Tex06 Posted November 28, 2023 Share Posted November 28, 2023 OK, I'm scratching my head on this one. Jeep starts fine when it's warm. Anytime its cold (below 60-65F..... yes I'm aware this isn't cold to some of you but I live in New Orleans ) I get one or both of two issues: 1) no crank, no start. Don't get a click. Starter doesn't move. Battery voltage drops ever so slightly (12.4 to 12.2) 2) no fuel pump. Key on, can usually hear my pump prime. When it's cold out, key to on and I get nothing. Truck will crank and crank but not start (duh, not getting fuel). If #1 happens, I've been able to push start it to get it to go. If #2 happens, sometimes I'll be able to start it by flicking the ignition on and off a few times to get enough pressure to start. If they both happen, I get my car keys and leave the truck at the house 🤷♂️ Battery is older (2017) but seems to be charged. This doesn't always happen when it's cold but it happens enough to where I don't trust the truck this time of year. As soon as the weather warms up, all of these issues go away. I haven't refreshed my grounds in 4 or 5 years, but I have cleaned the battery terminals fairly often trying to troubleshoot this one. Been ongoing for about 3 years now, but definitely worse this year. Link to comment Share on other sites More sharing options...
Pete M Posted November 28, 2023 Share Posted November 28, 2023 can you jump the battery to start the truck? 6 years old is kinda up there in age for a car battery. Link to comment Share on other sites More sharing options...
gogmorgo Posted November 28, 2023 Share Posted November 28, 2023 Have you load tested the battery? That is an odd one. Definitely shouldn’t be cold enough to cause problems. (Hasn’t been that warm here since September, lol) Makes me wonder if there’s maybe a humidity component or something. Maybe a loose or corroded connection or something in a shared circuit between fuel pump and starter circuits. And six years is getting up there… But even a weak battery, if it’s got enough charge to crank the engine over you’d think it would also be able to run the fuel pump. Link to comment Share on other sites More sharing options...
watchamakalit Posted November 28, 2023 Share Posted November 28, 2023 Bad fuel pump relay or ballast switch not making good connection? I wouldn't think a battery problem if the truck still cranks. Seem like it would be a fuel or spark issue. Could it be a coil going bad? Link to comment Share on other sites More sharing options...
Ωhm Posted November 28, 2023 Share Posted November 28, 2023 7 hours ago, Pete M said: 6 years old is kinda up there in age for a car battery. ↑↑∙That∙↑↑ Link to comment Share on other sites More sharing options...
Tex06 Posted November 28, 2023 Author Share Posted November 28, 2023 7 hours ago, Pete M said: can you jump the battery to start the truck? 6 years old is kinda up there in age for a car battery. Haven't tried lately but last December it didn't make a difference. Link to comment Share on other sites More sharing options...
Pete M Posted November 28, 2023 Share Posted November 28, 2023 what time of day are you trying? meaning is 60* the high for the day and you're trying in the morning when the truck itself is still at 40*? Link to comment Share on other sites More sharing options...
Tex06 Posted November 28, 2023 Author Share Posted November 28, 2023 6 hours ago, gogmorgo said: Have you load tested the battery? That is an odd one. Definitely shouldn’t be cold enough to cause problems. (Hasn’t been that warm here since September, lol) Makes me wonder if there’s maybe a humidity component or something. Maybe a loose or corroded connection or something in a shared circuit between fuel pump and starter circuits. And six years is getting up there… But even a weak battery, if it’s got enough charge to crank the engine over you’d think it would also be able to run the fuel pump. Have not load tested. Last night it was turning over but no fuel so I flipped the key a few times and it went to no crank, and still no fuel pump. This morning is the 48F and nothing happens when I turn the key. I'm def leaning towards bad connection but at this point I'm not sure where to look. Link to comment Share on other sites More sharing options...
Tex06 Posted November 28, 2023 Author Share Posted November 28, 2023 1 minute ago, Pete M said: what time of day are you trying? meaning is 60* the high for the day and you're trying in the morning when the truck itself is still at 40*? Morning, night, late afternoon..... if it's below 65 a start is iffy. Link to comment Share on other sites More sharing options...
Pete M Posted November 28, 2023 Share Posted November 28, 2023 weird. I would still start with the battery. getting it tested is free. I always like to start with the free options. Link to comment Share on other sites More sharing options...
Tex06 Posted November 28, 2023 Author Share Posted November 28, 2023 2 hours ago, watchamakalit said: Bad fuel pump relay or ballast switch not making good connection? I wouldn't think a battery problem if the truck still cranks. Seem like it would be a fuel or spark issue. Could it be a coil going bad? Swapped the relay for a known good one already, didn't kick the fuel pump on. Definitely a fuel issue. Truck doesn't always crank. Usually does but not always. See #1. Link to comment Share on other sites More sharing options...
Tex06 Posted November 28, 2023 Author Share Posted November 28, 2023 1 minute ago, Pete M said: weird. I would still start with the battery. getting it tested is free. I always like to start with the free options. Yeah. I did the poor man's load test as described above but maybe it's not enough 🤷♂️ Guess next weekend I'll be pulling my wiring schematics out and tracing each circuit, refreshing connections as I go. Link to comment Share on other sites More sharing options...
gogmorgo Posted November 28, 2023 Share Posted November 28, 2023 Poor man’s load test would need done with a heavy load on the battery, like cranking the engine. But if it’s not throwing the starter solenoid far enough due to low voltage you would see the voltage take a dive as you do that. Could this be an ignition switch issue, might just need adjustment? Push starting says manual trans so there’s no neutral safety switch in the circuit. Did you check for starter signal at the relay or solenoid? Kicking the bottom of the fuel tank change anything when the pump won’t run? Link to comment Share on other sites More sharing options...
JeepSchmidt O'Guinness Posted November 29, 2023 Share Posted November 29, 2023 Does the fuel pump share the ground behind the passenger tail light housing? Link to comment Share on other sites More sharing options...
schardein Posted November 29, 2023 Share Posted November 29, 2023 What do your battery terminals and cables look like? I'm on FB quite a bit helping people troubleshoot similar issues. I'm never surprised when it turns out they are using those bolt together "repair" battery terminals. They are garbage. And- even if the battery cables look good, they can have corrosion creeping under the insulation. Another issue I've had is burnt connections at the ignition switch on the steering column. This is on my open top CJ. Even though the switch is tucked up fairly well, the connections aren't sealed, so it is subject to moisture and dirt and dust in an open top CJ. That dust got into the connectors, and over time the terminals burnt and melted the connectors. I had to replace the switch, replace the plastic connectors, and splice on new terminals. I think it's less likely to be an issue in a normal closed vehicle like a Comanche, but still worth taking a look at as part of your troubleshooting. Link to comment Share on other sites More sharing options...
JYau Posted November 30, 2023 Share Posted November 30, 2023 To your #1 item, I had a very similar problem. For me it turned out to be corroded contacts on the starter relay. Whenever it got cold it wouldn't even click or start over, I also thought it was the battery but mine was fairly new and tested good. I cleaned the contacts and it's been working since, even in the cold. Link to comment Share on other sites More sharing options...
Tex06 Posted December 23, 2023 Author Share Posted December 23, 2023 Update on the truck. 1) fuel pump still doesn't prime/kick on when it's below about 65F for the first start. More on that later. 2) Battery load tested good. Starter was burned up (intermittent internal connection.... likely from cranking on it trying to start). Replaced and turns over fine now. The fuel pump thing really has my scratching my head. If it's below about 65F and the truck has sat all night, the fuel pump won't prime and truck won't start. If I turn the key on and let it sit on for 30 seconds or crank it *then turn it off and walk away for 15-20 minutes* it will start if I try again. Once it's started, I don't have any issues throughout the day, even if it sits for 6+ hours. I've replicated this 3x this week and it's got me stumped. I've bypassed the fuel pump resistor, swapped the relay for a known good one, battery terminals and cables are in great shape (Mean Lemons 0GA installed 3 years ago). The only thing for sure is cold weather means no fuel pump in the morning. Link to comment Share on other sites More sharing options...
Tex06 Posted December 23, 2023 Author Share Posted December 23, 2023 On 11/29/2023 at 5:04 AM, JeepSchmidt O'Guinness said: Does the fuel pump share the ground behind the passenger tail light housing? I'm not sure, but in the AM I might pull the taillight and clean (again) to see if that changes anything. Link to comment Share on other sites More sharing options...
watchamakalit Posted December 23, 2023 Share Posted December 23, 2023 3 hours ago, Tex06 said: I'm not sure, but in the AM I might pull the taillight and clean (again) to see if that changes anything. I'm pretty sure the tailight ground is the fuel pump ground. Have you tried testing power to the fuel pump on those days it won't prime? That could narrow it down to an electric problem up stream of the pump or a problem with the pump its self. Being temp dependent would make me think its the pump. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 23, 2023 Share Posted December 23, 2023 On 11/29/2023 at 4:04 AM, JeepSchmidt O'Guinness said: Does the fuel pump share the ground behind the passenger tail light housing? CRUISER'S MOSTLY RENIX TIPS IMPROVING THE FUEL PUMP GROUND JANUARY 3, 2016 CRUISER54 60 COMMENTS EDIT The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, and behind the driver’s taillamp on an MJ. Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture. Locate the black wire on the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire. Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.Solder the connection. Tape it up and reinstall the split loom covering. At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces. Link to comment Share on other sites More sharing options...
Tex06 Posted December 23, 2023 Author Share Posted December 23, 2023 9 minutes ago, cruiser54 said: CRUISER'S MOSTLY RENIX TIPS IMPROVING THE FUEL PUMP GROUND JANUARY 3, 2016 CRUISER54 60 COMMENTS EDIT The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, and behind the driver’s taillamp on an MJ. Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture. Locate the black wire on the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire. Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.Solder the connection. Tape it up and reinstall the split loom covering. At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces. Yup, did this a few years ago. Guess I'll check that new ground and see how she's holding up. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 23, 2023 Share Posted December 23, 2023 Yeah, and you can check that side's socket at the same time. Link to comment Share on other sites More sharing options...
Tex06 Posted December 23, 2023 Author Share Posted December 23, 2023 3 hours ago, watchamakalit said: I'm pretty sure the tailight ground is the fuel pump ground. Have you tried testing power to the fuel pump on those days it won't prime? That could narrow it down to an electric problem up stream of the pump or a problem with the pump its self. Being temp dependent would make me think its the pump. No, not yet. It's cold and wet here and I hate working on cold and wet ground 😅 I'm either parked in the street or on my grass. I installed a Bosch fuel pump back in 2016 so I didn't really think it could be the pump, especially since when it is running it keeps up fine. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 23, 2023 Share Posted December 23, 2023 ASSumptions can kick your @$$ when diagnosing these kind of issues. Link to comment Share on other sites More sharing options...
Tex06 Posted December 23, 2023 Author Share Posted December 23, 2023 1 minute ago, cruiser54 said: ASSumptions can kick your @$$ when diagnosing these kind of issues. Oh well aware. Intermittent electrical are my least favorite kind of problems. And with this Jeep nothing is ever easy to troubleshoot..... burnt connectors, cold solder joints, new sensors that are doa.... On the flip side, I don't complain about any of my GM products anymore. Between the Comanche and my diesel VW I've got enough shoddy workmanship and dumb engineering that any other brands seem great 😂 Link to comment Share on other sites More sharing options...
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