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electronic distributor earthing.
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Ray White



Joined: 02 Dec 2014
Posts: 6283
Location: Derby

PostPosted: Mon Sep 13, 2021 10:22 pm    Post subject: electronic distributor earthing. Reply with quote

I always like to have a wire from the distributor to a good grounding point. Very often this is missing on older cars.

Is this still a good idea with an electronic distributor?
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Peter_L



Joined: 10 Apr 2008
Posts: 2680
Location: New Brunswick. Canada.

PostPosted: Mon Oct 18, 2021 11:36 pm    Post subject: Reply with quote

Hi Ray......... Good to read the progress.

Re distributor grounding... I can feel fingers reaching for keyboards.

If your starter motor is bolted to an engine that is, in turn, bonded electrically to the chassis/battery and taking that the said starter motor will require several hundred amps (not the new fandy dandy high torque brushless)... then the miniscule amount of current required by the distributor is not a problem. The only part of the distributor that requires an (earth/ground return) is the capacitor or condenser, a small electrical device connected across the contact-breaker points in the distributor . It helps to give a crisper spark at the plugs and also retards erosion of the contact-breaker points. So... belt and braces, ground/earth, anything that requires an electrical route back to the battery, but in days gone by it was common to send power to a side light, headlight, whatever, and hope/expect that it would be able to find a route back to the battery in order for it to work... Now.. 2021 and fairly previous our modern vehicles have all sorts of things mounted to all sorts of materials that do not conduct electricity... so we now have ground/earth returns via electric wires.

On my modernish, there is not one light, one audible device, or even one, and there are many, sensors that don't have two electric wires.

But to return to your question....... "it cain't do any harm"
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MikeEdwards



Joined: 25 May 2011
Posts: 2463
Location: South Cheshire

PostPosted: Tue Oct 19, 2021 9:24 am    Post subject: Reply with quote

I guess it depends on what kind of electronic system you have.

My Firenza has Lumenition, which is an optical sensor (IR LED pair, I think) mounted in a plastic thing and a "chopper" plate to interrupt the beam which is used to trigger the spark mounted underneath the rotor arm. There are three wires connecting that LED module to the "box", which I think are earth, power in and power out, the box senses when the "power out" wire goes high (or low) and acts accordingly.

My point is, in that specific example, there is no need to earth the distributor at all, because nothing else in it has any electrical connection. If you have a different type of electronic system, it may be using the distributor body as an earth, in which case you'll need to make sure the body is earthed.
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1976 Vauxhall HP Firenza, 1976 Vauxhall Sportshatch (x2), 1986 Audi coupe quattro, 2000 Audi TT
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Ray White



Joined: 02 Dec 2014
Posts: 6283
Location: Derby

PostPosted: Tue Oct 19, 2021 10:59 am    Post subject: Reply with quote

Link to the CSI electronic distributor I am fitting:

http://www.csi-ignition.nl/bestanden/csi-ignition_positive_ground_instruction_manual_-_english.pdf

https://www.ukmgparts.com/userfiles/pdfs/27h5138csine.pdf

No mention of grounding the body of the distributor which is what I was asking about.

I found the earth wire on my 1926 Dodge Brothers had broken off. When I re attached it all my problems with the ignition disappeared!
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Peter_L



Joined: 10 Apr 2008
Posts: 2680
Location: New Brunswick. Canada.

PostPosted: Tue Oct 19, 2021 3:16 pm    Post subject: Reply with quote

Ray White wrote:
Link to the CSI electronic distributor I am fitting:

No mention of grounding the body of the distributor which is what I was asking about.

I found the earth wire on my 1926 Dodge Brothers had broken off. When I re attached it all my problems with the ignition disappeared!


I hope that the actual CSI device is of better quality than the instructions.

From what I see, the CSI "thingy" relies on the the body of the distributor to provide a +ve presence to the electronic switch, not the so called switching bit but the electronic bits that create the switch from open to closed. The current required would be miniscule and metal to metal should be OK. As for the ignition coil, depends where you mount it but a connection to something +ve is required.

The CSI "thingy" switches the -ve coming to it from the ignition switch and it is that very fast break in the circuit to the ignition coil that causes the coil to do its stuff and send a pulse of High Voltage, via the rotor arm to the spark plug, where it jumps the plug gap and goes to +ve ground. The High Voltage is also a complete circuit, so if the engine was totally isolated from the battery +ve there would be no spark.

Re the instructions... reads like so many eastern to English. Arhhh !!!
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Ray White



Joined: 02 Dec 2014
Posts: 6283
Location: Derby

PostPosted: Tue Oct 19, 2021 4:21 pm    Post subject: Reply with quote

The instructions that came with the distributor (ie. in the CSI box) were pretty clear. I also have a contact in the States; Len Fanelli, who is an agent for CSI and he has sent me several graphs showing the different torque curves (I think they are called) available. Any problems he seems happy to help.

Also, as mentioned, our tame auto electrician will be checking out all the electrics on the car before I fire her up.... just to be sure we don't have a bonfire in the garage.! Shocked
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