Tach Problem?

[sand1man]

I recently installed a new set of gauges everything works well except the tach, it seems to move to slowwhen at a constant speed its accurate but when I get on it , it doesn't keep up with the rpms like it's slow, I have it connected to the tach connection on a MSD6al any ideas???

 

[D.Hearne]

did you set the switch on the rear of the tach for a V8, or whatever # of cylinders your motor has?

 

[sand1man]

yes I have double checked that, that was my first thought it reads correct but when the engine turns up quick the tach is to slow my other tach with a 6000 rev limiter installed would hit right at 6000 before the limiter kicked in this one makes it to 5300 b4 the rev limiter kicks in you can also hear the motor reving aslot quicker than the tach moves this only happens at under hard acceleration under normal driving which with a 4.30 gear I don't do much of it's right on the money

 

[Blown4.6]

yes I have double checked that, that was my first thought it reads correct but when the engine turns up quick the tach is to slow my other tach with a 6000 rev limiter installed would hit right at 6000 before the limiter kicked in this one makes it to 5300 b4 the rev limiter kicks in you can also hear the motor reving aslot quicker than the tach moves this only happens at under hard acceleration under normal driving which with a 4.30 gear I don't do much of it's right on the money

Try a different ground, every tach problem I've ever experienced turned out to be a bad or non-ideal ground

 

[mdjay]

Msd

I recently installed a new set of gauges everything works well except the tach, it seems to move to slowwhen at a constant speed its accurate but when I get on it , it doesn't keep up with the rpms like it's slow, I have it connected to the tach connection on a MSD6al any ideas???

Call MSD. They have specific instructions for tach related problems in the installation instructions. These symptoms are explained and they give you the resolution. I don't remember what they prescribe off the top of my head...

 

[sand1man]

I have an email into them just waitning on a response, I've seen where they have some adapters but they specify what problem they correct so just trying to get some more info while waiting

 

[mdjay]

msd

I have an email into them just waitning on a response, I've seen where they have some adapters but they specify what problem they correct so just trying to get some more info while waiting

I found this .pdf instructions for your controller

http://www.msdignition.com/pdf/6series.pdf

This is the area of concern...

INOPERATIVE TACHOMETERS
If your tachometer fails to operate with the MSD installed you may need an MSD Tach Adapter. Before getting an Adapter, try connecting your tachometer trigger wire to the tach output terminal on the side of the MSD. This output produces a 12 volt, square wave (see page 2). If the tach still does not operate, you will need a Tach Adapter. There are two Tach
Adapters: PN 8920: If you are using the Magnetic Pickup connector (Green and Violet wires) to trigger the MSD, you will need the PN 8920.
Tachometer Compatibility List
AFTERMARKET TACHOMETER WHITE WIRE TRIGGER MAGNETIC TRIGGER CONNECTOR
AUTOGAGE 8910 8920
AUTOMETER NONE NONE
FORD MOTORSPORTS NONE NONE
MALLORY NONE NONE
MOROSO NONE NONE
STEWART 8910 8920
S.W. & BI TORX NONE NONE
SUN 8910 8920
VDO 8910 8920
AMC (JEEP) 8910 8920
CHRYSLER 8910 8920
FORD (Before 1976) 8910 8920
FORD (After 1976) 8910 8920
GENERAL MOTORS Bypass In-Line Filter Bypass In-line filter
IMPORTS 8910 8920
Note: On the list above, the trigger wire on tachometers that are marked NONE may be connected to the
Tach Output Terminal on the MSD 6 Series Ignition Unit using the supplied Female Faston Receptacle.
8 INSTALLATION INSTRUCTIONS
PN 8910: If your tachometer was triggered from the coil negative terminal (voltage trigger) and you are using the White wire to trigger the MSD you will need the PN 8910.

If your gauges are not listed, I would give their tech support line a try 915.855.7123 9-5p MT
Chances are the gauge manufacturer has heard this issue before as well.

Good Luck