pcard

With a points style ignition will grounding the tachometer lead connection at the tachometer prevent spark generation? I am thinking it will. Could it damage the tachometer?

MDchanic

The tach is connected to the negative coil terminal.
If you ground the negative coil terminal there will be no spark.

This is how you turn off many lawnmowers and motorcycles.

- Eric

pcard

Thanks Eric - I thought that was the case.

MDchanic

And, to answer the unasked question, a bad tach can kill your engine, or, even better, create an intermittent poor running condition that can drive you crazy.

Happened to me.

- Eric

pcard

Actually I am going to use this in a stealth cutoff.

MDchanic

Easiest way to do it.

Just don't accidentally leave the ignition on and the switch closed for more than a couple of minutes, as the switch will increase the odds of burning up your coil from 66% to 100% (assuming a dwell angle of 30°).

- Eric

pcard

I had not thought of that. If the bad guys shorted over the ign switch, with the negative terminal on the coil grounded, in addition to destroying the coil would it not also present a fire hazard if left too long?
Perhaps not the best idea.

MDchanic

Yeah, but if you think of every possibility you'll drive yourself crazy.

I wouldn't worry about it, but if you really wanted to, you could totally overdo it and create a timer connected to the oil pressure sender that cuts off power to the coil after 1 minute (or less) of showing no oil pressure, that resets when the ignition is switched off.

- Eric

oldcutlass

But what happens, god forbid someone actually tries to steal it. They crank and crank and crank... coil goes poof because you will have oil pressure. What scenario do you think it will get stolen? While your away from the house?

MDchanic

With several minutes of constant cranking, they'll fry the starter and wires before they fry the coil.

- Eric

pcard

I am planning a road trip from Rhode Island to California next year. This would be about 4-6 weeks on the road and with lots of opportunities for the car to go walk-about.
I am also looking at Viper-like systems, but these do not disable the car.

oldcutlass

IMHO, the biggest worry is having it hauled away on tow truck. I personally like to remove the rotor at night. Not much effort and I've never seen a thief carry one with them.

MDchanic

Coil wire works to.

For added fun, when I did this, I would replace it with a coil wire that had ends crimped on but not connected to the conductor. That way, if they looked, it would be there, and who'd think the wire would be a dummy?

- Eric

70cutty

I like that. I do the same, remove the coil wire.
I never thought of putting a dummy one on there.
Genius.

Fun71

That reminds me of a time back in school when I worked at a NAPA store. A couple school friends showed up in a '71 Mustang and parked in front of NAPA while they went to the grocery store next door, and we swapped their coil wire with a piece of vacuum hose with boots slipped on the ends. When they came back, they couldn't get the car started. We all went out and started giving suggestions, finally recommending they inspect the coil wire. One of them pulled the wire, looked at it and said "Wow, the center conductor burned out!"

We had a good laugh on that one.

I guess one point of my story is even the car's owner and his friend, who were both avid gear heads, had no idea why it wouldn't start, so a thief who is unfamiliar with the car wouldn't know how to start it.

oldcutlass

Sending a girl for a thermostat for a 67 VW Beetle to the parts store, then finding out the guy there actually spent an hour looking for 1.

Fun71

OK, that was funny and made me laugh!

pcard

Great ideas, and easy too. I doubt anyone would spend the time diagnosing with a meter, especially in the dark in a hotel parking lot.

pcard

I have just been doing some research on tracking devices in the US. It seems that they rely on the cell network to communicate. This seems crazy to me given the ability to easily; a. detect the cell signal and b. jam cell network frequencies. If you go on Amazon you can easily find cell phone signal detection and blocking devices.

classicmuscle442

I also use to take coil wire off and lock hood, never thought of dummy wire. You get the star for the day.