Gas gauge problems

Lonewolf · Post by **Lonewolf** » Fri Apr 30, 2004 10:21 pm

ECM was bad causing sending units to fry. Replaced ECM without replacing sending unit, fried ECM. Fix was to replace sending unit and ECM at same time. symptoms were gauge hanging below 1/4 tank and dropping to empty fast and fluctuation in level of fuel at start ups.

a2b · Post by **a2b** » Sat May 01, 2004 1:50 am

lonewolf, welcome to the site

ya the gas guage is messed up on all crewcabs accross america

24digger · Post by **24digger** » Sat May 01, 2004 3:50 pm

Not mine

knock on wood

Rusty · Post by **Rusty** » Sat May 01, 2004 5:06 pm

Mine seems to work fine until I get to about the 1/4 mark, then forget it. It just goes nuts. One of the weird things it does after the 1/4 mark is change readings every time I turn the key on. On time it will read empty, the next key cycle it will read higher than 1/4, next time somewhere in between, etc. It's like spinning a roulette wheel. Just never know where that needle is going to land. I just go looking for a gas station as soon as it hits 1/4 tank.

Post by **HenryJ** » Sat May 01, 2004 5:20 pm

I'd have to agree with the above posts that I have not really noticed a problem with my stock fuel gauge, but I never get to or below 1/4 in the main tank.

One more advantage of the aux. fuel tank

450 miles or so, and still above 1/4 tank left

Conman · Post by **Conman** » Sat May 01, 2004 8:05 pm

Try this when you get at 1/4 left:

Drive say 20MPH and then do a sudden stop. Once stopped, put it in park and see what happens to the gas guage.......

The guage moves with the movement of the gas sloshing around.

Cheers,
Con

Rusty · Post by **Rusty** » Sun May 02, 2004 4:24 am

Conman wrote:Try this when you get at 1/4 left:

Drive say 20MPH and then do a sudden stop. Once stopped, put it in park and see what happens to the gas guage.......

The guage moves with the movement of the gas sloshing around.

Cheers,
Con

Oh, this is an easy test. I do this stuff in traffic all the time!

And yeah the guage move when the gas sloshes around in the tank.

Oh, and Brule. About your 450 mile range:

(j/k)

Post by **HenryJ** » Sun May 02, 2004 6:34 am

someone finally found that

Rusty · Post by **Rusty** » Sun May 02, 2004 9:03 am

You should add more of them, but it might start something to be regretted later!

TheBigFitz · Post by **TheBigFitz** » Fri Aug 20, 2004 5:08 am

I have had the gas guage problem since I have had the truck and lived with it, I just use my tripometer to tell me when to fill the truck. This week, however, the gas guage has been going nuts. It either reads completely full or completely empty. Any ideas what is causing that?

Post by **HenryJ** » Fri Aug 20, 2004 5:30 am

The standard answer is "Bad ground".

I would check for a bad ground , although with the number of sender failures that I have seen, it very well could be something else.

What brand of gasoline do you use? Do you add a cleaner, or additive from time to time?b If so, what brand additive do you use?

Rumors are around suspecting additives as attacking the fuel tank sending unit causing premature failures. I am just curious if there could be any truth to it.

TheBigFitz · Post by **TheBigFitz** » Fri Aug 20, 2004 11:02 am

Ya, bad ground is the answer I have got a couple times.

I use whatever free gas is in our project tanks when I fill up, company perk.

As for additives, I have used fuel system cleaner before, and early last week I ran some in the tank and changed the fuel filter. Think it was Valvoline but I can't remember. If it is the sending unit, that involves removing the bed to access the top of the tank, right?

Post by **HenryJ** » Sun Aug 22, 2004 2:19 pm

TheBigFitz wrote:... If it is the sending unit, that involves removing the bed to access the top of the tank, right?

Right.

Looks like the common thread being a specific fuel treatment or additive in a regularly used fuel doesn't apply in this case.

I have heard of a reflash of the PCM that helps the jumpy gauge syndrome (basically drugs it, or slows it's function), but I do not think that will help in this situation.

killian96ss · Post by **killian96ss** » Wed Sep 01, 2004 3:22 pm

I have also had this problem since I bought my crew, and I have had it fixed under warranty 4 times now with no noticable change. The first time they reflashed the program on the ECM with an updated version. That didn't work, so they replaced the sending unit in the tank. Still didn't work, so they reflashed and replaced the sending unit again. Would you beleive it's still not working. Well one more refash, and guess what? Nothing! I have actually run out of gas twice because of this problem. Sometimes it will say 1/4 tank, and then 2 minutes later it's below empty! IMO this is a serious problem and GM needs to to something about it, instead of the same fixes every time, because it never does anything other than waste my time.

Steve

doughboy5499 · Post by **doughboy5499** » Sat May 20, 2006 4:46 pm

Ok my gauge is mess up now too! First it was stuck on full Now it is stuck on Empty with the low fuel light on. With truck off it reads E then when I start it it goes to full then goes right back down to E and Stays. Where is the ground that needs to be checked? Is it possible to check without removing the tank? AND if it is the sending unit, how big of a project is this? My Dad just built a garage with a lift for his '69 Camaro, and said that I could use the lift if needed. My truck is falling apart lately and have only had it 10 months!

doughboy5499 · Post by **doughboy5499** » Sun May 21, 2006 7:15 am

Any Info from anyone?

Post by **HenryJ** » Sun May 21, 2006 8:13 am

Do the symptoms change when you have a full tank from when the tank is nearing empty?

How many miles on your truck?

Checking the wiring, ground, and connections is the first step. After that look to the fuel pump module assembly.

The fuel sender has contacts that look like tiny fingers. They rub across a printed board and wear. Below half a tank of fuel they are in the "airspace". When the tank is full they are immersed in liquid. This tends to alter the symptoms.

In my experience the senders tend to wear out in the 100, 000-140,000 mile range , or around five years of use. This can vary depending upon how the assembly has been treated. Those who maintain the fuel tank above half a tank , and use high quality fuel seem to have the module last longer. Invariably they all seem to go by 150,000 miles. Some may have the fuel pump fail, others the gauge sender. I like to change the complete assembly when the problems become consistent. The fuel pump failure can be instantaneous and with out warning. Some times it may have the foot valve leakage as a symptom. This shows up as needing to crank over several times on a cold start. Another indicator can be poor performance from inadequate fuel pressure.

Plan on spending $200-$300 for the fuel pump module assembly. I like to use OEM ACDelco parts. There are some aftermarket suppliers, but I have had a couple of them , in different applications fail. This has tainted my confidence in them.

doughboy5499 · Post by **doughboy5499** » Sun May 21, 2006 9:52 am

HenryJ wrote:Do the symptoms change when you have a full tank from when the tank is nearing empty?

No there is no difference. It still stays on E with the low fuel light on.

HenryJ wrote:How many miles on your truck?

I have about 65000 miles on my truck.

What gets me is that when I turn the truck on it goes from Empty to Full like it is supposed to do but when it goes back down to the fuel level it keeps going all the back down to empty. Almost like it is not reading anything.

doughboy5499 · Post by **doughboy5499** » Sun May 21, 2006 10:01 am

TheBigFitz seemed to have the same problem with his. Does anyone know what he did to fix his problems. I think he has since sold his truck but, I wondered if he fixed it before he got rid of it.

doughboy5499 · Post by **doughboy5499** » Wed Aug 02, 2006 12:01 pm

BUMP OK I am thinking this is a fuel sending unit issue. I called the dealer and they said that there was a design change in '01 sonomas that year. So if I were to change the "fuel guage sensor," I would have to have it recalibrated. Which is not a bad idea anyways. I was going to just change the sending unit without replacing the pump but, while I am already in there I might as well change it all out. I found a couple used ones on e-bay that were pulled out of wrecked ones but, kinda iffy on doing that cause I might be right back in the same place I am now in a few thousand miles. I called autozone and they don't sell the sending units seperate from the pump. I would have to buy the whole thing there. What do I do? Figuring how far I can go on A tank of gas by my miles is getting old. My in-laws borrow my truck every so often and put like $10 in gas (without telling me) just for letting them borrow it and it messes things up. Its a wonder i have not ran out of gas yet.

Post by **HenryJ** » Wed Aug 02, 2006 1:21 pm

doughboy5499 wrote:... they said that there was a design change in '01 sonomas that year. So if I were to change the "fuel guage sensor," I would have to have it recalibrated.

Design change? I think not. There is a software revision though. I is like a "deadener" for the sending unit. Kind of like drugging it so it reacts slower.

I was going to just change the sending unit without replacing the pump but, while I am already in there I might as well change it all out. I found a couple used ones on e-bay that were pulled out of wrecked ones but, kinda iffy on doing that cause I might be right back in the same place I am now in a few thousand miles. I called autozone and they don't sell the sending units seperate from the pump. I would have to buy the whole thing there. What do I do? Figuring how far I can go on A tank of gas by my miles is getting old...

Grin and bear the cost of a new module assembly. It could be worse , you could have transmission problems that are much more expensive.

doughboy5499 · Post by **doughboy5499** » Wed Aug 02, 2006 1:33 pm

You would not happpen to have part numbers would ya? I tried looking it up but i get different names with different numbers and am not sure exactly what I need. Would THIS ONE be the correct one to buy?

Post by **HenryJ** » Wed Aug 02, 2006 1:48 pm

I would say that one should work.

killian96ss · Post by **killian96ss** » Wed Aug 02, 2006 1:55 pm

I have noticed one thing about the fuel gauge problem that is very consistent in my CC and SS. Chevron gas with Techron causes the fuel gauges in both of my vehicles to become very erratic.

When I use Shell or Union 76 gas the problem goes away.

A lot of people believe that Chevron gas is the best, and while it is one of the top tier gasolines the real problem lies with the Techron additive. Techron is a great cleaner, but it cleans so well that it causes the gasoline to lose its lubrication properties which is bad for fuel pumps, fuel injectors, sending units, or basically anything in the fuel system that relies on the gas for lubrication. I have heard about several lawsuits against Chevron for their gasoline additive Techron causing fuel injector failures and fuel pump failures. This is a well known problem on the B-Body forum due to owners having their fuel injectors seize up as a direct result of always using Chevron gas. Coincidence, maybe, but I almost never use Chevron gas anymore unless I have to.

Steve

Post by **HenryJ** » Wed Aug 02, 2006 2:12 pm

killian96ss wrote:... I almost never use Chevron gas anymore unless I have to.

Ditto. Fuel and fuel treatments

Post by **Walt** » Wed Aug 02, 2006 2:35 pm

Not to put a damper on things, but I'm one of the cases where replacing the entire pump assembly didn't fix the gauge problem.

doughboy5499 · Post by **doughboy5499** » Wed Aug 02, 2006 3:02 pm

What did you find out the problem was Walt?

WVHogRider · Post by **WVHogRider** » Wed Aug 02, 2006 3:22 pm

My father had all sorts of problems with his CC fuel gauge and instrument cluster. The cluster would just shut down on him while driving on the highway, so he couldn't tell how fast he was going or how much fuel he had.

GM tried to fix it three different time, and then just made him a sweet deal on a replacement ZR2.

I guess I've been lucky, as I've had no real problems with the fuel gauge. I just have the issue of the needle dropping real quick once it hits 1/4 tank. I found that the 1/4 tank issue also has to deal with how you parked. On a 1/4 tank, if I park with the nose of the truck up hill, it will read above a 1/4 and it steady back out once you pull away. Park facing downhill, and it will be below the E mark on start up and stay there until I pull on an uphill grade and put it in neutral.

Once the fuel light has come on a of couple times, then I fill up.

F9K9 · Post by **F9K9** » Wed Aug 02, 2006 4:33 pm

I think all of the CCs and probably most S series have fuel gauge problems. The was a member here that had many issues with his CC and even had a GM engineer look at his issues. What the former member or current member relayed on to us that the GM rep admitted that there was no "fix" for the issue. I do not recall if it was that particular member or another that went as far as arbitration and GM was judged to reimburse the member the majority of the vehicle's cost.

Bottom line is that it "ain't" ever gonna be right! Keep the tank above 1/4 full (which also serves to keep the pump cool and to prolong it's longevity) and truck on

I know it sucks and you paid hard earned bucks and expect perfection but, GM is barely afloat to expect that kind of service at this point in time. I hope they recover but, only time will tell.

04crewvt · Post by **04crewvt** » Wed Aug 02, 2006 4:49 pm

Time to fill the tank when it gets to 1/4 5 minutes, Time to walk to the nearest gas station 15-30 minutes, Avoiding the need to admit you ran out of gas PRICELESS.

Post by **Walt** » Wed Aug 02, 2006 5:00 pm

doughboy5499 wrote:What did you find out the problem was Walt?

Still haven't figured it out.

f9k9 wrote:Bottom line is that it "ain't" ever gonna be right!

Truer word we never spoken.

doughboy5499 · Post by **doughboy5499** » Mon Nov 06, 2006 10:49 am

doughboy5499 wrote: Where is the ground that needs to be checked? Is it possible to check without removing the tank?

Can someone tell me where and how to check for the ground?

Whats the GM part number for a new fuel pump/sending unit module?

daevans315 · Post by **daevans315** » Wed Nov 08, 2006 6:26 pm

doughboy5499 wrote: Can someone tell me where and how to check for the ground?

Whats the GM part number for a new fuel pump/sending unit module?

I'm not sure if they were talking about ground in general or something specific. There was a ground strap running from the fill on the side of the bed down to the frame. It ran right along with the rubber fill hose but did not have to be removed to remove the tank.

See my hard starting thread in this forum for a few tips on tank removal.

Here is the part number and cost from gmpartsdirect.com. Use at your own risk. Nobody would give me a part number without a VIN, so it might not be right for your crew.

25344814 MODULE KIT $316.02

Handling and Shipping: $69.52

ORDER TOTAL: $385.54