I replaced my Cold Start Injector harness plug. Truck has been a "two turn for start" during the cold weather this last winter. The plug was nearly 40 years old and showed definite signs of imminent failure. The below problem was present both before the replacement and after.

So after replacing the plug, when I test the voltage to the cold Start Injector on my '86 I only get .039 volts when the key is in ON. I'm 99.9% certain that it SHOULD be reading 12v when in the ON position. Is this correct? I do get a flat ZERO volts when the key is in the OFF.

Also, I get beeps for continuity between the two harness connections when the key is set to OFF with about 3.2 ohms. When in the key is in the ON position I get no continuity beeps and resistance of 132+ ohms.

What should that KEY ON voltage be? If it's supposed to be 12, where should I start diagnosis?


***Update***
I pulled the starter wire and cranked. Black wire with my fluke on vehicle ground measures 10.7v while cranking. The Time Switch at the time was reading about 32 ohms (correct Cold Start condition) and when warm it reads 56-ish ohms (correct war start condition).
***End Update***

Maybe I'm overthinking it. Will the Cold Start trigger at 10.7 volts? I know it does flow with direct battery voltage, I tested this function about 3 weeks ago.

Maybe the issue is something else? It definitely starts easier when I give it gas in start. I've is rough until warm (shaking hood), but it evens out within minutes of idle and giving it gas of course fixes it immediately

 

Good info here on CSI operation: https://www.yotatech.com/forums/f116...s-22re-302877/

CSI plug should get voltage on the STA pin of the connector only when you are cranking the starter, so key in the start position. Key ON is no voltage present on STA pin...if the CSI were to get 12V with key ON, then your CSI would continue dumping fuel into your intake for as long as the engine temperature was below 50 degrees and I don't think you want that. The other pin of the CSI plug is the STJ signal, which is grounded either thru the cold start timer switch itself or certain later 22res (I know my 1988 FSM shows this to be true) the STJ signal can also be grounded by the ECU.

 

Some people test the CSI by removing the 2 10mm bolts holding entire CSI into the intake manifold, stick it into a glass jar. Then crank the engine with distributor wire removed so it doesn't fire up. Cranking for so many seconds should give you a certain amount of fuel. This might even be in the FSM, I haven't looked for that particular test in a while. I'm pretty sure others on here have posted their results of this test.

 

In the FSM they have the test Cory mentioned, but they wire the injector straight to a battery using test leads.
I'd test both ways. If you get significantly less fuel when the injector is powered through the system, as opposed to straight wiring to a battery, I'd seriously scrutinize the thermal time switch.
bitd we replaced very few cold start injectors on any Toyota vehicle. We did thermal time switches all the time.

 

I'm stumped with a cold start time switch issue, 1993 22re. MY CSI ohm tests good and fires strong if I connect ST J to ground. Overall I've got good voltages / continuity on all the relevant harness wires.

ST A has 12v at all connectors, so heating circuit #2 below is good. Time switch connector ST J gets 12v when cranking, and If I ground ST J the CSI fires, so that circuit is good.

So that points to the time switch, right? So I've tried 3 different time switches, they all test the same, but none entirely correct according to the service manual.

Time switch ST A to it's threads (ground) is 80 ohms, that's good. BUT measuring my time switches I get 80 ohms between ST A and ST J, no matter if ice bath or room temp. 80 is ok at room temp, but this link says if cold should be below 50 ohm.

https://lcengineering.com/fuel-injec...r-time-switch/

More importantly, time switch ST J to ground threads is always 160 ohms, at any temp. From this diagram, when in the "Cold" "ON position", the switch SHOULD contact ST J to ground, zero ohms, to complete the CSI circuit.




Well, none of the 3 switches ever take ST J to ground, even when ice cold. I think they are stuck in "warm" position, since I always get 160 ohms, the 2 heating coils likely are connected in series, 80 + 80 = 160 ohms. Is it possible they get fried to warm position when I plug them in?

These 3 switches all ohm identically, fit, and have the correct connector. Two of them I didn't even put into the block, bench tested first (failed), then I just plugged them in and grounded the threads to test onboard (failed).

Why do none of these switch at all with temperature? Could I have 3 unlucky switches that are wrong part or defect? I used 2 different vendors, got one from A-Z, the others online.

Meantime I realize I could bypass the time switch by running a ground wire to ST J, maybe through a toggle switch to be fancy, but I'm a little stubborn about giving up on such a simple circuit. Thanks for any help.

 

Kudos for including the diagram; I don't think any of us have memorized the entire FSM. FWIW, here's the FSM page: http://web.archive.org/web/201501160...ne/39colds.pdf. Your resistance values match the manual.

But I can't add much to your tests; they look to have been done correctly. Below 10°C, STJ should connect to ground. If it doesn't, the CSI won't activate. I would offer that it probably takes at least one minute for the Time Switch to cool down, even in an ice bath.

I'm always suspicious of claims of parts being defective "out of the box," but I think that's what happened to you. I, too, would be wary of a "toggle switch" solution. If you leave the switch closed just a little too long, you could flood the engine.

 

Im a little leery condemning an electrical part simply based on ohm data from the FSM.

 

I wouldn't care as much about the heater resistances (~80 ohms), but STJ has to go pretty close to ground in order to switch on the CSI. STJ-ground is not in the FSM, but DinoR's test seems to show that the connection is not made.

 

Agreed😊

 

Though it's not a fsm test, can I assume many here have done ice bath and seen pin ST J go to ground?

I'm almost thinking to take my voltmeter and a cooler of ice to the junkyard, and pour it over my head if it's my mistake and not true I bought 3 bad time switches... Anyway I'll keep trying and post follow up, we all like to see a mystery solved.

 

I fixed it, sort of.

I decided to backprobe the ECU ST J connection, FSM says 6-12 volts when coolant @ 176f. So I put a 100 ohm resistor into the ECT connector to trick the ECU into thinking it's hot, then... Turns out the ST J wire was disconnected at the ECU! My smart friend was right again, there was something stupid.

Months ago when having a smog check nightmare I removed the ECU. I now remember I nicked the ST J the wire somehow, so I had spliced in a short length, when I put the ECU back in, one of my splices came apart. D'oh!

BUT:

The page below says ECU point ST J is an alternate ground path for slightly warm coolant starting. WHY would the CSI not fire without the ECU connection??? Considering that the CSI did fire when I grounded ST J at the time switch connector, I now realize something ---

The ECU is probably the ONLY CSI ground path I have, and the time switch isn't doing anything. Probably a lot of us are operating like this, the chart shows you'll still get up to 3 seconds of CSI every cool/cold start, so you never notice the time switch is bad... But this suggests I bought 3 defect time switches... Wow! I really want to know, has anybody done ice bath test for grounding of ST J?





To make a long story even more boring... For those interested, that smog problem was tough, I went to a half dozen mechanics before one figured it out. I had ohmmeter continuity and no short circuit from the O2 to the ECU, but turned out there was some invisible damage to the shielded O2 wire near the trans., such that there was O2 voltage at the diagnostic port, but it was corrupt noise, so no closed loop mode.

I have an old oscilloscope and did look at the O2 signal, it was noisy but I didn't trust myself and assumed it was my probe or environmental. The guy that found it used a kind of insulation tester called a megger, it puts like 200 volts (but very low current) on a wire and detects leakage. Strange, since the O2 makes less than 1 volt, you wouldn't think it would arc, or perhaps the shielding was compromised enough to act like an antenna and let noise in.

Thanks forum experts, hope someone gets some help or entertainment from my travails.



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Interesting finding, I recently became aware of that "alternate" STJ path to ground.

Back in 2011, I measured my STJ to GND and found it was 160Ohms, but FSM does not spec the STJ to GND so I just assumed it was normal. https://www.yotatech.com/forums/f199...l#post51834708

 

Did you test ST J to ground in ice water? Your test at 160 ohms suggests warm switch position, 2 heat coils in series. I'm thinking I might test if the CSI will fire if I use some resistors to connect ST J to ground through about 160 ohms, I don't think it will. Really it seems like when time switch is closed ST J to ground should be about zero ohm to fire CSI. Anybody done the ice test?

 

Has anybody tested for ST J connecting to ground when cold? Anybody have a "good" time switch on the shelf to test? Otherwise I have 3 bad time switches, hard to believe.