jtdesigns Posted December 16, 2008 Share Posted December 16, 2008 I don't understand how the fuel pump has much to do with this if it'll stay running when the keys in the crank position even after jumping the resistor. Plus he's had his hands on the switch and could have either A: installed it incorrectly, or B: gotten a bad switch. I do agree with cleaning the grounds even though they look good ... but I still think its in the switch.. Couldn't he test for continuity while the switch is being turned? It just sounds to much like the most obvious thing... Link to comment Share on other sites More sharing options...
BLHTAZ Posted December 16, 2008 Share Posted December 16, 2008 I'd recommend checking the main battery connections and then where they meet the block, as well as the computer grounds on the passenger side of the block by the dipstick.This is good advice. My previous 3 week battle with the running / idle issues was due to a ground problem where the battery grounds with the other 4 ground wires on the block right near the dip stick. I took it apart, replacaed all the battery cables and bolted all the wires back on the block and VIOLA...not more troubles. Link to comment Share on other sites More sharing options...
bilgamesh Posted December 16, 2008 Author Share Posted December 16, 2008 Thanks for all the replies. To clarify: The ignition switch was really inconvenient to replace, however, once the bolt and screw were in place, it was no problem to slide it back and forth along the column, and turn the key to make sure I was getting full movement into all positions. This was really pretty straightforward. I plan to replace the cables as recommended, as clearly a good hot charge is overcoming anything else that may be amiss. Please send any more thoughts that occur to you. If there are any electrical gurus out there, maybe you could expand on what circuits are different between the run and start positions. Obviously the starter is engaged, and as we have alluded to, current to the fuel pump is routed around the ballast resistor. The question is what else is different? Thanks, Bill Link to comment Share on other sites More sharing options...
tugalo Posted December 16, 2008 Share Posted December 16, 2008 The fuel pump relay is what switches the ballast resistor into the circuit. If it is bad, the jeep will start and run as long as you hold the switch in the start position. If the relay is bad, when you release the switch to the "run" position, the jeep will stall out, even if the ballast resistor is good. Swap around a couple of relays at the relay center and try it.....could just be corrosion on the plug-in contacts... Link to comment Share on other sites More sharing options...
bilgamesh Posted December 17, 2008 Author Share Posted December 17, 2008 Tugalo, this sounds promising, and like you are confident of the facts. I will check it out and report back. Thanks, Bill Link to comment Share on other sites More sharing options...
maddzz1 Posted December 17, 2008 Share Posted December 17, 2008 If the truck will stay running with the key held to the start position but stalls when you release the key back to the run position then this is the exact problem that lead me to find this site. If this is the case, it is a wire next to the fusible link next to the battery. I am not sure exactly which wire it is because I eventually brought it to an auto electrical shop and had them find the wire; after finding someone else who had the problem and told me how to fix it. I also tried the ignition switch and ballist resistor before finding the solution. To everyone: My feelings are badly hurt that no one remembers my first question on the board. :no: Link to comment Share on other sites More sharing options...
bilgamesh Posted December 17, 2008 Author Share Posted December 17, 2008 If anyone knows what fusible link he is talking about, please let me know. Maybe it is in the same circuit as the fuel pump relay?... Thanks Link to comment Share on other sites More sharing options...
tugalo Posted December 18, 2008 Share Posted December 18, 2008 If the truck will stay running with the key held to the start position but stalls when you release the key back to the run position then this is the exact problem that lead me to find this site. If this is the case, it is a wire next to the fusible link next to the battery. I am not sure exactly which wire it is because I eventually brought it to an auto electrical shop and had them find the wire; after finding someone else who had the problem and told me how to fix it. Jim is correct with the above statement, if the relay is good, then the problem is an open circuit in the orange wire that provides power from the relay to the fuel pump when the switch is released to the run position. It is more common for the problem to be in a moving part (the relay) than a piece of wire. Link to comment Share on other sites More sharing options...
bilgamesh Posted December 18, 2008 Author Share Posted December 18, 2008 Thanks again for the replies and updates. This was a difficult problem to get a handle on. When you start a vehicle, and it fires/starts, your instinct is to release the key so that you don't grind the starter. It was only after I had read of others being able to keep it running in the start position, that I got up the nerve to try it. Once I tried that and it worked, it was a simple step to try to rev the motor at this stage. Obviously I don't recommend either, but in this instance, it was key to figuring out what is amiss, assuming this latest input is helpful. I hope to look into it this weekend and post back the details and outcome. Link to comment Share on other sites More sharing options...
bilgamesh Posted December 22, 2008 Author Share Posted December 22, 2008 I did the chinese fire drill with the relays yesterday and though it started with no problems, I was still skeptical due to the fact the battery still had a pretty hot charge. Overnight, the truck sat out in the cold, and it was a noticably slower crank this morning as a result. Even so, it cranked up and stayed started. I am hopeful the relay was the problem. Does anyone know where to buy these relays? Unfortunately I went to drive tonight, and the dash lights don't work now. I am not sure if I screwed those up with swapping one of the relays, or if I loosened a connection in my work under the dash. Any thoughts? Thanks All, and Happy Holidays! Bill Link to comment Share on other sites More sharing options...
BLHTAZ Posted December 22, 2008 Share Posted December 22, 2008 Those relays are quite common and should be available at any auto parts store. The dash light issue is likely as you think...probably something you did in the swapping things around and now you just need to go back over it to find it. Link to comment Share on other sites More sharing options...
bilgamesh Posted December 22, 2008 Author Share Posted December 22, 2008 I swapped all the relays back around, with no help for my dash lights. Does anyone have an idea about what I might have screwed up? I am also curious to know if anyone can tell me how to determine which of the 4 relays goes to the fuel pump. Thanks Link to comment Share on other sites More sharing options...
tugalo Posted December 23, 2008 Share Posted December 23, 2008 Go to the NAXJA forum: http://www.naxja.org/forum/index.php : and do a search on fuel pump relay. Remember, Jeep Comanche trucks and Jeep Cherokees are practically identical from the back of the front seats to the front bumper.....if it applies to a Cherokee, its a good bet that it will also apply to your Comanche. Also poke around in the NAXJA site and you will find links to complete factory maintenance manuals and wiring diagrams. Link to comment Share on other sites More sharing options...
BLHTAZ Posted December 23, 2008 Share Posted December 23, 2008 Also poke around in the NAXJA site and you will find links to complete factory maintenance manuals and wiring diagrams.Those are on this site as well in the DIY Forums ;) Link to comment Share on other sites More sharing options...
bilgamesh Posted December 24, 2008 Author Share Posted December 24, 2008 The fuel pump relay was the problem. I bought a new relay and swapped it in and out until I was convinced the problem only happened when the old one was there. Thanks to everyone who replied with ideas and information. Link to comment Share on other sites More sharing options...
bilgamesh Posted January 9, 2009 Author Share Posted January 9, 2009 Problem Fixed! During work on this problem, I did several things which cascaded into more problems. I am detailing the solution here with the end in mind that someone may benefit at some point. After messing with the Idle Air Control Switch and the Ballast resistor and troubleshooting for a couple weeks, I replaced the ignition switch to no effect. During this repair, my instrument panel lights stopped working, so I replaced the light switch. This fixed my panel lights, but my dimmer switch stopped working. It would not stay on bright. I went out to drive that night and noticed my headlights would not work at all. I dug back into the dash and found that the hot wire had come out of the junction block on the light switch and was hanging. Once I reconnected it, the headlights and the dimmer worked. To fix the starting problem, after running the battery down one day, and re-charging overnight, I noticed that with a really hot charge, the truck started every time. I began to suspect a problem in the fuel pump circuit. Once I could duplicate the problem again, I started swapping around some of the relays along the passenger fender and found the problem went away. I bought a new relay for $6 at Autozone, swapped it in and out until I was convinced I found the bad one, and that the problem only happened when the bad one was in there. Evidently the fuel pump relay was faulty. I am happy to report everything is fixed! Thanks to everyone who replied with ideas and information. Link to comment Share on other sites More sharing options...
BLHTAZ Posted January 9, 2009 Share Posted January 9, 2009 Glad to hear you are back in shape :clapping: . Electrical trouble is a terrible thing...especially to folks like me that just don't get it when it comes to how electricity works. :wall: Link to comment Share on other sites More sharing options...
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