Tachometer not reading correctly

cuttyman

cuttyman

Not-quite-so-new-guy
Aug 3, 2014
14
9
3
#1
I bought a 1980 calais awhile back and the rpm gauge does not seem to read right at idle it says im at 2200 it sounds like it idles around 1000-1200 in park. When shifting into gear it reads 1500 or so but sounds like around 800. Any ideas on where i could start diagnosing the problem would be appreciated
 
mr evil

mr evil

Moderator
Moderator
Aug 4, 2009
829
399
43
Parksville, BC, Canada
#2
If it's the stock gauge cluster it's likely the 6-8 cylinder jumper at the back of the cluster. Over time that jumper gets loose and likes to jump around.or switch itself over to 6 cyl when it should be on 8. Fix is to pull the cluster and solder the jumper in the correct position. There are a few write ups online about this but I don't have a link handy, try search....
This is on my list of to-do's as mine is jumping back and forth as well....
 
cuttyman

cuttyman

Not-quite-so-new-guy
Aug 3, 2014
14
9
3
#3
If it's the stock gauge cluster it's likely the 6-8 cylinder jumper at the back of the cluster. Over time that jumper gets loose and likes to jump around.or switch itself over to 6 cyl when it should be on 8. Fix is to pull the cluster and solder the jumper in the correct position. There are a few write ups online about this but I don't have a link handy, try search....
This is on my list of to-do's as mine is jumping back and forth as well....

Thanks for reply . i did actually watch a youtube video shortly after this post which shows what you are talking about . if anyone wants to watch heres a link

 
cuttyman

cuttyman

Not-quite-so-new-guy
Aug 3, 2014
14
9
3
#4
If it's the stock gauge cluster it's likely the 6-8 cylinder jumper at the back of the cluster. Over time that jumper gets loose and likes to jump around.or switch itself over to 6 cyl when it should be on 8. Fix is to pull the cluster and solder the jumper in the correct position. There are a few write ups online about this but I don't have a link handy, try search....
This is on my list of to-do's as mine is jumping back and forth as well....

Little update..... I started having idle issues again , so i decided to try and fix this so atleast i could know roughly what my idle was. I pulled the whole cluster , that clip didnt seem to be loose but the contacts were worn out pretty bad where the clip goes on . i did a pretty ghetto solder job as my iron decided to $hlt the bed as i went to fix. But i also had to wedge some spacers into the little clips that contact the lead bolts on back of tach. It seems like it kind of worked ? Lol... Now it says im at about 1100 in gear at idle. And 1500 in park . which is roughly 500-600 lower then what it was reading. If i try to get the car to idle any lower then that it starts to hiccup and run like garbage. So im going to change the fuel filter and hopefully i can get it to idle lower . i went through the vacumn lines again to make sure no leaks . it doesnt seem like there is but i did find a plugged vacumn line not sure where it goes or came from as it was done by the previous owner.
If anyone has suggestions on what else i could check feel free to let me know...
 
cuttyman

cuttyman

Not-quite-so-new-guy
Aug 3, 2014
14
9
3
#5
Update :

Before messing with connections and board of cluster i was roughly seeing high 1900 rpm in gear at idle . lowest i could get this by adjusting idle speed screw was about 1750 before it would start to surge and die. The rpms didnt sound that high and the gauge was off forsure. I played with the board did a poor job soldering the connection for the engine size selector clip. Found some loose connections tightened them up . reinstalled . Tach was now reading roughly 1200 maybe 1250 in gear at idle and start to hesitate and surge. At times. Changed the fuel filter . started like a champ no hesitation. So i turned idle speed down a bit tach reading 1100 which sounds about right .
Now for the real twist .... I backed the idle speed down so far that the accelerator pump is bottomed out and i cannot actually lower the idle anymore .... Tach is reading about 1100 . it sounds like its running at about that it cruises down the back lane without hitting the gas . so the only thing i can think is maybe the mixture screws are cracked wide open , but if that was the case wouldnt it just flood itself out ? its kind of dark now and i dont even know where they are on this quadrajet. Hiding somewhere on me.... This car is such a headache .... I miss my supreme with with my 350 rocket . runs like a champ.... Damn those drunk ******** that smashed it all up....
 
Last edited:
O

oldsmobile joe

G-Body Guru
Nov 12, 2015
822
838
93
mpls
#6
I would suggest using a stand-a-lone tachometer/dwell meter hooked up to the distributor. If you don't have one, borrow one. Or find one used on craigslist. You can verify the accuracy of the factory tach and know what speed your engine is at without running back and forth , looking at the dash.
The engine should idle around 700 rpms. Check your emission label on the fan shroud. It will provide you with the necessary specs on your engine.
 
cuttyman

cuttyman

Not-quite-so-new-guy
Aug 3, 2014
14
9
3
#7
I would suggest using a stand-a-lone tachometer/dwell meter hooked up to the distributor. If you don't have one, borrow one. Or find one used on craigslist. You can verify the accuracy of the factory tach and know what speed your engine is at without running back and forth , looking at the dash.
The engine should idle around 700 rpms. Check your emission label on the fan shroud. It will provide you with the necessary specs on your engine.
Yeah that was my next step my other car i never really had any problems but this thing is all over the place. I would have allready checked that if i had one or knew someone with one. Trying to find if i can rent one. Was injured at work little while back so moneys tight otherwise i just go buy one...
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
23,800
8,892
113
Kitchener, Ontario
#9
contact Bonnewagon (Mark), I sent him my tach that was not reading properly and he fixed it. I wasn't using it any longer as I was using an aftermarket.
 

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