I just picked up a 04 pac with 65k miles that is in great shape. My wife needed something that got better mpg than her V10 Excursion. The first day that she had it the guage went from 1/2 full to empty while she was sitting in the driveway reading her manual and learning what all the buttons do. She drove right to the gas station and it only held about 5 gallons and the guage went to 3/4. Today she was headed to town and it died on her, like it ran out of gas. The guage said it was empty. I took a 5 gal can to her and poured that in. The guage went to 3/4 and I told her to go fill it up the rest of the way. It only took about 4 more gallons. So the car ran out of gas and died but it only took around 9 gallons to fill up a 23 gal tank.
I have been reading about all the guage problems but what I'm looking for is someone with the EXACT same problem and what it took to fix it. I'd like to do the repair myself, as I have access to a lift and have all the tools to make the repair. I dont like getting bent over at the dealer. I have Ford and Dodge dealer friends but none at Chrysler.
Thanks for any help, my wife is bummed that we may have bought a turd.

 

Dealer to update the software in the Body computer.



THIS BULLETIN IS BEING PROVIDED IN ADVANCE. THE SOFTWARE IN THE
DRBIIIĀ® MUST BE OPERATING WITH VERSION 59.0 OR HIGHER AVAILABLE
ON THE DRBIIIĀ® UPDATE CD ON JANUARY 19, 2004.
SUBJECT:
Fluctuating Fuel Gauge Operation
OVERVIEW:
This bulletin involves updating the fuel gauge parameters in the Body Control Module (BCM).
MODELS:
2004 (CS) Pacifica
NOTE: This bulletin applies to vehicles built on or before December
10, 2003 (MDH 1211XX).
SYMPTOM/CONDITION:
Vehicle operator may describe the fuel gauge drops to empty and then
returns to the correct reading.

 

So, you think it just needs a software update? How much should I expect to pay for this at the dealer? Do you think the senders are OK? How does the fuel get from one tank to the other? Which tank is the "main tank"?
Again, I appreciate the help.

 

It has two fuel pumps. One pump fuel from one side to the other. BCM calculates an est as to how much fuel is left. LOTS of vehicles use this type of fuel system.

 

Explain to me how this dual tank system works. Assuming the car is empty, and you are filling it up, how does it equalize between the two tanks as you are filling it? Then as you are burning the gas does it fill from one tank to the other or does it empty one and then start drawing from the other. Assuming there are two pumps, are they identical, or is one more of a transfer pump and the other a higher pressure pump to feed the injector rail.
Bare with me on the questions, I just like to know how things work.

 

It has ONE gas tank & TWO fuel pumps.

 

Yes it has one tank and two pumps. Tank is called a saddle type tank. If the car is an AWD,the tank stradles the rear driveshaft. FWD just uses the same tank. One pump is just a transfer pump.

 

OK it has one tank then. When I looked under it, it looked like 2 separate tanks. You have to understand that this is a 4x4 family and I'm not used to having to put a vehicle on a lift to look under it.
My wife took it in yesterday and had the software update $100 done. I let you know if it fixes it.

 

u wanted to know how the saddle tanks works here is the info


OPERATION The way the pump works is as follows, fuel enters the reservoir of the driver side module. The fuel pump pumps the fuel through the filter to the passenger side module through a supply line inside tank. The pressure regulator inside the passenger side module and regulates the pressure at 58 psi. All unused fuel that is not sent to the engine is fed through a venturi at the bottom of the passenger side module. This creates a low pressure siphoning effect and draws fuel from the passenger side of the tank and transfers it to the drivers side tank via siphon hose inside the tank. While the vehicle is running the fuel in the passenger side of tank is continuously transferred to the drivers side. Fuel will continue to fill the divers side tank till it reaches the bridge section and then start to spill over to the passenger side. As stated above we have two fuel level senders, the reading of these senders are averaged out to give us the fuel gauge reading. When we are diagnosing a sender concern the passenger side reading should never be higher than the Drivers side reading. It is possible, depending on fuel level and driving habit before diagnosing, to spill fuel over to the passenger side that might indeed show a lower resistance value than the driver side. The tech need to order the correct part when replacing, the senders, modules, and tank are all able to be replaced individually.

 

The reflash did not solve the problem, when the guage got to about 1/2 tank it suddenlydropped to empty. Based on Chrysler techs explanation it seems to me the module may be the problem. The pump is obviously working or the car wouldnt run properly. It seems that the fuel is not being transfered between the two sides of the tank.
Chrysler tech, have you seen these module/regulaters cause these types of problem? I would like to replace the correct part myself and not have the dealer just throw parts at it at my expense.
Thanks.