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Tacho not working after conversion

6K views 37 replies 4 participants last post by  JFF45 
#1 ·
So just done a td42ti swap in my 05 patrol. Im running a dakota SGI-100BT. I have the yellow and black wire (pin5) in the output and the tacho works when the unit does the 2000rpm test. My problem is that I've tried pin5 from the ecu, straight into the input of the unit and it doesn't work. I've also tried pin44 and pin47 (tach wires from sensor) and it still doesn't work. My question is what have I done wrong. Have I maybe wired the 3pin plug wrong where the cam sensor joins? Any help would be much appreciated
Cheers
 
#2 ·
If you have a look around you would find an old thread of mine, where I fitted a Ti engine into my GQ. It was a TD42 to start with, so the only change was to a Ti motor. All good as you would expect, except for the tacho. You name it, I tried it, but no go.

The Ti motor has a different can gear on it compared to the TD42 and TD42T engines. The old gears had big holes in them, and the Ti gear has no holes. In conjunction with the 3 wire Ti sensor, it produces about 0.5 volts AC. This is less than the old engines did.

I had a Dakota, a GQ sensor, a two wire GU sensor, a three wire GU sensor, and a gizmo box one of our brainy members on here built. None of the combinations would work. So I suspect you may be having a similar problem, even though you have a GU.

In my case I fitted a Silvertop TD42 camshaft gear to fix it.
 
#3 ·
If you have a look around you would find an old thread of mine, where I fitted a Ti engine into my GQ. It was a TD42 to start with, so the only change was to a Ti motor. All good as you would expect, except for the tacho. You name it, I tried it, but no go.

The Ti motor has a different can gear on it compared to the TD42 and TD42T engines. The old gears had big holes in them, and the Ti gear has no holes. In conjunction with the 3 wire Ti sensor, it produces about 0.5 volts AC. This is less than the old engines did.

I had a Dakota, a GQ sensor, a two wire GU sensor, a three wire GU sensor, and a gizmo box one of our brainy members on here built. None of the combinations would work. So I suspect you may be having a similar problem, even though you have a GU.

In my case I fitted a Silvertop TD42 camshaft gear to fix it.
Yeah wow righto, that's definitely not a simple little thing like trying a different wire. So you used a td42 2 wire sensor and gq cam gear to suit? That's a big job
 
#5 ·
Yep, two wire sensor and a GQ cam gear. Cam gear is the same as a GU TD42T cam gear, it is only the Ti that is different. Instead of the big holes in them that will create quite an effect on your sensor, they have small pimples about 4mm across. So instead of 1.5 volts AC or thereabouts, you only get 0.5 volts.

My understanding is that on the factory GU TD42Ti vehicle the sensor sends a signal to the ECU which then runs the dash, so the low voltage is not an issue obviously. But the Dakota needs a minimum of 1 volt to work, and it will not get that. That is what I found, and I was not able to correct it.

In your case, as you have a GU 3L dash, and I have not had anything to do with them. All I know is that a Dakota will sort them out usually. But the Dakota must have a min of 1 volt to work.
 
#6 ·
I just thought of something. I worked on a Navara with the ZD30 recently. It has the same 3 wire sensor as the TD42 Ti. It is mounted externally, just above the harmonic balancer. I have no idea of the voltages etc, as I did not look at any of this.

But it is possible that it can be made to work with the ZD30 electrics in your GU, which you would think would use the same sensor as the Navara.
 
#7 ·
If the 2000 rpm test works then you have the tachometer wired correctly on the output.
There should be a small flashing dot in the corner when it’s getting a sufficient signal. If not, is there an option to put the signal wire into a different voltage input?
Have you tried to raise rpm to see if the dot flashes? I’ve read of others getting the TD42Ti cam gear to work but usually only above 900 rpm or so.

Do you have a multimeter to be able to read the AC voltage coming from the inductive pickup?
 
#8 ·
I have thought about using a zd30 pickup and it would be so easy to wire up, no need for the dakota potentially. I've tried the inputs for the diesel section on the unit, maybe I could try different inputs for petrol motors? I'd rather use a zd30 pick-up if it would work on the td42ti balancer, then change cam gears
 
#10 ·
Unfortunately I did not look at it that closely. What I did do was swap the standard sensor with my Ti one, and it worked. Appearance is identical, right down to wiring colour. Only difference I could see was the wiring loom was longer on the ZD30 sensor.

So it has potential to work in a different location, as long as the trigger gives a stronger pulse, ie more than 1 v AC for the Dakota to then convert it from 6 cyl to 4cyl. As for getting it to operate the tacho without the Dakota, perhaps an instrument technician could help there. Lionel Otto Instruments are one place to talk to.
 
#12 ·
I was working on a Navara, and the sensor was a possible electrical fault, according to fault codes. I replaced the ZD30 sensor with the Ti sensor. They are interchangable, and it operated the same. What convinces me it is the same part, is that even though the ZD30 version bolts on a bracket above the harmonic balancer, it still has the groove in for the o ring.

So a ZD30 version will fit your engine if you put an o ring on it, but it will be exactly the same as you have now.
 
#14 ·
I expect it will not be any different unfortunately. The trigger is the issue, being the cam gear, rather than the sensor. I would be giving some thought to trying to use the ZD30 mounting position, and seeing if you can use the balancer as the trigger. Not sure how you would do that, but getting a look at a ZD30 may give you some ideas. Something on the balancer could give a stronger pulse to the sensor, and get you over the 1v AC you need for the Dakota to convert from 6cyl to 4cyl.
 
#16 ·
I think they use the old 2 wire inductive pickup sensor with a spacer so the sensor doesn’t hit the TD42Ti cam gear dimples. If that’s the case, it wouldn’t use the ZD ECU, it would connect directly to the Dakota box.
i think I recall reading that Patrolapart have the spacer.
 
#18 ·
None of the sensors will produce 1 volt AC using the Ti cam gear. I have tried all three versions.

If you have an auto sparky that says he can fix it I suggest you get him to do so. But I would advise to not be paying him by the hour if he only intends to do the same stuff that has already been tried.
 
#20 ·
As I said the cam gear is the problem. I have proven the sensor does not know what engine it is fitted in, as the TD42Ti sensor works on a ZD30 when tested. The sensor produces an output relative to the trigger, and the old cam gears with the big holes in them create more voltage from the sensor than the Ti cam gear with no holes in it.
 
#24 ·
Injector pump gear is a possibility, depending on what speed it runs at. Is it half engine speed or double or what??? I have no idea. You would need to set the depth in the cover plate, but that is not a big concern. Just need to know the ratio of rotation compered to the engine.

An auto sparky told me that using the alternator should be possible, but I did not look into it any further. Changing the cam was the better option for me, as it provided the extra advantage of the better cam timing of the earlier GQ cam gear. Factory turbo engines have a 5 degree difference in cam timing.
 
#26 ·
Injector pump gear is a possibility, depending on what speed it runs at. Is it half engine speed or double or what??? I have no idea. You would need to set the depth in the cover plate, but that is not a big concern. Just need to know the ratio of rotation compered to the engine.

An auto sparky told me that using the alternator should be possible, but I did not look into it any further. Changing the cam was the better option for me, as it provided the extra advantage of the better cam timing of the earlier GQ cam gear. Factory turbo engines have a 5 degree difference in cam timing.
I didn't know about the cam timing difference thats interesting. Yeah I think i may have made a radical decision buying the 2 wire pickup but i could still use it potentially if i use the injector gear, otherwise i can use alternator, or a flywheel/flexplate as the trigger gear. Dakota sell a pickup that uses the ring gear, so i bought a generic magnetic pickup that we use at work a lot to read the rpm of the conveyors at plants and quarries. So for $20 I had to buy one and give it a go too
I ended up using the TD42ti ECU and had to put the Dakota box between the ECU and the tacho.
I cannot do that as I'm using the zd30 ecu for the auto
 
#36 ·
Because you want to use the factory Transmission controller, no you cant use the TD42ti ECU. If you were using an after market transmission controller or a manual transmission, yes you could use the 4.2 ECU and everything will work. Some of the wiring under the bonnet needs to be lengthened.

Is the ecu plug the same or do I have to replace my who harness to the ti harness
The ZD30 ECU plug will plug straight into the 4.2 ECU. The ECU inputs and outputs are the same pin numbers for both ECUs, just the ZD30 has more of them. I am using a compushift for the transmission so was able to use the TD42ti ECU and just move and lengthen a couple of things under the bonnet. I also removed the unused pins from the ECU plug.
 
#38 ·
From the NissanPatrol forum:

”I now have a td42ti model which had an exposed dimple in the timing gear area as opposed to an indent on the td42, is that correct?

Apparently only the td42ti model had that, why?

I had to put a spacer on my tacho sensor for it to work and just curious if anyone knows how that actually measures and why the TI model was changed?”
 
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