84 720 2.4L, 5 spd, 2wd,King cab, What are the 3 Coolant Temperature Sensors on intake ?

[rinkadinc]

Any guesses?   First, a 1 wire yellow with black tracer, Sensor is on front of thermos housing on the intake.  2nd, a 2 wire sensor, yellow w/ green tracer and yellow w/ black tracer, to the rear of thermostat housing or hose to the radiator.  And 3rd, a 2 wire sensor next to the heater hose on the bottom rear of the intake, wires are green w/brown ring and a black w/ brown ring. In my 1984 FSM, page EC-8, it shows the 1 wire goes to the EEC ?  On page EC-10 it shows a 2 wire going to pins 8 & 16 on the 20 pin connector on the EEC ?  I was under the impression that the rear 2 wire sensor goes to 1 of the 2 relays behind the battery which switches from open loop to closed loop ? The other relay behind the batt is the EEC power relay, which is powered from a fuzable link. I replaced all of the fuzeable links years ago when I acquired this basket case. Its got a 30 ATO in a 10 space fuze panel. Does anyone know what amperage it's supposed to be ?   Is the 1 wire for the dash temp gage?  And the 2 wire next to the thermostat goes to the EEC ?  I'm trying make sure I'm tracking this right. Such as all the question marks. My dash is SpeedO, Fuel & Temperature gages and some Idiot lites. Hmm, I guess the temp gage is an idiot gage for those of us that are number challenged. And since it's leaning on it's side, maybe that why the radiator is always low on coolant ?

 

[datzenmike]

Yellow/Black is the temperature sender for the temperature gauge.

 

Yellow/Green and Yellow/Black (both wires) are the temperature sensor to tell the ECC unit under the driver's seat the state of the engine temperature so it can switch the O² sensor from open to closed loop 

 

Sensor under the intake near the heater hose??? no idea. Maybe a picture?

 

The two fusible links to the ECC are Brown and rated at 25 amps each (I think)

[ggzilla]

ECC is the Electronically Controlled Carburetor

 

1. The sensor with YB wire is unrelated to the ECC, it is the temperature sender for the dash gauge

2. Sensor with YG and TB wires is the ECC water temperature sensor

3. Is probably not related to ECC. Can you post a photo to imgur?

[rinkadinc]

Thank you for the corrections. AAhh, Picture ? yeah, no, this really embarrassing. How do I post a picture ? It's okay if you laugh. You know I've had cell phone since the mid 90's. It was a motarolla M 870 and a pager.  The 1st post took like an hr, to get my thoughts out. Cr%p I was going to get up at 4. maybe I'll do it anyway. I'll have to get back to this, in morning. Ta,TA 

[ggzilla]

Take a photo with your phone

then go to https:/imgur.com and tap the Upload icon (up arrow). There is no need to sign up

tap photo gallery and select your photo

 

tap Copy Link

tap Add Image

 

Then come back here, click in the reply box and paste the Link

 

 

[rinkadinc]

 

https://imgur.com/a/cqh3ack    https://imgur.com/a/grWgtQu     

[rinkadinc]

ggzilla, I hope the links work. Ah, thats why the FSM says ECC Control Box. Thank you, datzenmike. That was under the drivers seat and is now bolted to the rear of the drivers door opening on the upright. I changed the drivers seat. Not enough room under it now.

 

The green wire that comes from the 3rd sensor, ends up behind the batt and to the coil of the 2nd or rear most relay, when the wire comes out its blue with 2 brown rings. 1 end goes to the choke on the carb, another end goes to the white/blue tracer at the exhaust coil and module. The Black wire from sensor has .2 ohms resistance to ground. Have ta find where it goes, if not a ground.                        In my FSM pg EL-93, behind the batt, it shows 60M-fuel shut off except Calif; 49M main relay for E.C.C. (control box?) Calif models; 50M dropping resister; 51M  & 52M for the the A.S.C.D. relays with A/T, mine is 5-spd. No auto pilot.  My 5/84 VIN is JN6N06S4 EW020532 from door jam/piller.  okay, the fender is Hotter Than a 2 Doller Oil Stove, I'll have to wait for the shade.

https://imgur.com/a/9YgsBIz , is the other relay.   When cools a little I'll look for where the other wires from that relay go.  And before I forget, I paged through the

720 Part # Threads  and forgot to click on the loves for post ers. The Hearts !                 

[datzenmike]

 

[datzenmike]

 

 

[rinkadinc]

Thanks datzenmike, In the top 2 pics , the hose in the mirror is from the heater. The 1in hose is behind the convoluted tube, I seem to remember it's the thermostat bypass hose. Then the plug on the 2 wire 3rd coolant sensor.                                                                                                                                                           The 3rd pic is the right fender which shows the ECC main power relay and the one thats hanging is the one that the green wire from sensor comes to the coil and comes out as the blue wire shown, which goes to the choke on carb and also runs across the radiator to a splice which has the white/blue wire on the exhaust coil and distributor module.

The black wire from that coolant sensor has a .2 ohm resistance to ground.  Maybe it goes to the ECC Control Box as in, is there a sensor return wire to the control box ? I'll dig into that extra relay and wires to find out where they go.

Theres a wire bundle that goes into the passenger compartment. So, maybe I'll get pull the seat and stand on my head. At least I wont have to worry about the Ejection seat going off and reuning my day.

[rinkadinc]

I've over committed on my available time. I dont have time right now to dig into the wire bundles.

 

All of these continuity and voltage checks are with engine off, ignition key on, ECC control box hooked up.

Voltage checks with batt hooked up, Continuity checks either the with component unhooked or batt disconnected. 

 

I'm using my Fluke 116 true rms, a Autel power scan (power probe ). Some back probe dealies, spikes, pins, whatever, from an Hantek 2D82auto handheld O-scope, kit. From amazon.

 

1. The blue wire with red or faded to brown rings, it doesn't go straight to the exhaust coil, I misread where it was headed. It goes toward firewall.

     A. The blue wire eventually connects somewhere to the white/blue wire on exhaust coil. 

     B. With relay disconnected, the wire between relay and exhaust coil has 2 ohms resistance.

     C.    It also connects to the choke heater wire. Also 1.9 ohms.

     D.  I suspect it is a common power wire that only has batt voltage with engine running. **Powered from Alternator. ** And not when engine is off and ignition switch in run.

 

2. I cant find this 3rd coolant sensor and relay on any of the electrical schematics, in the 1984 FSM.      Maybe I dont know which system this is for ?

    This is why I included the VIN.                               

 

I cant check the engine run,( power from alternature )  cause it wouldn't pass smog 2 months past. The mid range would switch between super rich to super lean. And now mixture solenoid won't even click. Carb was in the rebuild stage with the Hygrade kit from Napa, (100.00, more better parts like the intake manifold gasket) when I figured out about mixture solenoid.  (Walker didn't know anything about the wierd shaped manifold gasket) I found it seperate,I think AutoZone.

My carburetor setup has that metal diverter plate, then the mixture heater, then the carb. For a total of 3 intake gaskets. The Hygrade kit had 5 intake gasket's.

Does anyone know of any waxed (reusable) gaskets ? Maybe I'll try the chap stick trick.

 

The carb was from National Carbs, except it was a DAT815, instead of a DAT815C for California emissions.  I dont know what the jet sizes difference between a DAT815 and DAT815C. This my mix solenoid, the numbers are for top jet and bottom jet---

 

https://imgur.com/a/c7q4yH9   

 

 

 

      

[ggzilla]

Maybe the wires have gone bad, they look frayed in the photo

 

On 7/11/2025 at 8:49 AM, rinkadinc said:

IThe carb was from National Carbs, except it was a DAT815, instead of a DAT815C for California emissions.  I dont know what the jet sizes difference between a DAT815 and DAT815C. This my mix solenoid, the numbers are for top jet and bottom jet---

 

      

 

[ggzilla]

Maybe the wires have gone bad, they look frayed in the photo

 

On 7/11/2025 at 8:49 AM, rinkadinc said:

IThe carb was from National Carbs, except it was a DAT815, instead of a DAT815C for California emissions.  I dont know what the jet sizes difference between a DAT815 and DAT815C. This my mix solenoid, the numbers are for top jet and bottom jet---

 

      

 

[datzenmike]

 

O ring at the bottom looks like it's coming apart.

[datzenmike]

Z24 California carburetor are #94 and #170 for primary and secondary jets.

 

Non-California are #107/#170

[rinkadinc]

I didn't think about what the wires looked like when I took the pic. The wires weren't that bad when I 1st pulled it apart.  I carried it to town and back,( better fone reception in town, it's about 5 miles )  calling around looking for another solenoid.  Yes, the bottom o-ring might be why it didn't pass the smog test. Gas would bypass the solenoid.

I moved the rubber seal up enough to dab a little solder on them and will move the seal down again. I need to hook it up to the vehicle wiring and check if it works.

 I have 2 carbs, 1 is assembled with a Hygrade kit. I don't remember exactly what the jet sizes in it. The gas inlet strainer is broken and leaks like a sieve. The carb is sitting on the bench, till I can find another inlet strainer and crush washer. If I can get it to stop leaking, I'll try to smog it.

On another post about rebuilding stock Hitachi carb, they mentioned Pacific Carburetors, I will try them Monday.

datzenmike, the jets inside the bowl, the left is a #94, the right is #107. 

The solenoids on e-bay and others only shows 2 holes on top, which makes the solenoid shorter.

I was wondering if the jets on my solenoid were different than the ones on the Calif emission carburetors?  

 

 

 

[Sephakrid]

According to my 1984 FSM, the fuel jet is #85 and the air bleed is #220 for the mixture control solenoid on the California carburetor. Later model feedback carburetors used #100 for the fuel jet, but kept #220 for the air bleed. I'm not sure if the solenoids are physically different in size, though. I recently rebuilt a DFP384-5 carburetor (ink stamp still visible) and my solenoid jet sizes are the same as yours.

 

Fyi, I'm currently running the rebuilt DFP384-5 carburetor in my 1984 California truck and it still operates under closed-loop control during normal driving. I haven't tried to smog the truck in this configuration, but I suspect there wouldn't be any issues. 

 

 

[Sephakrid]

I forgot I made a short video that shows how you assemble the gaskets and spacers on the intake manifold! I had to cut the lower gasket myself because no one had them in stock. Hope this helps!

 

https://youtu.be/jxAsPMiwNSA?si=_wfyUHIrOA-IiCej

 

 

 

[rinkadinc]

Sephakrid,  A couple of months ago autozone had that intake gasket. If'n I remember , it took 15 or 30 min for the tech to find it. Dont remember the p/n. Thats why I was using the Hygrade kit from napa, which includes that gasket. I've made that gasket a couple of times, gentle ball peen hammer work. Would chap stick keep them from sticking? Or would the intake heat melt the wax?

The solenoid in the pics, has no continuity, totaly open.  The solenoid on my other carb has 41 ohms resistance and It doesn't rattle when I patch it in. I dont have a O-scope to check the computer output to the carb. In the round connector to the carb, the red/yellow wire, has batt voltage and the yellow/green wire, has 10 volts. Should the 10 volts show as a pwm wave form on an o-scope ?  

[datzenmike]

On 7/12/2025 at 2:04 PM, rinkadinc said:

datzenmike, the jets inside the bowl, the left is a #94, the right is #107. 

 

 

107 is wrong. Secondary is much larger than the primary so will have to supply more fuel. Almost all secondaries are about 50% larger than the primary. All jets are same thread and easily mixed up so a previous owner may have messed this up. The '84 FSM shows 94/170 for 2wd. In fact all gas carburetors are 170 secondary except the Cab/Chassis option which is 165.

 

Vehicle will run well enough on primary but secondary, when engaged, will be severely lean. Power for passing would be very poor. 

 

Pull a secondary from a spare carburetor or Amazon sells any amount of motorcycle jets for tuning. Example...

 

https://www.amazon.ca/BYH-Carburetor-Copper-Injector-Compatible/dp/B0DK8BB294/ref=sr_1_10?

 

 

 

Not a perfect look alike match but should be the same thread.

 

Even easier is if you have a spare jet get a 1.7mm drill bit and drill it larger.

 

https://www.amazon.ca/PATIKIL-Straight-High-Speed-Titanium-Stainless/dp/B0F59FT9R4/ref=sr_1_1_sspa?

 

 

I've done this on my R-1 carburetors chasing the perfect mixture by buying some under size jets (needed four) and drilling them larger and larger.

[Sephakrid]

My mixture control solenoid is about 41 ohms as well. I forget the color, but if I probe the wire that connects the solenoid to the ECU I'll get a pulse wave with an average of 10.6V (key in ON position, engine OFF). I specifically probed pin F on the ECU harness connector.

Edited July 20 by Sephakrid
Changed "square ware" to "pulse wave"

[rinkadinc]

 

The "Factory Repair Manual" place in Seattle, Wa    Shows that my service manual, is FSM.  When I Binged (Microsoft bing)Nissan FSM, up popped a link to RATSUN Forums which showed what I have is a Dealer Service Manual. Which explains why my Haynes manual shows electrical circuits that my dealer service manual doesn't show. I'm now looking for a FSM

datzenmike, thank you for the information about the jets aand the 1.7mm drill. I like the nut driver head versus the straight bladed sheer prone type.

 

Nice flik, Sephakrid. 

   

 And I was wrong about the the red/yel wire, it's actually has 10.8 vdc.  With or without the control box hooked up.  Yes, I disconnected the battery before swapping boxs. I have 2 control boxs, an 84 and a 85. 

The yel/grn wire - pin F- has 10.1 vdc.

I have an Autel power scan checker. When I flip it over to ACv, it shows blips on both those wires. Just a small blip. 

[ggzilla]

Dealer Service Manual? All the dealer mechanics I knew used the factory service manual

 

The factory service manual has multiple wiring diagrams and wiring schematics, in the back for the entire vehicle, and in various sections has diagrams & schematics for subsystems, like headlight wiring, transmission wiring, carburetor wiring, etc

 

The Nissan factory service manual looks like this:

 

[datzenmike]

Haynes is a condensed pamphlet compared to the actual FSM. It jams all 7.5 years of 720 production into one 5/8" booklet. The FSM is 1.25" thick and strictly for the one year and is exhaustively complete. Indeed the '83 and on is a mere supplement in the back of the Haynes manual. Also, being a copy of the FSM, there is the chance of copying errors.   

[rinkadinc]

Thank you, ggzilla , my manual looks like yours except for the revision. 

I mentioned the Haynes, cause if I remember, it shows that lite blue wire that hooks to the wht/L wire on the the neg on the exhaust coil and to the red wire to the distributor. Which the FSM doesn't,show. I'll have to look around for my older (199-ish) Haynes.

 

My mixture heater has .98 k ohms resistance, my fluke didn't show 980 ohms. I need to check my switcholigy, or R&R the control stick actuator.    Pilots would get really upset when I'd sign off a MAF, that way. 

https://imgur.com/a/ppK4Vr8       my intake has the metal plate, then heater, then carb, gaskets between ea. The numbers on the edge of that heater plate are 4424T

Any idea where the yellow power wire gets it juice? The EEC control box? Or that extra relay? If when the engine warms, that extra coolant sensor could lift the ground to that relay to shut off some stuff. One of which could be that heater. Another reason to tear apart the wiring around that relay.