After installing aftermarket tach the truck will not start

mattheww2152 · Oct 22, 2024

Hey I’m new to the website and I’m not 100% sure if this is the right place to post this but in my 1986 k10 I wanted to add a aftermarket tach so I installed it and hooked it up to the tach port in the hei but it will not start. I have unplugged the tach from the hei and the truck runs. I relooked over the instructions and looked all over trying to find out why it’s doing what it is but, I haven’t found anything about the problem I’m facing. Any ideas?
-Matt

PrairieDrifter · Oct 22, 2024

Did you wire the tach correctly?

mattheww2152 · Oct 22, 2024

I believe so I’m going to double check again but I just hadn’t been able to find anyone talking about a no start issue after installing one

PrairieDrifter · Oct 22, 2024

mattheww2152 said:
I believe so I’m going to double check again but I just hadn’t been able to find anyone talking about a no start issue after installing one

Wiring can do weird crap if not hooked up correctly. Or in proper working order.

What brand tach?

mattheww2152 · Oct 22, 2024

It’s a equus tach I might mess with the ground and see if that does anything I’m just confused with it preventing it from starting

andybflo · Oct 28, 2024

mattheww2152 said:
It’s a equus tach I might mess with the ground and see if that does anything I’m just confused with it preventing it from starting

I'm assuming you used the tach output on the HEI? The wire that's next to the switched ignition power source for your spark? Check there...

I'd bet you jiggled that wire loose, or you have a dead short, somewhere on the tach signal input wire, drawing current off the HEI.

Unplug the tach lead. re-seat the HEI power. Try to start truck. If it starts, re-add tach lead. You'll chase it out that way.

75gmck25 · Oct 28, 2024

I speak from experience - if that tach lead connected to the HEI is grounded, it stops the engine from starting. In my case ( on a Ford E150) I had run the tach wire too close to the clutch linkage and a worn spot on the wire grounded on the linkage. I could push down the clutch and the engine would die.

scrap--metal · Oct 31, 2024

andybflo said:
I'd bet you jiggled that wire loose

I bet this is it, too.

mattheww2152 · Oct 31, 2024

I did a little more wiring and just added a whole new ground to the truck and it seems to work so thanks for the idea guys

PrairieDrifter · Oct 31, 2024

mattheww2152 said:
I did a little more wiring and just added a whole new ground to the truck and it seems to work so thanks for the idea guys

New tach ground?

After installing aftermarket tach the truck will not start

mattheww2152

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