Split tach signal from HEI

[TagAllen]

1995 GMC rcsb. Was a TBI 350/4l60e. Installed a carb 454 and a 4l80e Started it for the first time today. I used the pink wire to power my HEI. Then the tach wire from the cap I split. I hooked one of the wires to the purple/white wire to trigger the pump. The other I Hooked to the white wire in the same plug as the pink coil wire to run my tach. The Pump runs but my factor dash tach seems sluggish and as if its reading low.

I may still have ground issues because I have not fiddled with them much yet.
Do you think this is related to ground issues or should I be able to expect this to work?


Also what does the white wire in the 4 pin plug withe the purple/white wire do?

 

[LC2NLS6]

White is the tach signal out, don't run a pump off that. The pink on the coil from the ignition - is hot Run/Starting that can trigger a fuel pump.

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[LC2NLS6]

The 4L80E needs coolant temp, throttle position sensor and tach signal to work.

 

[TagAllen]

I installed a TPS on the side of the holley and plugged it into the factory tbi tps wire. I hooked the coolant temp sensor back up along with the normal temp gauge sending unit again to the factory tbi harness.

 

[TagAllen]

I am triggering the fuel pump from the HEI tach wire to the purple wire with the white stripe.
But I split the wire I made comming from the Tach spot on the HEI and hooked it to the white wire in the factory loom that is next to the pink wire for the coil.

Do I need to hook into the white wire in the 4 pin connector also?

 

[Sanctified]

I’m in a similar situation. Did you get your tach working?

 

[Schurkey]

Perhaps a moderator will move this thread to LSX Swaps + Carb Swaps sub-forum.

I am triggering the fuel pump from the HEI tach wire

Don't.

White is the tach signal out, don't run a pump off that. The pink on the coil from the ignition - is hot Run/Starting that can trigger a fuel pump.

The pump will run with the ignition turned on.

Most aftermarket installations route power from there, through a normally-open oil pressure switch so the pump quits if the engine stalls...so that in a crash when you're unconscious, the pump isn't flooding the burning engine with gasoline.