2012 Jeep Liberty - Starting Issues only when towing Uhaul Trailer

jeep12libertyjeep12liberty Member Posts: 3
edited November 2017 in Jeep
I am having an intermittent starting issue with my 2012 Jeep Liberty Sport (4WD/6 cyl) that ONLY occurs when towing a Uhaul trailer (the 6x12 enclosed cargo variety). I tow a boat just fine.

When starting car warm (like after getting gas or stopping for a few mins) it would attempt to start but is very rough sounding, but not turn over, lots of lights on dash. It always eventually turns on (after repeated starting attempts, sometimes after waiting a few minutes).

It seems to help somewhat (but not always) if I pull the trailer adapter out prior to shutting the engine down, then plug it back in after it starts.

Strangely, this problem temporarily resolved itself (for about a year, with many towing trips) after I replaced the factory 4pin adapter with an aftermarket. It has now recurred with the aftermarket adapter (and even another new aftermarket adapter).

Please HELP!


  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
    Ah, elusive electrical gremilns. Sure sounds like it has something to do with the electrical hookup for the Uhaul (at least on the surface), so start there. What, if anything can you think of that's different about the connection to the Uhaul and the boat trailer?

    I'm not sure why it would cause a starting issue, but shorts/bad connections can have some really odd consequences, and you have to start somewhere
  • jeep12libertyjeep12liberty Member Posts: 3
    The Uhaul and boat trailer both have the same flat 4 connector (3 female, 1 male) connector. I will review that in more detail - I have it hooked up right now. Any other ideas in the mean time?
  • 0patience0patience Oregon CoastMember Posts: 1,712
    I'm in agreement with @PF_Flyer

    When ever dealing with electrical problems, always look at the common denominator or the thing that causes the problem, if it isn't part of the vehicle.
    The fact that your boat trailer doesn't cause this problem, but the Uhaul trailer does, tells us that it probably has a direct short in the system.

    Next time this happens, disconnect the trailer plug and if it immediately cures the symptoms, then you know the trailer is the problem.

    Is the Uhaul trailer yours?
    If it is, then you need to double check the wiring on it. If it isn't, then inspect the wiring carefully. As was said, bad wiring can do some really weird things.

    Do you know who wired up the trailer? Could be that the wiring is wrong or a bulb is shorting or a host of many other things.
  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
    And I'll agree with @0patience :) Hook up the trailer, duplicate the issue and unhook the trailer to see what happens.

    The trouble spot sure seems to be the Uhaul trailer wiring. Since you say it's the same connector, and assuming the connector at least appears to be in normal condition ( no obvious corrosion or broken/bent bits), then it seems likely that something in the wiring is the culprit. Maybe a short, maybe a bad connection or wrongly wired connection. But start at the connector and work your way all the way to the end of the circuit. Heck, it could even be a screwy tail light or socket,
  • jeep12libertyjeep12liberty Member Posts: 3
    When the issue is occuring, again this is intermittant, unhooking the wiring for the trailer sometimes helps, but sometimes it does not. Meaning the starting issue will occur even with the trailer disconnected electrically. I have even pulled into a parking spot with the car in park, unplugged the trailer wiring, then turned the car off, had lunch or whatever, attempted to start the car up (unplugged from trialer still) and it will have the starting issue. It never does it once the trailer is unhooked from the hitch though. Its almost like it senses the trailer is there and to cause an issue!
  • thecardoc3thecardoc3 Member Posts: 5,557
    The right way to analyze this is to first ignore the trailer's presence. While I have considered that there might be a plausible association it is irrelevant to the diagnostics. That being said, it is far more likely that is a misdirection and has nothing directly to do with the hard start/no start. The information about the trailer only serves to help set the conditions to get the problem to occur to allow for proper testing to be performed. Beyond that it is a red herring.

    When this is hard to start, diagnose it the same as any other no-start. First, find out what is missing, ignition, fuel injector pulse, fuel pressure, or a combination of them. Pull data from the PCM to see what the critical sensor inputs for starting the engine are reporting. Then once you know what is missing, or incorrect work to prove why.
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