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EDIT: Looking around it seems on Prado and 4Runners as well this access panel is accessed by removal of second row seats and pulling back carpet. Extremely rare for this to fail so little info on it other than inquiries about a few who decided to replace the in-tank fuel sock which acts as the filter. I wasted the time doing this on an '02 Maxima which was setup the same way under the rear seat. The sock had little if any debris in it at 100k miles.
Sooo apparently my fuel pump is fine but my gas gauge is now off by about 1/8.
What got my attention is how hard it was to find info on replacing the fuel pump in the GX.
It would seem that the issue is atypical so why would my problem be atypical.
So I ditched the idea that it was the pump (thank God before I started tearing everything apart)
It was weird that I couldn't really hear the fuel pump at all, but then again the GX is super quiet in general.
I previously had the secondary air pump issue with my car. Plenty of info on that.
Running out of fuel is a bad idea. I would still suspect the fuel pump or the pressure regulator assuming the truck died after some hesitation and losing power. I only have access to the '14 SM (thanks to a generous member of this forum) and it looks like the GX does not have the typical schrader valve type access on its fuel line but you connect the pressure gauge using a T connector. Before doing any further troubleshooting I would definitely rule out the fuel pump and regulator.
Pressure supposed to be 46.5-47.4 PSI the SM calls for replacing the pressure regulator if the pressure is out of that range.
I believe that sediment in the gas tank is rare now with how fuel is filtered prior to being dispensed at the pump, but it is possible. Our cars do not have an external filter to change, rather they rely on a strainer assembly that is attached to the bottom of the pump. If you run it low or out of gas completely, the pump may work harder to draw in fuel and possibly clog up the strainer. Highly unlikely, but still a possibility.
I was chatting with a Lexus/Toyota tech over on GXOR and it would appear this access hole is not large enough to extract the fuel pump/sender unit through that hole. Further research indicates this is merely for disconnecting fuel lines and electrical from pump before one drops the tank for replacing fuel pump/sending unit. One could always make the hole bigger but doubtful that many will do that until these vehicles are way on in age and fuel pump or sender unit has failed.
I haven't seen anyone report here and elsewhere with the GX (or I missed it) but now seeing it in searches for Tundras but there is apparently a problem that occurs at a higher level than an anomaly where a sending unit fails to read below 1/8th of tank and out of fuel condition occurs. In addition the low fuel light also doesn't get triggered. He claimed he has fixed numerous of these on Tundras, LCs and GXs. Actual fuel pump failures are indeed almost unheard of but the fuel gauge sending unit appears to have the potential to be the weak link.
EDIT: If you never let your tank get that low like me one could have a problem they are not aware of as well.
EDIT2: I am seeing part number 77020-35150 but also 77020-35151 came along at some point. Looks like 151 showed up in 2017 sometime. That doesn't automatically mean it has any fixes it though.
Not sure if this is for a set number of years. I guess research of fuel pump part numbers is in order to see if any set year PN was superseded or if problem still occurs today.
Good example showing how fuel pump is held into tank and removed.
A tool like this is often seen removing the ring but apparently it can swell and some just cut it and replace with a new one. I think the Toyota one is 4 sided.
Slightly off topic... Our old Excursion that the GX replaced loved fuel pumps. I suspect that the thirsty V10 and single digit MPG sped up the demise of the fuel pump. Thing was, you had to drop the 44 (44!!!!) gallon tank to replace it. God forbid the fuel pump died after you topped the tank off. I swear, the wife totalling our Excursion was the best thing that ever happened to us...
Yikes... on the Excursion.... for the DIYer you'd probably want to have a 50 gallon barrel on hand or get ready to temporarily use the rig as your fuel truck for other cars. I entertained getting an old Excursion years back but wasn't gonna go diesel and the V10 puking spark plug stories scared me off.
Fortunately I have never lost a fuel pump. I did change the in-tank fuel sock one time on a '02 Maxima. It really didn't need to be changed but it was easily done pulling the rear seat out.
It certainly would have been a convenient time saver if this access hole was bigger
Last year I remember a post by a Lexus tech on GXOR site that mentioned he had seen a number of 460s that were brought in as stalls but were actually out of gas. I didn't hear if all years or a range.
Apparently the fuel gauge sending unit on these affected vehicle fails where gas gauge doesn't show below 1/8th of tank and the low fuel indicator doesn't come on as well. Owners who run low on fuel then run out of gas.
Other than this post hadn't really heard anyone have this issue and never came across any TSBs either. I didn't really go out of my way to look for issue on Tundra or 4Rs either though. Yesterday saw a guy on local GXOR branch report that his '12 stalled out and his wife couldn't restart it and on way to dealer. It got me thinking looking at the fuel gauge picture which was right around 1/8th of a tank and I stated "maybe out of gas?" and info that Lexus tech stated. It was exactly what dealer found. Vehicle out of gas with gauge showing 1/8th of a tank.
Just a heads up if you you notice your gauge not moving below 1/8th of a tank and/or low fuel light doesn't come on. I rarely ever go below 1/3 of a tank so I probably wouldn't know if I had issue or not.