When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was replacing the rotor, cap, wires, and plugs when I noticed a loose wire (thin black/green wire in first pic). Turns out it's disconnected and I have no idea where it should go. Based on the wiring diagram, it could be the sub-zero assists sensor (black wire with light green stripe), but I do not believe my car has it (84 GSL-SE, 13B, California car) and the connector looks a bit different (the subzero sensor seem to have a more molex looking pin). It appears to split from the same loom as the oil level sensor. Can anyone confirm what this should be connected to and if it should be disconnected for my model? What else could it be?
So there's no chance they just kept the wiring harness from regular versions of the car and that this wire was loose anyways? I've been looking around the wiring diagram but only found the sub-zero assist to be the only correct looking color/connector.
Yes, that is the Sub-Zero Oil Temp Sensor - which tells the ECU on an 84/85 GSL-SE whether the oil is hot or not.
For those not familiar with the Sub-Zero Start Assist mechanism on the SE model - that funny antifreeze bottle tucked over by the passenger firewall - on startup, the ECU takes into account Intake Air Temp from the Air Flow Meter & RE-EGI Airbox sensors, Coolant Temp from the Sensor at the back of the Water Pump, and Oil Temp from a sensor in the left side of the Oil Pan (*the one you don't have). Based on these conditions showing cold, the ECU will supply 12v to a motor on the Sub Zero Start Assist Fluid Tank, just like a windshield washer pump which flows pure concentrated antifreeze to the Lower Intake Manifold where there's a solenoid block on the top. This solenoid also receives 12v in these circumstances to open the valve allowing the antifreeze to be pumped into the Lower Intake Manifold and make it's way into the Primary Intake paths when the engine is cranked.
By injecting antifreeze into the intake, the thick fluid helps to seal the motor for better compression on super-cold startup conditions. Based on comments here, I don't think any of us actually use the Sub-Zero Start Assist system anymore, and most have removed the Fluid Tank and capped the vacuum port on the solenoid to avoid a vacuum leak. Given that most cars still on the roads today are babied to some degree - they likely don't get driven regularly in sub-zero conditions to need this system operational.
To the OP - since your Oil Pan doesn't have the sensor, you can leave this disconnected with no ill effects.
All first gen 7s came with sub zero start assist as far as I know. I’m pretty sure it’s zero Fahrenheit, though, so its gotta be pretty damned cold before it actually activates...
There was a TSB, Technical Service Bulletin, that called for unplugging the power connector to the zub-zero tank because the system in general never really worked as intended. I like removing the tank.
There was a TSB, Technical Service Bulletin, that called for unplugging the power connector to the zub-zero tank because the system in general never really worked as intended. I like removing the tank.
More or less to this point: has anyone ever actually witnessed this system activate in real life conditions? In all my years of driving rotaries I’ve never seen (or heard, presumably) the thing work. Having said that, I’ve never winter driven my RXs, so there’s that...
has anyone ever actually witnessed this system activate in real life conditions?
...
Yes, on my first 1983 RX-7 GSL mine worked. I was living in Central New York and as a student in the 90’s it was my only car so I drove it year round. When it was really cold out - 0F and below it would activate. On the top driver side of the carburator there is an inlet where it would just pour into the top of the carb as long as you were cranking the engine.
It was a mix of 90% antifreeze (Ethyl Glycol) and 10% water. At that mix rate it is flammable but I don't know if the purpose was to deice the carb, act as a starting fluid, or increase compression (or a combination of). I often found the car to be a filthy SOB to start when it was cold. It often seemed that it was necessary to have a primed line at that temperature, but also to have the very good battery too. Cranking it too long with a weak battery would flood the engine with the stuff and starting without it was nearly impossible too.
Yes, on my first 1983 RX-7 GSL mine worked. I was living in Central New York and as a student in the 90’s it was my only car so I drove it year round. When it was really cold out - 0F and below it would activate. On the top driver side of the carburator there is an inlet where it would just pour into the top of the carb as long as you were cranking the engine.
It was a mix of 90% antifreeze (Ethyl Glycol) and 10% water. At that mix rate it is flammable but I don't know if the purpose was to deice the carb, act as a starting fluid, or increase compression (or a combination of). I often found the car to be a filthy SOB to start when it was cold. It often seemed that it was necessary to have a primed line at that temperature, but also to have the very good battery too. Cranking it too long with a weak battery would flood the engine with the stuff and starting without it was nearly impossible too.
To me this is super cool info: probably the percentage of people here who have this knowledge/experience is pretty low. Yet it is part of the operating history of the rotary in it’s arguable heyday, and as these cars move from daily drivers to classics, this type of real world info is important. At least I think it is...
Today if it’s -5? Just hop in your car and go. Does anyone even use block heaters any more? So the behaviour of the rotary in the 80s and 90s under these conditions is cool (pun intended) history, if nothing more, cuz as pointed out above: it is likely that 99% of us will never drive our cars below 32F.
Agreed - thanks for sharing that, man. I never used the system, never heard of anyone using the system, and questioned the dubious nature of it's design - right up until I read your post above! Good to know Mazda had the right idea, but maybe fitting it to every vehicle sold wasn't such a good idea...
Is this the same wire everyone is talking about (sub-zero sensor?) I am in the process of (slowly) replacing my leaking oil cooler on my 85 GS and can't remember where this goes.
10-29-19, 06:41 PM
