Hello all. I am as usual doing something that I have no clue about. I had my motor start knocking bad last week so I called around and got prices on rebuild from different places and much to my surprise they ranged from 7 to 12k. So I decided to go to the bone yard and buy used and try to transplant my self. Much to my surprise the new transplant arrived in great looking condition as well as a fresh coat of yellow paint. I swapped out motors. It was actually a really simple job, or I got really lucky. However after the transplant the tach gauge dose not work upon start up. As long as you let the motor sit idle it never works. But as soon as you bump the throttle up the gauge pops up and works perfectly until you shut off the motor even at an idle. Also I got an alternator light on now that I didn't have before. These seem to be the only two problems to the new transplant. Any suggestions for me? Also none of the gauges work fuel, water temperature, or oil temperature. But them 3 didn't work with the old motor either. Any suggestions for me?
Funny, I have the same tachometer issue on a JD. Is that a motorola alternator? The fuel gauge has nothing to do with the motor. Did you swap the old sensors to the new engine? The first place to start is to ground the wire at the sender, this should cause the gauge to move up and down as you touch it to ground and "release". If the gauge doesn't move then the sender is not the (only?) issue.
I did not swap the old sensors over. None of them worked on the previous motor either. I replaced the fuel sending unit about 6 month ago hoping to make it work with no luck. I am guessing that the gauge problems lay in the cluster panels or in the wire harness but don't know where to start looking or how to test. I have no idea if it's a Motorola alternator.
My JD tack runs off the alternator. If the alternator is bad, the tack can be erratic or not work at all.
Sounds like your tach and alternator don't reach self-excitation at idle. Check your belt. If it's slipping the alternator isn't at engine speed.