A funny thing happened Behind the Rocks

BillArnett

New member
We ran the Behind the Rocks trail in Moab today. All (omitting White Knuckle) went well until the very end when we stopped at the top of the very first (unnamed) obstacle to see if we could go down it. We stopped at the top to check it out. Decided against it in favor of the easy way out. But when I got back in the Jeep it wouldn’t start!

We had been bouncing down the modestly easy stuff prior to the obstacle. And we stopped when the Jeep pointing downhill at a pitch angle of maybe 10 degrees. Nothing I haven’t done 100 times before. I had noticed a few minutes before that the gas gauge was reading 1/4 when it should have been more like 1/2. And now at the stop it was reading Empty. WTF?? Pressing the start button repeatedly turned the engine over a couple of revolutions then nothing. At the place I stopped I was unable to roll either direction because of a couple of medium rocks. Stuck!

I guessed that it had something to do with the angle I was parked at. So I broke out the winch (for the first time!) and pulled the Jeep forward enough to get it level again. (Which wasn’t easy given the dearth of winch points available.) The gas gauge then read 3/8 and it started right up. We drove back to Moab without further incident.

Anyone have any idea what was going on?
 

NFRs2000NYC

Member
How much gas was actually in the vehicle? NEver had it in my Jeep, but did have it on my s2000, where I had like 1/8th of a tank and parked in my friend's steep driveway. That night I couldn't start it again when I was leaving, until I rolled down to the street (level ground) so the pump has some gas to grab. In theory, with a low amount of gas and just the right angle, you can make it to where the pump pickup isn't touching any gas.
 

BillArnett

New member
I had at least 3/8 of a tank, probably more like 1/2. My theory is this: The fuel pump pulls from a point near the rear of the tank. Even when pointed down at an angle sufficiently steep to uncover the pickup point there’s still a little fuel left in the lines and that’s enough to start the engine. If the vehicle then returns to level soon enough there’s no problem. But I had been going downhill fairly steeply for several minutes. Maybe I used up the fuel in the lines.

I’ve been unable to find anything on the Net that shows the exact configuration of the JL fuel tank and fuel pump. But a simple calculation given the approximate dimensions of the tank shows that with 1/4 tank of gas and a 10 degree slope the rear end of the tank will be dry.
 

So, there are some things to point out that might make this experience more likely to happen on the JLU than the JKU.

First, the gas tank went from 23.5 gallons to 21.5 gallons while the gauge stayed calibrated for a tank of about 20 gallons. As such, there is less reserve gas to make sure the gas pump is properly fed.

Second is that the JLU’s gas gauge (at least in my limited experience of 2 months) is less linear than the JKU. This non-linear reading is going to mess with your perception of how much gas is in the tank.

Solution: make sure you wheel with more gas in the tank than you think you need. There is a reason why there are so many ways to add fuel storage systems to the vehicle.


Sent from my iPhone using JL Wrangler Jeep Forum mobile app
 

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