99 Blazer 4.3 Voltec with the unstable Fuel Gauge.

[ruger17hmr]

All right, you guys were right! I should have never said that everything is good to go after the Thermostat & Temperature issues were resolved. Now, Blazer's Fuel Gauge is unstable and stays on empty while driving even though the tank is not empty. I am leaning towards the Sender, which means the whole Fuel Pump assembly has to be replaced. But, I have heard that other issues might cause the similar symptoms. Grounded wire, Harness Plug wires ect. Any ideas or recommendations? Thanks in advance as always.

I am getting really tired of working on my SUV. Besides, I only have one lousy jack that came with the vehicle. Does anyone want to make some cash for the Holidays? Please PM if you are interested in installing the Fuel pump assembly for me. We can workout a reasonable compensation for your trouble.

Background:

Water Pump replaced 6 months ago
Intake Gasket & Thermostat replaced a couple of weeks ago
Anti Freeze flush last week.

 

[mom45]

When mine went out, the gauge was jumping around a lot. I ended up ordering the whole fuel pump assembly from carpartswarehouse.com for half the price of what the local auto parts store wanted for the one made in China. It has a warranty as well. We were nervous about ordering it online but saving a $100 made it worth it and a year later it is still working just fine. When I had the grounded wire in front of the tank, it kept causing the fuse to blow that controls the computer and it just wouldn't start. Every time I hit the key, the fuse would immediately blow. I got good at changing fuses but we finally found the short and hubby fixed it.

 

[red_zr24x4]

People say not to use an after market pump, I bought an aftermarket one and it lasted for 3 or 4 years before I sold the truck. Mine was a 98 ZR2 truck.
The problem I had with the replacement was the sending unit would stick,so I put the original on the new pump.
I still have the new sending unit in the garage, If you want to try and tweek it so it doesn't stick PM me your address and I'll get it out as soon as I can
Kenny

 

[ruger17hmr]

Was it easy to put the original on the new pump? I have never done it before.

 

[red_zr24x4]

Yeah it wasn't bad. Mine was in a pickup so I pulled the bed instead of dropping the tank.
When I switched the sending unit it took longer to un-bolt the bed than it did to switch the sending unit.
A lot of dirt accumulates on top of the tank, so make sure you clean it off before removing the pump/sending unit.

 

[remauto1187]

You can buy the pump and even the wiper that the fuel level float attaches too (Its just a potentiometer) all seperately. You DO NOT have to buy a whole assembly. I would not put anything in my tank that did not have AC DELCO or DELPHI on the box. The pump for a 99 GMC Sierra 5.7L is $50 and thats for a AC Delco and comes with hose, clamps, wiring pigtail, tank oring and even fuel strainer. The wiper is a seperate part. They can be had on Ebay all day long. Its a crapshoot with aftermarket fuel pumps and for me just is not worth the gamble. The wiper snaps onto the fuel pump module assembly.

The fuel gauge stepper motor could be the culprit also. The stepper motors are what actually move your needles in your instrument cluster. They are cheap and easy to replace IF you have the correct wattage soldering tool. Overheat it and you get to find a replacement instrument cluster.

I just rebuilt my girlfriends isntrument cluster on her 2003 Tahoe. It cost me like $30 in parts. Ive got the parts to do my Tahoe and plan on doing it this week. It takes about 1.5-2hrs remove/rebuild/reinstall.

 

[red_zr24x4]

The pump for my 98 S10 was almost $400 from 4 different parts stores. I agree that the aftermarket pumps are a crap shoot, but in my case I wasn't going to spend that on a vehicle that old.

 

[mom45]

The one we bought was $125 delivered to my door and the one at NAPA was around $300...Advance Auto was about $250. We replaced the whole unit because of the labor involved to drop the tank and didn't want to just try changing one part at a time to see what was really bad. With the trucks, we always take the bed off because it is so much easier.

 

[heavyhitter1k]

My bet is on sending unit....prob same reason mine is not working.

 

[ruger17hmr]

The one we bought was $125 delivered to my door and the one at NAPA was around $300...Advance Auto was about $250. We replaced the whole unit because of the labor involved to drop the tank and didn't want to just try changing one part at a time to see what was really bad. With the trucks, we always take the bed off because it is so much easier.

I wish I could do the same, but the fuel tank has to be dropped for Blazer. No easy way out!

 

[ruger17hmr]

My bet is on sending unit....prob same reason mine is not working.

Are you not going to fix it?

 

[partyboy6686]

General Motors original wiring harness for the fuel pump is crappy. That is the problem. Aftermarket fuel pump makers have redesigned the fuel pump to accept a upgraded wiring harness. I have been in the auto parts business for 9 years. I sell fuel pumps daily. I personally had the same issue on my 2001 Chevy Silverado. Replaced the whole sending unit with upgraded wiring harness and it fixed my gas level gauge problem.

 

[ruger17hmr]

General Motors original wiring harness for the fuel pump is crappy. That is the problem. Aftermarket fuel pump makers have redesigned the fuel pump to accept a upgraded wiring harness. I have been in the auto parts business for 9 years. I sell fuel pumps daily. I personally had the same issue on my 2001 Chevy Silverado. Replaced the whole sending unit with upgraded wiring harness and it fixed my gas level gauge problem.

Did you have to drop the fuel tank or pull the bed?

 

[partyboy6686]

Did you have to drop the fuel tank or pull the bed?

I dropped the tank. Being in the auto parts industry has its perks. One of my accounts let me use a lift at his shop to make my fuel pump replacement easy.

 

[ruger17hmr]

I dropped the tank. Being in the auto parts industry has its perks. One of my accounts let me use a lift at his shop to make my fuel pump replacement easy.

Must be nice!!!!

 

[remauto1187]

Must be nice!!!!

Its a piece of cake. Not rocket science and even easier than dislodging an arrow, dodge truck, wooden dowel, 10lbs of patches and 2lbs of liquids from a mosin nagant barrel !
Once again...YOU DO NOT HAVE TO BUY THE WHOLE FUEL PUMP MODULE !!! Fuel pump (AC DELCO) $49.95 New AC Delco Fuel Pump Strainer Kit GM Vehicles ACD1000 | eBay
Fuel level sensor $15.00 New Fuel Level Sensor Sending Unit Fits Chevrolet Buick Cadillac More | eBay

Want me to wipe yer nose for ya too?


You should have it ready to hit the concrete befor the parts even get here. You'll need the fuel line disconnect plastic tools also which are around $10 and all the auto parts stores have the set.

Some years ago you could only get the module assembly, but those days are gone. You can get the parts individually. The plastic module housing did not wear out!

 

[ruger17hmr]

You can buy the pump and even the wiper that the fuel level float attaches too (Its just a potentiometer) all seperately. You DO NOT have to buy a whole assembly. I would not put anything in my tank that did not have AC DELCO or DELPHI on the box. The pump for a 99 GMC Sierra 5.7L is $50 and thats for a AC Delco and comes with hose, clamps, wiring pigtail, tank oring and even fuel strainer. The wiper is a seperate part. They can be had on Ebay all day long. Its a crapshoot with aftermarket fuel pumps and for me just is not worth the gamble. The wiper snaps onto the fuel pump module assembly.

The fuel gauge stepper motor could be the culprit also. The stepper motors are what actually move your needles in your instrument cluster. They are cheap and easy to replace IF you have the correct wattage soldering tool. Overheat it and you get to find a replacement instrument cluster.

I just rebuilt my girlfriends isntrument cluster on her 2003 Tahoe. It cost me like $30 in parts. Ive got the parts to do my Tahoe and plan on doing it this week. It takes about 1.5-2hrs remove/rebuild/reinstall.

If the Stepper motor is the culprit here, wouldn't all the gauges in the instrument cluster act unstable?

 

[remauto1187]

If the Stepper motor is the culprit here, wouldn't all the gauges in the instrument cluster act unstable?

Each instrument cluster gauge has its own individual stepper motor, in other words there is one for the speedo, tach, temp gauge, oil pressure, voltmeter, etc. Here is a seller on ebay for them with pictures of the actual stepper motors. GM Stepper Motor Kit | eBay

 

[ruger17hmr]

Each instrument cluster gauge has its own individual stepper motor, in other words there is one for the speedo, tach, temp gauge, oil pressure, voltmeter, etc. Here is a seller on ebay for them with pictures of the actual stepper motors. GM Stepper Motor Kit | eBay

How would one differentiate which one is causing the Fuel Gauge malfunction?

My fuel gauge needle moves to Full when the key is in ignition after a bit of unstable swings, then it settles on Empty while the vehicle is in motion. Can you tell from the behavior which one is causing the problem?

 

[HoughMade]

How would one differentiate which one is causing the Fuel Gauge malfunction?

It's the one connected to the fuel gauge. The stepper motor physically moves the needle. My bet is still on the sending unit, though.