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davek

L28ET crank position sensor

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Hi guys

Can someone check the ohms on the crank position sensor of 83' turbo dizzy. I have big problems with my megasquirt re-install and would like to find out if my CAS sensor is bad.

Green wire to Black(ground) I get 103 ohm. White to ground I get open circuit. green to red(power) is 106 ohm. white to red is 6.8 ohm

I'm no electronic guy by any means I barely know what an ohm is. Please don't get to technical on me.

Another question s how does one change the sensor? Do I use a puller to get the center round dics off(see pic) then I assume the circuit board and sensor can be removed.

I posted this on Classic Zcar yesterday and had no response. I read on a forum an older Maxima has the same sensor, can anyone confirm?

1213171849[1].jpg

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An ohm meter is the wrong instrument to test this thing.  Best way is to hook up power to it, then manually turn the distributor to check the voltage goes high and low when the slots open inside the optical sensor.

 

+12V is applied to red, ground to black, measure voltage on the white and green wires.  I forget whether green or white is the ignition position and which is the fine slots, but the ignition position needs a resistor connected from the red to the white or green to measure the voltage properly.

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Thank you for replying.

FYI-I have the DIYautotune trigger wheel in the distributor.

Green wire is cam signal, white is crank position per DIY.

I get zero to 1.3v as I manually turn the distributor on the green wire.

Zero voltage on the white wire.

I'm checking these back to the black wire I have my power supply hooked to.

I don't understand the resistor instruction. My ignorance. Bridge a resistor directly across the 2 connectors? What size resistor. Not much to choose from in my garage shop. 10k, 2.2k

 

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here is latest MSQ, data log and composite log.

This engine ran OK for a couple years then I rewired using DIY MS & MSX wire harness. I mixed wired the green, white & black wires in the dizzy during the process. I hope it didn't burn anything but the optical sensor.

Dave

CurrentTune.msq

2017-12-12_17.43.26.msl

2017-12-11_19.02.48.csv

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Your Trigger wheel settings are configured using an using an MS3X Expansion board. Double check the wiring for the expansion board.

 

Also noted you are using really old Firmware on your MS3 ECU 1.34 with a signature version of version 0435.16. MS3 is now  on  Firmware 1.51 with a signature version 565.00. You should update your Firmware on the ECU.

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There is a wiring diagram for the distributor somewhere on DIY.  The resistor needs to be tied between the red wire and the green wire, that allows the signal to rise to 12V.  1.3V is too low to reliably trigger the ECU.  You can probably use either value, they only need to be rated for 1/4 watt.

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I have a Re-man 280ZX Turbo dizzy from A1-Cardone. Purchased from Rock Auto. I can confirm that it uses the Maxima Z31 CAS Module. It's a bit different than the original 280ZXT CAS in appearance. All the components are encapsulated in a smaller base. So no resistors and such visible like in your picture. 

 

A couple of notes on the A1-Cardone product. As received, the trigger wheel disc was rubbing on the Optical LED. This was caused by the mounting of the Maxima Z31 module.

 

1: The Maxima module has two locating " Tits" on the bottom of the plastic base. These have to be cut off with an Exacto knife or filed down. Other wise the base will not sit flat and that is what caused the interference between the Trigger Wheel and the Optical LED.  5 minute fix. 

 

2: The original 280ZX Turbo CAS used 3 screws that installed form the top and screwed into threads in the distributor body.  There were no threads in the original 280ZXT CAS housing. Only non-threaded holes. However, the Maxima distributor has holes in the distributor body ( but no threads ), the mounting screws go from the bottom up and screw into the CAS module,  which does have threaded Brass mounting inserts. So the mounting methods are opposite. 

 

A1-Cardone uses a mix of 280ZXT dizzy body and Maxima CAS. A1 Cardone installed the screws from the top. This meant that the screws went through both the threaded bars inserts in the CAS body and then into the threaded holes in the 280ZXT Distributor body. This can cause alignment problems.  What I did was to take a 1/8" ( might have been 5/32" . I can't remember ) and drilled out the threads form the bottom of the distributor body. Just large enough so that the screws would slip through. Now the screws installed from the bottom of the dizzy housing ( no threads now ) and then screwed into the threaded bosses on the Maxima CAS body. Result. Flat and proper mounting of CAS Module 10 minute fix.  

 

Bottom line. If you order a new CAS ( be it 280ZXT or Maxima Z31 ) check how the mounting of the CAS is made. It may be slightly different than how the original 280ZXT CAS was mounted. I think there is a fair amount of parts swapping going on in the aftermarket. So it may be hit and miss on what you receive. GL.

Edited by Chickenman

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SleeperZ

With 2.2k I get a steady 0.44v then a rise to 13.5 at that one spot on a revolution. I used the resistor on white wire and got zero to open line to 14v turning very slowly.

Are we confident enough it's shot for me drop $120 on a new one? I will see if the junk yard has one tomorrow.

 

Its been too long and I didn't take notes when I assembled MS but I'm sure I followed the direction on DIY and installed a resistor as described.

 

so what about white wire and no voltage.  Actually reads 0.035. CAS seen better days!!!

 

I'll follow your install info chickenman.

 report back soon as I can get used one.

thanks guys.

 

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Davek. Please note that I just edited my above Post and deleted the message. My image of the wiring is for a Haltech ECU. That uses the standard Nissan wiring. The DIY Trigger wheel has the Triggers flipped, as the Outer ring is now Cam signal ( 1 window ) and the inner Ring is now  the Crank signal ( 24 - 2 ) . But only for the DIY Custom trigger wheel. ( DIY use some funky programming for their wheel to get around Processor limitations on the MS1 and MS2 ) . Grounding info still stands if you read it. 

 

The image I posted matches with my AEM wheel, which has the Crank on the outer ring ( 24 holes ) and the Cam Trigger ( 1 hole ) on the inner . Same orientation as OEM Nissan trigger wheel,but opposite from DIY Caution L28T trigger wheel. 

 

I have my Dizzy setup for a Haltech as well. Which uses standard Nissan wheel orientation. Sorry for the confusion....

 

Edited by Chickenman

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Revised post Here is the standard Nissan Wiring. Note that the DIY Trigger wheel flips the usage of the Inner and Outer rings. This picture shows factory wiring setup. This picture is for a Haltech ECU, which does NOT flip the usage of the Inner and Outer rings. As does the DIY wheel. 

 

Outer Ring = Green Wire ( Cam signal for DIY Wheel ) 

Inner Ring = White Wire ( Crank Signal for DIY Wheel ) 

+12v = Red Wire

Trigger ground = Black wire ( Must connect to MS ECU sensor ground ) 

 

5a34657e046a4_280ZXTurboDizzywiring.thumb.JPG.521c9b0f49f41438ec20090f352769e6.JPG

 

 

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Adaptronic Grounding Tips link;  Note section ( about halfway down ) that explains why engines with a Nissan Optical CAS require that the ECU be grounded to the engine. Not to the Chassis or Negative battery terminal.

Nissan CAS has two ground. Black wire is Trigger ground that must be grounded through ECU sensor ground. But the Nissan Optical CAS also has a secondary main 12 Volt ground, that grounds through the dizzy metal body and then to the engine. This requires that the ECU be grounded to the Intake or cylinder head. Failure to do so ( chassis ground ) can create a large " Ground Loop " that introduces electrical noise to the Trigger system.

 

http://www.adaptronic.com.au/ecu-grounding-tips/

 

AS noted in Adaptronic article, ECU's should NEVER be grounded directly to the negative Battery Terminal. Starter can pull over 150 amps when cranking, and this can induce a feedback voltage in the ECU ground circuit ( if connected to Neg Batt terminal ). That is enough to damage sensitive Micro processors and semiconductors in the ECU

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WOW

For several thousands of miles I had the black distributor wire grounded to negative battery. MS pin #1 was not used. The distributor has a heavy paper gasket at the base that would not help grounding to the engine but does directly contact the front cover enough for a ground.

I will connect the ground wire to pin #1 per MS wire diagram.

 

as I skimmed the article. I have all grounds going to my fuse panel which has direct ground to the battery terminal. Nothing grounded directly through the engine, frame etc.

1215171915[1].jpg

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No luck at Pull A Part today. oldest maxima was 94 and it had the newer style CAS. with the connector sticking out the side instead of downward. I did bring the CAS home. It won't fit in the distributor of course. No pathfinders or frontiers old enough at Pull A Part. Villager and Quest as well.

 

Can someone confirm ZXT CAS white wire has zero volts when powered up like sleeperZ's  instruction's. Check green wire also.

cheers

 

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The CAS produces a 0v to 5v square wave as the slits pass.  If you were to pull the distributor and turn it by hand (with the CAS powered (ignition on)) you should measure 5v when the slit passes (open hole for the light to pass through) and 0v otherwise (when the disc is blocking the light).  And that should happen on both White and Green wires.  But Tuner Studio should show your crank and cam signals if it's getting them.  Easy to test the CAS by hand though...  If you're not getting a 5v spike, the module is bad.

 

Any Nissan or Infiniti with a VG30E should have the optical module you need.  But, I've gotten most of mine from M30's or Maxima's.  Might not hurt to check if the 4 cylinder cars of the era used that optical module.

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cgsheen

What you post about 5v is what I keep hearing. However my distributor is not doing that. If you look at my previous post that has my various logs there is something wierd going on. Maybe this is typical results of a CAS fault. Not defined.

I will continue trying to locate an older Nissan with a VG30 engine this week.

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I think that what's not clear, at least to me and maybe cgsheen knows for sure, is whether the 5 volts is passed through the CAS, where the CAS is a gate for 5 volts generated by the ECU, or if the 5 volts is generated within the CAS.  If it comes from within the CAS then powering those other CAS wires should give the 5 volts as expected.  If the 5 volts comes from the ECU, you're not going to see it, with a battery and jumper wires test.

 

If you do cg's test, which I've done, with the CAS/distributor plugged in to a Nissan harness, you'll see the 5 volts.  But I've not tested the wires from the ECU to see if they had 5 volts to start.

 

Easiest test for you might be to find a buddy with the proper Nissan who will let you unplug his CAS and plug in yours.  Turn the key on and spin the shaft by hand as described, with a meter attached.  I was able to do my test because I had a Pathfinder in the driveway.  It works.

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That's a nice schematic.  It doesn't really explain the 5 volt signal though, or how to wire up a CAS on the bench for testing.  Looks like DIY has repurposed Nissan's original design.

 

I'm sure it's clear to somebody out there.  If it is maybe they can add some detail.  How to wire it for standalone testing and what to measure when testing.  Volts or continuity, on which wires.

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Well, if the MS 3.0 expects a 5V signal, and we give it 12V, that might present a problem.  But I have reviewed all the input circuits, in the context of wiring the ZXT distributor, and I've not seen any 5V specific inputs.  The ZXT optical sensor does not output 5V unless you pull the CAS line to 5V instead of 12V (which would work), but from my research I'm fairly sure the ZXT dizzy does not generate or receive 5V in the factory implementation.

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SleeperZ

the link is DIYAUOTUNE direction for using the trigger wheel in an L28ET distributor. It does require a pull up resistor as you stated. This is done inside megasquirt. Or can be done right at the wires are you said. MS manual says this to do this or internal to MS.

I followed these direction when I assembled my MS.

It worked fine.

https://www.diyautotune.com/support/tech/hardware/nissan-trigger-disc/

Just ordered CAS on EBAY. Out of California via Taiwan. We see mid next week. New $49 delivered.

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Sorry I haven't been back to this. Nissan describes the optical module as creating a sine wave that is cleaned up by the electronics into a square wave. And ya, it's definitely a 5 volt to 0 volt wave.

 

I have MS3 (base) running my L28ET now using the diyautotune L28ET optical wheel for crank and cam input. (I did COP using Nissan coilpacks and ignitor. And installed the electronics for logic level spark outputs for full sequential.) The crank and cam inputs are Wired up as per their instructions - I put the pull-up on the MS board. I've been really impressed at how stable the signal is - never had a sync error...

Edited by cgsheen

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