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Dave Nova
Dave Nova, Buick Technician
Category: Buick
Satisfied Customers: 19451
Experience:  ASE Master Certification. GM World Class Certification
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Buick Century Custom I am having fuel level and fuel tank

Customer Question

I am having fuel level and fuel tank pressure problems with my 2002 Buick Century. The fuel pump is OK at the moment, but I am planning to replace the fuel pump assembly and the fuel tank pressure sensor to see if I can correct all my problems in one blow. I think all the problems may be related to the fuel pump assembly. I have a constant check engine light that my mechanic says is related to gas tank pressure. I installed a new fuel cap and that did not correct my problem. The fuel gauge reads either full or empty. but mostly full. I have over 100k miles on this car, and therefore I think I should replace the fuel pump and all the sensors/sending units that attach to this assembly. However; I have gotten myself very confused using internet research. I am not sure of my part numbers, nor exactly how to install them. Secondly, I am not sure what sensors/sending units are attached (or included) to the replacement fuel pump assembly. Would you please review the AC delco parts below for correctness? Also, except for the fuel filter, can I install all of these thru a port in the trunk? AC Delco OEM part numbers:

Part Number: MU1743
Product Notes:
Fuel Tank/Fuel Pump Module Kit
4DR ; Incls strainer
Per Vehicle: 1; Years: 2002-2002

Part Number: 16238399
Product Notes:
Fuel Tank Press Sensor
Per Vehicle: 1; Years: 2000-2003

Fuel Filter GF578
Submitted: 5 years ago.
Category: Buick
Expert:  Dave Nova replied 5 years ago.
Hello and thank you for using JustAnswer. My name is XXXXX XXXXX I will do my best to help you with your Buick problem.

The fuel pump assembly on your vehicle will come with a new fuel level sensor and a new fuel tank pressure sensor. If you purchase the fuel tank module kit, this should get you fixed up. The fuel tank must come out of the vehicle to replace the part.
Customer: replied 5 years ago.
Are you sure that if I order the AC Delco MU1743 fuel pump assembly, it will come with the fuel tank pressure sensor? Also, is there fuel level "sending" unit that is included in the assembly? Thirdly; in my internet research, I was convinced there was an access plate in the trunk for this assembly? Dropping the tank is beyond my expertise.
Expert:  Dave Nova replied 5 years ago.
Yes, I am sure that the fuel pump assembly listed comes with both the fuel level sensor and the fuel tank pressure sensor.

You are correct about there being an access panel. Remove the carpet liner from the trunk floor and you will see the access panel. Remove the screws in the panel.

Customer: replied 5 years ago.
When I see pics of the MU1743 assembly, there are no "parts" attached to the top of the pump assembly. I was under the impression that the fuel level "sending" unit, and the fuel tank pressure sensor/sending unit were mounted on top of the assembly? I think what has been troubling me is that AC Delco listed separate part numbers for these sensor/sending units?? Also, can you provide me with a high level step-by-step procedure for doing this replacement? Additionally; I expect to find some corrosion on the old sending unit (& wiring). This car used to be in a road salt area, and my guess is that corrosion may be the true cause of my problems. Anything I should look out for, or do?
Expert:  Dave Nova replied 5 years ago.
I am certain the MU1743 does come with both the sending unit and the fuel tank pressure sensor. I have attached a picture below. The black piece on the side is the sending unit. The float shown in the picture is shipped separate so that it will not get damaged, it simply snaps into the black piece. At the very top of the unit is where the fuel lines attach, as well as the electrical connections. It does not show well in this picture, but the black piece at the very top is the fuel tank pressure sensor. All AC Delco fuel pumps that are listed as "Modules" come complete with sensor and sending unit.

Customer: replied 5 years ago.
Can you provide me with a high level procedue for de-installing and installing? Also, what about my question regarding corrosion
Expert:  Dave Nova replied 5 years ago.
The connections are on top of the fuel tank and are sealed, so I do not expect that you will encounter any corrosion there.


CAUTION: Fuel Vapors can collect while servicing fuel system parts in enclosed areas such as a trunk. To reduce the risk of fire and Increased exposure to vapors:
  • Use forced air ventilation such as a fan set outside of the trunk.
  • Plug or cap any fuel system openings in order to reduce fuel vapor formation.
  • Clean up any spilled fuel Immediately.
  • Avoid sparks and any source of ignition.

NOTE: Clean all of the following areas before performing any disconnections in order to avoid possible contamination in the system:

  • The fuel pipe connections
  • The hose connections
  • The areas surrounding the connections

IMPORTANT: Always maintain cleanliness when servicing fuel system components.

  1. Relieve the fuel system pressure by removing fuel pump relay from underhood fuse panel and then crank the engine over.
  2. Remove the trunk carpet.
  3. Remove the fuel pump access panel nuts.
  4. Remove the fuel pump access panel.
  5. Disconnect the Fuel Tank Pressure (FTP) sensor electrical connector.
  6. Disconnect the fuel sender electrical connector.
  7. Clean the fuel pipes, and fuel sender assembly to prevent possible fuel contamination during removal.
  8. Disconnect the quick-connect fittings at the fuel sender assembly.

IMPORTANT: The retaining fuel sender assembly will spring-up when the ring is removed.

  1. Hold down the fuel sender and remove the fuel sender retaining ring.
  2. Remove the fuel sender assembly.
  3. Clean the fuel sender assembly sealing surfaces.
  4. Inspect the fuel sender assembly sealing surfaces
  5. Reverse procedure to reinstall.
Expert:  Dave Nova replied 5 years ago.
Please let me know if you need additional assistance with this.

Customer: replied 5 years ago.
Do I need to do anything special to "prime" the new fuel pump? -- On the fuel filter, is there a special tool needed to remove the old filter? I assume that once I have the old fuel pump out, I can replace the fuel filter before I start up the new fuel pump?
Expert:  Dave Nova replied 5 years ago.
No special procedure required to prime the fuel system. Cycle the key on and off a few times and the fuel system will be good to go. The fuel system is a recirculating type, so all air will be pushed out of the system automatically.

The ideal time to replace the fuel filter is while you are servicing the pump before you start the new pump while no pressure is in the system. There is a quick connect fitting on the inlet of the filter, just squeeze the two tangs in to release the fitting. Needle nose pliers are helpful here. The outlet fitting is threaded and just uses two wrenches (5/8 and 13/16) to remove.
Customer: replied 5 years ago.
Exactly where am I going to find the fuel filter? I think it is somewhere near the driver's door? -- Secondly; I went to order the fuel pump assembly and below is the pic of the top of the MU1743. Note that they show the sending units mounted on top of the assembly? Is this the same as the pic you sent me in the earlier post? I want to be sure I am getting the right part..graphic
Expert:  Dave Nova replied 5 years ago.
The picture of the unit you have in the picture is correct. The white electrical connector is for the pump and sending unit. The black electrical connector is the fuel tank pressure sensor. The tubes are the fuel line connections. These too are quick disconnect, just squeeze in the tabs on the end of the lines with needle nose pliers to release.

The fuel filter is located on the cross member just in front of the fuel tank

Expert:  Dave Nova replied 5 years ago.

Anything else I can assist you with on this?

Expert:  Dave Nova replied 5 years ago.

Please click the Accept button so that I may receive credit for helping you. If you need any additional information, please do not hesitate to ask. I will be glad to provide follow up information even after you click Accept. Thanks again for using justanswer.
Customer: replied 5 years ago.
Last question. I am having trouble finding the AC Delco MU1743 assembly at a reasonable price. Several places are trying to sell me the AC Delco MU177 assembly, which they say are the same thing. When I look up the MU177 it shows that it fits Olds Intrigue and Buick Regal for 2002 (my year), but does not list Buick Century. Are they really the same? My gut is telling me to hold out for the MU1743.. Your thoughts?
Expert:  Dave Nova replied 5 years ago.
The Buick Century and Regal are identical platforms (chassis underneath vehicle). The fuel pumps are identical. The GM part number that I have for the pumps are shown below. Any good parts store can cross the number over to AC Delco for you. When I cross the numbers, this is what I get. If the MU177 for sure fits the regal, then it will fit the Century as well.

regal GM # XXXXX AC Delco MU1743
regal supercharged GM # 25344968 AC Delco MU1741

century GM # XXXXX AC Delco MU1743
Expert:  Dave Nova replied 5 years ago.
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Customer: replied 5 years ago.
I have just received the AC Delco MU1743 fuel pump assembly. It contains a "new GT280 Chassis Electrical Connector". It does not mention if I have to replace the original or not? It "implies" that I have to replace it? My questions are: Is this new connector different from the OEM? If I have to replace it; can I do it from inside the trunk (i.e. enough slack to pull the old connector up into the trunk to replace)?
Expert:  Dave Nova replied 5 years ago.
The connector is a new design, your old connector will not plug into the new pump. There is enough slack in the wiring to change out this connector from inside the trunk, just did this same repair on a Bonneville a few weeks ago. Simply match up the wire colors on the new plug with the factory wires. Not too hard to do.
Customer: replied 5 years ago.
Follow-up. I am in the process of taking the old pump out and have run into a couple of problems. First; I can not seem to figure out how to "disconnect" the three fule line quick connects! The two outer ones are different than the center one. Someone said I needed a special tool? How do I remove these three with simple tools? -- Secondly; I saw somewhere that there was also a special tool to remove the pump locking ring? How can I also remove it with simple tools? -- Third; I have more than 3/4 tank of gas. To have to siphon some of it out?
Expert:  Dave Nova replied 5 years ago.
The tank will not need to be siphoned down. When you pull the tank module out, it will have fuel in th elower sump so be careful to pull it straight up then pour the fuel back into the tank opening.

There is a special spanner wrench for removing the locking ring but you can use a hammer and punch or hammer and flat bladed screwdriver to turn the locking ring. Counterclockwise removes the ring.

The quick disconnect fittings have tabs that extend from the fittings, squeeze these in with a needle nose pliers to release. After the lines are removed you will need to transfer the plastic retainer clips over to the new fuel pump module.
Customer: replied 5 years ago.
will now try to qet the quick connects off now and let you know
Expert:  Dave Nova replied 5 years ago.
Okay, let me know.
Customer: replied 5 years ago.
OK; got the old pump and the new one in place. I took "before" pics to be sure I got everything lined up, but am having a problem getting the lock plate to turn and lock. It "appears" that the pump is all the way down, and the lock plate is in the correct position. I get the lock plate started to turn (tits start over the lips of the holes), but no matter how much I bang on the plate to make it turn fully into place, I can not make it move into the final lock down position?? It only has to turn about 1/4", but it will not budge? I have put a large screwdriver on it and hit with a rubber hammer (trying to keep sparks down). Do I have to really slam it; or do you thinkt that the pump is not fully down; even though it is in the correct position?
Expert:  Dave Nova replied 5 years ago.
The pump has a single locating tang, if this tang is aligned properly then you will just need to use more force. The rubber mallet is absorbing a great deal of force, use a real hammer and you should be able to get it to turn. It does require a good whack. Also try hitting on opposing sides.
Customer: replied 5 years ago.
I pulled out the pump and compared the rubber sealing ring with the OEM on the old pump. The new AC Delco rubber ring was "thicker" at the flange at the very top. I put the old/OEM rubber ring on the new pump.. reinstalled... couple of taps of the hammer and it slid into place nicely. It does tick me off that I went with AC Delco (lot more money) so that I would not have these problems.. Will probably not finish the job til tomorrow as I have to splice in the new connector; and then change the fuel filter before I can crank it up and check for leaks... Thanks for your help..
Expert:  Dave Nova replied 5 years ago.
You are welcome. The new seal is thicker on purpose. This is to prevent vapor leaks from the fuel tank. It is normally okay to reuse the old seal if it is undamaged.
Customer: replied 5 years ago.
I old seal looked just fine. Giving how much I had to hit the hammer to get the lock ring to click into place, I do not think I have to worry about vapor leaks.. However; I ran into another problem. I went ahead and replaced the new connector that came with the new pump to the main power supply. Surprise Surprise.. It would not fit between the two vertical posts on the locking ring; as the OEM did! I had to take the ring back off; rotate it a 1/4 turn; and then put it back on. One of the vertical posts was so close to the pressure sensor connector, that I had to connect it before spinning the lock ring into place. Its tight, but I think just barely. My question for you is: I ordered an AC Delco because I thought it was the OEM; am I wrong? Will put on the fuel filter in the AM and test..
Expert:  Dave Nova replied 5 years ago.
The AC Delco is the OEM part, but just like lots of other companies, they have several suppliers for the same part, so design changes can occur.

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