What is this sensor on my 3FE? (1 Viewer)

[SteveMondragon]

The only things I can find a BLU/RED wire coming from on the FSM is either the Cold Start Injector (but there's only 1 wire going into that in my schematics) or from the heater blower motor. This sensor looks like it would be a coolant temp sensor, but those wires are supposed to be RED/WHT & BRN/BLK. This is on a 3FE engine on my 91.

You can clearly see the wires here to be BLU/RED and BLK/RED. Exactly what sensor is this and would it cause my car to not want to start periodically if the sensor is broken? I think the previous owner just super-glued the sensor, but I was going to order a new one from the dealership now since my truck is having starting problems more & more now (mostly when it's warm.... fires up when cold but idles a little rough).

 

[CJF]

...and would it cause my car to not want to start periodically if the sensor is broken?

Unplug it and find out. :shrug:

 

[SteveMondragon]

Unplug it and find out. :shrug:

No difference than what I'm experiencing now (probably because it's broken), and no CEL.

 

[CJF]

From the bowels of the 3FE Yahoo Group (Great place, but slow these days; check it out if you haven't yet.):



> Drivers side (USA) top of the water outlet housing, black connector, is the cold start injector time switch.

> Drivers side (USA) bottom of the water outlet housing, green connector, is the water temp. sensor.

> Passengers side (USA) top of the water outlet housing, is the water temp. switch.

 

[SteveMondragon]

From the bowels of the 3FE Yahoo Group (Great place, but slow these days; check it out if you haven't yet.):



> Drivers side (USA) top of the water outlet housing, black connector, is the cold start injector time switch.

> Drivers side (USA) bottom of the water outlet housing, green connector, is the water temp. sensor.

> Passengers side (USA) top of the water outlet housing, is the water temp. switch.

Hmm... looks like it could be the culprit to my starting problems (plus you can see the green water temp sensor underneath it in the pics above). I guess I'll be picking up a new one from the dealership tomorrow morning.

 

[CJF]

BTW, you've seen the simple check of the cold start injector in the FSM?: Listen for a "click" from the injector when the key is turned to ON. (Or something like that, IIRC...)

 

[SteveMondragon]

Listened for it, no clicking noises.


Going back to my other question: can a bad Cold Start Injector keep the car from starting? Like the engine is cranking & cranking but not catching and turning over (as if there's no fuel)?

 

[Moby]

Listened for it, no clicking noises.


Going back to my other question: can a bad Cold Start Injector keep the car from starting? Like the engine is cranking & cranking but not catching and turning over (as if there's no fuel)?

If the cold start injector is not working you will get significantly increased cranking time. I found this out after one of the wiring connectors backed out of my cold start injector connector. It would take forever to cold start but once warmed up it would start basically normally.

The cold start injector is there to dump in extra fuel on cold start up because a normal fuel ratio will not burn "normally" in a cold engine; you need extra fuel just to get the normal amount of fuel to burn. This is why emissions are so bad during start up and initial running in a cold engine - the mixture is very rich.

 

[jcj_78FJ40]

I had the same issue. I think I knocked it loose while changing a belt or thermostat.

Here's a description for the sensor from Alldata if it helps. Maybe you can jump it to ground, turn it over a few times and see what happens??

PURPOSE
The cold start injector time switch controls operation of the cold start injector.

OPERATION
When the engine is cold, (below 60°F), and the starter is activated, the time switch will ground allowing the cold start injector to spray fuel into the intake plenum.

Ground is interrupted in two ways. The first is by engine coolant temperature heating the switch to above its calibrated thermal point. This prevents the cold start injector from injecting fuel on warm engine restarts. The second interuption is by the internal time switch heater. When the starter is cranking, this heater will heat and break the circuit in approximately ten seconds or less to prevent engine flooding, if the engine does not start immediately.

 

[SteveMondragon]

Ground is interrupted in two ways. The first is by engine coolant temperature heating the switch to above its calibrated thermal point. This prevents the cold start injector from injecting fuel on warm engine restarts. The second interuption is by the internal time switch heater. When the starter is cranking, this heater will heat and break the circuit in approximately ten seconds or less to prevent engine flooding, if the engine does not start immediately.

This is what it sounds like my problem is. When the engine is already warm, it has trouble starting as if the engine is flooded (I can smell fuel). I'm wondering if the broken sensor causes the circuit to stick open so it fires up when it's cold, but possibly floods the engine when it's warm.

Either way, it's a broken sensor that I need to get replaced so I'll be trying to get one for the dealership tomorrow morning. I'm wondering if that will fix my rough idle problem when I first start up the engine.

 

[jcj_78FJ40]

Sorry, I misread your post. I was thinking you were having the problem during cold start. To your point, maybe the sensor is shorting to ground but it seems like you would have seen a difference when you unplugged it.
Hope the new sensor is the fix..Good luck!

 

[jcj_78FJ40]

This is what it sounds like my problem is. When the engine is already warm, it has trouble starting as if the engine is flooded (I can smell fuel). I'm wondering if the broken sensor causes the circuit to stick open so it fires up when it's cold, but possibly floods the engine when it's warm.

Did you try unplugging the cold start injector itself after warm-up?

 

[jmarsh1977]

Hmm... looks like it could be the culprit to my starting problems (plus you can see the green water temp sensor underneath it in the pics above). I guess I'll be picking up a new one from the dealership tomorrow morning.

Hey Steve, please update this post w/ pics once you get the part in from the dealer. I'm particularly interested in how the sensor on your 3fE looks unplugged and what the wiring harness connector looks like.

My sensor on my '88 FJ62 looks a little different - a cylindrical plastic connector. My sensor's fine but my wiring snapped off at the back end of the connector. I sautered it back but it snapped again after a few months and there's no more wire to graft to. I'm hoping the dealer can supply the length of wire and connector that mates to the sensor, on my '88 it looks to be a part of the original wiring harness and I would have to get one from a donor harness or rig something up again.

 

[Two 3FEs]

did that new CSI temp sensor solve the fuel flooding on start when hot issue? I have same problem on 92 3FE

 

[Josey1972]

I’m interested how the water temerature switch on the passenger side top of the housing plays into this. My wire is going bad there.

 

[Phildoh]

I’m interested how the water temerature switch on the passenger side top of the housing plays into this. My wire is going bad there.

Yeah it is!

 

[gnarlytoes]

Cold start injector time switch. Get the Beck/Arnley part #1580484 from rockauto.com. I replaced mine a few weeks ago. It turned out to be a genuine OEM Toyota part in a Beck/Arnley box.

 

[Rebelle110]

I’m interested how the water temerature switch on the passenger side top of the housing plays into this. My wire is going bad there.

Mine just broke off this weekend while I was replacing the thermostat. I cannot for the life of me find anywhere to buy a new connector, nor can I find anywhere (including the FSM) that explains what this switch does. Anybody that can shed any light on this?

 

[leonard_nemoy]

Mine just broke off this weekend while I was replacing the thermostat. I cannot for the life of me find anywhere to buy a new connector, nor can I find anywhere (including the FSM) that explains what this switch does. Anybody that can shed any light on this?

I could be completely wrong but I think the water temp switch does something with the efi.

 

[Rebelle110]

I actually plodded along in my research and found another thread here that said it tells the ECU to turn on the fuel pressure regulator. And I may have found a replacement from Yota Shop, woot!