Tach help

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dickyeb

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I got a 66 dart with 360 in it. Got electric ignition with stock ignition box and mad electrical amp meter removal. Now the problem I have is when hook up a aftermarket tach it won't rev past 4000, remove the tach and its good. I first use a tach with a shift light. Then got a plain Jane tach and it still does it. does any one know what cause or fix Is it back feeding in to the ignition box. Never ran into this. Thanks
 
Is there ANYTHING common to the two tachs? That is specifically, is the wire lead from coil NEG to the tach the same wire?

CHECK that wire if so.

Is there a capacitor/ condenser on the coil? IF so this belongs on the coil POSITIVE terminal, it's for radio noise suppression
 
GEO said:
Is the tach set for 8 cylinder engines?

Start with the simple stuff first
Click to expand...

I don't think that would cause the problem, but what ARE these tachs?

Brand, models, etc? ARE they for certain made for V8 coil triggered?

Some of this marine stuff, example, is made to be triggered off the ripple voltage from the alternator.
 
No not the same wire. There two separate Wires on the same post and there's no condenser on the coil,
the tach I'm ussing now is a sunpro basic. I can't tell how they set it up between v6 and v8
 
The other tach auto meter with rev limit and shift light the one I got is sunpro 2, just a tach
 
What I mean is when you changed tachs did you change the tach wire all the way from the tach to the coil?

Two wires total is what should be on the coil NEG terminal -- one going back to the ECU, and one going to the tach

When you unhooked the tach(s) and it ran OK, did you unhook at the coil neg?
 
Yea ea h time I un hooked from coil. And both tach had different wire. Heck the sunpro is bought brand new today with new wire
 
I read some where that some people put the tach wire on the distributor side
 
dickyeb said:
I read some where that some people put the tach wire on the distributor side
Click to expand...


This according to OP is Mopar electronic ignition. Tach trigger goes on the coil NEG. This is not true if using CD/ MSD, etc.
 
Being stock ign I assume its stock dizzy/cap as well? As 67dart273 said, I believe MSD will mess with the tach.
 
That tach fine its the engine. Won't rev past 4000 like it. It remove the tach and she fine. Like the engine misfire almost at 4000
 
That's why I said think the tach is messin with the igntion box cause the negitve coil goes to the box.
 
You absolutely sure the coil is not reversed pos/ neg? Yes it will still run
 
Well I didn't know it would still run if its backwards. Learn something new every day. Well on that note no I'm not sure. See I converted the point style harness to electronic ignition.
 
If I had it back wards would would there be any problems I should have notice. Or would there been no diffrence. Cause I just took this car to the track Friday and ran 9 in 1/8 mile with stock rear end and trans.
 
I don't understand what we are missing here.

THIS IS a Mopar ECU, right? Not a Mallory, not an MSD, not some other CDI?

And I do understand correctly? That it runs hard and winds good until you hook up either tach?
 
Yep got a stock mopar ignition box and yes on the last half. It's weird.
 
I figured the first autometer with the shift light and and the presets was interfering. So I bought the sun pro. Plain Jane. And it still does it.
 
Does it miss from a timing change, or from a flat out miss at RPM?
 
Once the tach hooked up its wont rev past 4000 it's like the engine cutting back. Un hook the tach and act like nothing happen
 
It like I got a rev limiter. Know how some cars when they hit a rev limiter it cuts back and does funky stuff. That's what it's doin
 
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