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Discussion Starter · #1 ·
I have a Ford 4000, D1014C, newer model (Nov 1968), independent PTO. When I throttle up and down my tach sometimes follows the change in rpms but often it bounces around and doesn't correspond to the change in rpms that I can hear when I move the throttle. The tach goes up and stays up as expected while the engine is running but I can be running along at 1800 rpm and the tach may go up to 2000 or down to 1500 without moving the throttle or any appreciable change in the sound of the engine speed. The tach never goes to zero while the engine is running. Often the tach response is delayed when I throttle up or down.
I put a new cable on but that didn't fix the tach bounce. How do I trouble shoot this? My IT shop service manual doesn't have anything on this that I can find.
I know, not a big problem, but thanks for any help you have.
 

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Discussion Starter · #4 ·
Yep. Removed the cable from sheath and inspected it. Nice, clean, freely moving. Lubed the length of the cable with a liquid lube I use on other cables I have. Reinserted the cable into the sheath and turned it with my thumb and finger. It spun easily. Installed it making sure there were no bends that restricted it from spinning. Made sure the squared ends were properly seated.

Is there any electrical component to this tachometer? It looks likes it's just a mechanical cable like a bicycle. How common is it for the mechanism on the generator end of the cable to fail? What are signs that it may be gettin ready to go? Anybody ever take that thing apart? How common is it for the tach dial itself to begin to fail and show pulsing or bouncing?

Thanks for any help.
 

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You might want to take the drive off the generator end and lube it as well. We all use graphite, not cable lube but I guess that would work, just never used it. Nothing inside the tachometer to cause it to bounce really and I believe it's sealed.
 

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Check if the fitting where the cable screws into the tach is loose, maybe from stress put on cable sometime is past. Tach works by a magnet spinning in a steel cup. if the fitting is loose, the alignment between magnet and cup will not be correct
 

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I have a Ford 4000, D1014C, newer model (Nov 1968), independent PTO. When I throttle up and down my tach sometimes follows the change in rpms but often it bounces around and doesn't correspond to the change in rpms that I can hear when I move the throttle. The tach goes up and stays up as expected while the engine is running but I can be running along at 1800 rpm and the tach may go up to 2000 or down to 1500 without moving the throttle or any appreciable change in the sound of the engine speed. The tach never goes to zero while the engine is running. Often the tach response is delayed when I throttle up or down.
I put a new cable on but that didn't fix the tach bounce. How do I trouble shoot this? My IT shop service manual doesn't have anything on this that I can find.
I know, not a big problem, but thanks for any help you have.
You are still better off than me.
I have 3 Fords of that vintage and the tachs don't work at all on any of them.
About the only thing you need a tach for is when mowing and that is iffy at best. When I'm bush hogging I set the engine speed to about 3/4 throttle and I'm good to go for hours.
 

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Discussion Starter · #9 ·
I'll take a look at the generator tach drive. Thanks for that exploded view. I want to see that gear shaft and get a good look at the part that receives the square end of the tach cable. When I was installing the cable on the tach gauge I spun the cable and could see the tach needle move so I thought the cable and the receiver were properly engaged but I didn't take a light and look down into the tach gauge cable receiver to see if it was rounded off. And I didn't take a close look at the tach cable receiver on the generator but I had to turn the cable a bit to get it into the receiver, like I'd expect if the receiver hole was still square. Based on what I got so far, I'm thinkin the money is in the generator tach drive, maybe that gear, part 25 in the exploded generator picture.
Thanks for the help.
 

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I'll take a look at the generator tach drive. Thanks for that exploded view. I want to see that gear shaft and get a good look at the part that receives the square end of the tach cable. When I was installing the cable on the tach gauge I spun the cable and could see the tach needle move so I thought the cable and the receiver were properly engaged but I didn't take a light and look down into the tach gauge cable receiver to see if it was rounded off. And I didn't take a close look at the tach cable receiver on the generator but I had to turn the cable a bit to get it into the receiver, like I'd expect if the receiver hole was still square. Based on what I got so far, I'm thinkin the money is in the generator tach drive, maybe that gear, part 25 in the exploded generator picture.
Thanks for the help.
Yes, sorry, of course it is #25. I have edited my earlier post.
The square portion of the hole is made by compressing the hollow shaft around a square die. Some are poorly pressed and that results in very little material that drives the cable, and it wears down.
 

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As a matter of reference, the tach on my M9 cab tractor has always bounced a bit, even when new, despite me applying graphite fortified lube to it where as the one on the open station is rock steady. Same tractors one has a cab one don't but the tach drive is the same as is the cable routing and cable sheath. I believe the bounce in the cabin tractor is due to the tach drive cable 'squirming' for lack of a better word, in the sheath. I ignore it. Only thing I really use the tach for is setting the PTO RPM at 540 anyway. I go by the 'seat of the pants' speed input most times and how the implement is acting if it's powered.
 
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