Wacky Tach-y

[SparkandFire]

So I noticed when I bought the truck that the tach is a little strange. Wondering if anyone's tackled this issue before-

Tach drops to ZERO any time RPM's are below 1500, seems accurate above that point.

When the blinker is on, tach goes nuts, bounces all over the place.

I have the suspicion that it's a bad ground in the cluster somewhere, just curious if anyone has any pointers on where to look first???

 

[icanfixall]

Well... That didn't take long to find something to work on... I really love these trucks.... I enjoy lifting the hood and looking for something I "need" to fix.... So, I'm thinking like you on this but.. Try removing the sender in the injection pump gear cover first... It may have some metal on it causing this tach issue. These senders are magnetic so they pickup metal thats sheading off "parts"... thats not really a bad thing cause you don't want those particals floating around in the system so.. The tach sender has more than one purpose.... Then I think its time to really kill your back and get under the dash with a flashlite... Thats the worst place for me to work.... Besides fixing a plugged up toilet here... We have a "special" toilet that sometimes just will plug up for now reason. A "clean" bowl will sometimes fill up and not drain but every other drain in the bath will work fine... Main line is always clear too... Its the toilet of the damned I tell you.... Gotta get rid of that insane thing....

 

[OLDBULL8]

Toilet under the hood?

 

[towcat]

So I noticed when I bought the truck that the tach is a little strange. Wondering if anyone's tackled this issue before-

Tach drops to ZERO any time RPM's are below 1500, seems accurate above that point.

When the blinker is on, tach goes nuts, bounces all over the place.

I have the suspicion that it's a bad ground in the cluster somewhere, just curious if anyone has any pointers on where to look first???

pull the tach sensor. clean off the magnetic face. put it back in. if it works, great! if not....time for a new sensor.

 

[funnyman06]

Well im glad this came up. I just put a tach in my truck and when im idleing, the tach reports about 300rpms. When i push the truck it will run right up to the yellow markings and wont go any further? I was thinking maybe a bad ground?

 

[MidnightBlade]

the governor kicks in right at the yellow markings dont it?

 

[rjglenn]

This is what mine is doing - anything below 1000 RPMs measures as zero, sometimes. Sometimes it works just fine. I've replaced the sending unit, same thing. I've taken the dash apart and cleaned contacts and tightened everything I could find, same thing. I just figure thats part of having a 19 year old truck with nearly a quarter of a million miles on it.

 

[SparkandFire]

To follow up-

I cleaned the sensor yesterday, and heat-shrinked the bare wires coming out of it... there was some improvement (starts to read a little lower now, like around 1000 rpm) but still goes to zero at idle.


Methinks I will do as rjglenn said and "live with it" as part of the old truck thing...

 

[rhkcommander]

Well im glad this came up. I just put a tach in my truck and when im idleing, the tach reports about 300rpms. When i push the truck it will run right up to the yellow markings and wont go any further? I was thinking maybe a bad ground?

same here... i think its the wiring but its raining again or i'd splice some new ones in

and the pos wont start

 

[BrandonMag]

To follow up-

I cleaned the sensor yesterday, and heat-shrinked the bare wires coming out of it... there was some improvement (starts to read a little lower now, like around 1000 rpm) but still goes to zero at idle.

For some reason my tach won't read below about 800 RPM. I did like you and chalked it up to owning a truck older than some of the people I work with.

 

[rhkcommander]

new sensors run about 50-75 and i heard if you use locktite or some other goop or shrink wrap maybe on the new unit that it'd last quite a bit longer from fraying

 

[yotee]

when i had mine, sometimes i would have to slap the top of the dash to make it come around to my way of thinking