So i filled up this afternoon and I had pretty close to a half tank. I drove about 20 miles on the highway and parked my car. I went back about an hour later and started it up within 2 minutes my gauge was reading under a quarter tank. I don't know what is going on!

I know it has to be the gauge there is no way It sucked all that gas down. Do the floats in the tank wear out?

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1994 SSEi, CAI, Custom Painted Rear Drums and Engine compartment, TR 55'*, JL subwoofer.

Fill your tank to the shutoff point, and reset your trip odometer. When you get to the low fuel warning, fill up again, and tell us how many miles (kilometers) you made it on how many gallons (liters) of fuel.

The bottom half of the tank holds 'less' fuel than the top half. It'* the shape of the tank that dictates this.

I'd think the sender in your tank is the culprit. You can try some fuel additive that contains the Techron additive, or the GM fuel cleaner, both of which claim to help fix a sender that is starting to go bad. Doing the test that Bill suggested will give us an idea of how much fuel you are really using versus what the gauge shows.

Pontiacs are notorious for gas gauge malfunctions - my parents on their van went bad, on their sle and on their ssei - mine went bad as well, so I replaced the sender...didn't work...found out there was a bad ground - turns out the gas cap sensor was bad which caused the whole system to go whacky - i disabled that sensor and now my gas gauge works...sort of...

Instead of registering from full to empty, it see'* a half tank as "full" and when i'm on E, I'm at a half tank...


I never trust gas guages anyway - I always use trip set.

good luck

Not sure what year car were talking about in this thread (can you update your sig to include this info Sharpshooter?)

But IIRC the lower part of the tank on my 94 was wider than the upper part of the tank. Also, the baffles may limit how much fuel is actually held in the lower part vs the top. I'd say I have to agree with Archon about your sender.

Do you smell any fuel when in or around your vehicle? Even if you do, thats allot of fuel to lose for driving only 20 miles. You may want to drop the tank to find out whats going on in there.

I put 5 gallons into my tank a few days ago, put 47 miles on the trip odometer, and now it'* on E. Can't help but wonder if my gas gauge is malfunctioning.

As of right now I am going to go get a bottle of the lubricant fuel additive and put that in to see if it helps anything. I will see what I am getting for mileage also but I don't drive the car much during the week so I will prolly post that information after this weekend.

Thanks
Josh

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1994 SSEi, CAI, TR 55'*,Custom Painted Rear Drums and Engine Compartment, JL Subwoofer

I just added a bottle of Mystery Oil from auto zone. It is supposed to lubricate the entire fuel system including the pump. I seemed to have results with in a few miles but now it'* back to it'* old self. It'* reading a quarter tank again. The gauge fluctuates a lot during normal driving. Things such as stops, corners, and take offs make the gauge move like crazy. I can have a half a tank and look a few minutes later to see that i only have a quarter.

Josh

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1994 SSEi, CAI, Custom painted rear drums and engine compartment, TR 55'*, JL subwoofer

OK, I just went for another drive to see what was happening. When I sat in the parking lot with the car and my JL subwoofer running I watched the gas needle drop for about a minute until it was once again down to a quarter tank. When I got back I turned my sub off and it seemed to start climbing again. Is my sending unit getting weak? I just replaced the alternator like 3 weeks ago.

The car also seems to take off faster when I am not at full throttle. When I do punch it and hold it down it almost seems as if the engine is running kinda rough. I hear a noise that sounds like a dull grind/rumble.

I don't know what is going on!?!?!?!?

Josh

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1994 SSEi, CAI, TR 55'*, Custom painted rear drums and engine compartment, JL subwoofer

Sounds to me like its a sending unit. If the gas gauge is going wacky when your driving and giving false readings, then thats typical of a sending unit going on you.

If an O2 sensor is bad, it could give you bad fuel mileage, but three quarters of a tank driving just 20 miles doesnt seem right.

You can find a sending unit at Advance Auto parts if theres one near you, and replace it yourself pretty easily.

EDIT You may also want to check your fuel pressure at the rail to make sure your fuel pump is still strong. If not, you may want to replace that too while you have the tank down for the sender.