Fuel Gauge Macarana?

[75BeauJames]

I've got a slight problem that's been annoying me, and the more I drive it, the worse it annoy's me!

With the engine stopped and the key in the on position, the fuel gauge reports the fuel, and seems to be accurate. However, as soon as it starts up, the fuel gauge does the macarana! It flops around anywhere between 1/4 and a 1/2 of play. (I.E. if the tank is 100% full, it will bounce anywhere between a full tank and a half tank). It never seems to go higher than accurate (i.e. half tank will bounce between a half tank and empty and not back towards full), but definatley goes under.

Someone at work suggested that I'm loosing a ground somewhere, and suggested I take a meter and read the ohms/voltage on the sender leads on the tank, and again at the dash gauage. Someone else suggested I just replace the float for the fuel sensor...

What do you guys think?

Scott

[Prerunner1982]

does it only do it when you are actually driving it? or when it is just sitting still idling?
if it does it while you are driving.. thats pretty much normal, just the float moving around as the fuel sloshes....if it does it when sitting still.. then yes probably a ground trying to go bad...

[75BeauJames]

Any time the engine is running, although at idle it is a very small amount... When driving down the road, it bounces all over the place...

[Slonaker]

My temp gauge did this once. It bounced so fast I couldn't see the needle. The wire going to the sending unit was grounding on the valve cover, and it bounced as I drove. Every time it touched the valve cover it pegged out, and when it lifted back up it read correctly. Going down the highway the needle was just an orange blur.

My guess is you have a similar problem, assuming the fuel gauge works the same way...

Slonaker

EDIT: I see you are in Austin. <waves in a northerly direction>

[75BeauJames]

Originally posted by Slonaker
My temp gauge did this once. It bounced so fast I couldn't see the needle. The wire going to the sending unit was grounding on the valve cover, and it bounced as I drove.

Haha, I have the same problem as well! I pulled the wire when I installed the new carb and have been too lazy to reach way down in there and plug it in! Figure the fuel gauge is probably more of a concern right now.

EDIT: I see you are in Austin. <waves in a northerly direction>

<waves back> Actually I'm in Leander, just north of Austin. I just get tired of fielding the "Where the hell is Leander?" questions and just put Austin for simplicity.

[Ric83]

Oh, oh, I know where Leander is!! lol
Welcome, BTW.

[75BeauJames]

Thanks for the welcome, Ric!

Okay, I think the problem is the float. After watching it closely on the way home last night, any movement of the truck makes it bounce. Sitting with the key on with the engine not running, I had a buddy rock the truck from side to side -- Gauge moved! Ya'll think this would be an accurate assumption?

Scott

[Slonaker]

Unless a wire is grounding when the truck moves...

Slonaker

Where the hell is Leander?

[Prerunner1982]

if its moving so fast you cant see it, more than likely a ground... if it gradually moves.... could be either.. but more than likely float.

[75BeauJames]

Yeah, it's gradually moving. In fact, the harder we rocked the truck, the more it moved. When idling, with just slight vibrations, it moves maybe an 1/8" of an inch. When rocking it back and fourth, we could get up to 1/2 tank of movement... So, I'm going to assume the float is extra floaty.... Or something