1986 mj 2.8 quirky tach

[The86manche]

 

So tonight i got around to installing my full cluster on my 86 mj with the 2.8.

Almost everything works beautifully. With the exception of the temp gauge because i havent swapped temp switches. I think i got sold the wrong one anyway..

So my issue is that my tach works but it seems oversensative.

If i turn the key to the on position the needle jumps to 0. But when i started it the needle looped all the way around past 70. Pounts almost straight down.

Hooked up an aftermarlet tack, pulled the needle off my tach and set it up to where the aftermarket tach was telling me it was idling. About 700rpm. Now it kind of reads better but its still oversensative. Tap the gas peddal and get it to rev to about 1000 rpm and it will jump up to the 30-35 mark and hover there for a minute before creeping back down almost to the 700 mark. More the 10 mark and would occasionally rise on its own.

Why is it doing this? Where should i start looking to fix this?

Thanks all!

[Green Mesa XJ]

I’ve had trouble with those clusters( 1984-85-86 & early 87) and bad printed circuits but so far not many others on the forums have shared my experiences. The buggy clusters I’ve had all had bad printed circuits, they were peeling away with the metal part of the circuit exposed. Dunno if it was the heat of the south or a exposure to water from a leaking windshield or something. Eventually I dropped a 89-90 cluster in.

Far as the temp sender goes you’ve got to look for a 2.8 s10 or camaro sender, the parts catalogues for the Jeep 2.8 are never correct. Seems like the 84-85-86 2.8 6cyl catalog gets the 87 4.0 senders and sensors.

There’s a recent thread where I posted the GM part number for the temp sender I used. I can try to look it up again if you need it.






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[The86manche]

Thank you for the responce! 

I actually went in and searched for your post about the temp sender and was able to find it, acdelco 213-80, and cross reference it to another brand. So i got that taken care of.

But thats having a bit of problems on its own. Either i don't have a good enough ground for the sender or my gauge/ contacts are improper.

Most of the time it reads right, 220 when warm but it likes to climb to 280 at random and i know its not running hot. It will climb back down to 220, it seems to random to actually be reading hot.

 

And I have reason to believe my tach is actually broken. A bummer.

When i bought the cluster it was damaged as i found out taking it apart to swap my milage into it. My speed gauge was frozen. Wouldnt turn at all. And it looked like it had been dropped on the back end where the cable goes into it. 

This is it. The little needle with the cup on it goes through that hole and into that spring. But the tabs were broken where the clip retains it all.

The housing had warpage on the tabs so thinking about it i wouldnt be surprised if the tach broke internally when it was theoretically dropped.

Mind you i only paid $45 for it and i have 2 others including the dummy light cluster that came out of my truck so i was able to salvage the speed gauge.

But what should i do about the tach? Do they make replacement parts like that? Or source? Or is it something i could fix?