FZJ80 to HZJ80 conversion Tach wiring problem.

[bj40green]

Putting some oil on the fire......
The signal from an ignitor is very different then a signal from a sensor.
The ignitor coils delivers a signal. It's available.
A signal from a pick up sensor has to be made. Maybe that is what's going on here and why you need a "Dakota" (I've no clue what a Dakota is but I've the feeling that somebody is going to explain this).

Rudi

 

[doug720]

Here is some info from Dakota Digital on their signal convertors. They have several and I would call their tech department to discuss your problem. They were very helpful when I called them.




Automotive Products > Speedometer & Tachometer Interfaces

Universal Flywheel Tachometer Interface

From Dakota Digital

​

​

The DSL-2 consists of an DSL-1 speedometer signal interface unit and an inductive gear tooth sensor. This unit will convert a signal from the flywheel-gear tooth sensor to an ignition tachometer signal. When using a standard 4-6-8 cylinder tachometer on a diesel engine the DSL-2 can convert the flywheel sensor signal into a 4 cylinder gas ignition signal. Calibration is accomplished by counting the number of teeth on the flywheel or using another tachometer as reference. The sensor should be mounted so the flywheel teeth pass by the end of the sensor.

Sensor: 2" Long, 3/4"-16 Threads

Product not compatible with '86-91 VW Vanagon's and other similar models




DSL-2

Flywheel Tachometer Interface Unit
Quantity: Only $129.95

 

[craigbuilt]

well....... its not a gap issue.

I pulled the pickup sensor and machined the back/ nut portion of it down by 1/8 inch so it will thread in deeper. I installed the sensor back in until it bottomed out on the teeth. I then ever so slightly backed it off, like 1/16th of a turn if that. Wired it back up to the same way I had it before, Tach to sending unit, to ground. No movement in the Tach needle! dang it! I then swapped the wires coming out of the pick up sensor, one to the tach the other to the ground. again no change, dead needle.

At this point Im assuming that the signal has to be converted by a processer/ecu of some sort before it goes back to the Tach. I find it interesting that the EWDs I have looked at don't show the signal from the pick up sensor running to a ECU and then to the Tach. Some do show it spliced in to a wire running from an ecu to the tach like the diagram in post 1. Honestly I don't understand how that would work being spliced in to a wire running from the ecu to the tach.? Unless there running two signals over the top of each other on the same wire.??

Im ready to throw in the towel and walk away from a factory Tach set up. I will be calling Dakota digital on Monday to see if I can get the signal from my sending unit to work with the stock FZJ80 Tach using one of there "processors". If not I will purchase the universal flywheel Tach interface as posted above. I have to pull the trans in the near future to put in a new torque converter any way. That may be a good time to drill and tap a hole for the flywheel pick up sensor.

Any one need a new HZJ80 diesel tach? $250 I will ship it to you! I paid $350 for it from cruiser parts.

Thanks for all the help and insight. Im tapping out on this one.

Craig

 

[craigbuilt]

Updated.

I spoke with a tech at Dakota Digital, very friendly and helpful. To sum it up, They said that none of there units will work with the output signal that comes from the pick up sensor i am using. They said it is too low voltage ect....and will not work with the factory fzj80 tach. He recommended the DSL-2 as Doug720 suggested earlier.

Hope this will help someone in the future. I spent $450 for tach, pick up sensor, IP mod. This route $130 and it works. Have a good one.

 

[craigbuilt]

Update.

I sold my tach to an other cruiser dude here on Ih8mud, he installed it in his rig and it works flawless. So the tachometer was not the issue. He has the tach wired the same way I did. Tach to sender to ground. It ends up that my pick up sensor is bad. Even with it touching the teeth it will not put out enough juice to get the tachometer to read the signal.

His tach was "At idle my sender was putting out 0.1V AC. As rpm increased, the voltage incrementally went up from 0.1 to 0.5V AC."

Any way. Hope this helps someone in the future.
Have a good one.

 

[veiloctane]

this is a super helpful post Thank you it doesn't look like I can get between 3v-16v and a min of 20Hz signal for Tach
Are there any voltage boosters I can use for remote start tach detection?

I tried a DEI 454T TACH SIGNAL GENERATOR but its been a hit and miss and also not being fully weather proof living under the hood concerns me.

so for now I just opped to use a chrank time of 0.8sec to remote start.