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Swapping my 75 280z engine to a 81 L28det need help


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I am swapping my engine out for a 81 turbo model on my 75 280z what I was wondering is what harnesses I need in order to get my car running I have all the harnesses from the 81 l28det from inside to outside would I have to swap all the harnesses but be able to run the 75 280z gage harness ? 

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You really just need the engine harness itself.  I usually keep the EFI Relay and Fuel Pump Relay intact (simpler than the 280Z circuitry) and sometimes use the 280ZX fusable links (that have to do with the ECCS and injector power).  There is a small harness on the 280ZX that comes from under the dash, up the driver fender, to the coil and ignitor that I find useful but it's not completely necessary.  There are several other wires in that harness that have nothing to do with the coil/ignitor so I strip them out if I use it.  (No point really - most of the wiring you need for the turbo coil/ignitor - and your Tach - is already there on the stock 280Z.  You just need to add one wire from the ECU to the Ignitor to make the whole thing work.) 

If you're going to use the stock harness: Get yourself some DeOxIt (made by Caig) and AFTER you clean each electrical connector on the harness, engine, ECU, AFM, sensors, (well, you get the idea - EVERYTHING!) use DeOxIt on the connections before you put them together!  There are specialty tools made to clean the oxide and corrosion off the brass connectors.  I would say that over 90% of the problems people generally have with these early EFI / ECCS engines are electrical - most having to do with wiring and connectors.  These old harnesses were never weatherproofed (and never meant to last this long).  EFI/ECCS is dependant on reliable signals from sensors to function properly.  Oxidation of the wire and connectors creates increased resistance which skews the signal from the sensors.  Eliminate as much of that as you can. 

In reality, most of us have had to abandon the stock harness.  After months of troubleshooting, my stock harness worked pretty well and I drove my turbo-swapped 260Z for years with it.  When I went to a different ECU and built a new harness, I came to the conclusion that I should have done that in the first place.  Live and learn as they say...  

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sound easy enough so you say you got a new harness and ecu what did you go with and anything helps thank you a lot i was having a big head ache because i was thinking that you needed all the relays and all that but it seams easier then that 

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You're swapping in a slightly newer version of the engine that that was already in the car. You'll be able to reconnect or reuse everything that has to do with your gauges.

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He means that your gauges are on a separate wiring harness than the engine control system harness.  That's the key to what you're talking about doing - the harness for the engine and its computer is separate from the body harness that controls your gauges.  You might have to swap oil pressure senders or bring over more 1981 parts than just engine control.  There's also fuel pump control to worry about.  It's not plug and play, it's complicated.

Get the wiring diagram from the Factory Service Manual and study it.  It shows all of the connectors. 

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  • 4 weeks later...

Ok so I get that I have to just put in the engine harness but what do I do with the old harness that hose into my passenger side that hooks up to my gauge I’m so confused on that if I want to run my old gauges what do I do 

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You'll have to tap in the old harness into the hardware that talks to the gauge. So things things like the voltmeter/tach/speedo (gearbox driven)/Fuel/oilpressure should remain unchanged. For the stuff that talks to the ECU, if the wiring allows you, you can jump in the corresponding connectors for the AFM / injectors / etc. 

 

Edit*  you might find what you're looking for by searching over on hybridz.org, they have loads of people that like to do these swaps, and might have good insight to the issue. 

here's links to get you started:

http://forums.hybridz.org/topic/113801-81-l28et-swap-into-73-240z-wiring-help/

http://forums.hybridz.org/topic/122072-l28et-swap-wiring-confusion/

http://forums.hybridz.org/topic/67309-l28et-swap-wiring-answer/

Edited by heyitsrama
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  • 3 weeks later...

the thing about the harness that is in the car now is weird because it dose not have the wiring for the side oil pressure or oil temp sensor (do not remember what it is) you find on the right side of the block.

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13 hours ago, jesus said:

the thing about the harness that is in the car now is weird because it dose not have the wiring for the side oil pressure or oil temp sensor (do not remember what it is) you find on the right side of the block.

I don't recall any 280z or 280zxt having a oil temp sensor. Maybe the auto's did?  I thought the later 280z ran the same 2 prong oil pressure sensor like the 280zxt. Regardless, if it's different unscrew the 280z one and screw it into the 280zxt. The oil pressure wire should be on the passenger side coming out of the engine bay harness from memory. (Not the Fuel Injection Harness).

Also, make sure you clean all the grounds on the ZXT harness very well and all the associated plugs andupgrade the injector clips to modern ones as I'm sure the old ones are likely toast.

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The L28ET has an oil temperature sensor in the back side of the oil pan.  The 280ZX Turbo also had a corresponding gauge.  While I'm sure someone has done it, I've never seen a turbo swapped early Z car with an oil temperature gauge...  My oil temperature sensor is there, just not connected to anything.

Edited by cgsheen1
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10 hours ago, cgsheen1 said:

The L28ET has an oil temperature sensor in the back side of the oil pan.  The 280ZX Turbo also had a corresponding gauge.  While I'm sure someone has done it, I've never seen a turbo swapped early Z car with an oil temperature gauge...  My oil temperature sensor is there, just not connected to anything.

Oh that’s right. It’s been so long I forgot all about that. 

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Yea ok so it is oil pressure and yes the old engine came with a auto transs but I swapped it to a five spd was going to ask have any of you heard of a custom wiring harness ? That I can just buy I rather buy a good one then end up Messing mine up 

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5 hours ago, jesus said:

Yea ok so it is oil pressure and yes the old engine came with a auto transs but I swapped it to a five spd was going to ask have any of you heard of a custom wiring harness ? That I can just buy I rather buy a good one then end up Messing mine up 

Messing which one up? The one that came with the car or the 280zxt harness your trying to install?

Im not aware of any harness/Ecu option for a stock configuration ZXT motor swap. If you decide to go MS you will need chickenmans help. My uncle just went to MS and said without his support it would be near Impossible on his own. 

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I might suggest you bust out the FSM. Look at your stock harness to see what wires go where and from where.

The only gauge from the passenger side harness is the oil pressure sending unit that I can recall. 

The tach signal and water temp switch should come from the new ZXT harness. I thought those came on the driver side. 

 

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On 6/19/2018 at 12:39 AM, jesus said:

i mean the harness that i need to cut up the passenger side harness for gages and relays and all that good stuff to run stock gages 

Dude...  You don't need to "cut up the passenger side harness for gages" (sic).

- You can use the stock coolant temp sender wiring (coolant temperature gauge) - the L28ET has the same temperature sender in the t-stat housing

- The Tach signal wire will connect to the turbo coil just like it did to the stock coil.

- The oil pressure sender:  IF the oil pressure sender is different on the L28ET, unscrew it!  Install your old oil pressure sender on the tee of the L28ET and plug it into the stock wiring!

You WILL have a bit of other wiring to connect into the stock harness, but it's minimal really and can be made reversible - if you're smart...

 

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