Spark/Electrical question

[Scooter311]

Hey Pelicanites
Now that I'm sorta running again, I was wondering what I can do to assure that I'm getting the best possible spark my system can provide. I'd like to clean and inspect all the contacts, cables, etc that have to do with the coil and ground system. Obviously, I've done the wires connecting to the coil, CDI wires, tranny ground strap, and battery leads, but is there anything else that can be done?
I don't have any problems, however when starting it for the first time, I had to jump the system, and I got MONSTER spark - after removing the jumper, it slowed a bit (but still runs and starts nice, just not with as much oomph). Is there a way to get that kinda 'oomph' all the time?

Thank yoo!
Jeff

[914GT]

The stock wiring to the coil through the ignition switch will cause a voltage drop (due to series resistance and inductance). If you wanted to improve things a bit you can use the original coil +12v lead to switch a relay, and connect the relay contacts with a heavier gauge wire directly to the battery and the coil (fuse recommended). On my V8 conversion I found the stock wiring and relay board too wimpy to power ignition and my pump and cooling fans. I replaced it all with two new 40A relays energized by the ignition switch. What a difference that made getting nearly a full +12V to the ignition and cooling system.

[lmcchesney]

Guy, would you provide a schematic or wiring diagram?
L.McC

[Dave at Pelican Parts]

It's a relay... The standard relay wiring setup should work fine.

If you use a relay with the standard Bosch labels, you would connect a large wire from the battery (+) terminal (with a fuse in line!) to pin #30, a ground to #85, the old coil power wire to #86, and a new thick wire from the coil (+) connection to #87.

A relay is an electrically-operated switch. It is spring-loaded to have no connection. When a current flows through the coil inside the relay (#85 to #86 on our round relays), the rest of the relay makes a connection from the input (#30) to the output (#87). When the current stops flowing, the spring breaks the connection.

Electrically-operated spring-loaded switch == relay.

--DD

[914GT]

Easier for me to describe it but I can sketch a diagram if needed. Get a commonly available 30A relay from FLAPS, find a good spot in the engine compartment to mount it. Disconnect the ignition switch +12V wire from the coil and put on a crimp-on terminal. This wire would go to either terminal 85 or 86 on the relay. The other terminal for the relay coil is grounded to the chassis. This does not need to be a heavy gauge wire, #18 to #22 is fine. Put a ring terminal on one end and use a self-tapping sheet metal screw with star washer if you can't find an existing ground screw. Or run the wire to an existing ground lug. The coil (or other switched load) goes to relay terminal 87 and the battery is connected to relay terminal 30. These wires should be a heavier gauge wire depending on length and total current load. A #14 or #12 ga. should be fine for about anything a few feet from the battery. I put in series fuse holders and size a fuse just above the rated load.

I have my coil and water pump off the same relay. I get about a .3 volt drop from a terminal strip mounted next to the battery. With the old stock wiring and relay I was measuring over a 3 volt drop. I don't know what the voltage drop was to the coil with stock wiring, but think of the total wire running from the battery to the ignition switch. Then through the switch back through the seat belt relay (if you have it bypassed) then back to the engine compartment. That's several feet of wire. Before going to the trouble you might take a voltmeter and measure the coil +12V referenced to the battery +12V terminal with engine running to see how much it is. If over a volt or two, it might be worth using a relay. If less than a volt I wouldn't bother with it.

This extra relay has an advantage, you can use it with an alarm system or hidden switch to lock out the ignition.

[Scooter311]

Thanks guys for the details, I'll be doing this as soon as it's settled in. It sounds like an easy, fun project for a change. And cheap, let's not forget that!