fuel gauge problem

[raidermark]

The fuel gauge on my 2003 Chevy Impala 3.8L is always showing a full tank of gas even when tank is low. Sometimes the gauge fluctuates a little but then returns to full even when low. Any suggestions?

 

[getnpsi]

Lots of positive testimonials of members using marvel mystery oil (MMO) in sticky fuel gauge sender situations. It's not expensive and a quart is many doses.

 

[mikered30]

Techron may work too.

 

[Nick R]

Yup, I'd use a couple tanks with techron treatment.

 

[Bluestream]

Float is likely stuck, or sending unit is defective. Bang the bottom of the tank with a rubber mallet to try and dislodge it. You can also check electrical connection at fuel tank for corrosion. If that doesn't work, remove the tank and check float. Check sending unit for varying resistance with an OHM meter. Replace defective sending unit if needed

Don't waste your money using MMO, a proper repair is needed here.

 

[bigmike]

I'd go with the fuel cleaner and lube first. Try techron or regane with some MMO and/or TCW3 2 cycle at 1 oz per 5 gallons of gas. Maybe a shock treatment of will free it up?

 

[pbm]

I had the same problem on my 2002 Buick Century and fuel treatments didn't help. I eventually changed the entire fuel pump (which included a new sending unit, float etc...) because it had over 100K and wasn't that much more than a new sending unit alone.
I got a SPECTRE brand at Rock Auto for under $200 ($180 I think) and it has worked great. PM me if you want some tips on doing the job.

 

[meep]

bad sending unit. 6oz of oil in 20 gallons of fuel isn't going to do much IMO, but no harm in trying.

 

[raidermark]

Thanks for the suggestions, I'll drop the the tank & see if I can recognize the sending unit & see if I can replace it. The car does have a 120K on it.

 

[sciphi]

Try the Techron or Regane first. Worst case it cleans the engine out, and you drop the tank anyhow. Best case it fixes it.

The sending unit is very easy to find. If you're lucky, an access hole will be in the rear seat, so dropping the tank will not be necessary.

 

[raidermark]

OK, Great suggestion, I should know by now to try the easiest thing first & work my way to the next step. I never thought about checking the rear seat. The trunk may be accessible also I suppose.
Thanks again

 

[MegaCorp]

Drop the tank with a floor jack under it. (piece of wood on the jack) Tap the fuel pump with a hammer and see if the guage starts working. If not, pull the unit out and test with ohm meter.

I bought a used tank and pump from wreckers for $75, and it had $30 worth of gas in it. Its was in good shape, and fixed my guage not working

 

[mechtech2]

Lots of good advice above.
MMO or Techron can work, but will take time.
If the part is actually faulty at this point, cleaning won't help.
But it is easy to try in tank products - there are many other benefits, and may fix the sending unit problem. It sure has in the past!

 

[raidermark]

Thanks a lot Sciphi.
There was an access hole in the trunk near the back seat. I couldn't find it at first so I started to lower the tank & found out it wasn't going to come out without taking out half the frame & dropping the exhaust system. So I checked again & found the access.
It turns out I will have to replace the whole fuel pump assembly unit. No one will sell the float arm / module unit separately even though it looks like an easy snap on. Chevy wanted $530 but NAPA will sell a Delphi for $310 which I'm getting in the morning. I may have to cut out part of the access hole to make it bigger with a dremmel tool so I can get the new assembly unit back in without damaging it. The access hole was small. But I'll try first.
Thanks again for everyone's advice.