vfb Posted January 28, 2016 Share Posted January 28, 2016 This is going to be pretty basic, but I hope I learn something at the least. I have an 89 4.0 manual 5 speed that is all stock. Recently, it began to quit after about 15 or 20 minutes of very light snow plowing or even idling. Felt like it ran out of gas. It would restart but then immediately quit after a few seconds. Once it had cooled down it was ok for another 10 or 15 minutes, so it seemed heat related. I changed the coil and ICM with another one I had around and there was no change. After reading up here, I looked at the ballast resistor and saw that one wire was loose although still attached and also corroded. I cleaned and reattached it, and it seems ok now. Runs like normal. So my question is... could this really have been the cause? I know that if the resistor is bad it can overheat and fail, but I don't understand how a bad connection could make it overheat. Also, because it's freezing here these days and I have very little knowledge or testing equipment, I had booked an appointment with my mechanic for next week. But for four days now it has run for 45 minutes to an hour without problems, and I feel that's a good indication that I can cancel the appointment. Is that dumb? I just don't what I would say other than it was broke but now it's not :(I'd appreciate any thoughts or education on this,Thanks Link to comment Share on other sites More sharing options...
Eagle Posted January 28, 2016 Share Posted January 28, 2016 I think you are correct on the CPS. I had the same thing happen on the '88 MJ, and it began immediately after the CPS was replaced. Too many other things happening in life to troubleshoot it, so it just sits, but I'm 95% sure that's the culprit. Link to comment Share on other sites More sharing options...
vfb Posted January 28, 2016 Author Share Posted January 28, 2016 Thanks Eagle but, I didn't think it was the CPS. Are you thinking that may be the cause even though it now runs ok? Over the phone the mechanic guessed that it might be the coil or ignition control module and I happened to have a spare one so I tried it, but it still consistently quit after 10 or 15 minutes. That's when I noticed and repaired the connection on the Ballast Resistor. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 28, 2016 Share Posted January 28, 2016 The ballast resistor is a wire-wound ceramic dropping resistor and does get very hot when it is in the fuel pump circuit. It sounds like your resistor is failing when hot. You can either replace it (my choice) or get rid of it altogether by disconnecting the end terminals and soldering them together. The resistor is there to reduce fuel pump noise, and your pump will run fine w/o it being in the circuit, just a bit louder. Either way will be fine........ Link to comment Share on other sites More sharing options...
vfb Posted January 28, 2016 Author Share Posted January 28, 2016 Thanks. What I am wondering is if (and how) the bad connection could have caused the resistor to overheat. Now that the connection is good, it seems fine. Link to comment Share on other sites More sharing options...
Rockfrog Posted January 28, 2016 Share Posted January 28, 2016 Resistance creates heat, bleeding off voltage as heat, the ballast resistor does this already, the corrosion simply added to the effect and likely reduced available amperage/voltage to below operating levels. Just the way I see it, I'm no electrical engineer. I'm on the bypass it and move along group, a little fuel pump noise is not an issue for me. Not that the pump is really all that noisy anyway. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted January 28, 2016 Share Posted January 28, 2016 Resistance creates heat, bleeding off voltage as heat, the ballast resistor does this already, the corrosion simply added to the effect and likely reduced available amperage/voltage to below operating levels. Just the way I see it, I'm no electrical engineer. I'm on the bypass it and move along group, a little fuel pump noise is not an issue for me. Not that the pump is really all that noisy anyway. Drown the pump noise out with a louder exhaust! lol Link to comment Share on other sites More sharing options...
cruiser54 Posted January 29, 2016 Share Posted January 29, 2016 Resistance creates heat, bleeding off voltage as heat, the ballast resistor does this already, the corrosion simply added to the effect and likely reduced available amperage/voltage to below operating levels. Just the way I see it, I'm no electrical engineer. I'm on the bypass it and move along group, a little fuel pump noise is not an issue for me. Not that the pump is really all that noisy anyway. This^^. Link to comment Share on other sites More sharing options...
vfb Posted January 29, 2016 Author Share Posted January 29, 2016 Thanks for the feedback, folks. Link to comment Share on other sites More sharing options...
Crash Posted January 30, 2016 Share Posted January 30, 2016 Xwhatever on by-passing the ballast resistor. One less thing to potentially be wrong in the future as well. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 31, 2016 Share Posted January 31, 2016 My life takes funny twists and turns. After reading this thread, I was driving my white MJ for the first time in months. My son and daughter-in-law have been hogging it as a second vehicle. Serviced it and went to the store for some adult beverages. I'd forgotten about the intermittent half second stutter/hiccup that would randomly occur. Happened about 4 times in a 12 mile trip. Brought it home and put it back into the garage. I decided to check the fuel pump ballast resistor connections. They were greenish and corroded so I proceeded to remove them, clean them, and put a dab of OxGard on the connectors before plugging things back together. Drove it 50 miles yesterday without a hiccup.................. Link to comment Share on other sites More sharing options...
vfb Posted January 31, 2016 Author Share Posted January 31, 2016 Ha! I'm glad to be in the same boat as one of our gurus :) Link to comment Share on other sites More sharing options...
cruiser54 Posted January 31, 2016 Share Posted January 31, 2016 Ha! I'm glad to be in the same boat as one of our gurus :) I guess I need to emphasize that in my #3 Tip: Connector Refreshing. Thanks for starting this thread. Link to comment Share on other sites More sharing options...
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