What are the facts about 280z ECU compatibility and differences

[Av8ferg]

Looking for the Z Oracles to help enlighten us neophytes on the 280z ECUs.   I have acquired several ECUs at junkyards, EBay and CL.  I thought it might be a good to have a couple extras and would sell the others I don’t need. I got them all at great prices...couldn’t pass them up.  Here’s my situation.  My car is a manual tranny,  it had a AT ECU (A11-601-000) in it. The wasn’t running and I thought I had isolated it to the fuel pump relay because the pump wouldn’t work when I turned the key on.  I replaced the ignition switch, pump relay and ECU all at the same time and the car was able to start so I never isolated it to any single part. Bench checking the old Fuel Pump Relay, I discovered it tested good.  So it led me to think I was the ECU.  The one I replaced it with was from a 1978 (A11-600-00) that I bought with a bunch of extra parts from a guy who converted his car to carbs. Okay so my car currently idles like crap, and current consensus is it’s a vacuum leak but unverified.

I was reading through many previous forums about ECUs and found conflicting info.  Some say the 78 is unique to the 78.  One guy said his wouldn’t idle right when he had a 1978 ECU in his 1976 car.  Other forums state they’re interchangeable.   Looking at all my ECUs I can see a difference but they all have the same part number (see pics).  Looks like the the 78 has more pins than the others.  To make maters more confusing is my car is a CA car, so it has that altitude sensor, not sure how that plays in here.   

So I’m bringing all these ECUs with me to test in the car.  I also have a replacement AFM I’m gonna test on the car too. Got it for $20 and I bench checked it today, readings were spot on with the FSM. 

What is the community consensus on the 280z ECU compatibility?  

 

Edited August 31, 2018 by Av8ferg

[Zed Head]

I'm pretty sure that I've tried the whole range of ECU's in my 76 MT and not found any difference.  I would guess that differences over the years might just be in refinement and durability.  There doesn't seem to be any change in circuitry and the descriptions in the Engine Fuel chapter don't indicate what might be different.  Fuel cut, for example, is still at 3200 and restart at 2800 in 1978, just as it was in 1975.  There are some errors in things like the cold start valve wiring schematic, that have been discussed before.

Much has been discussed but nothing has been demonstrated.  Always good to have spares though.  I got stranded once, a short way from home, when I was testing my spare to make sure it was good.  Forgot to bring the known good one with me.  Now I keep a spare ECU behind the seat.

You can test them just by letting them dangle by your foot on the connection.  They have their own ground.  Give them a good workout.

p.s. idle is its own little world, entered through the throttle valve switch.  Might be a change between years, and CA v Fed.  EFI started as an emissions control effort, not performance, so changes for emissions purposes are likely.

[Patcon]

I can't image all those extra pins in the later ECU don't do anything...That would be very "un-manufacture-ish"

[Av8ferg]

I agree, why put the extra pins. It requires the company to “change” something to justify the production modification and associated cost. Not profitable to change for no benefit but ZH makes a good point that the wiring diagram isn’t different.

I’ll post my findings after testing all these ECUs. I plan on marrying the ECU with the AFM that came off the same car too.


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[cgsheen1]

36 minutes ago, Patcon said:

I can't image all those extra pins in the later ECU don't do anything...That would be very "un-manufacture-ish"

Oh, I can!  They probably finally figured out that it was more of a bother to eliminate the unused pins than to just install and not use them...  I'm sure their connector manufacturer was complaining about having to leave out pins.  Now every ECU has any number of unused pins - but they're still in the connectors.

[Av8ferg]

Well, I’m very familiar with the Japanese culture having lived near Hiroshima for 3+ years. The details matter in their culture and they are VERY serious about the minutia. This is why they make great cars. They are super stubborn and don’t sway from the “rules”. I can assure you this details with the pins was a point of discussion in the design offices.
To give you an example I once ordered a Hamburger in Tokyo. The menu stated the hamburger had cheese on it. I asked for it without cheese and the lady said it wasn’t possible. Bizarre to an American but not really to a Japanese. They make it exactly as the menu specifies.
Not this is obviously a tangent and a big generalization of the culture and not representative of everyone but it give you an insight into the culture. They are AMAZING at process based things and not as good, pushing outside the norms.
So I think there was a reason for the pins addition but I have been know to be wrong.....ask my wife.


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[Zed Head]

Don't forget that we're talking about 1978.

The cover pops right off of the ECU.  Two little screws on the back and it slides off.  You can open it up and see where the pin leads are.  A good idea to examine anyway, they do get fried occasionally from backward battery hookups and corrosion.

[Captain Obvious]

I wouldn't get too hung up on the number of populated pins. From what I've seen, some of it may depend on when (and by whom), the ECU was assembled. The original first run ECUs seem to have only the used positions populated, but I've seen second source (or later replacement production units) that have all the positions populated. I think there are a number of factors at play with that.

I remember someone's assembly that used plastic DIP packages inside instead of the old spider legged cans? Wheee's maybe? Definitely a later production run after the 280Z was no longer being sold new. Probably newer production of the old design for repair business.

[Av8ferg]

I think CO just made the most reasonable explanation.  

[Captain Obvious]

Haha! Well just because it's reasonable, it doesn't guarantee accuracy. I could be all wet!  

Out of curiosity... Can you pop the lid on that 78 ECU and take a pic of the electronics inside?

 

[Av8ferg]

Here are some pics of the inside of the 1978 ECU.  It appears to me based on the last pic that there are no solder welds on those extra pins.  

[Captain Obvious]

You are correct. Those pins go nowhere. Even though the connector is populated, those pins are no-connects.

I'm thinking that they may have just received a shipment from Amp (the connector manufacturer) of connectors that had all the positions loaded instead of the partially populated versions they had used in the past. Reason being... I've got pics from later built ECUs that went back to the partially populated connector. Seems the fully populated ones were a temporary thing?

That sort of thing is a pretty common occurrence in manufacturing. The buyer places an order and the vendor asks if they can substitute a different (but compatible) part instead. Usually because of lead time. If it's acceptable with the buyer, they get the substitute. May be what happened here.

Reason I say this... Here's an ECU which I believe is built later than the one you posted above and it's got the partially loaded connector. I believe the later construction date based on three things... The ID numbers on the boards are higher. The plastic encapsulated capacitors in some locations (newer style), and the different heat sink style on the IC's. I bought this ECU used as a spare, and I was told it was for 77. I really have no way to verify that though. It may have actually came out of a 78.

Anyway, all this is academic... Use the ECU that works. The number of pins populated really doesn't matter much.