mfendley Posted October 10, 2018 Author Share Posted October 10, 2018 BTW, I am located in SE Georgia, between Brunswick GA and Jacksonville FL. Is there anyone nearby with diagnostic equipment for this year of vehicle? It would be helpful to have equipment attached when this occurs, so I could see if this is a spark failing, or an interruption in signal to a fuel injector, or something else completely. Link to comment Share on other sites More sharing options...
mfendley Posted October 10, 2018 Author Share Posted October 10, 2018 13 hours ago, kryptronic said: Something happening after the engine warms up versus before is an indication of a sensor or computer related issue. Looks like you handled the crank and cam sensors. Did you clean the throttle body, TPS and IAC valve? Have you run vacuum and fuel pressure tests? Will clean these tonight; I can check the vacuum but I will have to pick up a pressure gauge to test the fuel pressure. Did just change the fuel pump and filter, so I hope it is not that. PITA to drop the tank again. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 10, 2018 Share Posted October 10, 2018 3 hours ago, mfendley said: No codes registered. Even though this truck is not driven often (my son's daily driver is a Renegade) it has been a couple of years since its last tuneup. Will get cap, rotor, wires and plugs swapped. Will also run some Seafoam or similar to ensure the injectors are clean. That way, I know that portion of the ignition has no breakdowns (shorts to ground). No codes? You should have gotten a 12 and 55 at least. If not something's wrong or you didn't do the procedure correctly. Link to comment Share on other sites More sharing options...
mfendley Posted October 10, 2018 Author Share Posted October 10, 2018 1 hour ago, HOrnbrod said: No codes? You should have gotten a 12 and 55 at least. If not something's wrong or you didn't do the procedure correctly. I had my son do it. I will try myself after work. Link to comment Share on other sites More sharing options...
kryptronic Posted October 10, 2018 Share Posted October 10, 2018 Cleaning the TPS/IAC and throttle body as well as making sure those injectors are clean are routine maintenance procedures which might cure your issue. Beyond that, get those codes HOrnbrod keeps asking about. Before you spend any more coin replacing good parts. I would have mentioned cap, rotor and wires as part of routine maintenance - but you said you replaced the entire distributor and did new wires already. Link to comment Share on other sites More sharing options...
mfendley Posted October 10, 2018 Author Share Posted October 10, 2018 6 hours ago, mfendley said: I had my son do it. I will try myself after work. My son didn't know to wait a bit after the last move to on. I showed him the process, and we watched the codes flash 12 and 55. No other codes. Started to rain (from Hurricane Michael) so I'll have to wait a bit to swap the plugs, wires, rotor and cap. Link to comment Share on other sites More sharing options...
mfendley Posted October 10, 2018 Author Share Posted October 10, 2018 1 hour ago, mfendley said: My son didn't know to wait a bit after the last move to on. I showed him the process, and we watched the codes flash 12 and 55. No other codes. Started to rain (from Hurricane Michael) so I'll have to wait a bit to swap the plugs, wires, rotor and cap. Swapped all of the parts, seems to take a little longer to start missing (15 minutes instead of 5 or 6) but still have the issue. Will clean the TPS/IAC and throttle body tomorrow night. Here's a picture of the plugs that were removed, seem to have a pretty good pattern - no oil being burned, and not running too rich. I will also try replacing the resistor for the fuel pump. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 11, 2018 Share Posted October 11, 2018 What's the p/n on the ECU tag? Should be 56005707 (original) or 56027528 (optional). Link to comment Share on other sites More sharing options...
kryptronic Posted October 11, 2018 Share Posted October 11, 2018 On 10/2/2018 at 11:07 AM, mfendley said: Have replaced ECU, distributor, coil, wires, plug, CPS on electrical side What kind of spark plugs did you use? The OE replacement for our 4.0L engines is regular old Champion Copper 412 plugs gapped to .35". Using higher end platinum plugs can cause issues. Opinions will vary on this, but regardless I'm wondering what kind of plugs you installed and were they gapped correctly? Link to comment Share on other sites More sharing options...
mfendley Posted October 12, 2018 Author Share Posted October 12, 2018 On 10/10/2018 at 9:27 PM, HOrnbrod said: What's the p/n on the ECU tag? Should be 56005707 (original) or 56027528 (optional). I don't see any of those numbers on the tag. I see a 798528, and a 201608257928091. Link to comment Share on other sites More sharing options...
mfendley Posted October 12, 2018 Author Share Posted October 12, 2018 On 10/10/2018 at 10:53 PM, kryptronic said: What kind of spark plugs did you use? The OE replacement for our 4.0L engines is regular old Champion Copper 412 plugs gapped to .35". Using higher end platinum plugs can cause issues. Opinions will vary on this, but regardless I'm wondering what kind of plugs you installed and were they gapped correctly? Autolite APP 985 gapped at 0.035". I will look for the Champion 412. At this point I am ready to try most anything. Still need to get a pressure gauge to test the fuel pressure, and clean out the intake. Link to comment Share on other sites More sharing options...
mfendley Posted October 12, 2018 Author Share Posted October 12, 2018 On 10/10/2018 at 9:27 PM, HOrnbrod said: What's the p/n on the ECU tag? Should be 56005707 (original) or 56027528 (optional). I did a search online for the numbers you listed; and they list the 56005707 as being for an automatic - does that matter? We have a 5-speed. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 12, 2018 Share Posted October 12, 2018 57 minutes ago, mfendley said: I don't see any of those numbers on the tag. I see a 798528, and a 201608257928091. That's a re-man (probably by Cardone) ECU, not an original. See this LINK. Cardone Control Module - Remanufactured Part #79-8528 Line: A1 But it crosses to the correct ECU factory p/n, 56005707, so it should be correct. If you can find an original, I'd replace the re-man as a last resort. I'd rather have a correct original in there.... The originals have a tag like the below with the p/n and manufacturing date. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 12, 2018 Share Posted October 12, 2018 8 minutes ago, mfendley said: I did a search online for the numbers you listed; and they list the 56005707 as being for an automatic - does that matter? We have a 5-speed. No, it doesn't matter, at least in my case it didn't. I ran a 91 ECU supposedly for a manual in my automatic for a couple of months and it made no difference. But I did install the correct auto ECU in later. Link to comment Share on other sites More sharing options...
kryptronic Posted October 12, 2018 Share Posted October 12, 2018 1 hour ago, mfendley said: Autolite APP 985 gapped at 0.035". I will look for the Champion 412. At this point I am ready to try most anything. Still need to get a pressure gauge to test the fuel pressure, and clean out the intake. Autolite APP985 would be good in a coil pack 4.0L. AP985 would be the right choice, if not Champion 412 in a 4.0L like ours, with a distributor. Autolite APP985 plugs are known to cause ignition issues on 4.0L engines with distributors. At least with Wrangler people. This may be your issue. Link to comment Share on other sites More sharing options...
mfendley Posted October 12, 2018 Author Share Posted October 12, 2018 40 minutes ago, kryptronic said: Autolite APP985 would be good in a coil pack 4.0L. AP985 would be the right choice, if not Champion 412 in a 4.0L like ours, with a distributor. Autolite APP985 plugs are known to cause ignition issues on 4.0L engines with distributors. At least with Wrangler people. This may be your issue. I just looked. The APP985 are the plugs we pulled out, the AP985 are the plugs we installed. I will also look for some Champion 412 just in case. Link to comment Share on other sites More sharing options...
mfendley Posted October 12, 2018 Author Share Posted October 12, 2018 Is there any way to get a new ECU, or just find the correct part number our of a wrecking yard? Link to comment Share on other sites More sharing options...
mfendley Posted October 12, 2018 Author Share Posted October 12, 2018 Unplug the ECU to get the part number, and reinstalled. Cleaned the throttle body and MAF sensor, but everything back together - now it won't start. Cranks, and almost tries to start, but no go. I will charge the battery over night, and give it a go again in the morning. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 13, 2018 Share Posted October 13, 2018 1 hour ago, mfendley said: Unplug the ECU to get the part number, and reinstalled. Cleaned the throttle body and MAF sensor, but everything back together - now it won't start. Cranks, and almost tries to start, but no go. I will charge the battery over night, and give it a go again in the morning. Check the ECU 60-pin connector and receptacle for any bent or recessed pins. Use some contact cleaner and douche out and lightly brush clean the connectors. Might help, but I've never heard of an OBD1 ECU causing ignition cut-off problems when warm. If the ECU is bad, most the engine will not start and there will be a code. The most common causes of ignition cut-off I've experienced are a bad CPS (threw a code), bad distributor sync (cam) sensor (threw a code), and/or a bad ignition coil (did not throw a code). After all is said and done and you still have not found the cause of your cut-off problem, replace your original distributor with one from a 1994 and up OBD1 4.0 engine. It's a great upgrade, because when the distributor (cam) sensor fails with the 91 distributor, you have to pull the distributor, bench disassemble it entirely including the shaft and drive gear, replace the sensor, then do the reverse. On the 94 and up distributor, the cam sensor is right on top under the distributor cap. To replace the sync sensor simply pull off the cap, rotor, unplug the sync sensor and replace. Ten minutes tops. You can see the 4.0 Jeep engine distributor differences HERE. Link to comment Share on other sites More sharing options...
mfendley Posted October 13, 2018 Author Share Posted October 13, 2018 I will check for codes this morning. Do you have the part numbers for the 94+ coil and ECU? Is it possible to go much newer to the coil pack setup, or is that too far of a jump? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 13, 2018 Share Posted October 13, 2018 Here's the 94 coil and wiring harness on Ebay. These are rare and tough to find. From the FSM: Correct ECU for a US 91 w. standard trans., non-Cali, w. RFI: 56027532 Link to comment Share on other sites More sharing options...
mfendley Posted October 13, 2018 Author Share Posted October 13, 2018 Thanks HOrnbrod. That is the coil and harness that I just installed when this issue started. I have the coil mounted just behind the passenger side shock tower. The harness that came with the coil was long enough to reach this location, but I did have to get a longer coil wire. Thanks for the ECU info, I will start searching for one of those. This morning's update; first I searched for OBD codes, still only received 12 and 55. Took awhile to get started, seems like there was still residue from the cleaner used to clean out the throttle body and MAF sensor. Once it finally started, it was blowing all kinds of white smoke, until it burned off all the cleaner and raw fuel from the cranking process. Finally smoothed out, and had a great idle. Went on a test drive, and about 6.5 minutes into the drive, started missing / cutting out. Checked the fuel pressure, was between 38 and 40 psi. Link to comment Share on other sites More sharing options...
mfendley Posted October 18, 2018 Author Share Posted October 18, 2018 Thought I had found the issue. Decided to swap the CPS, since last one was a "cheap" one from Rock Auto. Dealer did not have any in stock, but was able to find one at NAPA. After swapping the sensor, noticed the old sensor had a melted shield and wire. Also changed the fuel pump ballast resistor at the same time. Went for a test drive, but the issue still exists. Threw the fuel pressure gauge on while is was sitting in the driveway. At 2500-3000, still misses, with no load on the engine, fuel pressure never dropped below 24 psi. I have an ECU coming (56027532) that will be here on Saturday. I also have an engine compartment wiring harness (from a junkyard) that I am going to go through wire by wire to ensure good connectivity and grounds, and will swap that. Any other ideas? Link to comment Share on other sites More sharing options...
mfendley Posted October 18, 2018 Author Share Posted October 18, 2018 On 10/12/2018 at 8:01 PM, HOrnbrod said: Check the ECU 60-pin connector and receptacle for any bent or recessed pins. Use some contact cleaner and douche out and lightly brush clean the connectors. Might help, but I've never heard of an OBD1 ECU causing ignition cut-off problems when warm. If the ECU is bad, most the engine will not start and there will be a code. The most common causes of ignition cut-off I've experienced are a bad CPS (threw a code), bad distributor sync (cam) sensor (threw a code), and/or a bad ignition coil (did not throw a code). After all is said and done and you still have not found the cause of your cut-off problem, replace your original distributor with one from a 1994 and up OBD1 4.0 engine. It's a great upgrade, because when the distributor (cam) sensor fails with the 91 distributor, you have to pull the distributor, bench disassemble it entirely including the shaft and drive gear, replace the sensor, then do the reverse. On the 94 and up distributor, the cam sensor is right on top under the distributor cap. To replace the sync sensor simply pull off the cap, rotor, unplug the sync sensor and replace. Ten minutes tops. You can see the 4.0 Jeep engine distributor differences HERE. HOrnbrod, is the distributor plug on the 94 the same as the 91 version? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 18, 2018 Share Posted October 18, 2018 2 hours ago, mfendley said: HOrnbrod, is the distributor plug on the 94 the same as the 91 version? Yes - same connector. Link to comment Share on other sites More sharing options...
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