FJ62 with 1HDT wirings and gauges

[Vulkyn]

Good day folks, needed to reach out to the wonderful gathering of 60's guru's to solve some issues i am facing in my rig.
The previous owner had swapped 3F with a 1HDT but a lot of the wiring was skipped.

I was able to connect the Reverse lights and 4WD engagement lights on the dashboard.
Temp, oil pressure, fuel and volt gauges are working.

Currently I need to connect:

• RPM gauge (from 1HDT pump to 12Volt Diesel RPM in dash)
• Low brake fluid master cylinder and reservoir for 80 series socket not connected (just had an issue with this, lost oil when car was stationary!!)
• Low clutch oil reservoir socket not connected

I am unable to find a direct solution as the car is no longer stock, I read quite a number of threads but have yet to wrap my head on a solution.

The car is scheduled for a full restoration so I will have the choice to re-wire or add additional equipment but having the diesel RPM working in dash is a must for me.

Any thoughts, ideas and general mockery of my lack of knowledge is more than welcome .....

 

[Vulkyn]

Bump !

 

[Vulkyn]

So still looking

Currently, trying to find a VR to TTL / VR signal converter module.
Since the output of the 1hdt diesel pump is Input Signal (from diesel pump VR sensor)

Variable Reluctance (VR), sine wave at idle: ~0.5–2 V AC (low amplitude)

At higher RPM: can rise to 30–50 V AC (sometimes more at redline)
{Based on chatGPT}

Frequency: proportional to engine RPM (the faster the pump spins, the faster the sine wave ) The tach cannot read raw sine wave, because it varies in amplitude and shape with speed.

It needs a clean, steady digital pulse.



2. Output Signal (from conditioner / LM1815 module)

Type: Square wave / digital pulse (0 → HIGH → 0)

Voltage: depends on supply

If powered from +12 V, output pulses swing from 0 V to +12 V

If powered from +5 V, output pulses swing from 0 V to +5 V
Frequency: proportional to engine RPM, same as input sine frequency (but now a clean on/off wave)


This square wave is what the Toyota diesel tachometer expects.

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So looks like I need to get a VR to TTL / VR signal converter module with LM1815. In order to conver signal and hopefully use my tach dash which is why I am going on this roller coaster ride ....

Any one with experience in this and can offer a helping hand ?

 

[PBcuiser]

it’s not super clear - do you have a diesel tach or not? If so will the 1hdt pump signal not work just directly?

If you want to keep the pump tach pick up easiest thing to do is try and source the tach out of an OE 1hdt vehicle.

For my 1hz swap I used a Dakota digital Hall effect sensor mounted off the fly wheel and their converter box to get my factory tach to work.

 

[Vulkyn]

I have a 2H diesel tech, 1hdt has the sensor on the diesel pump.(1hdt engine with a 2H tach).

No fly wheel sensor only on the diesel pump. Not sure if it has the location of the 1hz flywheel sensor or not.

It doesn't work since they are different signals hence the issue

 

[PBcuiser]

I drilled my bell housing for the Dakota digit sensor and have that hooked directly to the Dakota digital converter box which then goes to my tach

I have a 2H diesel tech, 1hdt has the sensor on the diesel pump.(1hdt engine with a 2H tach).

No fly wheel sensor only on the diesel pump. Not sure if it has the location of the 1hz flywheel sensor or not.

It doesn't work since they are different signals hence the issue

 

[franklin40]

i have a fj62 with a 1hdt. i was able to get a converter from shift kits australia that converts the tach sender signal to what the stock gas gauge needs. it was about the same price as getting a diesel tach so i did it that way. super easy install and works flawlessly.