80 series tachometer wiring - cummins swap (1 Viewer)

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Hey guys, I am in the middle of transplanting my 1996 80 from a cummins 4bt to 6bt and while I'm swapping the motors I figured I would attempt to get the factory tach working out since I'm not really happy with the diesel Tiny Tach I've been running. Electrical issues are not my strong suit so apologies in advance. I have looked over quite a few cummins build threads as well as the EWD and just can't come to a conclusion on how to wire it up so I'm hoping the great minds here can sort me out, I definitely wouldn't have made it this far without the wisdowm of kind people on this site.

I am trying to use a stock fzj80 crankshaft position sensor (90919-05041) without any other parts (no ECM, no Dakota Digital, etc...). Here's what I believe is the correct way to wire it - one wire to the sensor connector is a ground, one wire is keyed 12v (this may be unnecessary or incorrect I'm not sure), and one wire is the signal wire the sensor generates a small a/c current on that should go to the tach. I believe the tachometer itself is looking for 3 pulses per revolution and I will be making something to go on the crank pulley/balancer with 3 bosses for the sensor to pickup.

This is bypassing the ECM (it's been removed), but still using the same wire that the ECM would normally provide the signal on which I believe is a black wire pin 10 on E7 connector right behind the glovebox. It's my understanding this signal is not manipulated by the ECM, simply passes it along from the sensor to the tach.

Assuming I have this idea correct, the next thing I need to confirm is which wires on the sensor side are the ground, 12v if needed, and signal. I have made a diagram in ms paint demonstrating my digital art skills and showing what I believe is correct. I'll also include pictures of the sensor and harness wires for reference.
sensor.png


Harness connector:
PXL_20230213_033025858.jpg


PXL_20230213_032944339.MP.jpg
Sensor connector
PXL_20230213_032941461.jpg

PXL_20230213_032952215.MP.jpg


I am assuming two wires on the sensor are tied together before the connector (maybe the black and white?) since only two wires run into the sensor itself. If I need to cut open the insulation to confirm this I can. If this is the case, and 12v power is not needed, would just two wires to the sensor be needed even though it's a three wire connector? A ground and signal wire run to that e7 pin 10 black wire? Would this be the blue or grn/ylw wire or is it all interchangeable the way I'm wiring it up. Anything can be ground and the wire I run to the tach will be the signal wire.


After reviewing this post I happened to look at Wheelingnoob 's build thread and in a very recent post he specifies he used a 2 wire dodge crank sensor, not a toyota, and doesn't mention needing 12v power unless I missed it. Think I can still make this toyota sensor work?


I'm trying not to blow up the tachometer being a doofus so I appreciate the help,
Steve
 
I've put the tach sensor to the side for now to revisit after I've got the motor mounts fabbed up. I'll probably just try it without 12v power first to see if it generates the signal for the tach and if not I'll try adding power to the sensor and we'll see what happens then. I'll post updates some updates once I have some news.
 
The tach doesn't want to see an AC signal. You cannot run the 95-97 dash tachometer with a 2 wire sensor.

You are correct that the tach needs to see a clean 3 pulse/rev square wave 12V DC signal. To generate a square wave 12 volt DC signal you need a 3 wire sensor. Most 3 wire sensors work by grounding the signal wire- Called "sinking". The dash tach needs to see a +12V signal so you convert the sinking style 3 wire sensor to a sourcing type using a pullup resistor. I find a 1/4watt 3.3K ohm resistor does the job well.

I'm not a big fan of the Dodge 12 valve tach sensors. Dodge only used them for a couple years so there's very little support for them. The aftermarket sensors and connectors that are available for the 3 wire dodge sensors are poor at best. More often poor quality China junk and hard to find is the reality.

While you can basically use any 3 wire crankshaft position sensor that will handle 12 volts DC (this is most CPS's from the 90's through the early 2000's), I wanted to future proof my Cummins swapped 80 by using something common.

I tried several industrial ZF geartooth speed sensors and they work great. The problem, THE BIG PROBLEM, is these damn things are never in stock. I was trying to use the best of the best stuff and I can't buy any of it. So I changed my thinking and looked at which sensors are the most prolific and likely to be available in perpetuity. I came to the GM LS CPS's. There's 2 flavors- The early ones are 3 wire 12V, the later ones are 3 wire 5V. The sensors are dimensionally the same, they fit the same space.

Where I'm at now is mounting the senor to a Cummins 12 valve.

There's a few things I don't like about cummins swaps- I don't like mounting a skilsaw blade to the harmonic balancer to run a sensor. I don't like modifying the harmonic balancer to do it. I don't like $200 Dakota digital products comprised of a $4 chinese board in a 20 cent plastic box. I don't like the Dodge tach sensors (already mentioned that). I like to run hydroboost and don't like running the vacuum pump when it's not needed. I kinda like the 4BT style saginaw pump, but I really hate them when you have to change them or R&R the injection pump. Cummins did not think that short little pump out very good for ergonomics. Plus it's clocked wrong for all the common PS pump to hydroboost hoses to fit properly. Plus they want hundreds of dollars for that silly little thing.

That's a lot to read. Sorry. I've had a couple years worth of thinking/planning/testing.

So what I've concluded is if I make my own power steering pump drive using OE Cummins gears to drive the pump at the same exact speed as the crankshaft I can place a trigger wheel with 3 pulses inside the mount and drive an early style 12 volt GM LS tach sensor which will in turn drive the dash tach with only a pullup resistor. Then for a power steering pump I will use the 92-02 Dodge Saginaw pump which is easy to remove/Install and I will attach the pump to the housing with a V-band so it can be clocked wherever it fits the best.

Hopefully you can use some of that information for your benefit or you can just pick one of these pump drives up after they're proven to work well.
 
The tach doesn't want to see an AC signal. You cannot run the 95-97 dash tachometer with a 2 wire sensor.

You are correct that the tach needs to see a clean 3 pulse/rev square wave 12V DC signal. To generate a square wave 12 volt DC signal you need a 3 wire sensor. Most 3 wire sensors work by grounding the signal wire- Called "sinking". The dash tach needs to see a +12V signal so you convert the sinking style 3 wire sensor to a sourcing type using a pullup resistor. I find a 1/4watt 3.3K ohm resistor does the job well.

I'm not a big fan of the Dodge 12 valve tach sensors. Dodge only used them for a couple years so there's very little support for them. The aftermarket sensors and connectors that are available for the 3 wire dodge sensors are poor at best. More often poor quality China junk and hard to find is the reality.

While you can basically use any 3 wire crankshaft position sensor that will handle 12 volts DC (this is most CPS's from the 90's through the early 2000's), I wanted to future proof my Cummins swapped 80 by using something common.

I tried several industrial ZF geartooth speed sensors and they work great. The problem, THE BIG PROBLEM, is these damn things are never in stock. I was trying to use the best of the best stuff and I can't buy any of it. So I changed my thinking and looked at which sensors are the most prolific and likely to be available in perpetuity. I came to the GM LS CPS's. There's 2 flavors- The early ones are 3 wire 12V, the later ones are 3 wire 5V. The sensors are dimensionally the same, they fit the same space.

Where I'm at now is mounting the senor to a Cummins 12 valve.

There's a few things I don't like about cummins swaps- I don't like mounting a skilsaw blade to the harmonic balancer to run a sensor. I don't like modifying the harmonic balancer to do it. I don't like $200 Dakota digital products comprised of a $4 chinese board in a 20 cent plastic box. I don't like the Dodge tach sensors (already mentioned that). I like to run hydroboost and don't like running the vacuum pump when it's not needed. I kinda like the 4BT style saginaw pump, but I really hate them when you have to change them or R&R the injection pump. Cummins did not think that short little pump out very good for ergonomics. Plus it's clocked wrong for all the common PS pump to hydroboost hoses to fit properly. Plus they want hundreds of dollars for that silly little thing.

That's a lot to read. Sorry. I've had a couple years worth of thinking/planning/testing.

So what I've concluded is if I make my own power steering pump drive using OE Cummins gears to drive the pump at the same exact speed as the crankshaft I can place a trigger wheel with 3 pulses inside the mount and drive an early style 12 volt GM LS tach sensor which will in turn drive the dash tach with only a pullup resistor. Then for a power steering pump I will use the 92-02 Dodge Saginaw pump which is easy to remove/Install and I will attach the pump to the housing with a V-band so it can be clocked wherever it fits the best.

Hopefully you can use some of that information for your benefit or you can just pick one of these pump drives up after they're proven to work well.
Great info? Have you started your swap yet?
 
The tach doesn't want to see an AC signal. You cannot run the 95-97 dash tachometer with a 2 wire sensor.

You are correct that the tach needs to see a clean 3 pulse/rev square wave 12V DC signal. To generate a square wave 12 volt DC signal you need a 3 wire sensor. Most 3 wire sensors work by grounding the signal wire- Called "sinking". The dash tach needs to see a +12V signal so you convert the sinking style 3 wire sensor to a sourcing type using a pullup resistor. I find a 1/4watt 3.3K ohm resistor does the job well.

I'm not a big fan of the Dodge 12 valve tach sensors. Dodge only used them for a couple years so there's very little support for them. The aftermarket sensors and connectors that are available for the 3 wire dodge sensors are poor at best. More often poor quality China junk and hard to find is the reality.

While you can basically use any 3 wire crankshaft position sensor that will handle 12 volts DC (this is most CPS's from the 90's through the early 2000's), I wanted to future proof my Cummins swapped 80 by using something common.

I tried several industrial ZF geartooth speed sensors and they work great. The problem, THE BIG PROBLEM, is these damn things are never in stock. I was trying to use the best of the best stuff and I can't buy any of it. So I changed my thinking and looked at which sensors are the most prolific and likely to be available in perpetuity. I came to the GM LS CPS's. There's 2 flavors- The early ones are 3 wire 12V, the later ones are 3 wire 5V. The sensors are dimensionally the same, they fit the same space.

Where I'm at now is mounting the senor to a Cummins 12 valve.

There's a few things I don't like about cummins swaps- I don't like mounting a skilsaw blade to the harmonic balancer to run a sensor. I don't like modifying the harmonic balancer to do it. I don't like $200 Dakota digital products comprised of a $4 chinese board in a 20 cent plastic box. I don't like the Dodge tach sensors (already mentioned that). I like to run hydroboost and don't like running the vacuum pump when it's not needed. I kinda like the 4BT style saginaw pump, but I really hate them when you have to change them or R&R the injection pump. Cummins did not think that short little pump out very good for ergonomics. Plus it's clocked wrong for all the common PS pump to hydroboost hoses to fit properly. Plus they want hundreds of dollars for that silly little thing.

That's a lot to read. Sorry. I've had a couple years worth of thinking/planning/testing.

So what I've concluded is if I make my own power steering pump drive using OE Cummins gears to drive the pump at the same exact speed as the crankshaft I can place a trigger wheel with 3 pulses inside the mount and drive an early style 12 volt GM LS tach sensor which will in turn drive the dash tach with only a pullup resistor. Then for a power steering pump I will use the 92-02 Dodge Saginaw pump which is easy to remove/Install and I will attach the pump to the housing with a V-band so it can be clocked wherever it fits the best.

Hopefully you can use some of that information for your benefit or you can just pick one of these pump drives up after they're proven to work well.
Thanks for the info, I'll have to do more research on the "sinking" signal you mention, haven't heard of that before.

Are you able to confirm the 1996 toyota LC crankshaft sensor sends an AC signal and not DC? It does look to be a 2 wire which then splits into 3 wires at the connector, but is there any chance it would work or is it a waste of time to try it? I've heard of other cummins swaps using the 80's crankshaft position sensor as the tach pickup, but I think those usually use a dakota digital.

I have two ideas for getting the pulse generation, one temporary for testing and one more permanent. I have a Fluidampr harmonic damper/balancer, the version that doesn't have any notches. I figure I can rtv on some small 1/8" or 1/4" steel chunks, maybe 1/2" wide, onto the outside face of the damper at three evenly spaced positions. I don't know how long it would take before they fly off lol but I did a spot test and rtv sticks pretty well to the Fluidampr finish. The other idea is to make a really big clamp that goes around the damper that has 3 raised positions on it that the sensor would pick up. Think like a really big hose clamp but somehow not crap lol. Still working out the details...
 
Thanks for the info, I'll have to do more research on the "sinking" signal you mention, haven't heard of that before.

Are you able to confirm the 1996 toyota LC crankshaft sensor sends an AC signal and not DC? It does look to be a 2 wire which then splits into 3 wires at the connector, but is there any chance it would work or is it a waste of time to try it? I've heard of other cummins swaps using the 80's crankshaft position sensor as the tach pickup, but I think those usually use a dakota digital.

I have two ideas for getting the pulse generation, one temporary for testing and one more permanent. I have a Fluidampr harmonic damper/balancer, the version that doesn't have any notches. I figure I can rtv on some small 1/8" or 1/4" steel chunks, maybe 1/2" wide, onto the outside face of the damper at three evenly spaced positions. I don't know how long it would take before they fly off lol but I did a spot test and rtv sticks pretty well to the Fluidampr finish. The other idea is to make a really big clamp that goes around the damper that has 3 raised positions on it that the sensor would pick up. Think like a really big hose clamp but somehow not crap lol. Still working out the details...

If the cps has 2 wires it is most likely an ac sensor. It generates a small ac voltage as the steel targets pass by.

3 wire sensors have electronics inside. They need voltage, gnd, and they have one signal wire.

If you don't know what a sensor does just wire it up and hook up an oscilloscope and pass metal in front of it.

Or another way- just look at the wiring. Does it have +12v or +5v and ground going to it? Or do both wires just go directly to the ecm? If they both go straight to the ecm you can be pretty sure they are just sending an ac signal to the ecm.
 

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