Tachometers - JeepForum.com

 
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post #1 of 14 Old 07-22-2013, 07:33 AM Thread Starter
HeathFinnie
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Tachometers

Did different engines use different tachs? I ask because I see some on eBay and some list the engine and others don't. Just curious.

Thanks!

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post #2 of 14 Old 07-22-2013, 07:43 AM
walkerhoundvm
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Yes, all the originals were specific to the engine. The newer aftermarket Chinese junk tachs have a switch so you can change between engines.
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post #3 of 14 Old 07-22-2013, 07:45 AM Thread Starter
HeathFinnie
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Quote:
Originally Posted by walkerhoundvm
Yes, all the originals were specific to the engine. The newer aftermarket Chinese junk tachs have a switch so you can change between engines.
Great- thanks!

If you find an OEM does it say which engine it works with?
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post #4 of 14 Old 07-22-2013, 08:35 AM
walkerhoundvm
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I think there is a printed number - 4, 6, or 8cyl on the back?

You can see in this one I pulled from eBay that there's a "6" printed:

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post #5 of 14 Old 07-22-2013, 09:38 AM
John Strenk
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The 4 cylinder was a different design. It hooked up to the (-) post of the coil...

the 6 and 8 was an inline or series tach.

After market stuff was 4-6-8 selectable.
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post #6 of 14 Old 07-22-2013, 09:50 AM Thread Starter
HeathFinnie
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Quote:
Originally Posted by John Strenk
The 4 cylinder was a different design. It hooked up to the (-) post of the coil...

the 6 and 8 was an inline or series tach.

After market stuff was 4-6-8 selectable.
Thanks. I want an OEM one so just wanted to know what to look for. I also have an HEI so no longer have a coil. (V8 304)

Thanks!
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post #7 of 14 Old 07-22-2013, 09:59 AM
John Strenk
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You still have a coil but it's under the cap..

a Stock Tach will work if it's inline with the power to the HEI distributor.
An aftermarket tach is needed to hook up to the TACH terminal on an HEI.
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post #8 of 14 Old 07-22-2013, 10:08 AM
lsukevinc
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what tach will work with a MSD box?
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post #9 of 14 Old 07-22-2013, 11:06 AM Thread Starter
HeathFinnie
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Quote:
Originally Posted by John Strenk
You still have a coil but it's under the cap..

a Stock Tach will work if it's inline with the power to the HEI distributor.
An aftermarket tach is needed to hook up to the TACH terminal on an HEI.
Aftermarket like a crown OEM styled? My HEI does have a tach terminal that is currently connected to a huge sunpro tach mounted under the dash. I want to remove that and clean up my dash with an in-dash tach and I'm trying to get all the gauges back to stock style.


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post #10 of 14 Old 07-23-2013, 04:44 AM
John Strenk
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I'd have to see it, if it has wires that looks like it goes to a set of earplugs off you iPhone then it will plug into the Tach plug. If the wires are big gauge like you can jump your battery with it, then it will hook up like original tach.
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post #11 of 14 Old 07-23-2013, 10:02 AM
SLO_Ken
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Quote:
Originally Posted by John Strenk View Post
You still have a coil but it's under the cap..

a Stock Tach will work if it's inline with the power to the HEI distributor.
An aftermarket tach is needed to hook up to the TACH terminal on an HEI.
Is this true of any ignition system? Can I make the stock tach work with a later model 4.0 distributor/ignition?

I'm thinking if I splice the tach in K7 between S115 and the Cam Position Sensor? Or should it go inline with the coil (A142 after S109)? Or will this not work at all?
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post #12 of 14 Old 07-23-2013, 10:13 AM
John Strenk
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The crank shaft position sensor run off a 5 volt supply. Might not be enough juice there for the tach.

The last would probably work better, Anywhere between the fuse and the (+) on the ignition coil
but the designation "Ignition coil #1" has me a little worried.

is there more than 1 coil?
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post #13 of 14 Old 07-23-2013, 10:33 AM
SLO_Ken
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Quote:
Originally Posted by John Strenk View Post
The crank shaft position sensor run off a 5 volt supply. Might not be enough juice there for the tach.

The last would probably work better, Anywhere between the fuse and the (+) on the ignition coil
but the designation "Ignition coil #1" has me a little worried.

is there more than 1 coil?
No, only one coil on my '98 4.0. Jeep switched to coil-on-plug sometime in the early 2000's.
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post #14 of 14 Old 09-13-2013, 08:34 PM
SLO_Ken
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Quote:
Originally Posted by John Strenk View Post
The last would probably work better, Anywhere between the fuse and the (+) on the ignition coil
Yup, this works! Although, I did have to tap in AFTER S109... otherwise, the fuel injectors and computer were also drawing through the tach, and it would bounce all over the place.

Thanks for helping me figure this out!
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