Wacky Fuel Guage

[brickisred]

Fuel Guage Problem

Hi guys,
I wondered if anyone else might have had this problem. I had a CEL last night and after some reading, I decided to check my fuel cap. Sure enough, it was kind of loose after I filled the tank the day before. So I tightened it, and reset the light by disconnecting the battery. Well this morning I take the 5 to work, about 30 miles away and as soon as I arrive (and as I'm sitting in the parking lot idling) my fuel guage starts dropping. Drops all the way to E and the fuel warning light comes on. I shut the car off, wait a minute and then crank it back up. The needle climbs to about halfway, and then starts to descend again. (I should have over 3/4 tank of fuel) Then then the CEL pops back on. WTF? (dunno)

I should mention that I was cleaning under the hood the other day. Could I have knocked something loose? After I got the CEL last night, I checked all the vacuum hoses and electrical connections and didn't find anything loose. Will take it to get the code read today. Anyone have a clue about the guage? Thanks...

 

[brickisred]

Well, as I was driving home, my fuel gauge slowly crept back up to 3/4 tank, but the CEL is still on.

In case anyone is interested, I got the codes from Autozone, and I've got a P0463 and P0464 number.

P0463= The PCM has determined that the voltage signal from the fuel level sensor is intermittent

P0464= Poor electrical connection at the fuel level sending unit
Probable causes: 1. Failed fuel level sending unit

Voltage signal from the fuel level sensor is too high for the current engine operating conditions.

So I guess I'll check the connections from the fuel level sending unit (Is this accessible from under the rear seat?) to the gauge or computer, and when that doesn't solve the problem, replace the unit.

Can anyone tell me if the computer has a central location with all of the electrical connections going into it, or what I should look for here? Kind of a noob with this OBD thing...
Thanks.

 

[i12drivemyMP5]

I would check & make sure the connection is tight & not corroded where it plugs in by tank then go from there.

 

[bazooka joe]

bad ground as well....?

 

[brickisred]

Cool, thanks guys.
I will check it this weekend when I get a chance. Think it would be okay to put some dialectric grease on the connection at the tank? I didn't think about a bad ground, will check that too...

 

[pasadena_commut]

Cool, thanks guys.
I will check it this weekend when I get a chance. Think it would be okay to put some dialectric grease on the connection at the tank? I didn't think about a bad ground, will check that too...

The sensor in the tank may be bad. When the one on my 323 broke it acted a lot like that. That sensor was basically a long wire coil which acted as a variable resistor when the fluid level measuring part moved up and down along the coil. Once the wire in the coil broke and it started to unwind the readings were all over the map.

 

[i12drivemyMP5]

Yes, if connections OK then the sensor itself would be next suspect.

 

[Rusty]

WATER in the gas. It will usually clear up on its own. I,ve seen it several times on different cars, always after a fillup.

By any chance, was the tanker truck there while you were pumping gas? That's a good way to pump crap, because they stir everything up when they fill the station tanks.

 

[brickisred]

Wow I've never experienced that. So that could cause the gauge to go crazy? I don't think I saw a truck there when I filled up. I go to the same place pretty much every time and haven't had this problem before...

 

[brickisred]

I should also mention that this car sat for almost a year before I bought it a couple of months ago. The previous owner moved to NYC and didn't need the car so he parked it at his friend's house. I think the friend might have taken it out every once in a while, but probably not often. Maybe sitting there with a half empty tank might have caused something in there to corrode? I don't know. Gonna go check out the connections today.

Anyone know of a good OBD scanner I could get maybe online somewhere? Think I'd like to invest in one...

 

[Rusty]

If it sat for a long time you're right, it could br rust in the tank. The gas tank is under warranty for 7 years or 70,000 miles according to my '02 P5 Warranty manual. I don't know if it covers the pump and related parts, or rust. Let us know what you find.

 

[brickisred]

Well, I popped the cover off underneath the rear seat (I'm assuming that this is where the sending unit connection is) and found that it was pretty filthy under there. Also looks like the plastic on one of connectors has been chewed on!!! ??? Prongs are in good shape though.

Cleaned the area, took connectors apart, greased them, and reconnected. Cranked her up and CEL is gone. Gas gauge is also working normally. Hopefully my sending unit isn't on the way out (keeping fingers crossed) I guess time will tell. (As far as warranty goes, I'm SOL there at 73k miles).

I wonder though also, about the water in gas thing. May have just run enough fuel out and let enough time pass for it to "fix" itself...

 

[Rusty]

All's well that ends well. Hope she keeps on zoomin'

 

[P-Funk!]

Put RTV over the broken/exposed contacts to fight corrosion.

Find the mouse that is doing this!

 

[brickisred]

Find the mouse that is doing this!

May have been a mouse. I've been pulling a nest out of my hood for weeks now. Somehow something got INBETWEEN the sheet metal of the hood. I can only get at the stuff through the tiny little punched holes in the bottom of the hood metal. Not sure what it is. Looks like insulation material, plus nuts and the occasional twig! Sucks because everytime I open my hood, a little bit of debris will fall out onto the engine. However that's nothing compared to the snake I found nesting on top of the intake manifold in my old Jeep CJ...

 

[bucksatan]

^^ Try using some of that computer duster stuff to blow out the crap that is stuck up in there. Might blow some of it out.

 

[pasadena_commut]

^^ Try using some of that computer duster stuff to blow out the crap that is stuck up in there. Might blow some of it out.

Rodent crap can carry some very nasty diseases, most of which are contracted by inhaling bits of the droppings:

http://www.cdc.gov/rodents/diseases/direct_rodents.htm

So blowing out the rodent detritus in the hood space with compressed air may not be the greatest idea.

If you can find a couple of buddies to help you, on the next really hot day maybe remove the hood, hose it out thoroughly (wearing a mask), and then leave it in the sun to dry quickly so it doesn't rust. The water will probably work better than compressed air in any case. You could even use a bit of soap to loosen up the stuck bits. Plus if the hood is off the car you can stand it up on different edges to let the water go through in different directions.

 

[brickisred]

Yeah, pretty gross if you think about it. I don't think I want to take the entire hood off. I've been taking a bit out at time by fishing a piece of wire in there which seems to work okay. Think I've got most of it. I had to take apart the plastic parts in front of the air filter to get some nuts (as in acorns) out that were rattling around. But that's what happens when you just let a car sit like that.

Used to live out in the sticks and would check our cars literally every few days because creatures were always crawling up where they shouldn't be, chewing on things. Live in the city now, (notcool) pavement only so no problems with that anymore hopefully.

Anyway, thanks for the advice guys. I love this forum (drinks)