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Discussion Starter #1
Looking for any help, advice with a TD42 conversion for my son. I have installed a TD42 in a TB42 Maverick and am trying to get a Dakota SGI 8D to drive the tacho. I have installed the Dakota unit and set it up as 6cyl engine/ 6 cyl tacho. The green light flashes when the engine runs which means it recognizes the signal from the sensor. My Multimeter measures a 36Hz signal from both the outputs on the SGI unit at idle. Have wired the output of the SGI unit to the Yellow/ Black stripe wire on the back of the cluster, and confirmed it is the only Y/B wire that is connected to the tacho on the cluster. Have checked all the conections to the tacho seem to be ok, i.e. its getting power, ground and the output from the SGI unit. Have cleaned up all the connections to the tacho just in case there were some dodgy connections.

But the tacho needle just wont move. My son says it worked when he had the petrol engine in it. Is anyone else using this setup on a GQ with petrol tacho ? About the only thing I cant do is test the tacho works by feeding it a signal. I don't have a signal generator or an Oscilloscope. Open to any ideas ???
 

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I only have experience with the SGI 8E and it has a test option that sends a 2000 rpm signal to the tacho to confirm the connection to the tacho. It doesn’t need an input signal to do that.
So you have the user manual for your model?
 

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Discussion Starter #3
Here is a link. It does not have a test mode, which would be very useful. As near as I can tell it is working because the green LED is flashing and I get a frequency on the multimeter that is about right at idle on both the outputs (36Hz). If I rev it the frequency increases accordingly.

SGI-8D (dakotadigital.com)
 

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I’d already had a quick look at the manual. Your flashing green light suggests it’s working on that side of things. There looks to be a possibility of choosing an alternative OUT port?

Also, it’s possible that the tacho has an issue..
 

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Discussion Starter #5
I have tried both the normal and high voltage output and neither works. I am thinking it is an incompatibility with the tacho or the tacho is not working. Any ideas on how to test the tacho ?
 

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GQ Dual Cab. TD42Ti with fruit.
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What year of manufacture is the TD42 engine??

You have checked the Hz output, but have you checked the AC voltage?? The Dakota requires minimum 1 volt AC. The green light would suggest it has the correct input though, so this is just another test to do.
 

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Discussion Starter #7
I don't know the year of manufacture. Is there a way I can check ? It is a silver top TD42. Would be interested to know.

The sensor output meets the requirements of the Dakota unit of minimum 1 V at idle. It gets higher with engine speed, might have been 12 V but not 100% sure.
 

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GQ Dual Cab. TD42Ti with fruit.
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I don't know the year of manufacture. Is there a way I can check ? It is a silver top TD42. Would be interested to know.

The sensor output meets the requirements of the Dakota unit of minimum 1 V at idle. It gets higher with engine speed, might have been 12 V but not 100% sure.
Ok, well a Silvertop with a standard sensor should work ok. Later model Ti engines have different cam gears, and produce lower AC voltages from the sensor. Should not be an issue for you though. I am not aware of an easy way to get a year model on it though. But they finished that engine run in 1995.

And to be clear, I am referring to the AC voltage from the sensor. This is not a DC voltage. From memory you will likely see 1.5 to 2.5 volts AC, or something like that.

So I would confirm that you are getting your minimum AC voltage required for the Dakota to work. After that I can only suggest you go through the set-up process again, and test the second tacho wire in the loom.
 

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You could try one of those $25 tachos from eBay. What’s your location? I have a 6 cyl standalone tacho here you can have.
 

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Discussion Starter #10
Appreciate the offer. I am in Vic. But I think you are in Queensland ?

I will do some more tests today with the multimeter and report back.
 

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Discussion Starter #11
Rechecked the sensor input voltage. As suggested by GQShayne at idle its 1.00 V rising to 2.00 V with i would guess 2500 to 3000 rpm revs.
 

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Discussion Starter #12
Checked the out put voltages of the SGI 8D. The standard out measures 6V in both the A/C and DC ranges which seem sensible. The High volt out measures 6 V in the AC range and 10 V in the DC range.
 

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GQ Dual Cab. TD42Ti with fruit.
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If the vehicle was a new project then I would think the tacho was no1 suspect too, but if it worked before you did the engine swap, then that suggests it should still be ok.

@JFF45 can you remember what the test specifications for the sensor is, in terms of its Hz output???
 

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My recollection is that only the AC voltage is specified but the OP has checked that and the unit is flashing to indicate an adequate signal.
lf it’s not the tacho then it’s the wiring to the tacho.
lit should be possible to test it with a cheap standalone gauge.
 

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Discussion Starter #16
I was hoping to wire up the TB distributor and coil and spin it with a drill to test the tacho, but apparently the distributor has gone to god.

I am now thinking about trying Jimmy the Tulips approach to "shorting out the input resistor" on the GQ tacho. He seems to think it requires a high voltage to operate and I am wondering if the SGI module provides a high enough voltage for the GQ tacho. His link is below :-

(1) ls1 Conversion, Making GQ Tacho Work | Patrol 4x4 - Nissan Patrol Forum

This is idea supported by this ad for a high voltage convertor for pre '97 tachos.

JRP Tacho Booster Signal Adapter :: 3v-16v to 48v-63v Buy Here (justraceparts.com.au)

My brother runs the SGi 8D successfully in his GU but that is a different tacho. Anyway - open to other thoughts. Have been distracted by other things today.
 

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GQ Dual Cab. TD42Ti with fruit.
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There is a specification for the tacho sensor that you can test. I cannot remember what it is, so will have to think about where I can find it. It is a resistance test I think, so it will be 1.5k ohms or something.

I will put my thinking cap on. 🧢
 

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GQ Dual Cab. TD42Ti with fruit.
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Ok, check the resistance across the sensor wires. Engine off test this one, just looking for a reading across the winding. I cannot find my reference material on it, but a quick google turned up this spec.

1287 - 1573 ohms at 20 degrees C.
 
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