1HZ Tachometer only working when cold

[Blomdala]

Anyone seen their tach doing this? MY Tach is completely unresponsive when I first start the truck, then I slowly increases its sweep as it warms up until it finally works as expected.... The connector from the sensor on the pump is right under the oil filter so it has a little oil on it from changes, but other than that it seems like the wiring is in good shape (and its behavior doesn't point me towards faulty wiring)

 

[TreadingLight]

I'm resurrecting your thread as I too have an intermittent tach on my 1HZ (getting the input off the back of the injection pump). My wiring looks good at the IP.

In my case, I rarely get any reading on my tach. It's intermittent but doesn't seem to be temperature related.

Did you have any luck?

 

[Blomdala]

So I haven't made any progress ha! Its warmed up since I posted this so my tach works every time. I'm sure I'll revisit this in the winter, but based on this, I'm expecting that the sensor on the injection pump need to be replaced.

If yours in intermittent and not related to temp, I would definitely take a look at the wiring condition first.

 

[roscoFJ73]

I'm expecting that the sensor on the injection pump need to be replaced.

If yours in intermittent and not related to temp, I would definitely take a look at the wiring condition first.

I see it the same way. But I would check the wiring and connectors on the tacho harness and give them a clean

 

[TreadingLight]

I have been meaning to get into the dash and figure out how to turn off the timing belt light for a while now. Probably a good time to give it all a good once over.

 

[roscoFJ73]

I have been meaning to get into the dash and figure out how to turn off the timing belt light for a while now

An easier way is to remove the rubber plug on the clear dash plastic and poke something down the hole. It has a switch in there that resets it.

 

[Supra88]

So I haven't made any progress ha! Its warmed up since I posted this so my tach works every time. I'm sure I'll revisit this in the winter, but based on this, I'm expecting that the sensor on the injection pump need to be replaced.

If yours in intermittent and not related to temp, I would definitely take a look at the wiring condition first.

...

 

[roscoFJ73]

I tried pulling the gauge cluster today and there is absolutely zero slack in the harness so I was unable to pull the cluster off the harness. Is this normal or did a previous owner do some "rewiring"?

Ive had 3 of them off and you can unplug them and get enough room to look at the back. From memory they have a fixed plug the dash fascia sits in. I only had to replace oil pressure gauges or speedo cables

 

[whiteysrampage]

I have a similar issue. My tach will be zeroed out until 1500 or greater and then spring to life until I left off the throttle, then it drops dead. Only to jump back up as soon as I give it gas again.

Then of course sometimes it works perfectly normal. I have no clue what do do with it.

 

[Supra88]

I have a similar issue. My tach will be zeroed out until 1500 or greater and then spring to life until I left off the throttle, then it drops dead. Only to jump back up as soon as I give it gas again.

Then of course sometimes it works perfectly normal. I have no clue what do do with it.

My issue was 100% tied to the ground being disconnected on the back of the engine block. I had similar symptoms.

 

[whiteysrampage]

My issue was 100% tied to the ground being disconnected on the back of the engine block. I had similar symptoms.

Hey thanks! Guess I'll go rooting around for that.

 

[veiloctane]

had the same issue I found a ground screw that came loose off of the membrane circuit. probably dude to vibration.

 

[whiteysrampage]

had the same issue I found a ground screw that came loose off of the membrane circuit. probably dude to vibration.

On the back of the guage in the dash?

 

[veiloctane]

On the back of the guage in the dash?

On the back of the cluster right on the membrane there is a screw and a nut that was about to fall off. I simply tightened and it started to work again.

 

[whiteysrampage]

My issue was 100% tied to the ground being disconnected on the back of the engine block. I had similar symptoms.

Do you recall whereabouts this ground was? I have looked but am not too sure where I should be looking.

Thanks!