Tach Question

I've got a 78 225 even fire engine in my 67 cj5.
I have a Sun Super tach 2, she decided to give up the ghost, I think.
She's idling at 4500 rpm, when you give her gas the needle goes down.

I looked at some of the various sites on the computer, and am now really confused, electric, mechanical, etc.

All I want is a tach that I can plug into the tach side of my EFI ignition coil.

Any suggestions, on what I need?

Thanks
Jim

 

I'm guessing the tach is not operating correctly.
These are easy to connect. I've done the very same thing with mine and no trouble.
Make sure the switch on the tach is selected to the same number of cylinders of your engine (if so equipped). Make sure it has a good ground, too.
How to Install a Tachometer - OnAllCylinders

 

Pulled the tach out the other day, rechecked that the switch was in the correct cylinder position on the tach.
The ground wire runs right to the engine block.

 

Sounds like the tach is dead/dying. I’ve had them do similar before. Tachometers are readily available in many cost/quality levels. One thing I recommend is get one with a selector switch for number of cylinders and not the ones where the wire must be cut.

 

Ayuh,..... Electric tach's get their signal from the coil's (-) tiny terminal, which sounds like what you need,......

Boat tach's go crazy on occasion,. 'n rather than just checkin' the selector switch on the back, move to from one end to the other a few times,....
Many times, that "Fixes" it,....

 

Double check the power to and ground. Mine will go negative when the connector comes off the ignition switch. I thought the white wire was the backlight?

 

Not that I suggest this as a solution, but I have an ancient 2" tach in my 3B that wasn't working. After I flopped it on the Rubicon it started working again...

 

Does it have to be on the Rubicon or will any flop work?

 

Well, I only did it the one time, but I think the hard landing on granite helps knock the 50 years of silt out of it.

 

I did try moving the switch around when I had the tach out of the dash, but that didn't seem to help.
Hit it with the air compressor to, no change.
I don't have another running jeep around to flip flop the tach, thought about hooking it up to one of my other old "toys", but decided it's a cheaper in the long run to buy a new one.
Even when your retired, wasting time is not cost effective. LOL
I'm way ahead of you guy's. LOL

NO, even if it's junk, I'm not going to drop it on a granite slab!

Ordered a new tach last night.

Here's one on the flip-flop theory.

Bought some fancy new iridium plugs last week.
Installed them, got a little pop going on the right side.
Decided to pull the plugs, and flip-flop them to the left side.
Now I have a pop on the left side, hmm.
Obviously we have a bad plug, unless one of you guy's think I should throw them on the floor, to get-em to work. LOL
I'll pick up their replacements this morning, bought 8 plugs in case we get some more bad ones. lol

Thanks again
Jim