Just when I was getting ready to toss that 009 dizzy, there's now a good
> reason to keep it. Whatever gets you home, is worth packing under the
> back seat... )
>
> Tony

Sloppy, worn distributor shaft bearings?

Tony

anton wrote:
> The question that I have is why did the magnetic ring eat the points
> module?
>
> Anton