SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 9 minutes ago, Ωhm said: That's when I first used the word "confusing". 11 minutes ago, eaglescout526 said: Then in theory the engine should still run while jumped, but it does not, but runs with relay in socket with fuel poured down the throttle body. I just took two videos (via my lovely GoPro), showing the differences between jumper wire and relay, as well as how different the cranking sounds. Give me a second to upload them. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 If you for TOPIC under the following, its gone RED HOT again. Home - Comanche Club Forums - MJ Tech: Modification and Repairs Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 Here are the two videos, titled respectively. https://drive.google.com/open?id=1WHavMjKUHnE6tAeOgjdMAW3CgLITrh5Z Edit: If you make sure to change the resolution to 1080P, you can see the fuel pressure on both. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 I saw the fuel pressure for both, so that's definitely weird. One thing I did see was that you have the Power steering pressure switch and the WOT switch. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 4 minutes ago, eaglescout526 said: I saw the fuel pressure for both, so that's definitely weird. One thing I did see was that you have the Power steering pressure switch and the WOT switch. Is that bad? Contradictory? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 Just now, SoCalManche said: Is that bad? Contradictory? 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. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 6 minutes ago, eaglescout526 said: 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. Is this what you are referring to? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 Jumps behind coolant reservoir and into harness. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 @eaglescout526 can you determine if ECU part numbers are different? Do they ask question w/WOT or w/PS. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 87/88 show no power steering relay. Is it a 86 thing only? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 @SoCalManche do you have a WOT switch? Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 2 minutes ago, Ωhm said: @SoCalManche do you have a WOT switch? Yes. Apparently I have both a WOT and PS switch. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 7 minutes ago, eaglescout526 said: 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. I can video the attempt. You want me to play with the throttle while cranking with jumper wire in socket? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 Does D2_13 show any voltage or resistance? T25 on the ECU should show the same thing at D2_13 Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 16 minutes ago, eaglescout526 said: Does D2_13 show any voltage or resistance? T25 on the ECU should show the same thing at D2_13 D2_13 shows 0.48V with key OFF; 9.3V for roughly 3 seconds, then drops to ~8.8V, this is with key ON. Both interactions done with ground at Batt Neg. T25 does not show the same voltage. It fluctuates with key ON, fluctuation in mV. With key OFF, it doesn' t fluctuate as much, but still remains in mV. D2_13 and T25 show O.L. with key ON/OFF. Edit: forgot to mention, to ground T25, I used the firewall ground. I don't know if that's making things wonky or not. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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? Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 1 hour ago, eaglescout526 said: 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? My bad, was setting the GoPro up for a good angle to see everything going on. Here is a video of me playing with the throttle while cranking with jumper wire installed. Edit: let me re-upload, something happened and playback isn't working. Edit#2: Here is new link for that video for all those other out here following along. https://drive.google.com/open?id=14F2nY6TJoSbisbO83mhP9WnDW-uyX0Jc Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 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. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 1 minute ago, eaglescout526 said: 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. Oh good, you saw it. I'll get a video of the same angle with the relay in instead. Link to comment Share on other sites More sharing options...
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