Sucking dirt from the bottom of the tank, legend ?

I removed the screw in fuel tank fitting on my 84 308 to check the sock/screen. The sock was clean, but because it is plastic it has come off of the fitting, I reattached it with saftey wire.
While the fitting was out, I could look in the tank with a flashlight, absolutely perfectly clean.
Larry....

 

I have seen and heard of this fuel tank strainer being plugged--the symptom will be a a noisey fuel pump. If the pump makes noise, it is time to clean the strainer.
Mark

 

It depends on the car and what the fuel tank is made of. When I first got my '70 Jaguar XKE FHC a couple of years ago, it died on me driving home. Turned out the car had been sitting, the gas tank had rusted, as well as the pickup tube, and the fuel filter completely plugged with crap picked up from the sump. The restrictions in the pickup tube ended up killing the flow and burning out the pump. Had to drain the tank, remove it, have it boiled out and coated, plus replaced fuel pickup, fuel lines, filter and pump.

Cars with steel gas tanks are prone to rust. Alloy tanks not so much so. Depending on the coating used on a steel tank, it can break down over time, and moisture in the gas can cause rust. Especially on older cars that have sat around a lot, it's a good idea to open the tank drain, if it has one, and see what comes out, other than fuel. Over the winter or in humid climates, moisture can condense inside the tank and cause a real mess.

It is not a myth or urban legend. The good news is that it can take many years for it to happen, and newer cars aren't as prone to the problem because of the materials used in the tanks. But modern fuels turn to varnish more readily if left sitting, so if you are not using the car over the winter, definitely add Sta-Bil or some other gas stabilizer to the tank. Maybe some dry gas also, just to be safe.

 

Driving and cornering is going to stir up what ever is in the tank anyway so running it to the bottom is a moot point. Thats why they have fuel filters. It's a good idea to change them more than once every 10 years.

 

Not a myth at all, but Ferraris probably suffer less than other cars because hard cornering stirrs it up and keeps the petrol tanks clean.

My first race in my Alfa Sud caused this problem as I had not cleaned the tank out ... car started missing, etc. Fixed by removing the tank and giving it a good wash ... filters had already been changed.

Pete

 

I understand your question I think.

The reason low fuel level promotes picking up dirt is to do with the dillution of the dirt to clean fuel.

If you have "X" amount of dirt in the tank, and "500X" of clean fuel with a full tank, then you're pretty much running clean fuel, even though the dirt is in suspension in the fuel.

When the tank is nearly empty, the original "X" is the same as it can't pass through the filter but you now only have "10X" of clean fuel.

What then happens is that the surface of the filter becomes plugged with the dirt under vacuum from the pump.

This is why the largest possible surface area of pick up filter is required.

However, Most Ferrari tanks are alluminium, and rust is not a problem. Most pick up problems are from surge or contamination of water/stale fuel etc.

 

I don't believe it is ... close but not exactly on the bottom. Amazing how I gave you a real example and you have choosen to ignore it ...

What happens is that with around town driving the sedament (sp?) forms and solidifies a bit ... then a spirited bit of driving stirs it up ... just as I proved with my example.

Very few tank outlets are ever designed at the very bottom of a tank for this reason ... ie. try running your car out of gas ... there will still be a little bit of fuel left!

Anyway you choose to believe whatever you like ... you obviously will

Pete

 

Example for those interested: Alfa Romeo 105 series fuel tank contents

Pete

 

Good question ... not sure. One has to remember that old Alfa fuel tanks will be one of the rustiest , but that is a bad example that is for sure.

Pete

 

I can't say for sure on a 105, but my '79 (115) Alfa had that kind of combined fuel feed/level float originally. It mounts in the top of the tank, and hangs down, pulling fuel from near (not at) the bottom of the tank.

The '79 Spica cars had a recall mod, back around '80 or '81, to replace that feed with a submerged pump, due to problems with fuel feed during "brisk" cornering (there are no anti-slosh baffles in those Alfa tanks -- the fuel gauge is only even vaguely close to accurate when standing still).

In 25 years, the Alfa has only failed me five times -- four of them related to fuel feed ... and two of those were contaminated fuel from a gas station. The very dense tank filters the Spica cars used would be clogged even by water in the fuel. After 24 years, I had to remove the tank float and "vaccum" out the junk in the bottom of the tank -- including the remains of a tie-wrap that had been part of the recall tank pump.

I finally wound up removing the 90-degree entry tank filter mounted under the car, replacing it with an inline tank filter at the tank feed hose in the trunk. (It won't stop contaminated fuel from clogging the filter, but it's not a "lift" job to replace the filter, now.)

 

Yes I guess you are right. The only difference might be that running the tank low, due to the fuel pump suction, may stir up some sedimentation that would otherwise happy stay sediment at the bottom.

I do know that spirited driving can stir up this stuff and cause problems, whether tank low or not.

In the end keeping your tank clean is a good idea ... and probably one of the areas where old cars are unfairly given an unreliable status. Hardly the cars fault

Pete