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How to change your fuel pump- WITH PICS.

253K views 172 replies 96 participants last post by  pdcomm 
#1 ·
I did this on a 2003 Short wheelbase Trailblazer with the 18.7 gallon tank.
My vehicle had just turned 133,000. This was the Factory pump. It had not failed and I was NOT getting any fuel gauge problems.
I simply wanted to replace the pump now before it failed from age.... Preventative measure pretty much.
I bought a new AC Delco Pump with the level sender for about $270 and a new external fuel filter for about $22. Total about $327 with tax.
Drive vehicle as much as possible after low fuel light to get rid of as much gas.
I chose to lay thick plastic down (in ase of fuel spill) and raise the vehicle with car ramps. I also used wood on the ramps so that the metal ramps dont dig into the cement.



Pop the hood and access the fuse box. With the engine running pull the relay for the Fuel pump, within a few seconds the engine dies. Crank the engine a few times to relieve pressure.
Disconnected the negative battery terminal and then open gas cap.
Next step was to remove the cross bar that would be in the way for dropping the tank.
Using a short phillips screwdriver loosen the screw on the fuel filter. You also want to press in on the schraeder valve to release any pressure in the lines. Gas may come out of this if theres still pressure in the lines



here in pointing at the schraeder valve


Have a container ready to catch gas that will come out of the filter/line connections.
To disconnect the fuel lines- simply press in the clips (blue on the filter) and the other lines you simply squeeze. No special tools needed for these.
Note how the fuel filter is gone- and the lines are wet from gas that drained out of the lines



With my thumb and forefinger im pointing at 2 more lines that must be disconnected. one is at the top that may be partially hidden... you may miss it- so I figured Id point it out. I was using a flashlight to make sure I didnt miss any connections.


I then proceed to place a jack and a piece of wood under the tank for support-for when I remove the straps.



Then loosen the hose from the tank to gas filler tube. Using a small ratchet and 7mm socket




Loosen the straps using a size 15 socket, extension, and 1/2 inch ratchet.




Once the straps are removed- the jack/wood is helping hold the tank. You may have to jiggle the rearmost strap to get it to get out of the way, the front strap came right off.
I then dropped the tank a little... so that I could look around and see what electrical connections there are.

laying down in the rear by the driver rear tire- looking in between the coil spring and the red rubber stopper- there is an electrical connection.
remove this.. these are easily disconnected.



I dropped the tank a little more-- I was then able to pop my head from under the car and look at the top of the tank and see the power connection to the fuel pump.
In this picture-- I stuck my hand above the frame and with my other hand I snapped the picture. This is also an easy connector to undo.



We then lowered the tank more- and found 1 more connection... in this picture weve already removed the tank.
but it was one of those instances where the other person helping sees the 'hidden' connector and I quickly rush over to that side to disconnect it as to not cause damage to the wires. It was located on the rear right corner of the tank.
Yes.... I recommend a helper for bringing down the tank...

once the tank is down- I slid it out. though theres a module on the tank that was in the way and I had to turn the tank a bit to clear the frame. (if you have higher ramps you probably wont run into this).



Here is the top of my tank after 133,000 miles. Since this is a California Car... there is no rust whatsoever on the fuel pump module...
those of you in the rust belt are likely to find rusted pump modules.



I then used a vacuum to suck up dust and small rocks and debris from around the pump assembly. I also cleaned the area with a wet towel. THen I disconnected the fuel lines here... similar clips like on the fuel filter.
I then compare the old and the new pump. (note the fire extinguisher--- just in case).



Removing the ring that holds the pump in place is EASY. use a screwdriver or brass punch and hammer to hit the ring and get it to rotate loose...
Mine came off easily. Remember that metal on metal may create sparks-- and youre working on a gas tank full of fumes. I wrapped my tip with electrical tape to avoid metal on metal.
Once I removed the old pump- I compared it to the new one.
I was surprissed at how clean the filter was. Yeah there was some debris on the filter... but I was expecting ALOT more crud.




I also compared the tops of the pumps.
the parts numbers were the same on labels




I then looked in the tank and was surprissed at what I didnt see...
After 6 yrs and 133,000 miles.. there was very little debris inside. I used a turkey baster to suck up as much of the large particles as I could.



I then compare the level senders. they were identical on mine.




Now-
to put in the new pump....
You slide it in- and making sure its pointing in the right direction (theres a tab on the top of the pump assembly)
Make sure you have the new rubber o-ring in place and press down in the tops, its spring loaded.
the metal ring to fasten down the pump needs to be turned to fasten it into place. You have to apply enough pressure to compress the rubber oring.
Most people use the hammer/screwdriver method to put it in place.
(PLEASE READ THE NOTE ON THIS AT THE BOTTOM).... it may save you aggravation... I suffered so you wont....

Proceed to reconnect the lines at the pump assembly.
Reverse the procedure to put the tank back in. Use the jack to lift it. You may have to fiddle with the rear strap.
Make sure to reconnect the electrical connections and then lift the tank more and fasten the straps.Reconnect all the fuel lines and replace the fuel filter.
Dont forget to reconnect the filler neck hose.
Double check to make sure you didnt forget any connections.

Remove stuff from under the car.
I then reconnected battery and shifted into neutral and allowed the SUV to roll off the ramps. I then plugged in the relay and went to turn the key to start (without cranking) to prime the pump about 4-5 times.... I then proceeded to start the vehicle. it cranked for a bit.
Once i knew it was running- I turned off and disconnected battery and proceeded to clean the throttle body.
I then put in a gallon of fuel from my 1 gallon gas container. Went to gas station and refueled with 18 gallons.
I came back and got under car to make sure there was no leaks.

NOw..............
to ramp up and remove the tank- while taking pictures--- 45-50 minutes... being the 1st time Ive ever done it.
to put the tank back in and reconnect- about 20-25 minutes.....

I started at about 730 am and finished about 1:30 pm.... 6 hours.... so what happened?
once the tank was out- I took some time to clean the top area on the tank. I vacuumed that area.
I also noticed the new pump didnt have the clips for the connections.. I swapped them from the old pump.
Removing the ring was EASY.....
Mechanics and others on here say to put that ring back on--- use a screwdriver and hammer to put it back on.
I tried it..... then I had dad and I try it. We coudnt get it back on.
Now maybe we could have wacked harder............ but I thought of it this way.
The pump assembly could be damaged. We may accidently puncture the tank (expensive!!!), or damage the plastic on the top if the tank.
so we loaded the tank into the other car and drove around to Pep Boys, Kragen, Autozone, Napa, several other shops. No one sold the tool to put this back on. several shops also told us they would have used the hammer screwdriver method.......
In the end we drove to the local chevy dealer where I talked to a tech. I offered to pay him $20 to use the GM tool to turn that ring.
Since the owner was there... we waited for him to dissapear- I then left $20 on the seat- he drove the car to the back and a while later he came back with the ring fastened on.
All this driving around and waiting was a good 3+ hours.
Others say they can put that ring on without the tool....
But if you plan on doing this... make sure you CAN put it back on..... or buy the tool online (saw it for $80 online) or find a shop/dealer/tech/friend who can twist that sucker on for you.
To me.. that $20 was worth it. Better to have spent that $20-- than cause alot more damage- hammering on with the screwdriver. Why it wouldnt slip on? Maybe the new o-ring was bigger? Maybe we didnt use enough force? I tried adding a little WD-40 to help lubricate... but no go. Please consider the tool.
 
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#33 ·
bigbadbowtie088-
kinda, it seems like it wants to stall but at the last minute it will act normal. i had my tank and fuel filter (if thats what is in the tank) changed in april, so it cant be that, i dont think. i was gonna try to change the fuel pump but is it nessecary to drop the tank and all that just to change the pump. i read the post about changing it ( great instructions) but i dont have the nessecary means to do all that. just want to get my truck fixed and running strong like it used to. on a completely different note, ill be changing the motors for the gauge cluster out in a week or two, so hopefully i dont screw that up too bad.
 
#34 ·
You should look closely at your operating temperature. If the thermostat fails in these they tend to stick slightly open. This leads to over cooling and your truck runs like a dog because the PCM thinks it is cold and subsequently will richen the mixture. It can go on for months or longer before it officially meets the over cooling parameters to throw the code for the thermostat. By then you could have wasted hundreds of dollars on fuel. I did :bonk: because I thought it was good to run cool (old school). The temp gauge was always a notch under what other members described as their "normal" position of right at 210. :m2:
 
#38 ·
80,000 sounds about right.
I changed my pump at about 134K. It still ran fine and level sender worked great too....
but just peace of mind.
 
#39 ·
update for vehicles with slightly different setup w/pix

Ok guys. I just did my '04 Envoy 4x4 SWB and it was slightly different than rbarrios' truck was. I'm not going to re-write what he has, it's basically the same except a couple lines and connection types. The main part, the parts are different and that's the warning I wanted to give. My truck had a completely different lock ring, seal, and sending unit (which is what I was replacing). The diameter was much smaller. Also, I had purchased the J-45722 tool and it also was much too big for my setup. (luckily the dealer let me borrow the right tool, I'll get the number and post it later). It makes reassembly much easier if you're doing it by yourself.
I called my dealer and he said the part I had was correct and I said, no it's not (#19178477/sending unit). So I gave him my VIN # and it popped up a message on the screen. Something to do with Canadian parts or something. Don't have the TSB #. The part I needed was #19206123 Make sure when you order the parts, you check with the dealer parts counter first by referencing your VIN.

Anyways, here's a couple pics...You'll notice not all my lines were the same. You can still do them by hand, but they can be hard to compress. I also had to disconnect a small box on the back side of the tank by the filler next towards the passenger side that is connected to a metal bracket on the tank. It was easy to unhook, there is a metal tang, just bend it back and slide the box out of the bracket. Kind of like a electrical connection.

I only had two electrical connections to unhook. The one at the pump and one on the back by the filler tube. Outside of that, basically the same. Also a pic of how I put the truck on ramps to do the job. Worked out great. Did this by myself in about 3 hrs including running for new parts. Good luck.
 

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#40 ·
I just found in the parts guide that the box on the back I was referrencing is a "vent valve." Don't be afraid to make this repair. One of the easiest fuel tank drops/repairs I've ever done. For those of us in the "salt belt" those quick connect lines are a blessing:thumbsup:
 
#43 ·
i exceeded my bandwidth- pics are not viewable from my ISP till the 1st of the month...BUT Ive uploaded the pics to my photo gallery.
Click on my avatar- and look for my picture gallery.
to cross reference pics- rt click on the X in the picture thats missing and look for that filename in my photo gallery
 
#135 ·
I would love to see the photos. For some reason, I can't. I was looking at them a while back (assuming the ones I'm unable to view today are the same ones), and now I can't.

When I seen the pics, I was at work and on a PC, Windows OS.
Today, I'm at home, on a Mac OS.
Maybe the different OS is the problem, I don't know.
 
#44 ·
Great write up! My fuel gauge is going coo coo, and I'm thinking about replacing the sender unit myself. I'm having trouble finding the part online. My tb only has 48K on it, so I just want to replace the sending unit. I can't quite figure out what part I need. Any help would be greatly appreciated.
 
#45 ·
Welcome to the site. Define coo coo before you replace the sending unit. I replaced mine and that end up not being my problem. It was just a bad stepper motor in my gauge. Cost $5 to replace and about 30 min.:m2:
 
#46 ·
My gauge has been staying at E after filling up. it will periodically work and then not work. today, I ran out of gas. I thought the gauge was working, but i didn't get a warning light or ding.

I was indeed out of gas, but the 1 gallon combined with the incline were enough that it still wouldn't start. i thought something more was wrong, but after the tow truck put it back on level ground, it fired right up. It has started and run fine since. I filled it up, 23 gallons total, so i must have been out of fuel, however the gauge remains on empty.

Fun night! :)

I figure it is the sending unit, so i'd like to give that a try. I'd rather not replace the whole unit.

I'll take any help given as a great kindness.

thanks in advance.
 
#50 ·
I was indeed out of gas, I filled it up, 23 gallons total, so i must have been out of fuel, however the gauge remains on empty.

Fun night! :)

I'll take any help given as a great kindness.

thanks in advance.
this is why you should know approxmately how many miles per gallon you get....
now that your gas gauge doesnt work...

Gas up... reset your trip meter. and caculate your mileage.
lets assume you get about 15 mpg.... we will use 20 gallons(as there are about 2 or 3 gallons left in the tank when the light comes on)...

15x20=300 miles.
when you see your trip meter nearing 250, 275,280--- gas up.
 
#47 ·
Replaced Fuel Sensor

This past weekend I replaced the fuel sensor on my 2005 TB Ext LT. Took me about 3 hrs and I had the help of a friend. Getting the clamps off the hoses was a bit tricky, some of them even broke. I used wire tires to help secure them back in place once the hoses were reconnected. We struggled a little getting the pump out of the tank. It's a tight squeeze. I ordered the sensor part from gmpartsdirect.com. Saved me about 50 bucks from 137.00 quoted from the dealer. I want to point out that on my 05 TB, the Fuel Filter is not there. I stopped by local Advance to get a new Fuel Filter and computer stated it was a non serviceable item. Maybe the filter is in the fuel lines. I don't know.

Tsutaz
 
#48 ·
This past weekend I replaced the fuel sensor on my 2005 TB Ext LT. Took me about 3 hrs and I had the help of a friend. Getting the clamps off the hoses was a bit tricky, some of them even broke. I used wire tires to help secure them back in place once the hoses were reconnected. We struggled a little getting the pump out of the tank. It's a tight squeeze. I ordered the sensor part from gmpartsdirect.com. Saved me about 50 bucks from 137.00 quoted from the dealer. I want to point out that on my 05 TB, the Fuel Filter is not there. I stopped by local Advance to get a new Fuel Filter and computer stated it was a non serviceable item. Maybe the filter is in the fuel lines. I don't know.

Tsutaz
I believe the fuel filter on your truck is in the tank where as the older models are along the frame rail in front of the tank. As far as your fuel lines, you say you wire tied them? I hope you put clamps back on the lines. Wire tires will not hold up under that pressure and could cause leaks. Don't want anyone to get hurt:worried::m2:
 
#53 ·
Fill out your info so we can see what truck you have. Yes, the level sensor assembly is what you need. I got mine from gmpartsdirect for about $75 shipped. A word of caution though. I found with my truck, that the part listed was not correct. Not partsdirects fault, that is the number the dealer listed for it too. When I went to the dealer, he ran my VIN# and found a bulletin that my truck used a different part. Luckily they had it. You might call your dealer and give them the VIN and make sure of the part #.:m2:

Refer to post #39 in this thread to see my original comments about the parts and part numbers.
 
#60 · (Edited)
go to my gallery... I have put all the pics there.

in the article--- rightt click on the red x.... youll get a file name such as...

xxxxhttp://xxxxxxxxx/~rbarriosx/pumpdisconnecthoses2.JPG

that was the URL for the old location.... the pics name was pumpdisconnecthoses2.JPG .... simply go to my gallery-- and look for the pic with that name....
it will help if you have 2 browser windows open... one to view pics- the other to look at the how to...

youll also find alot of other how to pics there
 
#64 ·
Fuel Pumps

Keep this in mind about low fuel.
With only 1 or 2 gallons of fuel in the tank,all is well when you are driving under perfect conditions,in a straight line,on level ground.
As we make turns,go up and down hills,start,stop,that 1 or 2 gallons in a 20 gallon tank is moving all over the tank and away from the fuel pump pick up.
For several seconds sometimes more,the pump will not be getting the lubricating, cooling it needs from the fuel.
Compound this over a period of time and you are shortening the life of a fuel pump.

A restricted fuel filter (dirty)will cause the fuel pump to work harder,but thats another subject.

hec123.
 
#65 ·
Hi guys, I am new to this forum and to the TB/Envoy platform but not to cars in general or GM trucks. I am the owner of a highly modded 02 gmc yukon denali, with among other things an LS6 corvette engine swap.

Before I ever bought this truck I knew of the GM SUV proficiency for killing fuel pumps. In fact, prior to buying my 02, I had a 99 OBS denali, which was basically just a fancied up tahoe. That truck also killed a couple of fuel pumps.

Knowing of the fuel pump issues and the difficulty in changing them, I planned ahead. On both of my trucks, the first thing I did upon purchasing, during the first round of routine maintenance, was to locate the fuel pump position with the tank installed in the truck. Then I carefully cut the carpet and padding, and used a cutoff wheel to cut out a 12" x 12" access panel in the floor of the truck. In both trucks, this turned out to be inside the truck, driver side, under the back seat just in front of the driver rear wheel.

Now I know what you're thinking, no way you should be cutting the inside of your truck up. But this is not a structural area and will have no impact...after all, you never put your feet or weight under the seat so you have no significant risk of punching through this panel.

With this panel in place, all I have to do, to access the pump, is to fold the seat forward, pull back the carpet, remove the panel (which I seal back into place with the foil duct tape that you use for home HVAC), and there you are...instant access.

Now, I havent done this mod to the envoy that I just bought for my wife...but it is definitely in my plans to check into it and see if it will work as easily for it as it did on my last 2 full size suv's.

One time on my 99 denali I was towing a show car to atlanta and the fuel pump died on the way there. I was on the side of the interstate with a truck full of people and a dead pump. If I relied on the conventional method, I would have not only been sitting there for a few hours, but I would have had 2 or 3 seperate tow bills plus repair fees. Instead, because I was prepared with an access panel, basic tools and a spare pump in the truck with me, I was able to change the pump on the side of the road in about 15 minutes and proceed to the next town for a replacement pump, then go on about my weekend.

Also, ironically enough, 2 weeks ago when I made a 10 hour round trip to tow my wife's new truck home using my 02 denali, the truck died right as soon as I pulled into my driveway at home. Turns out the fuel pump had died. I was able to change the pump out within about 15 minutes and be back up and running.

Now, the GM truck pumps are a sealed, non serviceable unit. So you are stuck buying another new stock GM pump, or an even crappier aftermarket one (say, from autozone, etc.). This was unacceptable to me, both for cost, reliability, and performance reasons. Obviously my 02 denali demands a performance pump due to the mods I have. For many years I have run walbro 255 fuel pumps which can easily support 500hp, cost only $100, are readily available, and still relatively reliable. So I wanted to install one of these in my truck.

To accomplish this I cut up a spare pump assembly using a cutoff wheel. By slowly removing plastic from certain areas I eventually was able to access the fuel pump itself, and remove it. Then it was a simple matter to rig the walbro pump back in the same place which allowed me to use the same pump assembly, lines, wiring, sending unit, etc.

One other thing. This special tool you guys are using to remove the retaining ring for the pumps is totally unnecessary. All you need are a hammer and a medium size flatblade screwdriver that is fairly robust. Now again, I have not specifically examined the tb/envoy pump and ring itself, but I cannot imaging it is much of any different from the GM fullsize version. That version has several slots and tabs on the edges of the ring, plus one plastic retaining tab/finger. To remove the ring, all you need to do is rotate it counterclockwise about 3/4 of an inch. Just take the screwdriver and put it firmly into a slot or tab with a flat edge. Strike a couple of moderate blows to rotate it a little. Do this until the plastic retaining tab is being pressed. Pry this tab away from the ring, and it will stay there. Now strike the retaining ring a couple more times and it will pop right off. Install is the reverse of removal. This literally takes 30 seconds to get the ring off. I'd feel foolish if I bought a special tool for this ring.

I will keep you guys updated when I get around to investigating the envoy for these mods.
 
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