Tach jumps all over
05-28-2013, 04:48 PM
#1
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Tach jumps all over
I have a pair of 500efi's and the livorsi tachs jump all over around 3000 rpm on both engines. Under 3000 they work fine. I just changed to brand new tachs as I thought they were the problem. The result was the same. Anyone have this problem before?
05-28-2013, 05:36 PM
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Unfortunately anything more than replacing something electrical with an identical item is like chineese to me. I can do mechanical stuff no problem but electrical I suck at!
05-28-2013, 06:26 PM
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Join Date: Oct 2003
Location: Ballston Spa, New York
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I had the exact same issues with a 358 Sonic.I had one tach fail and couldn't get the replacement to sit still over 3000 rpm. I went back and forth with Gaffrig and probably tried 4 or 5 different tachs before I finally got them to operate correctly. They were baffled too and sent me all different wiring configurations before we found the right ones. I'd call them and tell them the issue. They were great with my problem
05-28-2013, 07:44 PM
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Do you have factory plug wires? I know you didn't mention anything about doing any other work then the tachs but I've witnessed the exact thing you mention when a friend had a 500 efi and he ran the 8.8 wires instead of the factory merc wires. Maybe something with the resistance? It was the only thing he changed on the motors, put a brand new set of factory wires back on and tach was "normal" again. Not an expert opinion just my .0000002
05-28-2013, 08:15 PM
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It has moroso wires. Factory merc wires might help?
06-02-2013, 08:59 AM
#9
I had the same problem on one of my 500 efi's it happened to be one of the wires on top of the coil that was defective. Crank the engine and jiggle wires on the coil and the distributor to see if there is a change in engine rpm or sound. It's definitely electrical problem though.
