Hello
I had a code P0462 along with the fuel gauge showing empty for the last few months since I have owned this 2005 6MT G35 Coupe. I decided to fix it by cleaning out both the fuel level sensors in the rear of the car.

Of course, the previous owner had tried the same trick since the fuel sensor potentiometer was clean already, and the fuel gauge was still showing empty. I knowingly bought a car with this error code, which is fine.

I did this procedure on August 3rd and drove the car around and didn't see/feel anything per se. There was a slight fuel smell and I thought it was due to the work I did.

Then on August 10th I decided to fill the car up with gas at the pump and the car would not stop leaking gas while I drove it. Did not realize that until I got home and luckily the car did not catch on fire.

So I decided I was out of my league at this point, and towed it to the dealer who now wants to replace the fuel tank and the "rusted subframe" to fix the fuel leak. They want over $4500 to do this job.

I have refused to do that since this car only cost me $4000 to buy and has 185,000 miles on it. It is not worth it.

I am going to do this myself now. What is the best way to determine where the fuel is leaking from ?

Is it something simple like I didn't set the fuel pump back in correctly and got the O-ring installed wrong ? Is it the fuel hose that's leaking ? When I drive the car the fuel leaks a lot and smells a lot and drips all the way.

When I purchased the car it was not leaking for the 3 months I drove it, so it clearly started doing this after I worked on the fuel sensor cleaning, which indicates I may have made mistakes in installing the fuel pump back or something.

- How do I figure this out ?
- Where can I buy replacement O-rings to make sure they are a perfect fit ?
- All the screws are rusted in the fuel pump and sensor area. What model/part number screws are these that I can buy ?
- Do I need to replace the fuel tank itself ?

I have documented this whole process on my blog https://vkmotorsports.com/blog/2021/...or-issues.html so you can see and advise if I have made a mistake somewhere.

A couple of images are attached and my driveway slopes downwards leading to the fuel leaking non-stop.



Fuel leaking when car is not moving.

Fuel keeps leaking

 

Get the car up on jackstands, use a battery flashlight NOT A 120V PLUG IN HALOGEN LIGHT! Look to see where the fuel is coming out from.

I would also lift up the back seat, pop the covers and see if you can just see the leak from the top.

 

When I've searched for leaks on a race car, it was easier to wipe the tank dry and follow the wetness to the source. Depending on the amount of gas we are talking about, don't use disposable paper towels (fire hazard). Use some rags and clean them quickly afterwards with vinegar and water: https://rockingreen.com/pages/how-to...out-of-clothes.

Good luck!

 

Did you figure out where the leak was coming from?

 

So I took the car to the dealer and they wanted an arm and a leg to fix it because the tank was too rusted and the subframe was too rusted to be removed etc.

I then spent some time reading the service manual and realized that the service manual says to replace the O-ring every time the fuel pump is taken out. So for $70 I bought 2 O-rings and new screws for the fuel pump and the other sender unit. I have not had time to reinstall the O-rings and the screws yet, but I will do it and retry.

I am pretty confident that earlier there was no fuel leak since I got the car, then I tried to clean the fuel sender sensor units and then there was a leak which most likely came from me not using a replacement O-ring as suggested in the manual. The Youtube videos did not suggest anything about O-rings so I guess I missed that.

I will do it this coming week and post here.

 

Also making sure to properly TORQUE that flange is critical. If you didn't torque the bolts to 20 INCH/lbs using a torque wrench that's probably what went wrong. It's very easy to overtorque the gasket and warp that ring on the top which causes the gasket to not seal properly. Then every time you take a corner and the fuel sloshes to the top it leaks out of the gasket.

Also possible you damage the sealing o-ring on the fuel line, remove the back seat and the fuel cover then turn the ignition to ON (put a towel over the line in case it sprays so you don't get fuel on the interior) and make sure it's all sealed up and not leaking from the line.

 

thank you for the advice. i will measure the torque properly and check the fuel line leak too.

 

I have successfully fixed the leak, it looks like, after driving 5 miles in the car. There were a few problems and I will outline them here for the next person who may need it (including me).

• The flange for both the fuel pump and fuel sensor sender units was not tightly fixed with the screws - first probable cause of a leak.
• The screws were too rusted, so I replaced them by buying a packet of new ones from the dealership Part #01436-01821. This is a Nissan part so you may get it cheap from a Nissan dealer. I bought it from an Infiniti dealership.
• The flange must not be over-torqued of course, but hand tightening new screws is enough. All the screws must be lightly screwed in before tightening, otherwise the flange does not tighten correctly.
• New O-rings are a must on each fuel sensor/pump module and I got new rings with Part #17342-CE800. It is a Nissan part too.
• My O-ring was loose in the fuel pump area and had fallen into the gas tank - second probable cause of the leak.
• While installing the fuel sensor floats back into the tank on the passenger side with the pump, I forcibly shoved it in and it actually broke the spring that the sensor float attaches to. I ended up removing the float for now and installed the pump as is. It works, but shows a full tank at all times since the resistance reading is set to full I guess.
• I also noticed that the sensor float on the driver side also had a bad spring.
• So code P0462 and P0463 still show up because the readings are inaccurate and resistance is high.

Next step will be for me to purchase new fuel sensor units on each side and try that to remove the codes and this time I am aware that I have to gently handle these units.

Lessons learned: read every line of the Factory Service Manual, be gentle with the fuel pump and sender units, and don't waste time going to a dealership. I spent 200$ getting this "diagnostic test" to check why the fuel was leaking and they didn't even do anything besides telling me all kinds of other problems like "change your fuel tank", rather than diagnosing the broken sensor and loose screws issue.

Thank you all who advised me.

 

Thanks for sharing your findings and the complete story. Sorry it wasn’t easier .