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  Tach doesn't work at start up or idle--not accurate at higher throttle either.

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Tach doesn't work at start up or idle--not accurate at higher throttle either. by maryjane
Started on: 05-04-2008 10:57 PM
Replies: 7
Last post by: Oreif on 05-06-2008 06:36 AM
maryjane
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Report this Post05-04-2008 10:57 PM Click Here to See the Profile for maryjaneSend a Private Message to maryjaneDirect Link to This Post
Key off-tach needle reads about 200rpm.
Key on-tach needle points to zero rpm.
Upon start, needle does not move, tho engine sounds about right-smooth and no misfire.
Tach needle will move abruptly up to approx 3K rpm if you punch the accelerator hard, but drops back to zero when accelerator is released.
No codes or illuminated check engine light.
84 Indy.

May or may not be related:
OEM radio inoperative, tho clock in radio does work.
Decklid solenoid inoperative--haven't checked to see if there is voltage at the solenoid.
Car starts quickly & easily, runs smoothly, charges @13.5 volts. Brand new battery. I have had the car for only 2 days, so don't know much else about it.

My primary concern is the tach. Is it a flaky tach filter? Where on the 84 Indy is the tach filter?

[This message has been edited by maryjane (edited 05-04-2008).]

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linuxpowered88
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Report this Post05-05-2008 06:16 AM Click Here to See the Profile for linuxpowered88Click Here to Email linuxpowered88Send a Private Message to linuxpowered88Direct Link to This Post
Im not sure where the filter is on the duke but i had a similar problem with my formula. I solved it or seemed to have by adding a 2nd ground and cleaning the one that was there. Its a cheap fix to try and it isn't going to hurt anything. BTW mine would start fine but after a cpl of mins of driving it would no rev past 2400 rpms and would read 0 at low rpms. and my lights would dim and brighten on there own. Good Luck

Edit:Btw it took a cpl of time of driving after i added the 2nd cable for it to work. So it may not be the solution or maybe it was just slow to reset or whatever.

[This message has been edited by linuxpowered88 (edited 05-05-2008).]

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maryjane
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Report this Post05-05-2008 08:20 PM Click Here to See the Profile for maryjaneSend a Private Message to maryjaneDirect Link to This Post
Grounds seem to be ok, and someone else has already added @ least 1 extra ground. Cleaned them anyway, but same results. I always understood the tach filter was sticking out of the wiring harness that crosses the left end of the cyl head. I did find a wire that just loops out of the harness, and goes back in, but it just looks like a wire. Could this be it? Any other suggestions?
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linuxpowered88
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Report this Post05-05-2008 10:19 PM Click Here to See the Profile for linuxpowered88Click Here to Email linuxpowered88Send a Private Message to linuxpowered88Direct Link to This Post
Yeah an easy way to check is to unplug the filter and put a wire jumper in there here is a pic of the filer on rodney's site http://www.rodneydickman.com/n27.html
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maryjane
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Report this Post05-05-2008 10:24 PM Click Here to See the Profile for maryjaneSend a Private Message to maryjaneDirect Link to This Post
Nothing like either one of those pics on mine that I can find. Maybe I am looking in the wrong place?
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ktthecarguy
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Report this Post05-06-2008 03:28 AM Click Here to See the Profile for ktthecarguyClick Here to visit ktthecarguy's HomePageSend a Private Message to ktthecarguyDirect Link to This Post
I am interested in the answer to this also, since I have the very same symptoms on my '84.
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linuxpowered88
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Report this Post05-06-2008 05:45 AM Click Here to See the Profile for linuxpowered88Click Here to Email linuxpowered88Send a Private Message to linuxpowered88Direct Link to This Post
It shouldnt be too far from the distbutor. Archie bolted mine to my head on the v8 swap maybe it was in a similar location stock since it has a holder with a bolt.
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Oreif
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Report this Post05-06-2008 06:36 AM Click Here to See the Profile for OreifClick Here to visit Oreif's HomePageClick Here to Email OreifSend a Private Message to OreifDirect Link to This Post
The tach filter is usually near the distributor. Usually the white wire coming from the distributor goes to it.


The radio clock and the decklid release could be a fuse. Odds are the cig lighter and or horn also has no power.
Check the fuses under the dash. If the fuse keeps blowing, disconnect the cig lighter power.

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