Fuel level sensor issue

[yoda009]

Hello all
Had the recent fun of replacing my rusted out oem fuel pump. Had a precision one i Had got for free with the truck.

Precision Fuel Sending Unit/Assembly - A33115​

Says something about possible wiring needing modification? Cause now that its changed im getting wildly inaccurate fuel levels. I added 9 gallons yesterday which took it from 1/8 tank to 3/4....very wrong. Drove about 50 miles and got home with it on 1/4. Even noticed when I replaced it the level was lowered then when I had the oem one. Everything plugged in but found you may need to switch wiring? Im just not sure cause I had a hell of a time getting the new one in due to rust and the opening being tweaked from lock ring removal. Level changes with fuel adding but its all over the place it seems
Added picture. Used the cut the floor method lol dont judge

 

[mikez71]

Love the access hole!

What kind of wiring modification? Moving wire to another section of the resistor maybe?

 

[yoda009]

Love the access hole!

What kind of wiring modification? Moving wire to another section of the resistor maybe?

I did the access hole in case there would be another problem. Thankfully I did in this case. Documents with pump say you may need to modify but I already had the correct plugs for the pump. Attached photos

 

[mikez71]

Oh I wasn't being snarky, I would like an access hole myself. Planning to drill the corners as you did.

Maybe you got a crappy unit..

Did see some TSB about new fuels with too much sulfur messing up fuel level readings. GM has some fuel additive that's supposed to coat the electrical contacts..

 

[yoda009]

Oh I wasn't being snarky, I would like an access hole myself. Planning to drill the corners as you did.

Maybe you got a crappy unit..

Did see some TSB about new fuels with too much sulfur messing up fuel level readings. GM has some fuel additive that's supposef to coat the electrical contacts..

Ya I was hoping it was something wiring wise cause I can't afford a gm pump right now. That's the plan is to change it to gm pump. See lots of negative reviews on aftermarket ones

 

[yoda009]

Oh I wasn't being snarky, I would like an access hole myself. Planning to drill the corners as you did.

Maybe you got a crappy unit..

Did see some TSB about new fuels with too much sulfur messing up fuel level readings. GM has some fuel additive that's supposef to coat the electrical contacts..

BTW I used a air shears to cut the floor. Worked really well. Couldn't use a grinder due to it having fuel everywhere. Just found a you tube short where the guy tells you where to cut and it was spot on

 

[Fless]

I would say it's a defective pump, or at least a bad level sensor. The connector issue is something that has been indicated over the years, so they changed the connector on the pump. Some vehicle harnesses have the old connector, hence the change if needed.

Need I say "use OE" when replacing fuel pumps?

 

[yoda009]

I would say it's a defective pump, or at least a bad level sensor. The connector issue is something that has been indicated over the years, so they changed the connector on the pump. Some vehicle harnesses have the old connector, hence the change if needed.

Need I say "use OE" when replacing fuel pumps?

Figured as much. Just had the pump for years and didn't have the money for an oe. It was leaking fuel pretty bad so at least ive put that behind me for now

 

[houstontaylor]

Not sure what type of electrical connector for the pump you have but I ran into similar sounding problems on my 2003 Tahoe. Dealers replaced my fuel pump twice (two different dealers on different occasions) and both had the bad (poorly designed) pump electrical connector, which gave wildly varying fuel level readings. The last dealer couldn't figure out the source of the problem. A shop I use tried wiggling the connector on the pump and the needle on the fuel guage moved at the same time. As an expensive experiment, I asked the shop to install the redesigned pump with the flat four (1x4) electrical connector instead of the original square connector (2x2). It also had a shorter float arm so as not to hit the side of the tank. That redesigned pump solved the fuel level fluctuations issue but it was not holding pressure with the engine shut off and starting took longer cranking to get the engine going. That problem turned out to be a bad pump check valve on the new pump. Had that pump replaced also, with the part under warranty, and it has been working just fine for the last 6 months or year, halleluyah.

 

[strutaeng]

@swathdiver has posted a table or chart that has various resistance values for these GM fuel tank setups. I want to say it's something on the performancetruck.net website?

Hopefully he'll chime in and you can check resistance and compare that your known fuel level to make the call if your sender is faulty or something...

 

[Fless]

Forum tip: It'd be helpful to add some vehicle info; not all parts over a model series are the same. Consider adding it to your signature so it's always there to reference.

 

[swathdiver]

@swathdiver has posted a table or chart that has various resistance values for these GM fuel tank setups. I want to say it's something on the performancetruck.net website?

Hopefully he'll chime in and you can check resistance and compare that your known fuel level to make the call if your sender is faulty or something...

It was probably here or over maybe at the SilveradoSierra forum.

 

[Fless]

I don't know what you're working on since I didn't see it stated, but the fuel level sender resistance values can be tested once it's removed from the vehicle. Here's an example, but verify that it's the same vehicle as yours or navigate to the appropriate year and section for yours. When you get to the right page, scroll all the way down to Component Testing, where it provides the resistance values.

P0463 — 2012 Chevrolet Tahoe 2WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2012 Chevrolet Tahoe 2WD V8-5.3L.

charm.li

Might be wise to always check a new pump before installing.