87 tach problem

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Jul 17, 2004 | 03:41 PM

TJ86

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From: Washington Pa.

87 tach problem

Hi all, I just updated from my old reliable 86 to this not so reliable 87, but I'am sure with your help we can get things sorted out.First problem --as soon a I turn on the key (before it's even running) the tach jumps to 800 rpm and just stays there. It doesn't matter how fast the engine turning it stays at 800 till you turn the key off then it drops to 0.I cleaned the sensor and the plug but it didn't make any differance. Any ideas??

Jul 17, 2004 | 05:14 PM

Dave Sponaugle

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From: Nutter Fort, WV

What does it do if you unplug the sensor and turn it on?

Jul 18, 2004 | 05:22 AM

TJ86

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From: Washington Pa.

That was a good question, it does the same thing unpluged...What does that imply a bad tach??

Jul 18, 2004 | 11:35 AM

Dave Sponaugle

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From: Nutter Fort, WV

That would be my first guess.

Jul 19, 2004 | 09:31 PM

thechad

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From: Ione, CA

I have found that the tach's themself go bad really easy in the 6.9 and 7.3 so if you know how take it out and test it, or take it somewhere to be tested.

Jul 20, 2004 | 11:51 PM

Spectramac

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From: Monroe, WA

This will sound horrible, but whenever my tach acts up, I give the dash a whack and it straightens back out. Helps my sticky voltmeter too.

I imagine my truck will get back at me some day by blowing all the dashlights in the middle of the night.

Jul 21, 2004 | 09:07 AM

lilbuj

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Voltage

Does anyone know the proper voltage that the tach sender should be putting out. I am getting ~.9 VAC at idle and it will go up to ~3 VAC when it the engine is reved up? Is this the correct range?

How can one test the tach?

Thanks,

Joshua