Fuel level sensor - rusted out after 2 years???

[ATL Cruiser]

I installed a brand new fuel level sensor (OEM Toyota) 2 years ago. During that time, it got all rusted up and eventually failed. What could be causing this?

1992 HZJ77 diesel. Driven daily. Normal gas station diesel.

 

[OGBeno]

Definitely water in your tank or in the diesel you are using.

 

[Eurasiaoverland]

Condensation from a system which is not sealed. Check the one way valves in your breather system and filler cap. Also the rubber seal in the filler cap and any of the ventilation hoses.

 

[ATL Cruiser]

Update on this: agreed that there is water getting into the tank somehow. Here's is what I've done so far:

• smoke tested the full rear fuel system. Zero leaks.
• tested the evap breather valve. Working great. Replaced anyway, along with all hoses.
• checked for water at the fuel filter drain. No water. Replaced filter anyway.

I'm honestly at a loss where this water has been coming from. Any thoughts are more than welcome.

 

[LDowney]

Appears puzzling. No good thoughts or experience to share, but a few questions come to mind (which you may have already run down)

Any signs of rust on the interior tank surfaces?​

How are you using this Cruiser? (driving regularly where fuel gets used-refilled regularly / driving irregularly - stored with full or partially filled tank)​

Are you filling with a bio-fuel blend? (might not be intentional because TN for example identifies that the diesel might contain up to x% of ethanol)​

How is the tank/fuel gauge grounded? (i.e., could it be galvanic in some nature)​

Is the truck garaged or sitting out? (could temperature/humidity cycles leading to moisture to be condensing in the tank voids above the fuel)​

Sorry to be nothing more that shotgunning here. Good luck

 

[Dprio34]

@ATL Cruiser , Not a permanent solution to your problem, but to limit condensation from forming inside the tank, maybe top the fuel tank off more often than you normally do, especially if you have the vehicle sitting for prolonged periods. This will limit the amount of air in the tank that could condensate. It is quite common in general aviation to top the fuel tank off after every flight to limit condensation from forming, especially if parking out in the sun.

 

[ATL Cruiser]

Thank you both for the advice. @LDowney @Dprio34

To answer a few questions:

• No rust inside the tank, except on the fuel level sender. Strange.
• The Cruiser sat around in the sun all summer while I drove my other car.
• Great question regarding bio-fuel at the pump. I need to look at that next time. Thank you.
• All the grounds on the entire truck are super clean. I just re-did the fuel and dash grounds again, and they were still clean. But there is no additional ground for the fuel tank.

My money is on condensation build up from the mystery fuel. The truck sat around all summer in the sun. I bet that's what caused all the rust.

 

[LDowney]

...
My money is on condensation build up from the mystery fuel. The truck sat around all summer in the sun. I bet that's what caused all the rust.

Heating up during the day and pulling very humid air each evening which resulted in condensation,

Repeat cycle daily for months ... could create the required conditions.

As a possible test; next time you let her set for extended periods, maybe ensure that the tank is full of non-bio blend diesel (but with enough to allow for expansion of heated fuel). After an extended storage cycle, would pulling the fuel level sending unit to check for corrosion be viable? [or is it a task from hades that should only be done in case of sending unit failure?]

Good luck

 

[Dprio34]

@ATL Cruiser , Not meaning to double tap on the topic, but after the auto-shutoff stops pumping at the pump, keep going until you see some diesel. Limit all the air that can possibly go into the tank to minimize the condensation risk. Park inside or under a carport if possible. I tend to think it was long summer days in the sun in a humid environment on a less than full tank that caused your problems. Hope you get it sorted quickly and the problem never returns!

 

[ATL Cruiser]

Thank you, gentleman. That is exactly what I will do next summer (if I remember). Great advice all around.

Thankfully, swapping out the fuel level sender is only a 10min job (unless you get the float stuck in one of the fuel tank baffles and end up needing to drain the entire tank. Whoops.)

 

[Kernal]

Consider sending a sample of the fuel you've been using to a Lab that specializes in Diesel Fuel Analysis, that will give you some insight as to the amount of water in the fuel but also whether the fuel is more corrosive than recommended (water, acid, biofilms,etc)

 

[jblueridge]

Sorry this happened to you.
I if find cleaning electrical connections doesn't bring my fuel gauge back, I now know where to look.

 

[svsisu]

@ATL Cruiser , Not a permanent solution to your problem, but to limit condensation from forming inside the tank, maybe top the fuel tank off more often than you normally do, especially if you have the vehicle sitting for prolonged periods. This will limit the amount of air in the tank that could condensate. It is quite common in general aviation to top the fuel tank off after every flight to limit condensation from forming, especially if parking out in the sun.

This, especially in the south east. Condensation in tanks is a huge problem with humidity and temperature fluctuations, and amazing amount of water can build up inside a tank, and it "floats" on the diesel. So depending of the level of your tank and the amount of time your truck is sitting it can be attacking the sender at all levels. In the marine environment it's top up or get algae in diesel tanks due to free water floating on the diesel. Very similar situation with our trucks.

Top up when sitting and drive it more often.