White_Comanche Posted August 20 Share Posted August 20 Hi again guys. I'd like some guidance on tackling a No-Start Issue that reared its ugly head again recently. My truck has had this issue since purchasing it from the previous owner in 2021. Thought that I had resolved the problem but it slowly resurfaced. 1986 2.5L MJ 5-Speed Manual Most notable symptoms that occurred BEFORE it began: • Driving: Sputtering during acceleration, and also when shifting upward • At Idle: sputtering when applying gas, and acted like it wanted to die when letting off • At idle: sometimes RPMs increased to, and sustained 2.5K - 3K for a few seconds (after working throttle for a while) Symptoms NOW: • NO Engine Starting (at all) Improvements that I've done up to this point (all within 2 years) Clean/Rebuilt Throttle Body - New Spark Plugs, Wires & Cap - New Vacuum Lines - Cleaned all or most Electrical Connectors - Reinforced & Cleaned All Grounds - New Oxygen Sensor - Transmission Professionally Rebuilt - Installed REM Clock My Evap Canister has been disconnected for several years - and all associated lines have been plugged. But please note that it never reeks of gas, and performance seems unaffected. Link to comment Share on other sites More sharing options...
eaglescout526 Posted August 20 Share Posted August 20 What’s the CPS outputting? Any spark? got fuel flow? Link to comment Share on other sites More sharing options...
White_Comanche Posted August 20 Author Share Posted August 20 Read up on Cruiser's preferred method of testing the CPS with AC volts. After re-familiarizing that area of the 2.5 I was glad to see that harness is relatively easy to get to. I should be able to check these things out soon. 16 hours ago, eaglescout526 said: got fuel flow? Also, what is an easy method of checking fuel flow? Will I see or smell fuel spray when looking into the throttle body? Link to comment Share on other sites More sharing options...
eaglescout526 Posted August 20 Share Posted August 20 44 minutes ago, White_Comanche said: Also, what is an easy method of checking fuel flow? Will I see or smell fuel spray when looking into the throttle body? Not exactly. My favorite method is to remove the injector and see but you could remove the line at the body or even the plug where a gauge would go. Link to comment Share on other sites More sharing options...
White_Comanche Posted August 25 Author Share Posted August 25 On 8/19/2024 at 10:14 PM, eaglescout526 said: What’s the CPS outputting? Any spark? got fuel flow? Somehow this thing is starting and running again. Today I checked all of these things. Fuel flow inside the TB was strong. When checking spark afterwards I wasn't seeing anything from my new inline spark tester. However, beforehand I did drop the bulb housing by accident, or it may just be defective. CPS shows strong AC volts maxing out at .55 After plugging the CPS back together I decided to try starting anyway. Good news, there is spark. It starts and runs. Idle seems fine, and it responds well to idle throttling. No sputtering was present. The thing that I spent some time on was cleaning and reseating the copper wires of the positive battery terminal. There were times that the + terminal needed tweaking for it to start. Don't know if this is related. A few days ago when I had to get it towed, there WAS positive connection to the battery. It just wouldn't turn over. Will try a few more times this weekend to see it it continues to start. Have not driven it yet. Still not confident with it. Could it be my Ignition Coil or ICM is going south, or something else? Link to comment Share on other sites More sharing options...
eaglescout526 Posted August 25 Share Posted August 25 I wouldn’t suspect the ICM just yet. I’d be more suspect of the battery cable. These Jeeps hate any and all resistance to the electrical system. I like to rule out electrical like ground and power resistance before pointing at a module or sensor. Link to comment Share on other sites More sharing options...
White_Comanche Posted August 25 Author Share Posted August 25 19 hours ago, eaglescout526 said: I’d be more suspect of the battery cable. A future project was to at least replace the positive cable. What I have looks factory. There is exposed copper wire on both battery terminals. Today I traced where each cable leads to. The positive was easy enough that it leads to the starter. For the negative cable it wasn't at all clear where it leads. Both the POS & NEG cables are in the same loom. I figured the negative terminates to the post by the dipstick. But the cable coming off the engine post heads somewhere backwards and I never saw it exiting from the loom. Am I missing something? Please let me know where the actual negative battery cable leads to. Link to comment Share on other sites More sharing options...
eaglescout526 Posted August 25 Share Posted August 25 Those don’t look factory. At least the terminal connections don’t. The ground cable goes to the engine block by the alternator. That’s where it should be from the factory. Then you have the ground strap from the block to the firewall. Then you have all the sensors ground at the dipstick tube. The. The blower motor, wipers, lights and a few others are grounded out at the drivers side. But with yours being an 86 that may not be entirely standard yet. positive should go to the starter relay and starter itself. Link to comment Share on other sites More sharing options...
White_Comanche Posted August 27 Author Share Posted August 27 On 8/25/2024 at 6:45 PM, eaglescout526 said: The ground cable goes to the engine block by the alternator Yes you are correct. It took a bit of time, but I did find the cable bolted by the alternator. I've learned that 'seeing' into an engine bay is a learned skill. Link to comment Share on other sites More sharing options...
eaglescout526 Posted August 27 Share Posted August 27 Gotta know the ins and outs of the beast to conquer it. Haha. That and the TBI is a misunderstood one too. I can imagine that ground for you is dirty if it hasn’t been touched for the past 40 years. Link to comment Share on other sites More sharing options...
White_Comanche Posted September 2 Author Share Posted September 2 As I've been doing this project there has been a few routes that I've considered. 1) get Deka pre-terminated battery cables, or 2) buy the kit from JeepCables. After undoing the wire conduits and old fabric tape I discovered this past repair. From the Starter Relay, the wire gets spliced into (2) paths. One goes to the rear of the Alternator, and the other is plugged into a harness at the top of the Alternator. Is this soldered crimp something that I should address? Should this be two separate wires from the Starter Relay? Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 2 Share Posted September 2 No. That’s factory. You’ll find a couple splices like that in the harness. You can always either do away with it and make it safer or cover it in some solder so it doesn’t corrode and wrap it up in some electrical tape and use some wire loom to hide it all. Link to comment Share on other sites More sharing options...
White_Comanche Posted September 9 Author Share Posted September 9 My 2.5L two-point-fives again. Between two weekends I properly replaced my battery cables, and also tidied up the wire in looms. Got my cable assemblies custom made locally. Very happy with the product. Definitely beats the price of 'premium' cable kits out there. It took a surprisingly amount of effort, but it was a fun MJ project. So far everything starts and runs fine. It responds quickly to revving up, and also letting off idle throttle. I'll take it on some drives soon, and will get back. Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 9 Share Posted September 9 Oooo yours has the factory AC. Link to comment Share on other sites More sharing options...
White_Comanche Posted September 9 Author Share Posted September 9 Yep it has AC, but I have never turned it on because the system needs work. Previous owner said he filled it for going somewhere on hot days, but the gas eventually leaks out. Always wondered what the performance is like with the AC on. Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 9 Share Posted September 9 4 minutes ago, White_Comanche said: Always wondered what the performance is like with the AC on. If I had to say it’s about 5 Hp less at take off but the system cycles off during hard acceleration to compensate. Otherwise you really don’t know you have the AC on. Link to comment Share on other sites More sharing options...
White_Comanche Posted October 8 Author Share Posted October 8 On 8/24/2024 at 9:34 PM, eaglescout526 said: suspect the battery cables Recently, I was able to get my Jeep out and daily-drive it for a straight week. It drives very well and starts quickly every time. Replacing the battery cables looks to have been the last weakest link for the no-start issue that plagued my truck. Until next time, thank you. Link to comment Share on other sites More sharing options...
eaglescout526 Posted October 8 Share Posted October 8 No problem! Link to comment Share on other sites More sharing options...
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