72 R500 351CJ 4V w/factory gages: My tachometer does not always give a good reading. Today, with the engine idling at what was surely 1000 rpm, the tach was reading something less than 200 rpm. Last Wednesday while tooling down the interstate, the tach was showing 900 rpm when it should have been showing something in the 2000 to 2500 rpm range. I don't yet know if the erratic stuff comes when the engine or tach is not fully warmed up but it would seem the tach should do its thing whether or not the engine is fully warmed up. Has anybody had this problem??

 

Not sure if this will help, but I was having a similiar problem with my electronic temp sender. The wire was grounding out, causing eratic readings.

Micahel.

 

Check your grounds on, at, or near the distributor and coil. If you don't have a ground strap off of the distributor, you may look at adding one. Check the bolt down clamp for the distributor and make certain it has a good emtal to metal contact with the block. Tach should be reading off of the coil or distributor. Had a similar problem with my boat. cleaned up the bolt down clamp on the distributor and the problem went away. Since the post is rather old, you may have already fixed it by now. Hope you di anyway.

 

texan2004, thanx for your reply. I haven't had a real chance to check anything: I had open heart surgery on the April 27th and my doctor has said NO to anything close to working on or driving a car. Hopefully within the next three weeks I will be able to check out some ground connections.

 

I think you have your priorities straight. Good luck with the ticker and hope you are feeling better.