HELP!!!! My tach is reading too high

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victa15

victa15

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I've tried 3 different tacks, and made sure they are on the v8 setting. I have a mild built 318. It idles in park about 900rpms. When I step on the gas (not redlining it) the tach jumps up to over 8000rpms (maxing it out and almost coming back to the begging). All three tachs were the same. I even swaped out the coil. I have the green wire going to the negative on the coil, black to ground and red to ignition. I even tried to put it straight to the battery. I don't know what to do.
 
what kind of ignition system msd example does not hook to coil
 
It's a stock distributor with stock electronic ignition and a stock coil
 
I tried it right off the battery and now I have it ignition on. Where else wouldcan I hook it to?
 
does tach have 4-6-8 setting> May not be set correctly?> I would also check reluctor gap.
 
I made sure its set at v8. Whats the reluctor gap?
 
The reluctor is a gear inside distributor cap, has 8 teeth, one for every cylinder. It spins and once it lines up with the Coil, it causes the magnetic pick up coil to send signal to ECU box. Check if the spacing is correct.
 
Oh ok. Would that cause the tach to be saying my rpms are too high. Thanks for the information. I will check that out in the morning
 
I'm puzzled to say the least, but I honestly can't see the reluctor gap being the problem.
 
Sounds to me like electrical noise.[ame]https://m.youtube.com/watch?v=-6j3glUtecY[/ame]
 
Ok I will try them both tomorrow. Thanks for all the information
 
What do you have for plug wires, and how old are they? Is your tach signal wire anywhere near any plug wires or the coil itself?
 
Thank you Dartman for posting that up,
Victa - does the tach ever settle down or does it just redline every time you give it some gas? What brand and model of tach is it?
C
 
If you have a Mopar Orange or Chrome Box ignition system on your vehicle, rather than connecting the Green signal wire of your tachometer to the negative side of your ignition coil, instead locate the Gray wire running between the Ignition Box and the Distributor. Connect your tach's Green signal wire to this Gray wire for a proper engine RPM signal.

You can try this
 
I have a dixco illuminator tach. But I tried the sunpro tach that I was going to use. My coil is really close to the wires and the wires are about a year old. I haven't been able to check it out today cause I feel a bit under the weather but I will try wiring it to the grey wire first. That might help cause it won't be close at any of the spark plug wires. Thanks for all this info. I'd be lost without it.
 
It's a little bouncy and as soon as I give it gas the tach pegs out past 8000rpms
 
By plug wires, are they "suppression core" or "spiral core". Any of the carbon core wires, "suppression" or not get really noisy when the internal conductor breaks down.

You want to keep the tach signal wire physically separated from the plug wires and the body of the coil.
 
Something that has not been said is to check the wiring at ignition coil. The (+) terminal goes to ignition supply from ballast resistor, the (-) to ignition box and tach.
Also keep plug wires away from the distributor pickup wires.

I do not think connecting the tach to gray pickup wire is desirable.
 
I tried the resistor and now it doesn't read anything on the tach also moved to coil and wires away from and plug wires. It still reads way too high
 
I'm going to switch out my altimator and distributor to see if it might fix the problem
 
victa15 said:
I'm going to switch out my altimator and distributor to see if it might fix the problem
Click to expand...

told you. unhook alternator field and test. alternator may / may not be problem. might be wiring layout, grounding, etc, several stuff
 
I unhooked it and the tach worked fine. So I replaced the altimator and fixed the problem. Thanks for the information. It helped. Also I'm glad I got a lifetime warranty on my altimator lol
 
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