Early low fuel warning light (comes on around 5/8 full tank)

[JB_2010GT500]

I'm revisiting this topic which I posted about last year hoping to get some more eyes on this. My trip computer is calculating my average mpg to be 6.3 mpg:

In this example, my trip computer is telling me I have 46 miles til I run out of gas. Notice the fuel gauge is around 5/8 FULL.

So, to get rid of the annoying low fuel light, I gas up. Car takes 5.57 gallons of gas.

Now on a full tank, I supposedly can drive only 101 miles to the next fill-up.

Now, after many, many fill-ups, I have calculated my average mpg to be approximately double what the trip computer is calculating for an average. I did the KAM reset but this only seemed to be a bandaid fix as eventually my mpg calculation drifted back down into the 6 mpg range after some length of time.

My car is running an aftermarket KB blower, ID1000s, stock pumps with KB BAP. I've used two different tuners and have yet to come up with a solution from either one.

Any help would be greatly appreciated.

Thanks,
John


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[klb2sweet]

I have an 09 with a VMP Gen II and mine comes on around 1/4 to 1/2 and after a couple times of it doing it I just ignore it as I use my trip gauge to let me know when to gas.

 

[JB_2010GT500]

I am wondering if a tune could adjust the mpg calculation somehow. I'm guessing it has to do with the flow rate of the injectors being different than stock, or the fuel pump booster. Maybe it's possible to adjust the flow rate assumption for mpg calc?

For my application, I wonder if the tune could adjust the mpg calculation to be multiplied by 2 (since I found my actual mpg to be about double the trip computer mpg). But I am not a tuner so neither of these options may be possible.


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[fullboogie]

Your crossover tube inside your tank has become disconnected one one side. You're only using one half of the gas in your tank - it's not being pumped from passenger side to driver's side. You, or somebody else, must have changed the pumps at some point or taken the pump hat out. It's very easy to have the crossover tube disconnect. I'be been through this and can promise you this is the problem.

 

[JB_2010GT500]

Ok. I had a shop change the differential and I know they dropped the gas tank as part of the job. I think that's the only time the fuel tank was touched. I will investigate this. Thank you fullboogie.


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[fullboogie]

Spent 45 minutes trying to find a picture of the crossover line and believe it or not, Google doesn't have a single one. So I climbed up into my hot ass garage attic, brought this down, and took a pic for you.

As you can see, one end connects to the booster pump on the passenger side, the other end connects to the main fuel hat. If either end is disconnected you will only use fuel from the driver's side, giving you the symptoms you're having. You owe me dude.

EDIT: looks like this crappy website is at it again. The picture hosted on Imgur is not showing except in Chrome. I'll see if I can post a Google Drive link.

Try this: https://drive.google.com/open?id=0B_0vnMYGVCTyZUJNVGNIOUpjSVU

 

[JB_2010GT500]

Thanks so much for posting. I will try to check this out over the weekend if possible. I definitely owe you a six pack man . Thank you again fulliboogie.


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[fullboogie]

I want my six pack!

 

[jazz]

I have similar problem as you op. I just installed fore fuel hat and its the not reading fuel accurately. I think i may have disconnected the crossover line because i pulled it out too much and now there is lot more slack.
Now how can i connect the line again? Do i have to drop the tank or it can be done another way?

 

[JB_2010GT500]

I was planning on looking into it today. I need to jack the car up and take a look. Otherwise, I'm wondering if it can be accessed from under the rear seat.


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[SCGallo2]

I was planning on looking into it today. I need to jack the car up and take a look. Otherwise, I'm wondering if it can be accessed from under the rear seat.


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The crossover tube connection on the fuel pump, driver's side, can be accessed from under the rear seat.

 

[jazz]

Its the passenger side that may be disconnected, wondering the samething if it can be accessed from the passenger side underneath the rear seat... i ll check tonight

 

[fullboogie]

OP - you ever pull your hats and see what's going on with that crossover tube?

 

[JB_2010GT500]

It's in process now. My mechanic should have an answer by the end of the day.


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[JB_2010GT500]

He just came back... says the crossover is hooked up correctly on both sides. I was really hoping he'd find it disconnected on one end.


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[fullboogie]

You gotta tug on those ends to make sure they're hooked up. Just doing a visual won't cut it. Also have him pull the entire line out of the tank and inspect for cuts or anything else that can cause a leak.

I really don't see any other explanation because you're using only 1/2 of your tank, and your gas gauge is showing the same thing. Fuel is not going from the passenger side to the driver's side of the tank.

 

[JB_2010GT500]

He tugged on both ends.


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[JB_2010GT500]

FYI I drove it down to 1/8 tank (thing was sitting at 0 miles to empty). Filled it up and the car took 13.8 gallons. And I know it's a 16 gallon tank. So I think the fuel gauge is correct. Could it be the sending unit?


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[HillbillyHotRod]

Something weird like this happened in the Edge today. Had run it down to about 1/4. Filled it up and it only read 1/2. So drove it home and it started coming back up and withing 15 mile it was reading full. Weird.

 

[Imatk]

I'm sure these cars don't have something as primitive as this... but this happens/happened on my '91 Fox because of an "anti-slosh" module.

Although with that the actual gas gauge had an incorrect reading.

Wondering if it is something electrical.

Did it start doing this after the diff swap? Was there something th at changed just before this started happening?