Starting Issues after Flat Towing behind RV

[WhippetTaxi]

I have a 2020 Gladiator Rubicon (gas) that I flat tow behind a Class A motorhome using the Ready Brute Elite tow arm package. I like the simplicity of the surge braking system with the mechanical cable that attaches to the backside of the brake pedal. I have been experiencing an ongoing intermittent issue where I arrive at my destination, unhook the tow arms, electrical cord, safety chains, etc. and try to start the Jeep and it acts as if the battery is dead. Today we arrived home from a short 90 minute trip and when I pushed the brake pedal and the start button, I got only a very faint clicking sound and it would not start.

So, I unboxed my new NOCO Boost unit that I thought might be able to jump start the Gladiator and it had absolutely no effect. It has a special mode for low voltage (<2V) conditions, but the NOCO didn't indicate that this was the case and still no success.

Just for grins, I tried the remote start button on the key fob and the Gladiator fired right up. So, I don't think battery drain is the issue.

I originally thought that there was some drain on the battery while towing, so I installed a little battery maintainer device that gets power off the 6 point connecting cord that powers the brake and running lights and then connects to the battery. This device made no difference.

Since the issue seems to happen when pressing the brake and then pushing the start button, I think something in that circuit may be causing the problem. I do notice that the brake pedal has a different, firmer feel when I unhook the Jeep and try to start it after a trip. So, maybe the vacuum braking system is needing time to relax after towing. I have found on previous trips that just waiting a while seemed to fix the failure to start issue. There are times, though, that you arrive at a campsite or other destination and don't have the luxury of waiting around for things to correct themselves.

I have had the dealer check the battery system and they found no issues. The Gladiator is not throwing any codes that they can pick up with their scanner and it's hard to find a service advisor these days who has the critical thinking skills to figure this out unless the computer shows an issue and recommended parts to replace. I really don't want to drive the motorhome to a dealership with the Gladiator attached since most service drives are so congested as it is.

Any recommendations on specific things to check or double check (battery, braking system, etc.) would be appreciated.

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[SamJ3]

Hi Scott,

No worries - I think I know the 'problem'.

I have a 2022 Jeep Gladiator Sport that I flat tow behind the RV. We installed a built-in cable actuated brake controller (BrakeBuddy Stealth) - very happy overall with the set up.

The Jeep has a vacuum assist for power brakes, so once you've articulated the brake pedal a few times, the vacuum chamber will deplete of any reserve vacuum, resulting in a significant increase in the necessary pressure to actuate your brakes. To counter this loss of assist, the BrakeBuddy kit includes a vacuum booster pump which is powered up when activating with the tow brake system.

If your braking system either 1) does not have an auxiliary vacuum pump, or 2) the pump does not produce enough 'negative pressure' (i.e., vacuum) to charge the brake booster. After a few stops, the brake pedal becomes 'hard' to press - because power assist is absent, and it's fully unassisted.

The vehicle is designed to only start if the brake pedal is depressed, so if the pedal is hard, you might not have depressed the pedal far enough. Next time this occurs, try pressing harder on the pedal, until you are sure it has traveled an inch or more. Also, once it does start in this scenario, you may notice it will take a few seconds to recover the boost because it take a bit of time for the Jeep's vacuum pump to recover the booster.

(Related to all of this . . . if your vehicle sits unused for 'too long', the vacuum can also bleed off, leading to a similar effect. Same solution here: just press a little harder, then wait a few seconds for the booster to recover after it starts.)

By the way, if you do not have an auxiliary vacuum booster pump for towing, I suggest adding that (or rigging up a diode protected circuit for manually powering the factory vacuum booster pump).

 

[WhippetTaxi]

Interesting. This is helpful and I'll try pressing harder on the pedal and/or investigating the Brake Buddy solution. I really appreciate the response and the info!

 

[Alan_Hepburn]

By the way, if you do not have an auxiliary vacuum booster pump for towing, I suggest adding that (or rigging up a diode protected circuit for manually powering the factory vacuum booster pump).

Good explanation of the issue, and NSA (the folks that make the Ready Brute tow bars) have a vacuum pump that they will sell you, but they also say it's not needed. No matter how hard you have to push on the brake pedal when you're towing the Jeep you've got the full weight of the Jeep pushing on the pedal so it works fine.

We see the same issue with my wife's 2022 JLU, even if it's just sitting in the driveway overnight - pressing the brake pedal is like pressing on a boulder: no apparent movement, and the Jeep won't start. But just adding some more pressure to the brake pedal "fixes" it. I've only experienced it a couple of times on my 2020 JT.

We've towed with the Ready Brute Elite on our old 2017 JKU, my 2020 JT, and my wife's 2022 JLU and all of them work great!

 

[WhippetTaxi]

Thanks for the response and the info. Yes, I love the Ready Brute set-up and have used it previously on my 2004 Wrangler and with three different motorhomes. And the no start symptoms are not every time we tow, but mostly with longer trips. Now that I've discovered the remote start as a possible workaround and the suggestion to keep pushing on the brake when using the start button, this helps.

 

[SamJ3]

Good explanation of the issue, and NSA (the folks that make the Ready Brute tow bars) have a vacuum pump that they will sell you, but they also say it's not needed. No matter how hard you have to push on the brake pedal when you're towing the Jeep you've got the full weight of the Jeep pushing on the pedal so it works fine.

We see the same issue with my wife's 2022 JLU, even if it's just sitting in the driveway overnight - pressing the brake pedal is like pressing on a boulder: no apparent movement, and the Jeep won't start. But just adding some more pressure to the brake pedal "fixes" it. I've only experienced it a couple of times on my 2020 JT.

We've towed with the Ready Brute Elite on our old 2017 JKU, my 2020 JT, and my wife's 2022 JLU and all of them work great!

Good to know about the optionality of the booster. Makes sense that you have the weight of the vehicle to assist - though I'd guess that using the boost would put less stress on the RB cables and Jeep pedal lever. I can definitely see the appeal of the simplicity of that system.

I noticed the 'problem' (loss of boost) if the Gladiator sat unused for more than about 3-4 days. At first I thought I did something to cause a leak when I installed the booster, but when I researched the issue I discovered this was not uncommon problem in Wranglers.

 

[Kevin_D]

The JT doesn't use manifold vacuum for the brake booster: as mentioned above, it uses a small vacuum pump, which is mounted on the front of the motor.
This vacuum pump doesn't run unless the motor is running. You could change the wiring so that it runs when the ignition is switched ON: that way, all you would need do is turn the ignition ON (run), wait a few seconds for the pump to build up vacuum, then start as normal. This would also save you from having to buy an auxiliary vacuum pump just for starting.
I use a Brake Buddy portable braking system, and it will purposely activate the brakes several times during initialization to bleed off the vacuum in the booster. Usually a good shove on the brakes is all it takes to get it to start after towing.

Kevin

 

[Kevin_D]

IIRC, you’re not supposed to tow the JT like that. Either flat tow, or all wheels off the ground.

Kevin

 

[JTpoor]

IIRC, you’re not supposed to tow the JT like that. Either flat tow, or all wheels off the ground.

Kevin

Yeah...after posting that I looked at some RV forums and saw that same answer, so I went back and deleted my original post bc it really didn't add anything to OP's original thread. Thanks for the answer though.

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