Erratic Fuel Level Gauge explained - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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  #1  
Old 05-25-2009, 12:35 AM
McMurrayTrail McMurrayTrail is offline
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Erratic Fuel Level Gauge explained

On this forum, a lot of people have complained about their fuel level gauge acting up. I had the same problem, and started with asking the GM dealership how much this repair would cost. Hmmm, let's see: $80 to diagnose, $250 for the parts and around $450 for labor. Almost $800?! So, I decided to tackle this job myself and bought the fuel level sender unit on line for around $80. (1/10th of the cost of the GM repair). Using the article on this website for the fuel pump replacement, I did the replacement in approximately 6 hours. This is with only 1 person, and as it turned out, half a tank of petrol. I would be simpler with 2 people and less gas in the tank....... After the replacement, everything works perfectly again.

Now, I had a close look at the parts that I removed to try to understand why it had failed. Many people have written about "bad gas" causing this, and Techron fuel system cleaner might solve the problem. After looking at the pictures below, my conclusion is that there is clearly a defective part here. There are two "slide contacts", that slide across the circuit board, acting like a potentiometer (changing resistor as the tank float changes level). The sliding contacts are almost all worn down, there is only one left which probably only made the erratic contact causing my fuel level gauge to act up.

A couple of conclusions:
  1. D
  2. Don't waste your money on Techron
  3. If anyone has a source to buy just the grey plastic part with the sliding contacts (probably $1 to fabricate) this would be all that is needed for the repair.
  4. Don't let the GM dealer tempt you into buying a complete now fuel pump assembly!

I hope this helps all with this same small but annoying problem!
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  #2  
Old 05-25-2009, 02:38 PM
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the roadie the roadie is offline
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As an engineer, I LOVE root cause reports like this, especially with pics. Thanks! I see very similar designs in the HVAC actuators and the 4WD system front axle actuator. The contact fingers should be designed for 200K miles worth of fuel tank fillups, but noooooooooo.

The gray plastic is a custom molded part, but a real do-it-yourselfer might be able to pop-rivet a new finger assembly from some other level sensor that has aftermarket support, and therefore cheaper sources. Boy, there's some cheap ones on Ebay (for Tahoe and Impalas) that look like you could strip the fingers off of and use. If my level sender ever fails, I know what I'll be doing.

This one anyway, for the archives is an ACDelco #SK1158, typically $70-80 on-line. GM #88966954, list $123 - parts4chevys.com $77.
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Old 06-08-2009, 03:35 PM
p e ski p e ski is offline
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Great pics, but how bout some step by step instructions from start to finish. Seems a alot of people are having this problem and could use a could set of instructions......
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Old 06-08-2009, 03:55 PM
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Had this same problem with mine earlier this year, paid the $100.00 warranty deductible and had the dealer fix it. I would say its definitely a defective part, mine failed after only 3 years of service and around 60K miles on it!

Thanks for the write up and the photos of the problem. Now if only my water pump, fan clutch, HVAC controls, t-stat, transmission, 4x4 switch and anything else that isn't designed to last over 75k (when my warranty runs out) will fail so I can get it replaced!
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Old 06-08-2009, 04:00 PM
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my girls is doing the same thing just started a couple of weeks ago. when you fill the take it goes to empty then after a few days it goes to half.
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Old 06-08-2009, 06:46 PM
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very interesting.

The techron use- has been succesful for a few people.
Though I think most report it did not fix the issue.
If you run into this problem- and youve never run a fuel injector and fuel system cleaner.. and have many miles on your ride..... then it may be to your advantage to run a bottle of techron (I mean- why not have nice clean injectors)...
and if it doesnt work- change out the part below.
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  #7  
Old 06-13-2009, 02:19 PM
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Quote:
Originally Posted by McMurrayTrail View Post
On this forum, a lot of people have complained about their fuel level gauge acting up. I had the same problem, and started with asking the GM dealership how much this repair would cost. Hmmm, let's see: $80 to diagnose, $250 for the parts and around $450 for labor. Almost $800?! So, I decided to tackle this job myself and bought the fuel level sender unit on line for around $80. (1/10th of the cost of the GM repair). Using the article on this website for the fuel pump replacement, I did the replacement in approximately 6 hours. This is with only 1 person, and as it turned out, half a tank of petrol. I would be simpler with 2 people and less gas in the tank....... After the replacement, everything works perfectly again.

Now, I had a close look at the parts that I removed to try to understand why it had failed. Many people have written about "bad gas" causing this, and Techron fuel system cleaner might solve the problem. After looking at the pictures below, my conclusion is that there is clearly a defective part here. There are two "slide contacts", that slide across the circuit board, acting like a potentiometer (changing resistor as the tank float changes level). The sliding contacts are almost all worn down, there is only one left which probably only made the erratic contact causing my fuel level gauge to act up.

A couple of conclusions:
  1. D
  2. Don't waste your money on Techron
  3. If anyone has a source to buy just the grey plastic part with the sliding contacts (probably $1 to fabricate) this would be all that is needed for the repair.
    [*]Don't let the GM dealer tempt you into buying a complete now fuel pump assembly!

I hope this helps all with this same small but annoying problem!
Personally I would have replaced the whole assembly. Reason being GM pumps are not known for their longevity. You didn't put the year or mileage of your vehicle in your post, but if you are anywhere close to 100,000 I would replace the whole assembly. As much work as it is, I'd be ticked off if 6 months down the road the fuel pump itself dies!

Techron may not be the cure all for this problem, but as Rbarrios said it is a very good injector cleaner.
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  #8  
Old 10-10-2011, 07:03 PM
LikeEnvoy LikeEnvoy is offline
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I found a vendor for the level sender on Ebay canada;
alanisdeals- has one for $34 US incl shipping to Canada,

Has anybody dealt with this vendor? Are they OK?
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  #9  
Old 01-17-2013, 07:13 PM
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brainardsj brainardsj is offline
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Sensor Replaced - Calibration in Question

Thanks for the good information. I, like so many others, replaced the fuel level sensor myself. I found a Dorman replacement for my 2005 TB. After the normally struggle with all the clips and connectors, managed to complete the task. Went to test it and had to put almost 6 gallons of fuel into the tank to move it off of empty. A few days later, when I used up all that fuel, and gage was reading E, I filled up the tank completely. I expected to put the normal 18-20 gallons in, but it would only take 16. Seems like my replacement caused the sensor to read less than what's really in the tank. I hate to disassemble it all again to "adjust" the float arm, but I don't know what alternatives I have. Anyone else run into this problem? How'd you solve it?
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  #10  
Old 01-21-2013, 12:48 PM
Gullzjr Gullzjr is offline
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be aware there are 2 different parts for the fuel level sender, depending on if you have the Std length TB or EXT. As the EXT has a larger tank. If you put the wrong one it it could cause you to have incorrect fuel level readings.
I don't honestly knowthe part No's, but I did mine in our EXT about a yr ago when that level sender became available.
Got mine through Rock Auto.
Been workin great since.
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