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Mopar Certified
Mopar Certified, Technician
Category: Chrysler
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Experience:  24 Year Factory Trained and Certified
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2007 Chrysler Pacifica: fuel sending..gas tank..fuel pump..fuel tank

Resolved Question:

Having a fuel sending / gas tank prblem problem on my 2007 Chrysler Pacifica. After searching on-line answers, it could possibly be the fuel pump, or the equalizer pump. How do you test to find out which pump is the problem, or if it needs a "sensor" on the one side of the fuel tank?
Submitted: 6 years ago.
Category: Chrysler
Expert:  Mopar Certified replied 6 years ago.

Welcome to Just Answer Chrysler my name is Mark.

 

What sort of problem are you having?

Customer: replied 6 years ago.

The fuel gage suddenly became inacurrate, I can't get it to take anymore than 5 or 6 gallons of fuel and it acts "full" but gage reads 1/2 or 3/4, then drive for 20 mile and goes to "low fuel" 0 miles to empty, then I try to add gas and it will still only accept 5 or 6 gallons. I read on the site here about someone else with the same problem and there is a "weak" fuel pump, OR the equalizer pump" is bad, or there is a problem with the module, and the fuel is not gettting from the "full" side of the tank to the "sending" side. I was wondering how it is determined which problem it is? Is this detectable with the diagnostic computer at the service garage? I don't want to have them fix the wrong part in order to get to the "real" problem.

Thanks.

Expert:  Mopar Certified replied 6 years ago.

An accurate diagnosis of this fuel system will require the use of a GOOD scan tool. Preferably dealer quality that has the ability to read the fuel levels of both sides. The following is a procedure to follow....

 

With a properly working system, fuel is continually transferred from the passenger side to the driver side of the fuel tank while the fuel pump is running. Using an appropriate scan tool, the fuel level in each tank side can be monitored. NOTE: PRIMARY FUEL LEV is the driver side. SECONDARY FUEL LEV is the passenger side. Start the engine and let idle while monitoring the fuel levels. The PRIMARY FUEL LEV should increase while the SECONDARY FUEL LEV decreases. Approximately one gallon of fuel should transfer in about 60-90 seconds. If after a few minutes the PRIMARY side does not increase, or if the SECONDARY side increases instead of decreasing, then the fuel is not transferring correctly. NOTE: The PRIMARY side holds approximately 14.8 gallons of fuel. When starting this test, the PRIMARY side should be less than 13 gallons to allow room for fuel to transfer into. If the vehicle has been parked with the engine off for a sufficient length of time, fuel will naturally siphon from the Primary side to the Secondary side, up to approximately 9 gallons remaining in the Primary side. The vehicle can also be driven in a couple of tight counterclockwise circles to spill fuel over from the Primary side to the Secondary side. If the SECONDARY FUEL LEV already reads 0 gals, then the fuel is transferring properly to the Primary side, since it has drained that side. Simply checking the fuel levels on each side of the tank when the fuel pump is not running is not always sufficient in determining whether the system is working properly, due to the natural siphoning effect with the pump off. A lack of fuel transfer can be caused by several situations, including insufficient voltage to the fuel pump (should be at least 12.5 volts), a worn fuel pump, or a leak within the pump module (either the primary or secondary module). An issue with the primary module is usually the cause for a lack of fuel transfer, since a sufficient flow of fuel through the secondary module venture is required to create the fuel transfer, and the primary module provides the fuel flow. If a lack of transfer is determined, first check the voltage at the fuel tank wire harness. If the voltage is at least 12 12.5 volts, then a primary module change is likely required.

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