Tach Hookup - FJ60 12H-T install

[circle456]

Well, my 1986 FJ60 with a G & S Cruisers (thanks Sheldon) 12H-T is now "officially" on the road - California DMV checked to see that it is in fact a Diesel and that was that. FWIW, this FJ60 is a previously California registered truck for the last 340,000 miles, so this was just an engine/transmission swap.

Now for the TACH: Is it possible to use the existing FJ60 tach and attach it somehow to the sender unit on the HF55 trans/bellhousing that came with the 12H-T ?

I'll get some video of this truck up on youtube in a few weeks. Runs great with new OME suspension, rebuilt front end, rebuilt transfer case, BFG AT 33 x 10.5 on 8x15 rims, 3 inch exhaust and AeroTurbine. Toggle switch for glow screen. It is now dual batteries setup to charge together but operate separately via a selector switch.

So the tach is a problem, plus gotta hook up the water temp gauge, alt charging gauge, and plumb in the water separator to the fuel feed line.

Throttle is a bit twitchy, but fine for road use. Really looking forward to getting in the woods with this after a few hundred miles of local travel to shakedown the rig.

Thanks in advance for any tips with the tachometer hookup.

 

[watrob]

Hi, the tacho hooks up to this sender on the bellhouse. My motor is 2H, the same nearly as a 12HT but without the turbo. You will have the same bellhousing etc and the sender on the side is for the tacho.

 

[roscoFJ73]

Now for the TACH: Is it possible to use the existing FJ60 tach and attach it somehow to the sender unit on the HF55 trans/bellhousing that came with the 12H-T ?

You should be able to find the wire that went to the alternator and connect it the sender. Im not sure but you may need a diesel tacho. Some of them accept a different signal


.

Toggle switch for glow screen.

You will need something heavy duty for glow plugs

plus gotta hook up the water temp gauge,
.

This should be a straight plug in

 

[circle456]

12H-T, pre heat chamber, gauges....

Thank you for your response. The 12H-T doesn't have glow plugs, it's more like a chamber that pre heats the fuel.

We wired in a spring loaded toggle switch that is to be engaged for "about 15 seconds".

As an experiment, the truck was left outside during a 28 deg F night and the engine fired right up the next morning without the fuel heater being engaged. I figure that the robust start is due to the direct injection.

Glad to hear that the engine/alternator gauges are a straight ahead plug in or wire up.

 

[circle456]

Hi, the tacho hooks up to this sender on the bellhouse. My motor is 2H, the same nearly as a 12HT but without the turbo. You will have the same bellhousing etc and the sender on the side is for the tacho.

So THAT's what the harness that G & S Cruisers sent along is for !! We have done so much to the rig that the harness got set aside and forgotten.

G & S also sent a diesel tach..... I had read somewhere (maybe here at IH8MUD) that the FJ60 tach could be used, so, as it's easier, I had stopped thinking about the large tachometer that had been shipped with engine. Duh...

Still, perhaps the harness could be attached to the existing tach; we will pursue this. Thanks for the photo - good looking engine.

 

[Creeker]

I have a 12HT dropped into an FJ62. I need to hook up an aftermarket tach to 12HT. Thanks to this thread I found the sender on the bell housing:

Unfortunately, the engine/tranny came with these wires snipped. Question - any idea if an aftermarket gauge can be spliced to this sender? If so, which one? There's got to be some out there that read the hall effect.

Like this one? http://www.isspro.com/installation/IS128.pdf

Or should I just abandon the sender and hook up to a coil or magnets on the pulley (Isspro)? Other approaches on the board: https://forum.ih8mud.com/diesel-tech-24-volts-systems/41271-diesel-tachometer.html

 

[Creeker]

I guess I'll keep jabbering to myself... does anyone know for sure that the sensor is reading a Hall effect for the tach? I'm thinking that it looks more like it's a magnetic sender (see pic above). Here's a page from the VDO catalogue showing the 2 types of sensors.

I have a call in to VDO, so we shall see...

 

[Creeker]

.meh.

 

[AGreekBoy]

creeker and circle456 i am doing the same swap and i purchased a 12volt tach sender and will try to hook it up to the coil reading off the gas engine i will let you know what happens

 

[Creeker]

Greekboy - I've seen a few diesel tachs for sale with a variety of hook-ups for the sender: magnets on a pully, wire to the alternator, etc. However, I'm stubborn and I can't see why I can't use a perfectly good sender location that Toyota provided. Stewart Warner has a tach in their catalogue described as using a mag sensor at the flywheel. I'm still trying to figure out if my existing sensor will work.

Mag Sensors / Speed Sensors / Hall Effect - Stewart Warner

The other issue is that it looks like the SW diesel tachs top out at 3500 rpm. Don't I need at least 4000?

 

[panoramic]

Thank you for starting this thread!

I have also been looking into this same issue for my 12HT conversion. Here is my brain-dump of thought I have collected on the subject for the past 18 months while working on my diesel conversion.

The sensor is indeed a Hall-Effect Sensor (confirmed on several MUD threads).
I have NEVER seen the electrical diagram for the HJ61 that details the tach wires - would love to though! Words to the wise: Since this is actually a semiconductor, reverse biasing or overloading it could damage or ruin the device. I don't know how much Toyota replacements cost, but please be sure you know what you are doing if you are experimenting with it.

I am not sure if there is a different unit for 12V pickup versus 24V but someone should be able to see if they are different part numbers. Any takers?

Hall-Effect sensors use a magnet (on the flywheel) to sense. A problem is the number teeth or magnets that are on the flywheel for each revolution - I have no idea how many there are on the 12HT and how that is compatible with an aftermarket Hall-Effect gauge or 2F guage. If the both use 1-pulse per revolution then it makes things easier...
Also note that some Hall-Effect sensors have built in amplifier circuits so these are not necessarily aftermarket drop-in replaceable!

One saving grace is that even if the pulse count per revolution requirement is different between gauges, a pulse multiplier or divider would be relatively simple to fabricate.

I should also note that I actually own a 24-Volt tach from a HJ-61 and a 12-Volt tach from a Aussie 40-series. The units look identical from the rear with the same connections. Only the clocking of the plastic mount tabs differ and the faceplates are totally different. Too bad I can't read Japanese because I do not know what the connection labels are (guessing is NOT an option for me).

Another difficult part (for me) is how to calibrate the actual RPM of the engine against the gauge reading? This could be done with a oscilloscope or a frequency counter - which I could borrow for the final calibration.


The only other solutions posted elsewhere on MUD are devices that strap to the alternator (isspro) or strap around an injection line (tinytach). Either of these will work, but I don't like the way they have to strap around components in the engine. I would MUCH rather use the existing sensor pickup.


Here is a hybrid solution that could use the existing hall-effect sensor with a frequency counter posted on youtube: YouTube - Hall Effect Tachometer for Electric Motor Demo
After some experimentation it would be possible to take the digital frequency count and produce an analog output for a simple analog gauge (digital-to-voltage converter).

I haven't addressed this whole tach issue yet because I have been focused on getting my truck running reliably.

Sorry if this has all been too wordy - I have put a lot of thought (and worry) into this.

Best Regards,
Eric

Ps. I can/will post pictures on request of my OEM tachs.

 

[AGreekBoy]

Creeker i installed an autometer tach on my 3b that reads off the alternator but i am not happy with it. i will take my time on my tach install and if i get it to work ill let you know right know just pulled my motor and cleaning the underbody from grease.


Panoramic lots of good info thanks .

 

[panoramic]

UPDATE : Sensor Tests!!!

Okay,
I just could NOT leave this subject alone! I spent 1/2 the night researching Hall Effect circuits and tachs.

I decided to move my scope and test leads to the flywheel sensor.

 

[AGreekBoy]

so you used the stock tach with the bellhousing reading?

 

[panoramic]

I don't have a tachometer installed yet.
My FJ40 has a 12HT with a factory 12HT bellhousing tach sensor installed.
I simply measured the sensor while the engine was off and then when it was running.

 

[AGreekBoy]

for me it is just a little too scientificy

 

[Creeker]

I don't have a tachometer installed yet.
My FJ40 has a 12HT with a factory 12HT bellhousing tach sensor installed.
I simply measured the sensor while the engine was off and then when it was running.
fwiw: The sinusoid frequency increases with engine speed.

Next step is to buy/borrow a cheap laser tach and measure frequency vs. rpm to determine what conditioning (divisor) needs to be done....

Does any of this info help anyone?

Awesome work panoramic!!!! So from your previous post, it seems we have an inductive proximity sensor? So please correct me if I'm wrong - this means that it is not a Hall effect sensor.

My understanding is that a Hall effect sensor is based on reading a magnetic field issued by the object being measured. That would mean the flywheel was magnetized (unlikely). Instead, we have a sensor that operates as a "variable inductance balanced bridge", according to Honeywell:

Mode of operation
If a metal object enters the electromagnetic field of the oscillator coil, eddy currents are induced in this coil which change the amplitude of oscillation. The demodulator converts the change in the amplitude to a dc signal which causes the trigger stage to trip and the semiconductor output stage to switch.
​

The reason that this is important is that I need to know what the sender is in order to buy the gauge (choice between Hall effect and Magnetic)! I don't have the expertise to figure it out, so props to panoramic!

Now, from what I've read, a tach that reads how fast the teeth on the flywheel are spinning. To get the rpm, the gauge needs to be adjusted for the number of teeth on the flywheel. Isspro has a product called the Programmable Tach #8585M that might work.

Programmable Tachometers
These instruments are designed to accept signals from pulse generators, magnetic senders or alternator taps. For 24 VDC NG applications, a 24 VDC bulb must be purchased separately. See page 32 in Specialty Products & Accessories section of this catalog.
■ Hourmeters count only when a signal is present (engine running).
■ M designates microprocessor (non-microprocessor units are available for special applications). See page 12 for details.
■ Optional styling − bezels, ranges, custom face dials and pointer colors available. Consult factory.
■ Consult factory for positive ground applications.​

 

[Creeker]

Here's my e-mail correspondence with Stewart Warner tech dept:

From: [Creeker]
Sent: Monday, August 18, 2008 5:42 PM
To: Tech Support [Stewart Warner]
Subject: Deisel Tachometer

Hello – I am looking for a new tachometer for my diesel truck. There is a sensor in the transmission bell housing that I have been told reads the flywheel. The engine is a Toyota 12-HT, 6-cyl turbo’d with approx 4,000 rpm max. Here is what the sensor looks like:

[PIC OF SENSOR]

Please let me know if you have a gauge that would work with this sensor, or if not, whether you have a gauge/sensor combination that might work in this location (in the bell housing).

From: [Stewart Warner]
Sent: Tuesday, August 19, 2008 5:19 PM
To: [Creeker]
Subject: RE: Deisel Tachometer

We have several mag sensor Tachs that would work. I can recommend our p/n 82636 from our Deluxe line that has white graphics on a black back ground with a polished stainless steel bezel. It can be ordered online at Summit Racing or thru your local Napa dealer.

From: [Creeker]
Sent: Tuesday, August 19, 2008 5:52 PM
To: [Stewart Warner]
Subject: RE: Deisel Tachometer

Thank you for your reply. Do you suggest hooking up that tach to my stock sensor then?

From: [Stewart Warner]
Sent: Wednesday, August 20, 2008 2:19 PM
To: [Creeker]
Subject: RE: Deisel Tachometer

Yes.
​

Unfortunately the suggested SW gauge maxes out at 3500 rpm. Don't I need 4000 rpm? I'm still trying to coordinate with ISSPRO, and will report on that. Finally, a tach from an older Toyota diesel engine would probably work, if you can get one...

 

[Creeker]

OK, telecon with ISSPRO is pointing me in the direction I think I'll go. A very nice guy, Don, advised that their Tach R8585M should be able to read the signal from the Toyota sensor.

One wire to ground, one wire to the sensor, calibrate to the number of teeth on the flywheel, and I'll be done (I hope). Now I just need to figure out where to mount a 3 3/8" gauge...

 

[BlueHZT60]

Personally - I'm tactless according to some, and tachless for 2+ years now.

Autometer - alternator sensor tach: have it, but need to do some surgery on the dash which hasn't happened.
Ispro - Have seen it in a 12ht-60, flywheel sensors, tach sits in a rubber gasket, looks good, but not factory
Kevin Moreland has it figured out also - search mud, it's there somewhere.

Bob
hzt-60