FZJ80 to HZJ80 conversion Tach wiring problem. (1 Viewer)

[craigbuilt]

Hello All,
I have a 97 FZJ80 that now has a 1hz diesel in it. Everything on the vehicle works great no wiring issues ect.. except for the tachometer. I finally got around to wiring it up the, last thing on the list, and I am stumped. I will do my best to explain what i have done and how I have it wired; any advice from one of the gurus would be very welcome. I have spent days digging through wiring diagrams, Forums ect.. I believe it is wired correctly but it is still not working.
any way here is what I have.

Tachometer.
I Installed a NEW OEM Tach PN 83242-6A280 specific for HZJ80. Pulled out the fully functional one for the FZJ80 prior to the swap and installed the Diesel version Tach, adding the additional screw for the T-belt light. changed none of the wiring coming in to the back of the tach, input signal is coming in the same wire prior to the tach swap. when I turn the key to the on position the t-belt light comes on and stays lit until the engine is started then the light turns off.

Pick up sensor
Installed a new Pick up sensor PN 83180-60070. The fuel pump was not originally set up with a pick up sensor. The Fuel pump was drilled and tapped to accept the pick up sensor in the OEM location on the Fuel pump. sensor floating slightly above the teeth inside the fuel pump ect...

Wiring
The wire from the back of the tach runs uninterrupted to the number 1 wire of the pick up sensor, installed on the fuel pump. Checked it with a voltmeter for continuity ect.. several times, good to go. The number 2 wire on the pick up sensor is grounded per the wiring diagram. For testing purposes it is grounded directly to the battery.

No workie....

Wiring Diagram

*11 is for the 1hz HZJ80.

In the wiring diagram
I notice that there is an ECT ECU wire that splices in to the wiring inbetween the tach and sensor. Im guessing this is for the 1hd-t that has some electronic emissions where the 1hz I believe does not. so I am to believe this wire is a non issue to make the 1hz sending unit talk to the tachometer. ????

My understanding of the pick up sensor and how it works is that every time a steel tooth passes by the pick up sensor it is creating or breaking a magnetic field.??? In turn creating a pulse signal that travels back to the tachometer that is regurgitated into an RPM reading on the gauge. If Im wrong in my understanding please correct me.

Question #1
Is the way I have the tach and pick up sensor wired correct? OR am I missing something?


Pick up sensor
In the FSM it states (depending on the wiring diagram you are looking at) that the Pick up sensor should have a resistance of 600-800 ohms or approximately 730 ohms. The new one I installed has a resistance of 851 ohms. obviously this is not is spec and according it the FSM it should be replaced. But it is new so im hesitant to replace it yet.

Question #2
Besides testing the resistance on the pick up sensor, is there any other way to test it to see if it is outputting pulses/ signal to the tach?

Any guidance of help would be great. Im totally stumped. It looks right to me but is not working.
Thank you

 

[Tapage]

Maybe not to helpful ... but in my HDJ80 Tach signal wasn't going directly from the Tach sender to the Tach in the dash .. it goes through my ETC ( my 80 was automatic ) box and then to the dash tach ..

When engine running did you get something from the IP tach sender .. ?

 

[craigbuilt]

Thank you for the reply.

With the engine running I did not get anything from the sending unit. But i could be testing it wrong. With the engine running I tried testing the resistance to see if I could see any fluctuations indicating a pulse.? But there were none it stayed at 851ohms. I also tried ever other setting on the volt meter in various conditions, grounding one or the other wire from the sending unit ect..with no noticeable fluctuations. I am curious to see if there is a way to test the sending unit with the car running, to see if it is pulsing or working properly.

I don't believe the fzj80 has an ect box like the diesels do. It has an ecu that the ignitor wires go in to, then one wire from the ecu goes to the tach. I am wondering... I may have to buy an ect box from a hdj80 to run the signal through to get it to work. ?
I will do some more digging on the ect wiring diagrams to see what I can find out.

Anyone out there have a HZJ80 with a functional tach that can tell me how it is wired? Does it have an ect box?

Thanks

 

[doug720]

I'm not an an electrical engineer, but I did stay at a Holiday Inn one time...

I assume this is a "Hall Affect" type sensor. If so, the gears passing by the sensor tip should produce a low AC voltage. On my Isuzu 4BD2, the stock sensor uses the IP drive gear that turns at 1/2 speed of the crank. This sensor generates about 7 volts AC. I would check this first.

Second, these sensors are sensitive to the air gap distance between sensor tip and gear, make sure it is close.

All I got, hope it helps.

 

[bj40green]

I don't have much experience with tach systems but here is some info.
There are 4 ways to get a tach signal.
- From the Ignition system if it's a Gasoline engine.
- From the IP system if it's a Diesel engine.
- From the alternator. Works always no matter what engine.
- From a Hall sensor.

You're using a Hall sensor. This Hall sensor makes a square wave signal (AC is considered a sinus wave signal) which is difficult to read for DMM's (Digital Multi Meter). Old school AMM"s (Analog Multi Meter) are better in reading this signal. An oscilloscope is the preferred instrument to check this. A square wave signal is low - high - low -high and the time between high and low is converted to your rpm number. This is low rpm's _______-________-_______ and this is high rpm's _--------_-------_-------_ (and all combinations in between of course).
If your sensor is a bit out of spec AND the distance is not close enough you'll get no reading.
What you can do is check for voltage coming out of the tach unit that goes to the Tach sensor. There should be a DC voltage (Key in the on position, engine not running).
Check if this voltage is also present on the tach sender.
Here is a pic for explanation purposes only. This is how it basically works with a Hall sensor.

Hope this helps finding your problem.

Rudi

 

[craigbuilt]

Wow! Thank you both for the replys. It does help. I will check the dc voltage coming from the tach tomorrow night. I believe I have access to an oscilloscope at work that I can use. I will run the test as suggested in the next day or so and report back my findings.

Thanks again!

 

[doug720]

Interesting on the hall sensor voltage being DC. On my Isuzu, I only get AC and the factory workshop manual lists out put value as AC? See #35 in the scan below.


I could never read DC, but I was using a DMM?

In addition, I have a Dakota Digital signal convertor on my swap. It converts the hall sensor to a signal that the factory Toyota tach can read. According to Dakota, the hall sensor output is AC?

Just wondering?

 

[bj40green]

The voltage is DC until the engine starts spinning/turning. The Hall sensor picks up the rotation and makes it (transforms it into) an AC signal.
It's like toggling a switch very fast. To keep it simple for us DIY people, they talk about AC (sinus wave) while it's actually more square wave. Doesn't matter, I was only explaining how it (a Hall sensor) works.

Rudi

EDIT: Here is some reading stuff: http://en.wikipedia.org/wiki/Hall_effect_sensor

 

[george_tlc]

Hall sensors are DC, they are a semiconductor device. They can generate a pulse train, but that just means they transition from 0V to the operating voltage.

There are inductive sensors and they are just a bunch of wire wound around a magnet and as the 'tip' passes by metal an AC signal is generated.

Hall sensors will 'typically' be 3 wires. One wire is ground, one wire is power and one wire is the hall sensor signal. Many hall sensors have internal electronics to buffer the hall effect signal and also 'clean' it up to be a digital pulse train.

Inductive sensors will have 2 wires.

So, step #1, WHAT KIND OF SENSOR DO YOU HAVE...

cheers,
george.

 

[Jan-78FJ40]

As far as I know the sensors on the Denso pumps are 2 wire.

 

[craigbuilt]

Thats correct, the injection pump sensor on my 1hz is a 2 wire sensor.

 

[doug720]

Just for reference, the Isuzu 4BD2 sensor is a two wire also on the Diesel Kiki - Bosch pump - Induction type

Thanks for the explanations of the difference between a hall effect and an induction sensor!

 

[craigbuilt]

ok so I did some digging this evening and here is what I have found...

Below is the back of my cluster panel, (sorry for the orientation couldn't flip the image) With the cluster panel all hooked up and the key in the On position I took some DC voltage readings of all the points connected to the tachometer. I used the battery as the ground. The readings are listed below.

The wire from the Tach to the pick up sensor has a resistance of 3-4 ohms.

I also hooked up the volt meter to the IP Pick up sensor again with the car running, below shows the reading.

So the pick up sensor is putting out a signal. .015 AC. should there be more juice coming out?

Conclusions
it appears to me that both the tach and the pick up sensor are putting out a signal. both are very low voltage. I cant find anywhere in the FSM EWD ect that gives the output voltage of the Tach or pick up sensor.

Below is a pic of the sending unit before installation. The hole that it is threaded into is below where im holding the sensor. The orientation and depth where im holding it is correct. The sensor has a 40 stamped on it.

Question#1
Is the wiring shown in the FSM, the same way I have it wired up correct. tach direct to sender to ground??

Question #2
Do the voltage reading I took on the Tach and on the Pick up sensor look correct?

Question #3
I don't know im stumped..... bad sensor? is the output voltage from tach to low?

Thanks guys

 

[langsen]

As mentioned earlier, it is most likely a VR sensor and not a hall sensor. The sensor needs to be very close to the teeth, pretty much as close to the teeth as possible without hitting them.

I'm confused about your wiring. You say you "changed none of the wiring coming in to the back of the tach, input signal is coming in the same wire prior to the tach swap" but then you say "the wire from the back of the tach runs uninterrupted to the number 1 wire of the [previously non-existent] pick up sensor".

I think it's either a wiring problem or the sensor isn't close enough to the teeth. Have you tried switching the sensor wires around? I'd be surprised if it makes a difference but it will invert the signal so it might. Can you run the number 2 wire straight to the tach ground instead of using the battery as a ground?

The sensor resistance you measured should be fine. You can test the sensor with an oscilloscope if you have one. If not, you could hook the sensor wires up to some headphones using alligator clips and you should be able to hear the sine wave being output. It's basically just like a guitar pickup. I just tried testing a sensor with the headphones and it works but is pretty quiet, definitely couldn't hear it while standing next to a running engine.

Just saw your latest post... The voltage on the sensor looks fine. The sensor output is a sine wave, so AC voltage. The voltage will increase as the speed of the metal moving past the sensor increases, so if you rev it up the voltmeter should read higher. The period of the sine wave, not the voltage, is what matters to the tach, but the voltage shows the sensor is working.

 

[george_tlc]

The low resistance of the sensor you have measured pretty well confirms that it is a inductive (variable reluctance) sensor. The only way to actually observe the signal is with an oscilloscope.

You can verify you have a VR sensor by putting an iron object to the tip area of the sensor - it should be magnetic.

As langsen stated, separation distance from the sensor tip to the gear teeth is critical. Connect up a scope and verify the sine signal and position the sensor tip close enough for reliable pickup.

cheers,
george.

 

[doug720]

On my set up, the sensor has a specific thickness washer that places the sensor at the correct air gap to the gear. On an Isuzu, it is very close - about .007-8"!

In fact, when I did my swap, the washer had a lip on it from being tightened a few times. I filled it smooth and the sensor contacted the gear. It close.

 

[craigbuilt]

Thanks for the responses,

To clarify what I said about the wiring, as far as the tachometer is concerned I unplugged the fzj80 one plugged in the hzj80 tach. The signal wire or where the signal comes in to the tachometer has not changed. The wire it self is modified, instead of running from the tach to the ecu, ( where it passes along the signal from the ignitor on an fzj80 set up) It now runs directly from the tach to the pick up sensor as shown in the fsm wiring diagram in my first post. Sorry for the confusion.

This morning I hooked up the volt meter to the pick up sensor again with the car running. At idol it showed .015 AC. I reved the motor up as suggested and the volts increased gradually based on engine speed. The volt meter read .031 AC at 3/4 throttle.

I think the gap between the pick up sensor and the teeth is too large as suggested. When I modified the injection pump housing, drilled/ tapped to accept the sensor, the injection pump housing immediately around the pick up sensor hole was not machined down. The sensor was threaded all the way in, until it butted up to the IP housing. I'm guessing there is probably an 1/8 inch gap possibly more between the sensor and teeth. I did not realize, until you pointed it out how sensitive this type of sensor is to standoff from the teeth. I'm going to pull the sensor if not today this weekend, measure the gap, and reinstall it as close as possible with out it touching. Hopefully this will fix the problem.

I will get back to you soon . Thanks

 

[doug720]

On my Isuzu swap, I needed to use a Dakota Digital signal convertor to make my stock tach work. I don't know the 80 tach or wiring, but the Isuzu truck my engine came from used the Trans Control Unit (TCU) to convert the sensor signal - VR/Induction type - to a useable signal.

In my 60 series, I used the Dakota to do the same thing and it works great.

I would hazard a guess, you may need a way to make the sensor signal useable to the stock tach also.

Since your 80 was gasser, the tach signal was a 1 to 1 based on actual engine rpm. Now the IP, and I think this will be the case on the 1HZ, the pump is turning at 1/2 speed of the crank. So the sensor will be reading 1/2 the rpm and you will need to correct this also. Again, the Dakota does this. This situation is what I had to do on mine.

Hope this helps.

 

[Tapage]

Since your 80 was gasser, the tach signal was a 1 to 1 based on actual engine rpm. Now the IP, and I think this will be the case on the 1HZ, the pump is turning at 1/2 speed of the crank.

OP said he replace the gasser tach with the diesel Tach ..

 

[doug720]

I forgot he swapped tachs to the diesel version. Maybe it's just the air gap, which appears too large, but several others swapping diesels have had the same issue getting a diesel tach to work and used a Dakota to correct it.