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Dave Nova
Dave Nova, Cadillac Technician
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Experience:  ASE Master Certification. GM World Class Certification
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2004 CTS 3.6 L. Replaced fuel pump in tank.

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2004 CTS 3.6 L. Replaced fuel pump in tank. Now lose fuel at 25% level in tank and when tank level gets below 50% it getsreal erratic. Level goes from 50% to 0%. Been told that there is somekind of transfer system to get fuel from one side to other. What is going here?
Submitted: 3 years ago.
Category: Cadillac
Expert:  Dave Nova replied 3 years ago.
Hello and thank you for using JustAnswer. My name is XXXXX XXXXX I will do my best to help you with your Cadillac problem.

The problem you are experiencing is a bad fuel level sensor within the tank. This should have been part of the fuel pump assembly you replaced. My suggestion is to go back and replace the fuel level sensor.

There is also a bulletin out about reprogramming the PCM for false readings from the fuel gauge. I have included this bulletin below, but it does not match your symptoms exactly.

Bulletin No.: 08-08-49-001

Date: February 05, 2008

TECHNICAL

Subject:
Inaccurate Fuel Gage Readings, Fuel Gage Reads Empty when There is Fuel in Tank, Fuel Level Low Message in DIC, DTC P2066 Set (Reprogram ECM) Models:
2004-2006 Cadillac SRX
2004-2007 Cadillac CTS
2005-2007 Cadillac STS

with 2.8L or 3.6L Engine (VINS T, 7 - RPOs LP1, LY7)

Condition

Some customers may comment that the fuel gage reads empty when there is fuel in the tank. Also, the driver information center may display the "Fuel Level Low" message.

A scan tool may reveal DTC P2066 set in the ECM.

Cause

An issue with the ECM software has been identified that will cause the ECM to increment the fuel used incorrectly if the vehicle is driven for a number of short trips with frequent key cycles between refueling events.

Correction

If routine diagnosis using SI does not reveal any obvious cause, then reprogram the ECM with updated calibration files using the TIS2WEB Service Programming System (SPS) application.

Customer: replied 3 years ago.
The fuel tank in this car is "horseshoe" shaped and is molded arounded the drive shaft. There is some kind of system to get fuel from one side to the other. The fule pump we replaced is on one side of the tank. I have read something about a "transfer" system and fuel gage for the side of the tank that does not have the pump in it. I understand that the "tank empty at 25%" is because the transfer system from one side to the other is not working.
Expert:  Dave Nova replied 3 years ago.
Did some more research and there are some common problems with the fuel transfer system. They are outlined in the bulletin below.

Bulletin No.: 04-06-04-077A

Date: November 01, 2005

TECHNICAL

Subject:
No Start, Inaccurate Fuel Gauge (Replace Sender Fuel Feed (Transfer) Pipe and Inspect Primary Module Transfer (Jet) Pump) Models:
2004-2005 Cadillac CTS, CTS-V, SRX

Supercede:

This bulletin is being revised to add VIN Breakpoints for each model. Please discard Corporate Bulletin Number 04-06-04-077 (Section 06 - Engine/Propulsion System).

Built Prior to the VIN Breakpoints shown.

Condition

Some customers may comment on an inaccurate fuel level gauge reading. In a small number of cases, the vehicle ran out of fuel when the gauge still indicated 1/8 tank.

Cause

The cause of this condition may be insufficient fuel transfer from the left fuel reservoir to the right fuel reservoir. The poor fuel transfer may be the result of one or a combination of both of the following:

^ The sender fuel feed (transfer) pipe has two anti-siphon holes in the middle of the pipe which are too large.
^ A clogged/restricted transfer (jet) pump - part of the RH primary fuel tank module.

Diagnosis

Important: DO NOT replace the instrument panel cluster (IPC) or the engine control module (ECM) unless diagnosis has determined them to be at fault.

Follow published diagnostics for any stored diagnostic trouble codes (DTC) or use the diagnosis information for fuel gauge inaccuracy (SI Document). If the diagnosis leads you inside the fuel tank, determine if the vehicle came in an as-failed condition; pay particular attention to the quantity of fuel in the left and right reservoirs as the tank is lowered from the vehicle. Fuel remaining in the left reservoir and no fuel in the right reservoir is a good indication of poor fuel transfer. If the vehicle is not in a failed condition, it may be necessary to run the vehicle out of fuel to duplicate the concern.

Correction

Replace the sender fuel feed (transfer) pipe with P/N 10388380. This new pipe has one anti-siphon hole. Also, inspect the RH primary fuel tank module for a clogged/restricted transfer (jet) pump. Use the procedure listed below:

1. Remove the RH primary fuel tank module from the fuel tank. Refer to the Primary Fuel Tank Module Replacement procedure in the Engine Controls sub-section of the Service Manual.
2. Disconnect the electrical connector from the LH secondary fuel tank module.
3. Rotate the cam lock ring counter-clockwise using the J 45747.
4. Remove the cam lock ring from the fuel tank.
5. Carefully lift the LH secondary fuel tank module from the fuel tank only enough to access the transfer pipe.
6. Disconnect the transfer pipe from the LH secondary fuel tank module by pulling the locking mechanism down and away from the module.
7. Remove the transfer pipe from the fuel tank.
8. Install the new transfer pipe into the fuel tank.
9. Connect the transfer pipe to the LH secondary fuel tank module.
10. Install the cam lock to the fuel tank and rotate clockwise using the J 45747 until fully seated.

11. Connect the electrical connector to the LH secondary fuel module.

12. On the RH primary fuel tank module, inspect the jet pump by releasing the tab (1) securing the pump to the module. Position the jet pump with light at the rear and look through the tube. The hole should be clear from debris and not black in color. If the jet pump shows signs of being plugged, replace the RH primary fuel tank module.
13. Install the RH primary fuel tank module into the fuel tank. Refer to the Primary Fuel Tank Module Replacement procedure in the Engine Controls sub-section of the Service Manual.
Dave Nova, Cadillac Technician
Category: Cadillac
Satisfied Customers: 18959
Experience: ASE Master Certification. GM World Class Certification
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