Ford F150 won't start if trailer plug is connected

[TheWhitesInCO]

We just picked up our new-to-us 2670 MK on Monday in Tulsa (giving a shout out to Camperland of OK who were great to work with and worth the 10+ hour drive each way). While driving home, we stopped to get gas (many times) and our 2012 Ford F150 would not start up after filling up. My husband checked under the hood and then unplugged the wire harness to the trailer and it started right up. He then plugged it back in and we were on our way. This happened every time we turned the truck off. Any suggestions as to what the issue might be?

I know, I know, it is a Ford, but he loves his truck (and I love my Mustang convertible so there is no going back).

 

[FT4NOW]

Never heard of that, wonder if it's a short somewhere? I would see if you can plug a different trailer into the truck and try to start it and see what happens. That will at least isolate the problem to the truck or the trailer.

Sent from my SM-G950U using Tapatalk

 

[traveldawg]

Maybe the folks over on the Ford Truck Enthusiasts can help.... https://www.ford-trucks.com/

 

[MidwestCamper]

We just picked up our new-to-us 2670 MK on Monday in Tulsa (giving a shout out to Camperland of OK who were great to work with and worth the 10+ hour drive each way). While driving home, we stopped to get gas (many times) and our 2012 Ford F150 would not start up after filling up. My husband checked under the hood and then unplugged the wire harness to the trailer and it started right up. He then plugged it back in and we were on our way. This happened every time we turned the truck off. Any suggestions as to what the issue might be?

I know, I know, it is a Ford, but he loves his truck (and I love my Mustang convertible so there is no going back).

Looks like a software bug. What does it do when you start it unplugged then once its running, plug the trailer back in?

 

[jkwilson]

My gut would tell me to look at the brake controller. Wouldn't seem like anything else could affect engine cranking.

 

[TheWhitesInCO]

Jim, it runs like normal when the trailer is plugged in once it is started. There is no hesitation or any kind of “hiccup” and the brake controller works normally as well.

We will check out Ford Enthusiasts and I’ll have him look at the brake controller. I’ll see if we have a friend with a trailer he can connect to. We’ve only had the truck since October so this is the first time we’ve had a trailer connected to it.

 

[Txfivver]

My first thought is hold old are the truck and trailer batteries, are they marginal at all? With the trailer plugged in the charge wire goes hot when you turn the key to start. If the trailer battery is going bad or has an internal short it will pull power from the trucks starting battery. That may be enough of a load where there's not enough left to start the truck. Unhook the trailer and the extra load is gone and it will start. If it starts fine with a different trailer then I'd get the trailer battery/batteries tested. Most all late model Ford trucks come with at least a 150 amp alternator anymore which will run the truck fine even with a weak battery. Just a thought.

 

[RMAD]

I have the same problem with my F140 5.0 2018 when pulling my trailer. If I turn off the engine after driving for a couple of hours, the truck will not start. I was on another forum and their were many folks who had the same problem and in most cases they seemed to conclude that the starter was overheating. Allowing the engine to cool a bit then allowed them to start the engine. I am going to discuss this with my mechanic, and possibly the local Ford dealer tomorrow. Some replaced their original equipment starter with a higher performance starter, which in most cases fixed the problem. It would seem that the engine, under the heavier load is generating a bit more heat. Maybe.