rpm tach signal

[RI-Viper]

im installing my INNOVATE 3851 boost and rpm tach. i was wondering where should i grab the signal wire. injector?

[Steve M]

On my Gen 4, I grabbed it off of a coil wire using an MSD 8918 Tach Signal GMR Pickup:

https://driveviper.com/forums/threads/17051-gen-4-shift-light?p=296461&viewfull=1#post296461

This wouldn't be an option on a Gen 3 since they don't use the same coil near plug setup. A fuel injector wire should work though.

[RI-Viper]

any wire on the injector? cylinder 9 should be fine?

[Back In Black]

any wire on the injector? cylinder 9 should be fine?

Are you using the MSD GMR? I would stick with a coil wire. Follow the installation instructions and you should be fine. Any cylinder will work but #9 is closest to cockpit access points.

[Steve M]

Not sure which wire does what on the fuel injectors, but the cylinder # shouldn't matter. If it doesn't work for one wire, try the other. If you have access to a wiring diagram, that would help eliminate the guess work.

- - - Updated - - -


Are you using the MSD GMR? I would stick with a coil wire. Follow the installation instructions and you should be fine. Any cylinder will work but #9 is closest to cockpit access points.

I think he's working with a Gen 3, so I'm not sure that would work for him.

[Ramtuff]

42404
Coil wire will not work on a gen3 period.
This will work.

[RI-Viper]

i have a pectel ecu stand alone system. so i dont wanna mess with this ECU i think the injector wire its going to be

[Ramtuff]

I would contact pectel as you may have a tach signal from the ecu.
I just don’t like tapping into injector signals. Just me. Probably fine.

[LATAMUD]

42404
Coil wire will not work on a gen3 period.
This will work.

Quick comment on the Viper truck and Viper car, the engine harnesses are very different, possibly the pinout for the truck ECUs are different too. I tried to save $100 a few years ago and get a truck engine harness and just "stretch" it so to speak to work in a car that needed a harness. I made it work but it wasn't worth the time I put into it.

To obtain a ECU pinout wire to work in C101 C31, I find ECU pigtails on ebay for like $20-30, the wires separate easily.
https://www.ebay.com/itm/03-Dodge-Durango-ECU-ENGINE-COMPUTER-ECM-WIRING-PIGTAILS-PLUGS-482-OEM-36/174159418766?hash=item288cb5d58e:g:ecIAAOSwFN9eIgx R
42405

[pokeyl]

This is what you want.
https://www.holley.com/products/accessories/gauges_and_gauge_accessories/tach_adapters/parts/8918

[RI-Viper]

i got it off the injector wire. thanks for the replys

[RI-Viper]

update i had to purchase the MSD Ignition 8918. i hope to hook up too the injector wire. since i cant get a coil signal. waiting on part should be here friday

[Steve M]

So I'm assuming you were tapping directly into the injector wire? Was it just not a good connection?

Let us know if the MSD unit works.

[RI-Viper]

the msd unit doesnt work on either injector wire

[RI-Viper]

i tapped into the c31 wire off my pectel system and still no signal to shift light.

[pokeyl]

the msd unit doesnt work on either injector wire

Did you try the coil wire?

[Steve M]

Did you try something other than that vampire tap? Those things regularly make poor connections.

[RI-Viper]

Did you try the coil wire?

didnt think that was a option on a gen 3.

[RI-Viper]

Did you try something other than that vampire tap? Those things regularly make poor connections.

i ohm it out to make sure is make a good connection.

[pokeyl]

didnt think that was a option on a gen 3.

I looked over the specs on your gauge, you just need to set it to one pulse per revolution. This is due to the waisted spark fires once each crank revolution. Try any of the 5 coil driver outputs should work. The coils have much higher amp draw then the injector driver.

[RI-Viper]

I looked over the specs on your gauge, you just need to set it to one pulse per revolution. This is due to the waisted spark fires once each crank revolution. Try any of the 5 coil driver outputs should work. The coils have much higher amp draw then the injector driver.

i have the gauge setup like this

[Viper Specialty]

1. You cannot use an injector signal to reliably get any kind of RPM info. Injectors turn off at decel, go static open at high loads, and have a very tiny PW at low loads. You need either a Coil output, or, a Tach output from the Pectel ECU which it can be programmed to do.

2. Using aftermarket "stuff" to do things that a Pectel controller can do directly, is an exercise in redundancy.

3. Those quick taps will absolutely cost you your sanity, wiring harness, and engine.... eventually.

[Steve M]

1. You cannot use an injector signal to reliably get any kind of RPM info. Injectors turn off at decel, go static open at high loads, and have a very tiny PW at low loads. You need either a Coil output, or, a Tach output from the Pectel ECU which it can be programmed to do.

I didn't think about that...thanks for the insight.

[RI-Viper]

1. You cannot use an injector signal to reliably get any kind of RPM info. Injectors turn off at decel, go static open at high loads, and have a very tiny PW at low loads. You need either a Coil output, or, a Tach output from the Pectel ECU which it can be programmed to do.

2. Using aftermarket "stuff" to do things that a Pectel controller can do directly, is an exercise in redundancy.

3. Those quick taps will absolutely cost you your sanity, wiring harness, and engine.... eventually.

do you know which wire i will need to tap into? either coil (coils under intake) or pectel system? thank you much

[Viper Specialty]

do you know which wire i will need to tap into? either coil (coils under intake) or pectel system? thank you much

Any coil output from either coil block will do the job. I cannot tell you how your car is wired, you will have to trace it. Any of the connected IGN outputs from the Pectel will work just fine.

[RI-Viper]

Any coil output from either coil block will do the job. I cannot tell you how your car is wired, you will have to trace it. Any of the connected IGN outputs from the Pectel will work just fine.

can it be any of these?? pins 1,3,5???

thank you

[Viper Specialty]

Could use 1, 3, 5, 7, or 9.

[RI-Viper]

it worked!! i had to use the MSD unit tho. i tap off pin 1 yellow gray wire. now how do i seal the broken insulation from the t taps? lol

thank you

[Steve M]

it worked!! i had to use the MSD unit tho. i tap off pin 1 yellow gray wire. now how do i seal the broken insulation from the t taps? lol

thank you

Adhesive lined shrink wrap.

[RI-Viper]

that means i have to cute wire and solder it? i just order this Scotch 06149 Electrical Moisture Sealant. wire is just pierced.

[Steve M]

that means i have to cute wire and solder it? i just order this Scotch 06149 Electrical Moisture Sealant. wire is just pierced.

It's not worth cutting/soldering/heat shrinking just for that. If you can remove the wire from its terminal, that would be the way I'd want to do it. If not, it just needs to be sealed from moisture. I've never used Scotch 06149, but that looks like something that would probably do the trick, although it would probably be messy. You could also probably get away with liquid electrical tape.