Interesting issue, When tach is hooked up car won't turn off Options

[oildrips]

Lots of progress today/tonight. All vacuum lines rerun, dwell/timing set, new oilnpressure switch, oil changed, and I've isolated the issue where the car won't turn off when the key is removed, but there's some funky stuff happening.

So, before I started working on stuff, the car would start, and the engine would continue to run without the key. You'd have to stall it to shut it off. Once off, it would maintain power to the gauges (the generator light stayed lit), so you'd have to undo the battery. to reset everything.

I traced everything back to the tach. Without the tach signal wire hooked up, the key works fine. Engine starts/stops with the key.

Now, after doing all the work. I started the car, and decided to try the tach. Hooked it up, and sure enough the key didn't work to shut it off. I pulled the positive cable off the battery, and the car kept running on its own. I had to pull the coil leads to kill the engine.

Thoughts?

[904svo]

Just a WAG, try connecting the tack wire to the other side of the coil. Should be connected to the points side.

[Spoke]

I pulled the positive cable off the battery, and the car kept running on its own.

Do you mean you disconnected the positive terminal off of the battery? Or just one of the small wires coming off the positive terminal, leaving the heavy wire to the starter still on?

Don't pull the heavy wire off of the battery positive or negative terminal when the engine is running. This could damage the alternator.

Is the tach working when it is connected?

Not sure how the tach is causing the engine to run after the key is turned off.

Is this something that has been happening since you bought/restored the car? If not, what did you change before this started happening?

With the engine off, measure the voltage on the coil positive; what do you read?

With the help of a friend, measure the voltage on the coil positive. Have the friend turn the key to on, then off. What do you read? The friend is needed so you don't overheat the coil or damage the points with the key on and the engine not running for a period of time like a minute or 2.

[stugray]

When you unplug the battery you are getting run-on due to the alternator providing the power.

In my racecar I have the alternator charge wire go through a second set of contacts in the main switch for exactly this reason.

I have no idea why it is behaving like it is with the tach hooked up.
It must somehow be completing the circuit to ground for something.

And as Spoke says - dont unplug the battery with the car running.
It is the main voltage regulator for the system.
From now on when troubleshooting, to kill the engine, pull the + wire from the coil.
If it keeps running then, there is something very strange going on.

There is a guy at the track whose car will run with the distributor cap laying on top of the engine. We have never figured that one out....

[oildrips]

Ok. So I encountered the same issue today. It's not the tach. And I pulled the switched wire from the coil, and it's still running. I believe I know what the issues is 100%, but need to have a question answered. In the engine bay, aside from the switched coil wire, is there another switched source? Possibly on the relay panel? The PO wired the relay panel (the plug on the driver's side rear corner that has 4 terminals on it) to the coil (it's spliced coil power/cold start valve). So I believe that they intended to use the coil wire (switched with the key) to trigger the relay board.

Sound feasible?

Sound legit?

[stugray]

I pulled the switched wire from the coil, and it's still running.

Sorry I stopped reading right there.

IF the engine is still running with no wires hooked to the + side of the coil, then the engine is "dieseling" which could only mean:
You are using gas that has about 40 octane OR
The engine is severely overheated.

Since I dont believe either of those things, then there MUST be a misunderstanding of something else.

When you say you unhooked the + wire from the coil: So there is NO wire hooked to the + side of the coil, and the engine is still running?

[SLITS]

While this may not be applicable, on my boat with a GM alternator I had to wire in a diode to prevent the Bat terminal on the alternator from feeding the ignition circuit voltage before the engine would shut off with the key switch. I don't remember which wire it was installed in.

[oildrips]

Mission accomplished. So, the PO added an extra wire from the coil power to the relay board power that kept the relay board powered up. With the relay board powered up, it didn't matter whether or not the key was on (the wire on the relay board is connected to the ECU and fuel pump, so the key didn't affect it at all).

The relay is triggered by the switched coil wire, and now everything works, including the tach (IMG:style_emoticons/default/smile.gif)

Super successful weekend.
Electrical issue resolved
Oil changed
Points/condenser replaced
Timing/Dwell set
Idle speed set
Interior panels recovered and installed
Dash vents/pad reinstalled
Wheels/tires swapped over
Broken fog lamps removed (need a new bolt to put the replacement in)

Now all I have to do is drive it.

[theleschyouknow]

Mission accomplished. So, the PO added an extra wire from the coil power to the relay board power that kept the relay board powered up. With the relay board powered up, it didn't matter whether or not the key was on (the wire on the relay board is connected to the ECU and fuel pump, so the key didn't affect it at all).

The relay is triggered by the switched coil wire, and now everything works, including the tach (IMG:style_emoticons/default/smile.gif)

Super successful weekend.
Electrical issue resolved
Oil changed
Points/condenser replaced
Timing/Dwell set
Idle speed set
Interior panels recovered and installed
Dash vents/pad reinstalled
Wheels/tires swapped over
Broken fog lamps removed (need a new bolt to put the replacement in)

Now all I have to do is drive it.

(IMG:style_emoticons/default/smilie_pokal.gif)
way to go! now go drive it!

[oildrips]

Does anyone have a picture of what the inside of the fog light hole should look like/what the brackets are that attach the fog lights to the body look like?