tach is freaking out

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needsaresto

needsaresto

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My stewart warner tach has recently begun to behave erratically. The needle bounces around when the motor is revved and fluctuates wildy. It seems to hold steady at idle though.

What gives?
 
I had a tach do the exact same thing and just thought it was bad until one day I went and changed my ballast resistor and presto! after that it was steady as a rock. I was checking for something unrelated and notice my coil voltage while running seemed low for my new electronic ignition so you might want to look at your voltage to the coil since it reads the signal from it.
 
Wires are MSD and in good condition. Not that old really as the car didnt see much use after putting them on.

I installed a new electronic ign harness yesterday,but it was acting weird prior to that.

Will double check the ground. Been going through them all one at a time.

Ballast is 1/4 ohm msd and ecu is fbo,as is the coil.Plugs are Bosch irridium.

Nice,reliable ign for the street.

I'll check the voltage and ground,get back to you tommorow.
 
If you are running E3 sparkplugs your tach will start to bounce about 3 days after you install them. They are the biggest overpriced piles of crap on the planet.
 
360scamp said:
If you are running E3 sparkplugs your tach will start to bounce about 3 days after you install them. They are the biggest overpriced piles of crap on the planet.
Click to expand...


????????

Why would a plug cause a tach to act wonky?

I was actually temted by the E3,if only because of the good luck I had with splitfires in the past. They stayed so clean you could never read the plug as a tuning aid!

They are pricey though. I'll wait till the're on sale and try em in the Van.

I had the tach directly grounded to the battery negative. Maybe I'll ground it elsewhere,or tap into the line and add an additional ground somewhere in the interior.
 
I had them in the 360 that was in my Scamp and my tach started bouncing at idle and it wouldn't read right. I did some research and found out that they did it to a lot of people. There was someone on FABO whose wife drove a newer Ram and it did it as well, the kid at the parts store had a duster with a slant six, we got talking and he said that he had a weird electrical problem with his tach, I asked if he was running E3's, he swapped them out and the problem went away.
As far as I'm concerned I wouldn't even put E3's in a lawnmower!
 
Why waste your money on platinum or iridium for carbureted vehicle? Fuel injection will use them more wisely. Just get a good NGK,ND, or Autolite plug.


PS, I hope you didn't gap them......you can destroy the points on platinum and iridium.
 
Nope,didnt gap em,just jammed em in,lol...as for why irridium,I dunno guess Im a plug junkie,lol!

You guys will be happy to know that the problem is fixed! I simply tapped another ground into the existing one but much closer.Put a ring terminal on it and ground it with the stereo ground which is a known good ground. Problem went away.

Then I got dissatisfied with where it was mounted,so I moved it. Now I need to rewire it,lol!!!
 
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