A funny thing happened Behind the Rocks

[BillArnett]

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?

Sponsored

 

[multicam]

Seems odd to me. If you really had 3/8 of a tank left that would be 6.9 gallons (of 18.5). Generally I take the fuel guage with a grain of salt, so let’s say you had anywhere from 5-9 gallons left. Even with 5 gallons I wouldn’t think a ten degree incline would be enough to starve the fuel pump.

It probably was an issue that simple though. Occam’s razor and all that... it was probably just starved of fuel on the angled surface. I wouldn’t worry unless it happens again, and with more fuel in the tank. You could test it but I’ve heard it’s not good for fuel pumps to dry-crank ‘em.

 

[BillArnett]

Anyone know what the dimensions of the JLU gas tank are? I did a little math and IF the tank was a rectangular solid 48 inches long x 12 inches wide then it would be only about 8 inches tall. And if the fuel tap is at the back end it would be dry at a 10 degree angle with 1/2 a tank. Does that sound right?

 

[tjeeper]

Have you looked at your gas tank skid?

Happened to me once in my JK. I had a dent in the front of it. We stopped leaning downhill, and it wouldn't start up. It is my understanding in the JK there are two pickup tubes, one in, one in back. The back one must have been sucking air as the Jeep was leaning forward. The front one was probably also sucking air because the dent pushed it up off the bottom of the tank.

A friend had a petcock in the bottom of his tank, we emptied enough out of his Jeep until mine would start. When I got the JK on level ground the gauge read 5 gallons left in the tank. When I got home I dropped the tank and pounded the skid straight. Worked fine after that.

 

[Deleted member 29417]

I had a similar thing happen but just driving on an extremely steep hill up on a mountain road. My range showed "30" miles left (I know that's pretty low already but should have been enough to get to the top). on the way back down to fill up the range dropped to "11" and dropping fast. I ended up with "low fuel" message when I reached the bottom. Pretty weird and scary stuff.

I know I should have probably filled up before going up. It was still pretty odd though.

 

[BillArnett]

Have you looked at your gas tank skid?

Happened to me once in my JK. I had a dent in the front of it. We stopped leaning downhill, and it wouldn't start up. It is my understanding in the JK there are two pickup tubes, one in, one in back. The back one must have been sucking air as the Jeep was leaning forward. The front one was probably also sucking air because the dent pushed it up off the bottom of the tank.

A friend had a petcock in the bottom of his tank, we emptied enough out of his Jeep until mine would start. When I got the JK on level ground the gauge read 5 gallons left in the tank. When I got home I dropped the tank and pounded the skid straight. Worked fine after that.

My gas tank skid is pristine (except for a couple scratches No way the sensor is dented.

 

[BillArnett]

I had a similar thing happen but just driving on an extremely steep hill up on a mountain road. My range showed "30" miles left (I know that's pretty low already but should have been enough to get to the top). on the way back down to fill up the range dropped to "11" and dropping fast. I ended up with "low fuel" message when I reached the bottom. Pretty weird and scary stuff.

I know I should have probably filled up before going up. It was still pretty odd though.

Yeah, I’m sure the sensor is affected by pitch. But it seems to me that the car should run if there’s gas in the tank despite what the sensor says.

 

[BillArnett]

I asked my dealer about it yesterday. He said what I experienced is "normal".

 

[Zazoh]

I asked my dealer about it yesterday. He said what I experienced is "normal".

I’d say it’s a flaw that has been experienced by many, to the dealer that is normal?

There have been other posts in this group with similar stories. I’ve also experienced the huge fluctuations in miles before empty when going up hills for a sustained period.

 

[Stampede.Offroad]

Yeah, I’m sure the sensor is affected by pitch. But it seems to me that the car should run if there’s gas in the tank despite what the sensor says.

Sadly, one of the "features" of many modern electronic systems, is to prevent damage by disallowing the operator to do things when the sensor decides it shouldn't be done.

The default design has become to assume the operator is an idiot and save the manufacturer from liability.

 

[D60]

Sadly, one of the "features" of many modern electronic systems, is to prevent damage by disallowing the operator to do things when the sensor decides it shouldn't be done.

The default design has become to assume the operator is an idiot and save the manufacturer from liability.

Do we know this to be the case for a fact? ie if the gauge reads empty the vehicle won't even try to start?

I'm not challenging you, this is just good tech to know if true. I don't want a sending unit dictating if my engine runs. The presence or absence of fuel should dictate that, as God and physics intended. Unless these pumps have a special (inferior) design running 'em dry while cranking if you're truly out of fuel should not hurt them.

 

[BillArnett]

Sadly, one of the "features" of many modern electronic systems, is to prevent damage by disallowing the operator to do things when the sensor decides it shouldn't be done.

The default design has become to assume the operator is an idiot and save the manufacturer from liability.

I agree. Sounds just like the problem Boeing is having with the 737 Max 8.

 

[brazos]

I agree. Sounds just like the problem Boeing is having with the 737 Max 8.

I love my new Jeep. But it does many things which I do not want or need it to do.
The nanny state considers me to be a moron, when in fact the administrators of the nanny state are the clueless ones.
Bill Clinton once said “You cannot simultaneously love your country and hate your government”.
He was wrong then. He remains wrong now.
I do both.

 

[Ma$$iveDebtAche]

Am I the only one who thought of this when they saw this thread title?

Sponsored