Abyx Posted March 17, 2012 Share Posted March 17, 2012 Hey guys, I did a bunch of searching, I can't seem to find a thread that isn't about the CPS. 87 4.0 Renix/Manual trans I have a no start issue, the fuel pump does not run, and there is no spark. However, it ran fine up until I shut it off and went to restart it. Things I tried so far up until a stranger towed me home - Confirmed Fuel Pump activates by jumping power from battery to pump Swapped Relays Ran Jumper wire from Fusible Link G to Starter Relay Disconnected/Reconnected CPS Confirmed all electrical connections are connected. Now get this, it was running fine up until the other night when it started sputtering and almost dying....like the fuel pump wasn't functioning. I ended up pulling over because I was afraid it wouldn't go much further....I ended up being right - it wouldn't start after that...I was having the same issue, no fuel, but I had spark. I originally thought the ballast resistor was bad, but it turns out that I don't actually have one...I had jumped two wires for an EGR valve on the fender well, and miracuously it started after that...I don't quite know what I did to get it to go, because it just suddenly worked. Today, having no issues with it, having started it, driven it and run it several miles since that issue; I started to smell burning plastic with a full load of scrap in the bed - I decided to pull over into a church parking lot to find the front half of the O2 sensor harness smoking. I shut the truck off, pulled the sheathing off and found....nothing wrong. The wires were extremely hot, though. I later found the O2 sensor guts have disconnected from the actual sensor and were touching the front differential - I'm thinking it was grounding itself and getting excessively hot and smoking...I go to restart the jeep to turn around and head home - nothing. Several hours later, a complete stranger towed me home in exchange for a front drive shaft I had laying around, and I'm now I'm stuck with a truck that doesn't start and has a full load of scrap in it. My dad found a couple of wires that were melted together on a small connector off the injector harness that goes into the top of the firewall; still no start after repairing those. I had called the local jeep shop and for the most part I was told the computer is fried. But, I want to get second opinions, I also want to know 'why' my computer fried? Is it because of the O2 sensor? Those wires? The fact that I'm running a 100amp Alternator? What would/could it be?? IS my computer fried? Any ideas here?? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 17, 2012 Share Posted March 17, 2012 I had jumped two wires for an EGR valve on the fender well, and miracuously it started after that...I don't quite know what I did to get it to go, because it just suddenly worked. Sure those weren't the ballast resistor wires? Link to comment Share on other sites More sharing options...
Abyx Posted March 17, 2012 Author Share Posted March 17, 2012 I had jumped two wires for an EGR valve on the fender well, and miracuously it started after that...I don't quite know what I did to get it to go, because it just suddenly worked. Sure those weren't the ballast resistor wires? I'm pretty sure...I was told the ballast resistor is a little white ceramic resistor with two wires running to it...the thing that I jumped(having thought it was the resistor, but didn't know any better simply due to lack of knowledge), has two vacuum lines running to the intake and EGR diaphragm on the side of the intake, and is black. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 18, 2012 Share Posted March 18, 2012 Perhaps you better inspect the harness that the O2 sensor wires travel through. They could have melted together with some other wires in the harness? Also check the relays on the passenger side inner fender. One of them is for the O2 sensor and perhaps has something to do with power delivery things. If so, that relay may have become damaged from the shorting O2 sensor incident. Link to comment Share on other sites More sharing options...
Abyx Posted March 18, 2012 Author Share Posted March 18, 2012 There were some melted together; up on the firewall I believe it's connector C116, it diverts off of the engine harness right before C101 and connects to the firewall harness right as it jumps through the firewall. If I'm not mistaken, that's the harness for the engine sensors to the ECU. Do you think there are more melted? Also, a new symptom is none of my gauges indicate; meaning when I turn the key on..literally nothing happens. I had tried swapping around the relays, but nothing seems to work, maybe I can swap them all from my Cherokee to be safe. It just baffles me because I was driving it literally a minute prior to it not starting. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 18, 2012 Share Posted March 18, 2012 Check where terminal 30 connects to the plug at the O2 sensor relay. Should have power from the ignition switch with the key on. Also check all the fuse links in the orange, green, red, and blue wires from the starter relay. Link to comment Share on other sites More sharing options...
Abyx Posted March 18, 2012 Author Share Posted March 18, 2012 I'm sorry, I'm having trouble finding the 'Connector 30' you mentioned. Which plug? There's the O2 sensor relay that's wired directly into the harness...are you talking about the ECU connector? That's the only plug I can find that has over 30 pins to have a connector 30. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 18, 2012 Share Posted March 18, 2012 The receptacle the O2 sensor heater relay pin # 30 plugs into. Link to comment Share on other sites More sharing options...
Abyx Posted March 18, 2012 Author Share Posted March 18, 2012 I'm sorry, I'm still a little confused as to what you're refering to. I'm just not seeing it. I'm going off the assumption that you're refering to the plug that connects into the ECU; and to confirm...I do not have power in any of the 30 connectors with the key on, battery connected and fusible links jumped..It's entirely possible that I have the wrong fusible links jumped, but as far as I can tell I do. Using another doner computer from a '90 Renix automatic..I still have 'nothing'. So, I'm not getting power somewhere? Link to comment Share on other sites More sharing options...
Abyx Posted March 18, 2012 Author Share Posted March 18, 2012 After having read my service manual a little bit more I believe you're talking about the upper most connector on the relay block. No power with the key on, the other two have power though. Link to comment Share on other sites More sharing options...
Abyx Posted March 18, 2012 Author Share Posted March 18, 2012 Ignition switch. Replaced it; jeep fired right up. Thanks again for the help, Cruiser. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 19, 2012 Share Posted March 19, 2012 That's what we were shooting for. No power to pin 30 on oxygen sensor relay. And other places along the way. Glad it's fixed. Link to comment Share on other sites More sharing options...
carnuck Posted March 19, 2012 Share Posted March 19, 2012 Probably the short ruined the ignition switch. That sounds like maybe the CPS harness? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 19, 2012 Share Posted March 19, 2012 Probably the short ruined the ignition switch. That sounds like maybe the CPS harness? Nah. The O2 sensor relay is powered directly by the ignition switch and it was the O2 sensor that shorted. I'd be putting my energy that direction. Link to comment Share on other sites More sharing options...
carnuck Posted March 19, 2012 Share Posted March 19, 2012 Then the excessive power passing through the switch caused it to fail because of the short from the O2 sensor Link to comment Share on other sites More sharing options...
cruiser54 Posted March 19, 2012 Share Posted March 19, 2012 Then the excessive power passing through the switch caused it to fail because of the short from the O2 sensor I'm guessing.......... Link to comment Share on other sites More sharing options...
Abyx Posted March 19, 2012 Author Share Posted March 19, 2012 It was the ignition switch, the 14 gauge yellow wire was the culprit in the connector. I would imagine that it was the O2 sensors' fault, considering everything relating to the O2 sensor was mostly melted. Do you guys think a lack of an O2 sensor would cause a random stumbling idle/engine tries to die when you let off the gas slowly? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 19, 2012 Share Posted March 19, 2012 Yes, it can and will. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now