oldgoat Posted January 19, 2016 Author Share Posted January 19, 2016 So it just keeps gettin better. Yesterday morning tried to start - dead. Came home last evening to pull the ICU to have it tested - Started right up. This morning - Started right up. Took the ICU to have it tested. Tests good. Brought it home hooked it up - dead. How can I test the ECU - I wonder if it is shorted internal on the ignition output side. The injectors don't fire which tells me that either I don't have a tach signal from the ICU or the CPS signal doesn't process in the ECU. Link to comment Share on other sites More sharing options...
oldgoat Posted January 20, 2016 Author Share Posted January 20, 2016 I forgot to mention that I have never seen a "Check Engine" light come on, ever. Also discovered that the FP relay has been bypassed in the harness for some reason. It is direct wired to an Ignition on terminal at the fuse panel. The 2 orange wires to the pump are ganged together with the 12v hot signal. right next to the resistor. Do you think this could have created a back feed to the ECU causing a problem? I have yet to determine why the FP relay was by passed. I wonder if the ground signal from the ECU to the relay is dead? More wiring to validate. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 20, 2016 Share Posted January 20, 2016 No CEL on a Renix. Only way to test an eCU is to try a known good one. Link to comment Share on other sites More sharing options...
oldgoat Posted January 20, 2016 Author Share Posted January 20, 2016 We have a diagnostic code reader that will interface with the Renix. Are the readings reliable? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 20, 2016 Share Posted January 20, 2016 We have a diagnostic code reader that will interface with the Renix. Are the readings reliable? An MT2500? I have the factory tester. All I ever use is the State Display feature for the most part. The System Tests leave a lot to be desired. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 20, 2016 Share Posted January 20, 2016 Have you refreshed all the connectors you can see in the engine bay? Link to comment Share on other sites More sharing options...
oldgoat Posted January 21, 2016 Author Share Posted January 21, 2016 Pretty much all applicable. I did remove the ECU and took it apart. I see one chip that has what might be a white burn bubble on it. I am going to see if I can test it tomorrow. I also found an abraded wire in the bundle from the ECU going out the bulkhead. Obviously lots more testing before I go any further. Link to comment Share on other sites More sharing options...
oldgoat Posted January 21, 2016 Author Share Posted January 21, 2016 Cruiser, I don't find the C101 that everyone refers to. Should I ? Link to comment Share on other sites More sharing options...
oldgoat Posted January 24, 2016 Author Share Posted January 24, 2016 Yesterday I removed the entire Renix wiring harness and laid it out on the bench. I stripped off all of the convo tubing and tape. I discovered that someone had previously done the same thing since all of the gang connections were wrapped in duct tape. I did validate each wire for continuity and cleaned all of the connectors and re taped and wrapped the whole thing then reinstalled. Still no fire. I went back and validated all of the fusible links at the starter relay. There is 12V getting to the ECU with the switch on and in the crank position. Tried to start again. Still cranks, no fire. It appears that it is either the ICU or the ECM. Interesting , the ECM has been replaced with a Cardone reman unit. I am checking with the guys I work with for a known good ICU. It is confusing that after the problem manifest I have been able to get it to start sometimes and not others. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 24, 2016 Share Posted January 24, 2016 That duct tape is factory. See Tip 5 and 6 at www.cruiser54.com. Only have a C101 connector in 87 and 88. Link to comment Share on other sites More sharing options...
oldgoat Posted January 27, 2016 Author Share Posted January 27, 2016 I solved the riddle, drum roll please............... ICU, swapped from running Cherokee, lit right off first hit. I also discovered that the scanner I was promised would work, won't. Now on to the next. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 27, 2016 Share Posted January 27, 2016 I solved the riddle, drum roll please............... ICU, swapped from running Cherokee, lit right off first hit. I also discovered that the scanner I was promised would work, won't. Now on to the next. Refresh my memory. Had you done Tip 3, coil and ICU connector refreshing already? Link to comment Share on other sites More sharing options...
oldgoat Posted January 28, 2016 Author Share Posted January 28, 2016 Oh yeah, that was one of the first steps. At that point I could get it to start once in a while after prolonged cranking. That made me think CPS signal was weak. Installed new CPS, discovered existing was fairly new. Same story. With a used ICU/coil it lights up on the first crank. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 28, 2016 Share Posted January 28, 2016 Glad to hear it's fixed. I'd love to find a reliable test procedure for the ICU/Coil. Link to comment Share on other sites More sharing options...
oldgoat Posted January 29, 2016 Author Share Posted January 29, 2016 I can promise that the tester at O'Reillys is not accurate. Over the years I have grown to not trust "testers". Real life is the best test. Link to comment Share on other sites More sharing options...
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