Water in fuel

[donstevens]

I think I have some water in my fuel tank.

Last Sunday on my weekly "exercise drive" upon making a right hand turn the car suddenly began popping and cracking and acted starved for fuel. The fuel indicator read just under 1/2 way but as many early 911s the light was flashing under braking and on right turns. Being right by a gas station I pulled in, topped up, and the problem disappeared.

FTR - I did also check the coil wire as the symptoms were similar to those experienced by the R-Gruppe run a month or so ago. The coil wire was tight and no leakage.

My theory is that as I was getting toward the bottom of the tank (where the water will lie) I picked up some water. Make Sense?
How does one get the water out? (I wish it had one of those little needle valve drains like small aircraft have). Is there some kind of product that one can add to the tank that absorbs the water without hurting the fuel system?

Don

[tonythetarga]

Use Dry Gas or gas line antifreeze.
More likely it is your gauge not working correctly. You were probably much lower on fuel, especially if the light came on. Did you fill up all the way? How many gallons went in?

[donstevens]

10-4,

I did not fill all the way. I put about 6 gallons in.

[sammyg2]

A good alchohol based additive will absorb the water and keep it in suspension so it can pass through the engine with no harmful effects. As previously posted, dry gas is one of those products.

[Grady Clay]

Don,

Products that are “gas line antifreeze” are alcohol. The
alcohol absorbs the water and then the mixture becomes
miscible in gasoline and runs harmlessly through the engine.

If you think this might have been a periodic occurrence over
a long period you should do some investigation. The
easiest is to get a spare gas level sender gasket, remove
the sender and make yourself a long swab to wipe the
bottom of the tank and see what is there. Most likely you
will find rust and sludge.

A fine rust restricted screen filter fitting can act in the same
manner you describe.

While the sender is out of the tank, confirm that the float is
free to travel the entire length of the sender. It isn’t
uncommon for the float to stick on the way down,
indicating ½ tank when it is almost empty.

If there is much of anything on the bottom of the tank,
some cleaning is in order. This is an easy Saturday project.
Some things to get beforehand are the sender gasket
mentioned above, the aluminum sealing rings for the drain
plug/return fitting and the filter screen fitting and the
gasket between the tank and body. I recall someone
finding a product at a home center that was a direct
replacement for the Factory gasket. You should get a
lengths of 7 mm and 11 mm hose and new Norma-Schellen
(N-S) hose clamps. Your ’72 has them on the return hose
but probably not on the supply hose.

Check on the availability of a new screen filter fitting. It is
possible you may want to replace it. Get the brass 911
version, not the plastic 914 type.

Inspect your breather hoses. Your ’72 has plastic breather
hoses. They typically get hard and shrink with age. They
were originally installed without N-S clamps. It is a good
idea to replace the hoses with new and install clamps
everywhere.

You will need to remove the front pan under the steering
rack. Start early with penetrante to loosen the four bolts.
You might get them loose and retighten a week prior to
your fuel tank cleaning. While there, inspect for the
condition of the pan and trailing edge seal.

Before you start, disconnect both battery ground straps
at the wing-nuts. Un-do the positive terminals and remove
the batteries to somewhere else.

Gasoline is the most dangerous substance we normally
come in contact with. Be VERY careful! Do this outdoors,
away from your house or other cars. Have a BIG fire
extinguisher available upwind and away from the 911.
Be VERY careful.

Start with the fuel level low. Siphon out the remaining
gas via the level sender port into a suitable fuel container.
Seal the container. Your gas tank is a 62 liter air-fuel bomb.
Treat it accordingly.

Before you loosen the tank, loosen the screen filter fitting
and the drain/return fitting. The screen filter fitting is
usually difficult to break loose. A 27 mm box wrench
and a sharp blow should get it loose. You will need to
disconnect the breather hose and the fill hose (both ends).
Take the supply and return hoses off the fittings being
careful to not damage the fittings. There are three
removable clamps that hold the tank in place. Getting the
tank un-stuck from the gasket will be the greatest
challenge. Don’t damage the tank trying to pry it out.

Now that the tank is out, unscrew the screen filter fitting
and the drain/return fitting. Be careful with any remaining
gasoline – drain it into some suitable container.

Cleaning can be anything from your garden hose to your
local 25¢ pressure wash to professional cleaning. The
general aviation aircraft have an industry of cleaning fuel
tanks. Hot soapy water and a lot of agitation works best.
Even after cleaning, treat your fuel tank as you would an
empty gun – the same as if it were loaded. The only “safe”
fuel tank is one purged with CO2 and no
oxygen.

While the tank is out, clean behind and around the tank
in the chassis. This is difficult to get to when the tank is
installed. Use some aerosol silicone spray to lube the
inboard side of the front sway bar bushings. Inspect for
any rust damage or damage from battery acid. Clean the
battery boxes. If necessary clean and paint the surfaces
where the tank seal goes. Test fit the hold-down bolts.

Remove the old supply and return hoses being careful to
not damage the fuel pipes. Measure the lengths and cut
new hoses to fit. An extra cm doesn’t hurt so long as the
hose can’t get kinked. “Measure twice – cut once.” Install
new N-S clamps with the screw oriented so you can service
them by just removing the front pan. The condition o
f these hoses will give you a clue to the need to replace the
remaining fuel hoses at the rear.
Check ”Braided Fuel Hose for a 72T MFI”

Some may want to reposition their electric fuel pump to the
front. This is the time to do it but subject for another thread.

Clean the screen filter fitting with carb cleaner and a fine
brush. Be careful with the fine screen. Reinstall the screen
filter fitting with a new aluminum O-ring and tighten. You
can’t install this with the tank and front suspension in place.

Push the fill hose up the filler pipe as far as easy. Remember
the hose clamps. It is a good idea to test fit the tank
without the seal so you see how it has to slide into the
filler hose. It is much easier coming out than going in.

Once everything is ready, glue the seal onto the tank. Slide
the tank and filler into place. Be careful to not displace the
seal. Reaffix the three hold-down clamps with anti-seize
on the threads. Slide the filler hose onto the tank so there
is equal hose on the filler pipe and tank. Tighten the hose
clamps. Reaffix the breather hose with N-S clamp. Reinstall
the fuel level sender with a new gasket. With a box wrench,
check the tightness of the screen filter fitting. Put new N-S
clamps on the fuel hoses and push the hoses on the fittings.
Position the clamps so the screw is accessible with just
removing the front pan and tighten the clamps. Install the
drain/return banjo fitting with new aluminum O-rings.

Double check everything. Install the two M10 suspension
bolts without the front pan. Fill with 5 gallons of fresh clean
gasoline and inspect for any leaks at the filler hose,
drain/return fitting, screen filter fitting and hoses. If there
is any signs of leak or seep, fix it now. Even the smallest
seep is unacceptable.

Here is an opportunity to clean all the battery connections.
Reinstall the batteries, ground straps last. Be aware there
may be a spark from the clock so make sure there aren’t
ANY gasoline fumes.

Turn the ignition to “on” and let the pump run. Check for
fuel leaks.

Start the 911. Check for fuel leaks.

Go for a drive and fill the tank all the way full. Check for
fuel leaks.

Let it set overnight. Check for fuel leaks.

Reinstall the front pan. Check for fuel leaks.

Go back and double check everything you touched or
disturbed. Check for fuel leaks.

Go for a drive and enjoy. C….


Remember … Gasoline is the most dangerous substance
we normally come in contact with. Be VERY careful! Do
this outdoors, away from your house or other cars. Have
a BIG fire extinguisher available upwind and away from
the 911. Be VERY careful.

You don’t want to die from burn injuries … or worse yet,
destroy the 911.





Best,
Grady

[donstevens]

Wow Grady,

Great reply. Thank you very much.

Despite the fact that such a tank cleaning job might be a Saturday job for some folks on this board it is not for me. I can check the float valve for sticking but that is about it. I am a rank amatuer mechanic and I am not confident enough in my skills to tackle that job. If it has to be done, it will go to a professional.

The job you describe was performed by a professional on this car by one of the previous owners in 2003. The tank was removed and cleaned and reinstalled with all new hoses (including those in the engine compartment), clamps and seals. So while there may be some crud in there it is not 34 year old crud.

I'll try the dry gas first and see if that solves it.

Thanks again,

Don