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Turbo swap various questions


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I've performed an 83 turbo swap into my 75 280z. The car is running great, however, I now need to go through the various sensors and bugs to get everything 100%. I've done the searching and can't find a definitive answer.

 

1st question: I swapped the oil pressure sensor from the 75 block to the 83 block in the car and hooked up the stock 75 harness oil pressure wire to the nipple on the sensor (teehee... nipple...), but still don't get any pressure reading. Is this the correct way of doing this? The pressure sensor seemed like it was on it's way out any way, but I just wanted to verify I'm doing it correctly before splashing out more bucks.

 

2nd question: the water temperature sensor still needs to be hooked up. All I have down there is the stock harness with the wires for the water temperature and the stock 83 water temperature sensor attached to the block (or hose.. I don't have the car in front of me right now). Is it merely just a plug and play affair?

 

3rd question: And this is probably a stupid one. I've got the heater core hoses all hooked up correctly, but there's this other hose coming out of the firewall just above the heater core hoses and I have no idea where it goes. I can't seem to find anything in the FSM about it. I'm assuming it has something to do with the coolant system because when the engine had been running for a bit, coolant started to pour out of it (I'm assuming it's got something to do with the thermostat opening up)

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Does this need to T into one of the other hoses?

 

4th Question:

The Relay that was hidden inside the passanger side fender well on the 83. I'm not entirely sure what it's called, but it has something to do with getting charge/signal to the fuel pump relay. Now because of this relay, my fuel pump works intermitently. Sometimes the fuel pump relay will just repeatively click, sometimes randomly, sometimes not at all, and sometimes flawlessly. It's not the fuel pump relay, it's this other relay causing this. I replaced it with other relays that I knew were working. I tried heating it with the heat gun (it was cold outside) and viola! It works! What could be causing this to happen? And how would one go about fixing it?

 

Thanks in advance! This site has proved invaluable to getting me this far on the swap. Looking forward to posting some pictures and vids!

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#1 - That's what I did on my '74... I used the existing wiring and installed my "one-wire" oil pressure sender on the L28ET. It works. We did the same thing on my son's '76...

 

#2 - Not plug-n-play but not difficult. The Turbo engine harness has a yellow wire and a white wire that go up to the front of the engine and attach to the coolant temperature sender (yellow) and the thermotime switch (white). Unless you're using the injector blower and it's fan timer box from the 280zxt, you ignore the thermotime switch and it's white wire.

 

The yellow wire hooks up to your temperature guage. On the turbo engine harness, the yellow wire terminates on "connector 3" - which is white plastic 6-pin connector (5 pins are used - other wires to the connector are Black/white, Blue/red, Green, and White)

 

#3 - Nope, something is not quite right there. Shouldn't be any water in the small hose, I believe that should be vacuum and connected to the vacuum bottle or the vacuum solenoids just forward of the battery.

 

Yep... Just looked at the Factory Service Manual. There's a vacuum line connected to the "Vacuum Cock" (which is a valve in the heater core hose beside the core itself. The valve is operated by a vacuum source which runs through the heating & cooling selectors and then to the "Magnet Valves" (solenoid valves) near the vacuum bottle attached to the fender well...). I'd bet actual money that your "Vacuum Cock" is broken / has a bad diaphram, and is leaking water where it shouldn't... Don't hook that tube up to vacuum! Not until you replace that valve near the heater core. (That may also mean water is throughout all the vacuum tubing & vacuum operated devices under the dash...)

 

#4 - I'm pretty sure the relay in the '83 fender IS the Fuel Pump Relay... Your '75 has one of it's own. If you're using both it's redundant... When I did my swap, I used the EFI and Fuel Pump Relays from the 280ZXT and wired them into my existing harnesses, abandoning the original fuel pump relay (I didn't have an EFI relay to begin with). The fuel pump relay is controlled by the ECU on the turbo engine. For safety reasons, I'd leave it that way. Check your wiring and make sure you follow the 280ZXT wiring method for the fuel pump. The '83's also had a fuel pump modulator box that attached to the ECU harness. It varied the voltage to the fuel pump. Are you using that?

Edited by cgsheen
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Thanks for the information! Helps tremendously. Oil pressure is working now.

 

It's not the vacuum line I was talking about in question 3, but the water hose that comes out of the same hole as that vacuum line (it's got a pretty new worm clamp on the end). Like I said, it's probably a really stupid question, but I can't find anything pertaining to THAT water hose. I'm assuming it T's into one of the other hoses.

 

Question 4:

I'm not using the stock 75 fuel pump relay. It's unplugged. I've got the fuel pump relay from the 83 turbo rewired under the dash and then that other relay on the passenger side that comes out of the same side of the EFI loom as the EFI harness connector that has 1 black wire, 2 black and white wires and a brown (or orange wire). What is that relay for?

Edited by neilbey
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I only have the wiring diagrams from my '74 and my son's '76. They both show the stock wiring from the "thermal transmitter" as yellow, then yellow/white going from the sensor into the "engine room harness" then through the firewall to connector C-5 under the glove box. Connector C-5 is on the lower row, 2nd from the left and is green in color. The yellow/white wire is at one end (of the 5 pairs of smaller wires) and has a yellow/black wire directly opposite (the small wires at the other end of the connector are green/white and white/red).

 

The engine room harness runs along the frame on the passenger side, goes across the beam in front of the radiator, and over to the coil location if I remember my son's '76 280 correctly. There's a 4-pin connector (round, I think) near the coil that gets abandoned when you do the swap. I think the yellow/white from the sensor starts there and runs to C-5, then into the dash harness and straight to the temperature guage.

 

I ran my turbo harness much like the donor it came out of. That put "connector 3" and the yellow wire from the temp sensor near the battery. I ran the yellow wire through the firewall (where all the other wires come through) and connected it to the yellow/white coming out of C-5 running to the guage...

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Question 4:

I'm not using the stock 75 fuel pump relay. It's unplugged. I've got the fuel pump relay from the 83 turbo rewired under the dash and then that other relay on the passenger side that comes out of the same side of the EFI loom as the EFI harness connector that has 1 black wire, 2 black and white wires and a brown (or orange wire). What is that relay for?

 

That's the EFI relay for the L28ET. The Brown wire is +12v from the battery through a fusable link, Black is GND, and one Black/white is "signal" from the Ignition switch (+12v when in the "ON" and "Start" positions), the other Black/white is switched +12v to power the ECU, VCM, and CAS...

 

With stock wiring, the ECU on the L28ET has complete control of the fuel pump... The ECU sends the "signal" voltage to the coil in the fuel pump relay, so it controls switching the relay on and off.

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#3 - That big hose shouldn't be there... Only two are needed, one inlet to the heater core, one outlet. Someone did something funky under the dash?? There's the aforementioned valve connected to one side of the core by a short piece of hose (and it's operated by the temperature control cable NOT a vacuum solenoid like I said above...). One of the water hoses connects to that valve, the other directly to the core. But still, there should only be 2 water lines under there...

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#3 - That big hose shouldn't be there... Only two are needed, one inlet to the heater core, one outlet. Someone did something funky under the dash?? There's the aforementioned valve connected to one side of the core by a short piece of hose (and it's operated by the temperature control cable NOT a vacuum solenoid like I said above...). One of the water hoses connects to that valve, the other directly to the core. But still, there should only be 2 water lines under there...

 

Agreed. I was scratching my head on that one too. Never seen that before.

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I recently purchased a '77 280z and am thinking about putting my l28et into it. It's in my p.o.s. 240z now. This may be another dumb question, but did the L28et make your 280z feel much quicker? It made my 240z into a little rocket, I'm just not sure, because of the weight of the 280z, it'll feel much faster. Am I totally here? I kind of like the stock feel of the stock motor, but I'm lacking the pick up I enjoyed from the 240zet. Any comments?

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Thanks for the replies. I will get cracking on the temp gauge as soon as I'm near the car.

 

About the hose though, I figured that wasn't supposed to be there. There was water leaking under the dash too. I did some prodding and it turns out that there's an outlet/inlet for a water hose that was disconnected - really not sure which one without removing the dash. Plugged that for the time being. I definitely think there's something funky under the dash. Sigh... Dash removal is my LEAST favourite thing to do.

 

While I'm in there though, I'll probably install a boost gauge in place of the non-working clock. The tach is jumping from zero to whatever the revs are at the time - basically acting erratic. I have the tach hooked up from the coil, to the stock 83t resistor for the tach on the harness, to the stock tach wire on the 75 ignition harness (didn't want to separate it from the headlight harness). Is this the right way to do it? Because when I hooked the stock 75 tach wire to the coil, it didn't work and killed the ignition (by killed, I mean stopped the ignitor from creating spark and stopping the engine) Should I just hook up the stock 75 tach via a radioshock resistor to the coil? What resistor would be needed?

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Hmmmm... When I did my swap, I used the coil wiring (and coil / ignitor) from the 280ZXT. It's a little different arrangement than the 280 coil wiring. It goes from the ECU up the driver fender to the coil location. Then I just ran the Tach signal wire from the ECU location to my existing in-line resistor (which is under the glove box on my 260) and tied it into the wiring from the original Tach feed...

 

Sounds to me like you're running the Tach signal through TWO resistors. Correct me if I'm wrong here: The original coil wiring on the 280Z comes from the transistor ignition box under the dash near the glove box? It goes up the wire bundle along the passenger side, across the radiator, and down the driver fender to the coil? The tach signal wire follows the same path from the coil BACK to the wiring junction under the glove box, thru the resistor, and then to the tach gauge?

 

To me it sounds valid to run the Tach signal from the coil to the original tach signal wire near the AFM, but you shouldn't have the 280ZXT Tach resistor in line... You already have the correct resistor for your Tach in the signal wire - unless you've removed it.

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Hmmmm... When I did my swap, I used the coil wiring (and coil / ignitor) from the 280ZXT. It's a little different arrangement than the 280 coil wiring. It goes from the ECU up the driver fender to the coil location. Then I just ran the Tach signal wire from the ECU location to my existing in-line resistor (which is under the glove box on my 260) and tied it into the wiring from the original Tach feed...

 

Sounds to me like you're running the Tach signal through TWO resistors. Correct me if I'm wrong here: The original coil wiring on the 280Z comes from the transistor ignition box under the dash near the glove box? It goes up the wire bundle along the passenger side, across the radiator, and down the driver fender to the coil? The tach signal wire follows the same path from the coil BACK to the wiring junction under the glove box, thru the resistor, and then to the tach gauge?

 

To me it sounds valid to run the Tach signal from the coil to the original tach signal wire near the AFM, but you shouldn't have the 280ZXT Tach resistor in line... You already have the correct resistor for your Tach in the signal wire - unless you've removed it.

 

I have not removed anything yet. That was what I was originally trying to do (what you did), but for the life of me, couldn't find the 75 stock tach signal wire under the dash (only the wire at the coil that fed the tach signal)

 

I did try to wire it without the 83zxt resistor, coil-->stock 75 signal wire at the coil-->tach, but it would kill the engine. I'll try it again. I must have had a wire shorting out or something. Bare in mind, I have an aftermarket coil as well, not the stock 280zxt coil.

 

Another note: just ordered my baddogparts.com frame rails and a walbro inline fuel pump rated at 255lph. The rails look to be of great quality, and at a fraction of the price of what other companies are selling them for. Break out the wire wheel and cutting tools - the cure-all for car cancer! I haven't seen too many people on this forum who have used them, I will post before and after pics for everyone to see.

 

I've also got some rust holes on the front quarter panels too that I will eventually cut out (once I can source a MIG welder). I've seen people use sheet metal from old washers. Will this work? I've got an 83 parts car that I suppose I can just scavange off of.

Edited by neilbey
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Got my toyota calipers mounted!

 

There's a problem though. They are dragging badly. I had to force the pads back in there. Am I supposed to be using a different brake pad with these things? The stock toyota ones seem really thick.

 

Is there a different pad to use with the toyota calipers maybe?

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So looks like the calipers are seized. Sucks. Send them back or get a partial refund to have them rebuilt...

 

Got the dash off today. Update on the mystery hose....

 

The the spout that comes out of the vacuum cock was completely open (the spout under the dash that I plugged up). Where that hose would feed to the heater core, was where the mystery hose was coming out of (out of where the water cock is). Come to find out, looks like this was done because A: the vacuum lines were all fucked up under the dash (I mean **** that had tee connections coming out of it that should not have had them and ;lines going to nowhere); and B: the actuator cable for the water cock doesn't seem to be working properly and will get stuck open (which I've temporarily fixed with a bicycle spoke sticking out of the mystery hose hole that I can pull on to close it).

 

So to summarize, this mystery hose was to reroute the heater core hosing and bypass the vacuum cock.

 

I will be the first to say that this was an undertaking... Still going. They hide so much crap under there!

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