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spitting back through Carbs

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Kbeal
Posts: 148
Joined: Mon Feb 15, 2016 9:01 pm

Re: spitting back through Carbs

Post by Kbeal »

Well after much head scratching, stripping down, cleaning and re tuning the carbs, checking timing, compression, distributor advance mechanisms I turned my attention to the electronic ignition, which apparently is very sensitive to voltage drop. I found I had 1.8v drop across the LT winding in the coil (a 1.5 ohm PerTronix flame thrower) and as the live feed for the ignition module (a PerTronix Ignitor) is taken from the SW terminal of the coil that appeared to be the cause. Insufficient voltage to the ignitor module once the coil was under more than ‘idle’ load. I checked all wires and cleaned the connections to the electronic ignition including the earth - all good. But no better performance. Finally I reinstated the old points and condenser taken out 10 years ago - a quick re set of the timing to suit and hey presto full power restored. I also put the old 3 ohm coil back in so as not to burn out the points. So I’m still a bit in the dark as to why the electronic ignition which had worked faultlessly for 10 + years should start playing up but at least the car is running fine now.

Moral of story - if it ain’t broke don’t fix it!

Kevin

bobtills
Posts: 186
Joined: Wed Sep 25, 2019 6:05 pm
Location: North Wales

Re: spitting back through Carbs

Post by bobtills »

Ah, yes, you see. I don't understand all this electrickery stuff.

It's points for me, although I'm not even sure if I understand how to change them, which I must do as I now have a bit of a misfire and it stalls occasionally so I must begin the long task of checking and/or changing all the relevant bits.

Glad you got it sorted.

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Kbeal
Posts: 148
Joined: Mon Feb 15, 2016 9:01 pm

Re: spitting back through Carbs

Post by Kbeal »

Changing the points and condenser is pretty straightforward - I find it's easiest to remove the lot in one from the distributor and disassemble and reassemble on the bench before putting everything back in That way you can make sure that all the wires insulating washers and nuts are in the right place without dropping them into the distributor body.

Now there are reliable condensers available again there is really no reason to switch to electronic ignition for the type of use our old cars get.

Kevin

Tony250w
Posts: 25
Joined: Sun Feb 14, 2016 11:54 am
Location: Leicestershire

Re: spitting back through Carbs

Post by Tony250w »

Having had this same trouble about 18 months ago I was told it was because I had new copper HT leads which were not compatible with Electronic ignition, I reverted to points and have not had any problem since. The electronic ignition was great for a while but I was told that within months, unless I changed the leads that this would happen and it did after about 1 month. Having just purchased the leads from Barry I did not want to lay out for another suitable set so removed the electronic ignition as you have. Glad it seems to have been sorted now

Tony

Bud
Posts: 318
Joined: Fri Feb 12, 2016 9:06 pm
Location: Rochester, NY

Re: spitting back through Carbs

Post by Bud »

Googled this:

https://www.jalopyjournal.com/forum/thr ... es.391152/

I read it through to post #11 to find this from PERTRONIX

Brian-H
Very Wise Man
Very Wise Man
Posts: 1095
Joined: Fri Aug 09, 2019 6:04 pm
Location: UK

Re: spitting back through Carbs

Post by Brian-H »

^ that thread is a gem, especially #11

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Kbeal
Posts: 148
Joined: Mon Feb 15, 2016 9:01 pm

Re: spitting back through Carbs

Post by Kbeal »

Interesting reading post #11

Does he mean that the copper core wires can fail because of the voltage drops and spikes or the PerTronix unit? It’s not clear from the way it’s written,

Kevin

Brian-H
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Location: UK

Re: spitting back through Carbs

Post by Brian-H »

Hmm the ambiguity of the English language , in #11 its the use of "them" in an ambiguous context

#11 says
"With the Ignitor you can use copper core plug wires. We prefer you don't use
these wires because they have caused us issues in the past. We have seen
that the copper core wires leak off the voltage and it can spike the Ignitor
causing them to fail.
I would tell you to change your wires just make sure you keep a good eye on
them. Make sure the connection stay secure and you don't get any breaks in
the wire insulation."

#10 is more precise but relates to a different matter
"The reason for not recommending Solid Core wires with the Ignitor I has to do with voltage spikes, not EMI. The hall effect can be blown out by large voltage spikes and what seems to happen is that as solid core wires in particular get old they tend to leak voltage even more. When this happens they can seek a ground path that causes a high voltage spike and that can fry the hall effect sensor. It does not happen all the time, but it does happen. We see it predominantly in Industrial applications like Fork Lifts where they Never change the plug wires. We'll get a customer that tells us he has blown a couple of modules and after we tell him to change the plug wires to suppression, we don't get the call anymore.
It can happen with old crappy suppression wires as well but is much less likely and frequent."

I think that what they're saying is 2 possible problems
1. poor/irregular spark at the plug gaps due to degradation over time in copper-cored HT wires - the degradation presumably worsened by output from a high energy coil driven from an electronic unit (because electronic units do give a faster rise-time to the driving current in the primary)
2. if you are using a Hall sensor in the distributor, total failure of the Hall sensor

daimlersteve
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Re: spitting back through Carbs

Post by daimlersteve »

Update ?

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Kbeal
Posts: 148
Joined: Mon Feb 15, 2016 9:01 pm

Re: spitting back through Carbs

Post by Kbeal »

Reverted to points and condenser with 3 ohm coil. Re timed and re tuned carbs to suit and now running like the proverbial Swiss watch. The HT leads, dizzy cap and rotor arm were all new 2 years ago so I kept them as I didn't think there would be too much degradation in the 1000 or so miles driven since.

Kevin

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