Fuel gauge inaccurate?

My fuel gauge seems to be losing its accuracy. This is the 2nd time in the last 6 months it's just died while driving. I've had it much lower in the past. I understand it's not best practice to let it get super close to E but this seems off.
Is there a way to reset something or is this a sign that the fuel pump is going out or there's a problem with the float or something?

 

Sounds like a worn out fuel sending unit to me.

 

Resistance-based circuit, failure to function properly would suggest bad contact somewhere. I know you don't want to hear this, but you have two options:

• Drop the tank, pull the pump assembly, and clean whatever contacts you can on the sender
• Replace the pump assembly with OEM (neg that - you can just buy the sender, see my next reply below)

If you buy a replacement Denso pump, they're just going to send you the pump, you pull the assembly, pop the old pump out, pop the new pump in. If you buy OEM, it's going to cost 3x as much, but they'll give you the entire assembly, which will include the float/slide system for the sender.

At least that's my understanding from what others have experienced on here, and what I see in the catalog.

 

So what you're saying is to get the sending unit which sounds like it may be the real problem. I need to buy the whole assembly? After a quick look, the whole assembly is pretty GD expensive. Pat, it also looks like you can just buy the sending unit or the pump and they're about a hundred bucks each but I haven't verified Vin or anything yet.... I don't have a problem pulling to bed to get to it. I've already done it once. It's fairly easy.

 

You're right! They put the fuel pump in a weird place in the diagrams, it's under Body & Interior -> Fuel Tank & Tube.

I dunno if your '06 is also UCK40 frame, but this is what I found for mine. In the diagram, I missed the reference link to the float/sender, here:

​

That takes you over to Body & Interior -> Switch & Relay. From there you can click on "GAGE ASSY, FUEL SENDER" (on Schema 8 for me). MSRP is ~$131 at the time of this post. Most local dealerships to me have it marked at ~$90.

​

 

Until you fix the sending unit, measure your mileage.

When I had a broken leg (good jump, bad landing) I drove my sister's old Ford van since it was easy to put my crutches in there when I got in. The electronics were crazy! Once I ran out of gas literally 10 feet from the pump!

Since I was on crutches a guy came over and pushed me the 10 feet. That point forward, I refilled after 250 miles had been run. At least the odometer worked.

Sold it as soon as I could walk without crutches. Had a video on my old phone of all the needles going haywire on one drive. Nuts.

 

How do you find the frame code? It's not part of the vin is it?

I've got this to deal with and a leaking rear shocks to deal with...sounds like rebuilding can be a pita so I'll deal with that after this whole thing.

 

It's on the driver door jamb sticker. But if you plug your VIN into the EPC-DATA site (process described here), it'll also tell you what what frame/chassis you've got under the "Complectation" info. Literally gives you everything that's on the door sticker (color code, trim code, all that).

I can never find the f'n door jamb sticker picture I created, so here I tossed this together really fast rather than search.

​

 

Here's my door jamb sticker which explains why I can't find the frame code...was.like this when I got it
Thank for the info. Hopefully I can get just the sending unit if needed. Gauge seems to work fine until getting close to E. Around 290 on that tank of gas is give or take normal for my truck from past tracking of miles.

Mine is uck41

 

I've got two stickers. The one you're showing on the post/hoop side of the jamb, and another one on the latch side of the jamb. Maybe my wording is off, I dunno how to describe something in that section other than "jamb". A lot of our older model trucks the latch-side sticker is black.

 

This looks the same as the breakdown when I put my VIN in. Schematic is sorta hard to follow but is the sending unit part of the whole assembly and can be basically unplugged/unhooked and the new one be inserted and good to go? I'm wondering if even though the pumps don't tend to go bad very often if it's a better idea to replace the whole assembly. I thought they were well over 500. I think it's around 300 which isn't horrible.

Edit* it's like 520. After some more looking at those parts and diagrams the resistor seems like it could present the same symptoms if it was failing but it sounds like if.it were bad it would do it at any level of gas in the tank. Is my train of thought correct?

 

It's a resistance-based circuit. Almost all fuel tanks I've dealt with have a float of some sort - it's either a bulb on an arm/level that floats up and down, or a donut bulb on a slide that float up and down - and the float position change makes a change in the contact position of the circuit. As the position changes, resistance on the circuit goes up or down and the needle position is actually a basically showing the resistance level.

Because a contact is involved, corrosion becomes a factor. Corrosion would change the ability of contact to happen, which could leave you with dead spots (i.e. fuel drops to nothing when you reach a certain gas fullness, as the float is contacting a bad spot), or if the corrosion was consistent and/or the float bulb was cracked and letting fuel inside, it may read as some weird lower-than-normal value because the float isn't, uh, floating.

I really hope that answers your question. To install, you'd likely need to fully pull the pump assembly, unbolt the float/sender from the assembly, bolt in the new, then reinstall the pump. Naturally, if your pump has more than 150k-200k miles on it, I'd recommend replacing the pump, or the entire assembly just to get back to factory, but ... your money, not mine.

 

Yeah, makes sense. Also, makes sense as to why I thought I was gettin better gas mileage on the first 3/4 of my tank just in my last couple 220 mile round trips recently. Sounds like a good reason to get new leaf springs or get them re-arched, make a long weekend of it while the bed is off and do them same time. Ugh, well upside is I won't have to mess with these particular items for quite some time after this.

Thanks man.