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FIguring out swap electronics (7m->280zx)


Jbeck45

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Hi, been browsing around for a while and decided to make an account to try and get some advice. I picked up a '79 280zx in pretty good shape for not much money. Looking at the engine it came with I'd rather not try and rely on it (Not the L28s in general, just this particular one). So after looking at wanting to do an engine swap, I was able to pick up a '89 Cressida for next to nothing. In terms of the mechanical side of things, fitting the new 7M and the W58 I plan on bolting onto it into the 280, I'm pretty confident in getting done. However, this being my first engine swap for a motor that wasn't made for the car, the electrical side of things has me not so sure. My main focus is on getting the engine itself just running with functional instruments (tach, speedo, etc) and things like the heater and AC can come later. My main question is, what from the Cressida do I need to transfer over (I've got the ECU obviously) to make things go a little smoother. Also just some general advice as to how people get the electrical side of something like this done. Thanks in advance for any help, its appreciated.

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Your best option is to study the wiring diagram.  That's why they were created.  Read the FSM Engine Fuel chapter also, it explains the fundamentals of how an EFI system works.  That will help you.  The EFI harness is separate from the main harness for the most part.  The gauges might take some work if the sensors are different between Nissan and Toyota.  Getting the fuel pump control system to work will be difficult, probably.  It's described in the FSM also.

 

Using the Cressida EFI system in a Z or ZX is not common.  You're kind of on your own.

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Be wary of the 7M, everyone I met with who had one spun the rods at some point. Lots of oil restrictions, low oil pressure, and a pickup height that is on the high side can lead to mishap. Or just someone using cheap clamps on a remote oil filter...

 

There is a video on youtube of a guy who goes over the wiring for his swapped truck. You need the ECU and the harness, including fuse and relay box, and you need to splice power to the ECU power, fuel pump, and general electronics (injectors, spark, etc). That is if you want to keep the stock ECU, my wiring harness was absolutely falling apart on mine so I abandoned it pretty quick.

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Naysayer! In all honesty I am aware of the 7M's shortcomings and luckily there are some ways to help rectify them. In the end at least its better than what was in the car before. From what I've been gathering, not a lot whole needs to come with the engine, just the harness, ECU, some relays and such. Probably the fuse box as you mention. From a glance it looks like an overwhelming obstacle to tackle but I think once you have things in place and you can section it down it becomes much more simplified.

 

I imagine getting aftermarket instruments, fuel pump and such make things go a bit easier rather than trying to put a square peg in a round hole. I've never really liked working with wiring so the idea of having to do this much doesn't excite me, but oh well. If anyone else happens to have any more tips related to this kind of swap I'd love to hear em. Seems the attitude is to just go out and do it 😜

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  • 5 weeks later...

7m is great when it is running well. Make sure you have a dummy light or a good oil pressure gauge hooked up that you monitor religiously.

 

A point to consider is a 7mge isn't that much better figure to figure compared to a L28E.  I had a 7mgte JDM block without the oil squirters so I wanted to really go for it on the rebuild after blowing all the oil out on the freeway, but $800 for just the oil mods was a lot, on top of attempting to source a non-warped crank, and the subsequent micro fissures from the piston destruction kind of sealed the fate. My 2jz ended up being cheaper then the oil mods. Machine shop guy told me I was making the right choice, and even waved all the labor they had done on the 7m, and put it towards my 2jz if that is any indication of how happy they were for me.

 

With that said, depends on how integrated you want everything to be. Without looking up the specs I don't know if the tach and speedo will communicate, but getting the engine running is as mentioned just a matter of a few wires to the Toyota harness. No one really likes to do wiring, but if you don't want to be chasing gremlins down the road, buy some decent tools and learn how to do it yourself, or shell out the money for a professional, although that may end up costing more than you have into both cars depending on where you go.

Edited by seattlejester
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  • 1 year later...

I can help you with the wiring, it is pretty simple on the 7MGE.  You can either run from the Toyota Fusebox or integrate into your own.  

There will be a fuel pump relay (controlled by the AFM on stock 7MGE), main relay (key to on position), and a constant 12V power to ECU so that it can remember it's last fuel trims.

If you want to go old school you can just make a switch for everything.  Let me know if you need help with wiring.



 

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