Was driving home from work this morning, and the tach needle flatlined.


Now here's the clutch- I drive a L-jet car. So the problem can't be at the dizzy because the tach signal triggers the F.I.,, Right???

Any help would be appreciated...

The tach signal is from the + side of the coil .... how 'bout the wire from the + side of the coil to the relay board to the main harness thru the fuse panel to the guage? Run a wire, temporarily from the + side of the coil to the tach input and see if it works again.

I am pretty sure that the tach circuit is an independant circuit, so it can have and issue and the car will still run.

I agree with above, run a seperate wire to the tach for a test.
I have seen the tachs with two conditions so far, and I am sure there are more.
One is the bearling that supports the needle is starting to fail, and can lock up tight...so not movement.
The other is the inner circuit in the tach is corroded, so the tach bounces around alot.
Both can be fixed by Palo Alto Speedometer/North Hollywood speedometer.
I am pretty sure the signal for the FI is from the coil, not the tach.
The tach gets its signal from the coil also.

Rich

Slits, the tach and L-jet signals come from the (-) side of the coil, where the points plug in.

Sounds like the tach is dead, probably mechanically. Electrical problems in the tach would tend to make the car run poorly due to inconsistent ignition and/or injection.

--DD

New tach?

Uhhhhh, Slits? WROOOOONNNNGGGGG!!!!!!!!!!!!! Tach signal is from coil terminal 1, which is the point side of the coil, and that's NEGATIVE. Also known as ground, or (-).

The Cap'n

Boy. I'm sure glad I didn't listen to slits....







My tach used to be really bouncy. I guess that means that I've got to go and get that mechanical tach out of that junk RSK over at Al's....

That "ratchet down" thing is wicked cool.

How exactly would a 'mechanical' tach work on a Type 4?

Unless the electrical problem was high resistance or an open between the coil and the tach. I agree that the needle is a high probablilty suspect but I think I'd be checking continuity before writing off the tach itself. Try an ohm meter between the - coil and pin 7 of the big plug at the top of the relay board.

I stand admonished for misinfomation .... guess I shoulda read what I wrote.

Maybe that's why none of my cars run.