eaglescout526

CTS switch is good. That's really really really close to zero and the book asks for it to be close to zero. Throttle open is greater than 2 volts. Lets do the WOT test again. With ign on D2_6 power probe and D2_7 ground probe No voltage at WOT position and greater than 2V not at WOT position. Basically the opposite of the CTS.

No D2_7 needs to have the ground probe and then D2_13 is the input to the ECU. We need to see if theres 0 volts with the throttle closed and then 2 volts with throttle open and off the plunger.

Not me, Pirate, MJCARENA or AMC86kid. It honestly doesn't surprise me that theres Arizonans out here who have MJ's but never popped in to say hello.

So I wonder what D2_7 and 13 will show for voltage once you got it all back together.

Ok so it is probably safe to say that circuit is fine.

Ok I went out and got some baselines from my ISA with key on, ISA unplugged. A is ground, ground probe went there B is closed throttle input, I got 5V there C is retract, I got .141V D is extend, I got .141V

CTS or the ISA? For the CTS it is the opposite of the WOT for voltage. D2_13 is voltage and D2_7 is ground Voltage should be close to zero at closed throttle and greater than 2 volts when off closed throttle. ISA doesn't have any voltage specs in the book. Suspect somewhere around 5-12VDC

Hopefully the ISA comes back to life.

Yeah when I did mine I just put some lithium grease in there around the gears and called it good.

Lol gets the best of us. Doesn't look terrible but grease is pretty dried.

I hauled a 2.5L and an AX4 aside from the time I hauled home NOS stuffs.

Theres a switch and a motor in the ISA, when the throttle plate hits the plunger, it clicks the CST switch inside telling the ECU that the engine is in idle position. The motor inside turns gears to either extend or retract the plunger to give the desired idle speed for open and closed loops of operation. Like I was saying, the ISA can be take apart to be cleaned and lubed. But the manual will say to just replace it if it is bad.

Hmm, still weird to see no fuel pressure, but the engine sounds fine an healthy, I wonder where the plum of smoke comes from. But yeah that ISA isn't doing anything. Its not extending for the next start up or nothin. It can be taken apart, cleaned and lubed up just so that way you don't have to buy a new one. A on the ISA connector is ground, and D is the extend for the motor. If that can be tested to make sure the motor works, I would suspect the ISA gears are jammed.

Once it starts and dies, don't attempt to restart it, I want to observe the ISA, I suspect it to be faulty and causing some issues.

Hmmm. Didn't confirm that theory. I don't think the ISA is acting right, it doesn't look to be in an extended position like it would for start up. but I also never heard it go to extended position with the relay in place after that one start up.

Ok so the note in the book says that the CTS test is to be done with the plunger fully extended as it would be after normal engine shut down. If it is necessary to extend the ISA plunger to test the switch, an ISA motor failure can be suspected. So by watching your videos, is the ISA motor tip in contact with the throttle plate? If not then the motor is jammed, but the motor can be taken apart, cleaned and lubed up. We can get back to testing the CTS in a second. Was there any change with the jumped relay and opening the throttle?

Does D2_13 show any voltage or resistance? T25 on the ECU should show the same thing at D2_13

Yeah just a little bit. See we missed something because my dumbass thought that your ISA is functioning. Welllll one of the possible causes is the ISA plunger is not extended thus causing a no start condition. I am wondering if the closed throttle switch in the ISA is not triggering something in the ECU that energizes the fuel pump relay. Yes the CPS can still tell the ECU to send spark.

This makes me want to do mine now. Yall gotta stop giving me ideas. Did you wire wheel them?

I just realized something after watching those videos for the 5th time. After shut down or failure to start while cranking, the ISA should return to open throttle position for the next start. Not once did I see the ISA do that. What if you jumped the relay but used the accelerator pedal to open the throttle just enough to fire. I am almost wondering if during crank the injector is pulsing the fuel that is being pumped from the jumped relay and its not enough fuel to get down in there because the throttle plate is closed. But when putting enough fuel down the throttle body yields a successful start but rich condition because of the lack of O2 from the closed throttle plate.

So 1986 used the ECU with AMC number 8953002099 87-90 uses 8953004763 or Mopar 53004763. Both these numbers are for manual trans. 86 auto used AMC 8953002100 87-90 auto used 8953004764 or Mopar 53004764 Nothing is mentioned on both switches just model year.

Ok I got my parts books. I think 86 only had the power steering relay as I can find that in my 86/87 parts catalog. Let me get the ECU numbers.

So that switch probably traces back to the power steering relay then. So I wonder what the purpose of the power steering relay is, especially with the amount of wires that go into it.

Yup that's the switch. In the 88 electronic manual it shows that switch in place of the WOT switch but both my hard copies of the 86 and 87 electronics manual shows only the WOT switch instead of the power steering pressure switch. But I never found anything on the PS circuit.

Well I want to say the 84-86 but mostly 86 had the WOT switch. 87-90 that switch was replaced with the power steering pressure switch. It gives the ECU a better reading on if the engine is at WOT or not via the pressure of the power steering fluid. I will go check my schematics to see if that switch is in the circuit for 86. Can you trace the wire and see where it goes? I kinda am thinking it could be contradictory.