Adrenalin62 Posted 13November, 2023 Report Share Posted 13November, 2023 The tacho in my '76 2.7 is fine on startup but then goes all over the place when driving commences before sitting on zero! Changed the coil without any noticeable change. Looking for recommendations of "experts" interested in sorting! Quote Link to comment Share on other sites More sharing options...
MFX Posted 13November, 2023 Report Share Posted 13November, 2023 I looked this when I was trying to sort out my bouncing tach issue, but mine basically needs a dampener as it is a different issue. Your issue is likely coming from the signal from your distributor. This is cut from a Datsun forum, but I believe that your issue is probably along these lines.. "..Take off your distributer cap and pull the rotor off, then locate the connecter beside your distributor where the wires connect to the distributor. Disconnect the wires at the connection, using an ohm meter check the resistance of the wires coming out of the distributor, right this number down. With the ohm meter still connected use a halogen work light (or any other hot lamp) and heat up the top portion of your distributer and watch to see if your resistance changes, then after the thing is hot tap on the side of the distributer with a rubber mallet or something similar that will not damage your distributor, again watch for a change in resistance. If you see any eratic or obvious changes in resistance your pickup coil is bad and needs to be changed. Changing the pickup coil can be done yourself but it is not a job for the mechanicaly timid. If this is your problem it will only get worse and your car will start to die on you for no apparent reason, what is even worse is when you take it in to a mechanic they will not be able to find the problem and will probably just replace your entire distributor and charge you an arm and a leg for all there trouble shooting time..." Quote Link to comment Share on other sites More sharing options...
Yeatesy Posted 13November, 2023 Report Share Posted 13November, 2023 If it’s bouncing from 0 to 7,000rpm it could be the alternator and if it’s bouncing in a smaller range like 2,000 to 4,000rpm it’s the tachometer itself. Mine has the later issue is getting repaired soon. Quote Link to comment Share on other sites More sharing options...
Adrenalin62 Posted 15November, 2023 Author Report Share Posted 15November, 2023 Thanks for your input @Yeatesy and @MFX. Much appreciated, will give the suggestions a try! Keen to have it sorted before selling. MFX and Yeatesy 2 Quote Link to comment Share on other sites More sharing options...
Russ Posted 16November, 2023 Report Share Posted 16November, 2023 i'd suggest checking your earth straps too Quote Link to comment Share on other sites More sharing options...
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