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280zxt ecu compatibility


S30Turbo

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After reading the manual and troubleshooting I found out that my ecu is not sending ground to the CAS In my 81 L28et. I went online and found replacement ecu's for $400. But my question is can I run the 82/83 ecu. I read that my harness has external dropping resistors compared to the 82/83 that has them inside the ecu. If I can do I jut disconnect the ecternal ones from the harness or do I have to require something up or open up the ecu and mess with It? I really need my car to run now for the reason that it's my daily driver.

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Dude... Do you have the 1981 280ZX Factory Service Manual? Do you have the (1981 280ZX) Turbo Supplement? The wiring diagram is right there.

 

A. The C.A.S. gets NO "ground signal" from the ECU. It's just grounded to the engine along with a bunch of other grounds - including some ground connections to the ECU. (The ground for the CHTS, Air Regulator, & etc. are all connected to this particular ground as is most of the sensor wire shielding...)

 

- Just make sure the C.A.S. has a good GROUND.

 

- Check it has +12V (battery voltage) at IGN ON (power to the CAS comes from the EFI Relay which powers the ECU at pin 35 and several other sensors & devices)

 

- CAS wiring is: Red +12V, Black GND, White & Green are the 1 degree / 120 degree signal to the ECU (sorry, don't remember which is which)

 

B. NORMAL operation for the ECU: Green LED comes ON (stays ON) at IGN ON. Green LED goes OFF at engine crack or engine start. Green DOES NOT COME ON AGAIN until ECU tries to go into "closed loop" mode. In closed loop the ECU is monitoring the O2 sensor and constantly adjusting the injectors to ride the edge of "just Rich" and "just Lean". The LED ON at this point indicates the engine is running rich. The ECU does not even try closed loop mode until the CHTS reaches a certain temp - several minutes after engine start.

 

- I don't believe the ECU LED will go OFF if the ECU isn't getting a CAS signal. (disconnect your CAS where it plugs into the ECCS harness (by the thermostat housing), crank the engine, see if it stays lit or goes out upon cranking)

 

- check your spark. There will be NO SPARK if the CAS isn't working. The ECU creates (sends) the spark signal to the Ignitor/Coil. It can't (won't) if it's not getting a CAS signal.

 

C. You CAN use an '82-'83 ECU with an '81 harness. You have to remove the dropping resistor pack AND REWIRE the connector OTHERWISE the injectors have NO power. (the resistor pack has one +12V "feed" that runs to 6 different resistors then to each injector. 7 wires. Hook them all together.) The '81 Turbo Supplement says the injectors are powered through the EFI relay at IGN ON. In the '82-'83 they are powered constantly from the battery through a fusable link.

 

D. ALL this information is in the FSM (and several places in these Forums).

 

E. There is a COMPLETE TROUBLESHOOTING GUIDE in the FSM.

 

F. It's easy to follow.

 

G. It you follow the guide, you'll find EXACTLY why your engine won't start (without having to replace parts that don't need to be replaced).

 

I have a working 1981 280ZXT ECU. Just removed from my running L28ET a couple of months ago when I swapped to the M30 ECU. (Heck, I have the whole thing - ECU, Harness, AFM, Coil/Ignitor (no CAS)) I also have a 1983 280ZXT ECU. PM me if you want to spend money on parts...

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Edit - Now I feel kind of bad. After referring Francisco to the xenons130 site for the FSM and the Turbo Supplement, I realize that the site download for the Turbo Supplement doesn't contain the most critical document, the EL chapter. Without that chapter, troubleshooting an 81 turbo is very difficult. If someone knows another source for the EL chapter, I'd like to have it myself, for future reference.

 

 

I have to admit, the 1981 instructions are difficult to decipher. Nissan designed a magic ECCS analyzer and if you don't have it, you have to put your engineer hat on and try to figure things out. And I looked and can't find the wiring for the ECCS or CECU system anywhere.

 

 

Isn't the 81 CAS a VR type? The basic test is resistance of the pickup coil. More involved would be watching for voltage while running a tooth past the CAS, or spinning the engine.

 

You could at least do some simple tests. You should do them before you install the new parts anyway, otherwise you'll do a lot of parts replacement and probably end up in the same situation.

 

Look at page EF-32 to get some ideas. Find the wiring diagram for the CAS, if you can, and measure resistance across the pickup coils. Make sure that clearances described on EF-32 and -33 for CAS adjustment are correct.

 

 

Looks like a pain in the butt.

Edited by NewZed
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I tested the coil and both + and - have Power n they switch off as supposed to. The guy that said he worked on z cara for 30 years told unplugged the CAS cable and power probled the pins for signal. We found power, ground, but e said he didnt see switched ground that supposedly comes from the ecu. I have to admit 81 l28et is a PITA

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We found power, ground, but e said he didnt see switched ground that supposedly comes from the ecu.

 

There is no "switched ground" from the ECU.

 

There are 4 wires to the CAS: red = +12V (battery voltage through EFI relay), black = GND (to intake manifold with others), white & green = 1 degree & 120 degree signal to ECU.

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You're right CG, the ECCS wiring diagram is there. I missed it, got stuck in the first half of the chapter. Although, I see it's not the typical VR pickup like a Z's electronic distributor. There's power supplied to certain pins, like Pin 40, and two to the ECU alone, maybe powered, maybe not. I still don't see a troubleshooting method, or a way to verify correct function of the components, without the ECCS Analyzer, or more inside knowledge.

 

Good luck Francisco!

 

 

 

Would still like to see the EL section.

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You don't need the ECCS Analyzer. For everything it tests, the FSM shows an alternate way to test the wiring and the component using a simple electrical meter. All the information you need to test every ECCS component is right there in the "EF" section...

 

EF-31 describes the operation of the C.A.S. and how to adjust it's position.

EF-33 TPS operation and how to adjust

EF-41 Power to Injectors and how dropping resistors are wired

EF-60 Component and harness tests (to be done with electrical meter)

Edited by cgsheen
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I think I see the disconnect here. I've been focused on the CAS and how to test that it's sending the proper signal to the ECU/ECCS. That's where I would be if I had Francisco's problem, make sure that the individual components are sending the proper signals or have the proper functions for the ECU to do its "job".

 

You are right, there is a list of tests for a variety of components. But there is none for testing the function of the CAS alone (that I can find). For the 280Z's for example, there is a procedure to measure the resistance of the pickup coil in the distributor to at least confirm that it's not shorted or broken. But for the 1981 turbo system, there seems to be an assumption that the CAS always works, or they just overlooked the fact that it might break at some time. Even the ECCS Analyzer says to have the engine running, to test the CAS. But nothing is mentioned about confirming that the CAS actually works correctly.

 

Adjusting the position is important but only if you know that the CAS works.

 

Anyway, we're kind of in to the philosophy of problem solving now. Personally, I'd like to be able to test every circuit in the ECU individually,pin by pin along with all of the individual components. I love the 280Z FSMs. The ZX FSMs seem to the start of the trend toward the "replace components until engine runs" philosophy that a lot of today's cars use.

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There is a way to test the CAS. It's electronics needs power and ground. The FSM describes the wave forming circuit. The CAS produces an "ON" & "OFF" pulse (signal) with every tooth passage.

 

You can test the 120 degree signal by cranking the engine and testing the voltage on ECU pin 17 or 8. When the tooth passes, it should read voltage (5 volts maybe), otherwise no voltage. The 1 degree signal will be harder with an external CAS, but the engine could be spun by hand (plugs pulled, socket wrench on the crank pulley bolt to turn the engine slowly by hand). Testing for the same voltage spike when a tooth passes. Maybe you could see it while cranking, but I don't think so. ( This is easier with the CAS in the distributor - you can pull the dizzy and spin it by hand to test. ) I don't remember which pin is which, but one is the 120 degree signal and the other is the 1 degree signal.

 

I'll check this tomorrow on my L28ET...

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Cgaheen I will try that tomorrow morning.

Voong413 all the grounds that were on the injectors side by the AFM I connected them to the intake manifold for ground. The other grounds that I connected are the one in the ignition harness to the body of the car. Did I miss any grounds anyone ?

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