Tachometer ***SPLIT FROM OIL PRESSURE***

[dmc6960]

Yeah, always floats up like that when I turn it off. Not always 5000, but somewhere around there. Thought that was a DeLorean thing, heard of others that do that same. But maybe it's just a select few of us?

Its normal for it to sit somewhere between 1000 and 2500, occasionally going higher. The needle is supposed to be perfectly balanced, and the actuator for the tach goes limp when powered off. Jumping to 5000 when turning off means that something in the tach's circuitry is spiking it the moment power is cut off. I wouldn't worry about it though as long as it reads properly when the engine is running. FYI, it will also read "fast" if the dash has low power due to a bad ground or bad connection or other, but you've checked most of that out now so I wouldn't worry about it.

[dmc6960]

That's interresting - My temp guage and votage guage are acting funny. NOt sure about my tach when I shut the car off but I do have a high idle - around 1000 rpms. I originally thought this was something wrong at the engine but now I'm suspecting it might just be the goround at the dash.

Some high quality automotive multi-meters have a built-in tach function. You could use one of these to verify your actual engine speed to determine what is wrong.

1000rpm IS about what a under-powered tach will display a standard 775rpm idle. 1000rpm is also a common spot for mucked idles to sit at.

[mluder]

Some high quality automotive multi-meters have a built-in tach function. You could use one of these to verify your actual engine speed to determine what is wrong.

1000rpm IS about what a under-powered tach will display a standard 775rpm idle. 1000rpm is also a common spot for mucked idles to sit at.

I don't know if my meter has an tach function. I'll have to look. I went through the idle adjustment provided by Dave at DMCMW but couldn't get it any lower than the 1000 rpms the dash reads.
If my meter does have a tach function where do I hook it up?

Cheers
Steven

[LordFly]

If my meter does have a tach function where do I hook it up?

If you have a Hz setting on your meter, you might be able to get away with black lead on ground and red lead wrapped around a spark plug wire. ....then multiply by 2 (or 1 if these engines fire on the exhaust stroke, I'm not sure if they do or not).

[Bitsyncmaster]

You normaly connect the tach wire to "-" side of the coil. Ground to engine block.

[LordFly]

Yeah, that might be easier :) But that 1 coil fires 3 (or 6) times per rev, so keep that in mind.

And being that it's a 90° V6, all those firings aren't perfectly spaced. Might confuse the meter slightly, but probably not too much.

[Ron]

If you have a Hz setting on your meter, you might be able to get away with black lead on ground and red lead wrapped around a spark plug wire. ....then multiply by 2 (or 1 if these engines fire on the exhaust stroke, I'm not sure if they do or not).I'm thinking that would toast most of the meters floating around.

=========

Any meter with 6 Cly RPMs will read correctly.

[LordFly]

I'm thinking that would toast most of the meters floating around.

Not directly too the plug wire, just around the insulated part. Spark voltages are generally high enough that a few wraps of the meter lead around the plug wire will induce a readable voltage. Essentially a transformer. Timing lights work off the same principle.

[Ron]

Got Ya!
But, I understand transformers ...and w/o the iron core I doubt it would do anything that way ??
Anyway, Hz = cycles per second, not rounds per minute.

[LordFly]

Got Ya!
But, I understand transformers ...and w/o the iron core I doubt it would do anything that way ??
Anyway, Hz = cycles per second, not rounds per minute.

A transformer will function without the iron core, but magnetic flux travels through iron a lot better than through open air. The iron increases inefficiency greatly. Man, taking electronics in college is finally paying off! :yesss:

You're right, that would give you cycles per second. But it could be converted. 775 rpm +/-50 = 12.9 Hz +/- 0.8 It's not a perfect system, but if you just want to confirm your tachs accuracy, it should work as a cheap solution. Or just get one of the really good timing lights that tells you RPM :D

[Ron]

A transformer will function without the iron core, but magnetic flux travels through iron a lot better than through open air. The iron increases inefficiency greatly. Man, taking electronics in college is finally paying off! :yesss:
Yeah, there are all kinds, but there IS an iron core in the clip you place over today's timing lights. And I'd be surprised if it read any thing intelligible if you did as you said but even wraped it around the coil itself!

Now, If you are going to do all of the converting...there are RPM, MPH, and Mileage formulas floating around on the site somewhere.... LOL