Fuel Gauge Issue

In the interest of not dropping the tank 2-3 more times I plan to go ahead and buy a Toyota brand fuel level sending unit just to eliminate any discrepancies between the factory Toyota sending unit and my aftermarket Delphi unit. My old fuel pump assembly was in fine shape when I removed it so I’m debating returning the new unit and ordering the URD fuel pump kit for my truck. The refund from the Delphi pump will cover the cost of the Toyota sending unit and the URD kit.

 

Im going to order a new Toyota sending unit tonight, the holidays have been a bit crazy around my home.

Toyota P/N-8332004030 is what my research shows is the correct part.

In the meantime I’ve made a few interesting observations. Now that I know my exact tank capacity- 21 gallons, and my average of 17 MPG (over 4 tanks). I can say with a great deal of certainty that my gauge is extremely accurate. It’s just indicating 1/4 of a tank high all the time. I’m hoping that’s a sign that the wiring is good and the replacement unit resistance was mis-calibrated.

With that said I’ll swing the full arc of the sending unit before installation again and if it fails the test with a Toyota brand part I’ll dig further upstream to try to isolate the variable.

HAPPY NEW YEAR!

 

Alright, I decided to go the buy the Toyota sending unit and the URD fuel pump kit to retro fit my old sending unit instead of using the non-OE Delphi that I originally bought.

I’ve compared the resistance values from the old Toyota sending unit to the new Toyota sending unit and using my jacked up DVOM they look very close. Sort of disappointing but all hope isn’t lost. My cheap meter has been through a lot and I’m hoping it’s off it’s calibration.

With that said the URD kit should arrive in the next couple days. I plan to burn most of the fuel out of the tank and drop it again. I’m hoping the new unit fixes the issue but I’m not holding my breath.

Looking forward, for anyone out there with a Toyota Service Manual; can you look and see where the fuel gauge/combination meter are grounded? Also, it would be great to know where the fuel level sensing unit wires run after the leave the tank? I found a bundle of wires inside of split loom under the truck that leads upwards into a large grommet under the cab. I’m guessing the wiring is in that bundle. I’ll check for excess resistance in the circuit if the gauge still reads erroneously.

Interestingly, the old part was Toyota branded but not Denso branded. The new part isn’t Toyota branded but is Denso branded!? They are functionally the same but the newer part has been redesigned with a semi-triangular float. Lastly the parts counter did not ask me which model or trim truck I have so I’m guessing for the 05’s all the sending units are the same, I only mention that in reference to a third wire for the low fuel level light.

Next update coming soon!

 

Also, the accuracy of my fuel gauge has also tanked. (Pun intended) Today, at 286 miles since the last fill-up my gauge indicated just below half! Ha, 25MPG!! I wish!!!

Oddly enough, the gauge was down around 3/8 this morning and after restarting the truck a little later the gauge indicated higher at about 7/16! Wondering if humidity and/or corrosion are manipulating the resistance readings somewhere between the tank wiring and the gauge.

 

Here’s a sight I’ve never seen before!! So my truck does have the low fuel light, I’m installing the URD kit at the same time I’m working through my fuel gauge issue. I’ll report back soon

 

You are focusing way too hard on the fuel gauge. You have an issue elsewhere. Especially since you indicated that your PCM reads .5 to 1 entire volt lower than the rest of the system. That alone is a huge grounds for concern and should be addressed well before your fuel system debacle because I'm willing to bet that your issue is 100% stemming from that.

 

I could be wrong but after an extensive investigation into my ECU voltage I don't think that's a factor here.

After installing the new Toyota fuel level sending unit the gauge accuracy improved. My gauge seemed to indicate the absolute fuel level and not a pessimistic indication ("3/16 or so less than the tank actually has, if you've ever run your tank so low that the gauge goes below E you should know what I mean here) like most OEM gauges do to keep those of us who like to push the limits from running out of fuel.

But the issue with the gauge bottoming out at 1/8th of a tank and not activating the low fuel level light is still present. I'm going to keep hunting and I'll post any relevant findings. Stay tuned...

 

I scoured the FSM last night and found some additional external ground points that I’d like to check. I’ll report back if cleaning them makes any difference. A few grounds under the bed of the truck interest me in particular.

 

Found two rather cruddy looking ground points today. One on the frame rail onboard of the drivers side rear tire, and another under the intake plenum on the front clip. Neither made any immediate difference in the fuel level indication. I also checked the interior ground on the bottom of the drivers side door pillar and it looked good.
Cleaning ground connections usually only help with DC electrical circuits. I’ll keep digging and report back what I try next!

 

Just to be safe I'd check the voltage regulation. The computer modules should each have there own individual power supplies but the 12V system voltage might be running high. I could see added resistance from poor grounds or connectors causing it to read incorrectly low but reading high means the voltage is propped up.

 

Well I’ve been monitoring the gauge which had been steady in its error up until this week. I’m at 276 miles on this tank and the needle seems stuck around half a tank. Based off the fact that the gauge always drops below zero when I cut the ignition off, and it always rises to full when I fill up I really think this is a voltage problem. The gauge itself passes the test in the Toyota service manual. I’m going to look into testing my ECU-B and make sure that it is putting out the proper voltage to the instrument cluster.

 

Hey Scalleywag
I feel ur pain and I know exactly what u mean
I have the very same issue
Soon after getting my truck it was in my driveway gauge at 1/4 tank and died. Out of gas it took me a while to get around to testing I did fill up drive it till gauge at 1/4 mark then carried 5 gallons with me
Truck ran till gauge was on E low fuel light came on
Was good for a while after that now just this week at 1/4 mark ran out of gas
I’m stumped. Prob gonna have to fill up when approaching 1/4 mark from now on

 

Thanks for posting, so if I read your post correctly your gauge is a moving target too? Sometimes it indicates “more-correctly” and sometimes it is way off such as running out at 1/4 of a tank?

My gut feeling is that the gauge cluster is at fault here. But I don’t want to spend $360 to find out that my gut is wrong! If anyone is in the triad area of NC and has a working cluster, and was willing to let me do some part swapping I’d love to swap the clusters and see if the fuel gauge indication changes?

 

Scalleywag,
Any answers! I just bought an 06 Tacoma for my son. I am having the same 1/8 of a tank left false gas reading when it should be E! Also, the a/c only works on high. I know the blower is causing the wiring to short circuit, but I don’t know which blower and wiring to replace it with. HELP! Thank you for your research!

 

The blower connector is under the glovebox. There’s a series of resistors incorporated into it but the heat generated fries one of the connector pins over time. The resistors are supposed to be cooled by the fan but it doesn’t work well enough. You can get both the connector and resistor for your model on Amazon. Don’t know about the gage thing as mine doesn’t have that problem, good luck.

 

Thank you. So, what is the root of the problem? Is the blower not cooling the resistors, so all 3 need to be replaced?

 

I have not investigated the fuel gauge any further, I suspect that the gauge cluster itself is at fault. If Toyota offers the same deals this November as they did last year over Black Friday I should be able to get a new cluster for 1/2 price. That’s what my plan is for now, I usually just fuel up around 300 miles and haven’t had any issues with fuel range even towing the boat or my utility trailer. When I buy a new cluster I will report back what I find for everyone!

 

That’s pretty much it. They’re a set that installs into the blower stream of air but even with that the heat from the resistors is too much and one of the terminals overheats. High bypasses the resistors altogether so it still works on that setting. There's a thread about it with some decent pics of the connector and what happens to it.
https://www.tacomaworld.com/threads/replacement-of-hvac-blower-motor-resistor.8310/

 

Here's where I am at with my fuel gauge issue. Moving on from my previous posting. Truck showed a 1/4 tank I went to local Home depot for supplies and when I got home shut truck off, unloaded supplies went to move truck . . . would not start. Hmm been here.
Same symptoms as before, added about two gallons of gas, truck fired right up, went to gas station could only get approx 9 gallons in tank. After talking with a few well versed mechanics I bought new pump assembly and vapor canister. When I got into opening the tank after hardly driving it since I filled up, I found tank to be almost full. So that explains why I could only get 9 gallons in it when filling.
I installed the new pump assembly and vapor canister. But WHY does it act like its empty when nearing/at a gauge reading of 1/4 tank??? Still at this point now I have driven it, runs great. Had two fill ups of around 18 gallons with gauge light coming on when it should, leaving me with approx 3 gallons in the tank. Still somewhat perplexed. Do I think its strangely fixed . . .no. I still carry a gas can when approaching the 1/4 tank mark.

 

For those who are researching the issue of the gauge stopping at 1/4 tank, l originally thought it was corrosion at the terminal of the fuel level sender, the part that connects to the plastic top. I had this problem, pulled my fuel pump measure the sender and got 109.6 ohms at the bottom, and 4 at the top. Checked it out of tank and was all good. However the contacts of the connector at the top were corroded. I tried to clean them but they were bad, and hard to get to without disassembly of the connector.. I didn't want to pay $170 for a new sender when all that was a problem appeared to be corroded terminals, so I had it working, than put it all together, and although it was showing properly (empty with light on at the gauge, when I tightened the white ringt down with the tank empty it showed 1/4 tank. Unfortunately I had put the bed back on and could not diagnose further, but I thought the corroded connection was causing an increase in resistance.....but hmmm. Now that I think about it, for the tank level to read higher, resistance should have decreased? 1/4 tank corresponds to about 90 ohms when it should be getting 110. Damn. The unit consistently showed 109 ohms when the float was at the bottom when out of the tank. When I placed it IN the tank, and battened down everything, it went back to 1/4. The only way I think this could all fit together is that the bottom.of the tank is warped, or something else is not allowing the float to go to the bottom when in the tank. Although I haven't finished figuring this out, I hope it can somehow help someone.