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Tach Headscratcher
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Author:  6shotvanner [ Mon Oct 12, 2009 12:03 pm ]
Post subject:  Tach Headscratcher
I'm on my second tach in the slantvan in like three years the headscratching part is,The needle wants to 'flutter' when idling :?
This one's an AutoMeter tach and it doesn't always 'flutter'just often enough for a WTF moment now an then.All the wires are good,clean,tight etc.,I don't know coil maybe? I should mention that I've also been through a couple ballast/ecu/magnetic pickups and coils(just for chuckles on the coils) and that this is a retrofit conversion on a leanburn setup and it has died/no restart on me twice which is why the ballast/ecu etc replacement.What say you all? Tach telling me I have other problems?
Thanks
Signed,Fluttered and Flustered :wink:
Author:  KBB_of_TMC [ Tue Oct 13, 2009 9:22 am ]
Post subject: 
It's hard to say much w/o knowing more about your system, but I've opened up a number of tachs (not an Autometer though). The aftermarket ones I've opened up were pretty simple and often based on the NE555 monostable chip or similar.

At very low RPM, most tachs want to flutter a bit and so people put a capacitor across the meter to smooth it out, which also makes it respond a bit slower. If that cap or the input signal filtering goes bad, you could see more flutter. I'd also compare that tach to a diagnostic one and see how they compare.

A more sophisticated tach could use a frequency-locked oscillator to effectively multiply the base frequency, but I've never opened up one that did that.
Author:  zedpapa [ Tue Oct 13, 2009 10:13 am ]
Post subject: 
i had an Equus tach that did that in my dart. ran the power and ground srtaight from the battery and the flutter went away. don't know why.

zedpapa
Author:  6shotvanner [ Tue Oct 13, 2009 10:54 am ]
Post subject: 
First tach did the intermitent flutter thing and then just up and died.This ones been doing it for months now and when I say flutter I mean it's really nervous acting with maybe a 2-3hundred rpm spike with no coresponding engine problems(running nice an smooth)then ok for a week or more then back to flutter/spike.Since I seem to be killing ign pieces just wondering if the two items are connected.Guess I'll just wait for the smoke to come out of something :) :wink:
Author:  KBB_of_TMC [ Fri Oct 16, 2009 12:53 pm ]
Post subject: 
I've seen bad tachs make ignitions run badly, and I've seen bad coils kill ignition modules (and could imagine it killing tachs too) by arcing internally.
Author:  Reed [ Fri Oct 16, 2009 1:01 pm ]
Post subject: 
Might be you are getting high RPM misfire and the tach is actually acting correctly.

A couple weeks ago I installed HEI ignition on my brother's 83 Dodge van. Before the swap, the cheapo tach I had installed was working fine. After the swap, the tach read about 500 RPM too high. Further, after the HEI swap, the engine idle rough, lacked power, and died whenever I connected my external tach to try and adjust the carb.

After scratching my head, I decided to try hooking the old factory Mopar ignition up. This solved all the problems as well as made it run much better.

My point is all your problems might very well be the ignition module.

Since the van was a lean burn originally, I would double check all the wiring and components used. Is seems odd that you are burning out so many ignition components. Seems like maybe someone wired something wrong in the conversion.
Author:  6shotvanner [ Fri Oct 16, 2009 3:58 pm ]
Post subject: 
Somebody wired something wrong you say? Hhhuuummm,guess I'll talk to the 'wiring' guy that did the job.Be back in a minute, have to go find a mirror and talk with him :shock: :lol: OK,he said his confedence is high that he wired it right but if I don't trust him I'm more then welcome to have Reed look at it when I go over to his place with a bunch of parts one day soon. :lol:
Author:  Reed [ Fri Oct 16, 2009 4:19 pm ]
Post subject: 
Hey, I'm not knocking your abilities, I am just saying that we all make mistakes. I have delved into the wiring of vans that have ben converted from lean-burn to something else and it is confusing as heck.

If you are confident that everything is wired up, then I would suspect a coil, ignition module, or distributor pickup issue.

I'll be happy to take a peek when you drop by. I have an 84 van shop manual for the lean burn and some older shop manuals for the standard electronic ignition wiring diagrams. 8)
Author:  6shotvanner [ Fri Oct 16, 2009 4:45 pm ]
Post subject: 
I understand Reed,just joking wit ya abit :wink:
My abilities as an electrical type guy make me a good plumber :lol:
Although when someone dis's my abilities does that make them disabilities? :lol: :lol:
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