Tachometer break and fix and break again and fix again?

[None_zero]

So I'm trying to figure out something simple and dumb (like usual) when the engine is off should the tach sit directly on zero or does it drop lower like some gauges?

 

[None_zero]

I think I can feel datzenmike fuming from all the way in Vancouver Island over the revelation that I broke the tach needle and forgot about it.... lol

[datzenmike]

I have a late 720 tach laying around somewhere, that said it drops against a stop and there is a very fine clockwork spring that returns it to the zero and holds it there. If the needle was off I don't know how that will affect the return spring.

[None_zero]

Do you mean a stop on the face like the speedo has? If so mine doesn't have that. To return the tach to a zero setting I pushed it around until the spindle stopped and the needle kept going so that it changed position on the spindle and dropped back to zero when released

Edited March 3, 2023 by None_zero

[None_zero]

That being said. Where before it was reading zero at idle now when it's idling it sits at like 1500 if I slow the idle down enough to barely get it under 1k it's starting to shake a bit like it wants to stall and my timing adjustment is maxed out to make the 5° when it reads 1200 rpms or so 

[None_zero]

I get a steady timing read on intake one but on exhaust one the timing mark occasionally vanishes for a couple beats or it jumps around sometimes between 3° and 7° ... skitters would be the verb I'd invent to describe the motion 

Edited March 3, 2023 by None_zero

[None_zero]

Also the tach does seem to be moving more like a tach should now. Before it was pretty much topping out at 2k and I'd have to rev it really high to get past that. Now it seems more responsive to the throttle and jumps up to 3k easily on a Rev but even this variation of response probably means it's screwed and can't be relied upon I guess 

Edited March 3, 2023 by None_zero

[None_zero]

I just took it for a drive and it was driving pretty nice actually. Snappy acceleration and I could even accelerate up a hill in 4th gear (remember it's a 4 spd not a 5 spd) but when I come to a stop it definitely would die if I didn't keep it going with the gas pedal so Maybe the issue here has been I've had the rpms set to high because I don't have an accurate reading and the idle mix isn't right because the throttle is sticking and so it's difficult to tell where my best idle is when it isn't representative of the actual idle after I goose the throttle a couple times as per the instructions in the fsm. I suppose the throttle is sticking either because the cable is bad or the spindle on the throttle plate is gummed up. So I guess when I get the new throttle cable I can rule that out and if I still have trouble it's gotta be the throttle itself sticking right?

[None_zero]

And the higher rpms seem right because right now it's the only way I can get a smooth idle which unless I'm mistaken would also explain the crap gas mileage?? Tell me I'm right one time Mike! Unless you think I'm wrong then say that instead.  

Edited March 3, 2023 by None_zero

[None_zero]

One more thing. Are we absolutely sure that the tach drops to zero flat when off? Every other gauge drops lower when powered down. I really would rather fix that than replace it if there is any way possible because if I have to replace the tach I might as well do a whole new cluster. Make a little custom one with a tach a temp gauge and a fuel gauge and a place to clip my phone in where the speedo goes. Since I use waze to track my speed if I'm worried about it 

Edited March 3, 2023 by None_zero

[None_zero]

I've never gotten a speeding ticket in this truck though because even the times I've had it going 92 miles an hour (that's with the pedal floored going down a hill) any cop that clocked me would just pull me over to say he couldn't believe this old truck would go that fast. I've gotten out of at least 3 tickets one for a tail light, one because the truck isn't the color its registered as and another for the same tail light. As soon as they get done asking my if I know why they pulled me over I launch into a protracted story about all the things I've done to fix the truck or just keep it running. And by the end their so ready to shut me up they say alright well get that fixed and drive away as fast as they can. You'd be surprised how much you can say about taking a bucket seat from a van and cutting a section out of the middle and welding it back together so it will fit and match the bolt holes. 

Edited March 3, 2023 by None_zero

[datzenmike]

10 hours ago, None_zero said:

I just took it for a drive and it was driving pretty nice actually. Snappy acceleration and I could even accelerate up a hill in 4th gear (remember it's a 4 spd not a 5 spd) but when I come to a stop it definitely would die if I didn't keep it going with the gas pedal so Maybe the issue here has been I've had the rpms set to high because I don't have an accurate reading and the idle mix isn't right because the throttle is sticking and so it's difficult to tell where my best idle is when it isn't representative of the actual idle after I goose the throttle a couple times as per the instructions in the fsm. I suppose the throttle is sticking either because the cable is bad or the spindle on the throttle plate is gummed up. So I guess when I get the new throttle cable I can rule that out and if I still have trouble it's gotta be the throttle itself sticking right?

 

What appears to be a hanging throttle cold be the BCDD. Did you take the rubber plug off and turn the adjusting screw counter clockwise a turn or two. I mentioned this several times. Might cause over rich also.

 

Distributor is maxed out again?????? How??? I said to leave the vacuum advance hose off. And single wire plug disconnected.

 

Tach reading is a function of the coil firing. If ignition is breaking up (miss firing) then it will read erratically. Tach is not to be trusted at the moment.