allenw@icsgroup.com

Yep, I got water in gas tank of my 85 Vette.

symptoms:
Running rough
At first it only seemed to happen when
the tank was less than half. One of the other respondents
mention there is a class problem with the gas tank when less than half full
and going around long turns. I ignored that because I have driven the
tank empty many times and not had that problem in the past. (I was not pushing the turns much to have that problem -street driver )
Then one day I drove it to work and let the vette sit out in the rain.
It rained non stop for 6 hours. That night I started up to go home and drove about a mile and things got real bad. Running rough then stalling.
Fortunately I got it started again and took it back to the office running
on what felt like an odd number of pistons.
My good fortune made me look at the gas cap filler overflow tray.
The water was over the top of the non-venting gas cap Ya so.
As I found out, a non venting cap means non venting out to the atmosphere if
pressure is low or moderate in the gas tank. But what if the tank goes into
a vacuum. Like when the fuel pump pushes gas out for
engine use and air is taken in from cap to make up the volume. Also, if warmed up, then allowed to cool the tank will get a slight vacuum. It sucks.
My guess is that the submerged gas cap allowed water to get into
my tank in a big way. Along with any other water from weeks before made it
hard for any dryers in the fuel to absorb that much water.
Even a desperately added gallon of 99% Isopropyl in 18 gals of water/gas I had a milky mess being injected into the engine. It hardly would run at all. (we later estimated a total of two gallons of water was in tank. Only some had been suspended, but not all)

Solution:
remove water. DA
I found in the manual if you supply B+ (12V+) to terminal point "G" of computer test port, the fuel relay will turn on the fuel pump. (in 85 C4's that is-don't know about other C4 years)
We ended up pumping out every drop of liquid via the fuel rail pressure test fitting into plastic clear jugs. The test fitting is the same thread size
as the suction side (low pressure side)of the air-conditioning fitting. A quick modification to a old extra freon 12 coolant hose made a good connection and got the distance I needed to the jugs on the ground. All fluid was semi milky color on top and a inch of water was at the bottom of each jug. This was the case with every jug-all 18 gallons in tank. I think I made the problem worse by adding so much alcohol that it suspended the water in all that fuel. If I had just pumped without the suspended water I may have just got water first from bottom of tank, then been able to save the gas.
Ok, tank now empty we put in 5 gallons of fresh gas. To be safe I ran the fuel pump again and found the first gallon to come out was also milkish and water at the bottom. Fortunately, after that first gallon it cleared up and was crystal clear and the color of gas. The color of gas-never thought I'd be so happy. I think that when pumping the tank empty the pump went dry
and some contaminated fuel was still in the fuel lines, filter, canister, and return line. That all cycled out and finally got the color of gas. What little was still there got mixed with a fill up and bottle of injector cleaner. Yes, I changed the fuel filter a few days later just to make sure the old one did not get water damaged. And yes, it is very dangerous to let a fuel pump go dry in the tank. As soon as fluid stopped I cut off the fuel pump relay.
This is one of those don't do at home kind of things, vapors where every where.

Cause:

How the heck did the fuel cap get underwater you say?
The fuel cap and fuel filler neck sits in a little rubber five inch square reservoir
that has a drain hole in the bottom. I discovered that all of the water from the back window drains into this same little reservoir. When the car is standing still in the rain or being washed by hand the water goes
to this little reservoir to drain out.
But what if the hole is plugged? Crup the hole was plugged!
Reservoir filled up to bottom of fuel cap with water, tank went into a vacuum condition as the day got colder with rain. I had not checked the hole for years to see if water or gas would drain out. My bad.

Long term solution and prevention:
Keep the hole and drain unplugged. Test for proper drainage more often than once a year.
And, make a bigger drain hole with filter screen . The original drain
hole is about 1/4 inch id. A piece of lint and two dust particles could
plug it up. Also the drain hose from the drain hole does not exit straight down.
It does two small bends and drains out over near the left muffler. I found
that this original hose had pretty much collapsed at the bends restricting
drainage even more. If anyone has read this far, I still cannot figure out why
they routed the drain hose to the side like that. Why not straight down and out?
I can only think that if hose was routed straight down,
one would splatter gas on their shoes if gas spilled into reservoir and then drained when standing there
at the center of the bumper at fill up. So they drained it to the left 18 inches.

allen

J Z06

I'm getting flashbacks!! :eek: :U This very same thing happened to me! I was filling up in the rain once. I didn't think twice about the water near the filler cap. I parked it outside 'cause there was stuff in the garage. Next day...I came out to fire it, it is TAKING FOREVER! But it started. Ran fine. I went to wash the car...and came to drying it off...opened the fuel door and the gas neck was under water! :cuss The hose to the drain completely clogged itself with debris. I took a spin to my mechanics,and we switched the fuel filter. I ought to say WATER FILTER! The thing was pure H20. Water,and lots of it snuck inside my tank and cause the car to run like crap. We took my back bumper off, drained the tank and ran compressed air through the lines etc. I also had another drain area drilled in.

I can't stress enough for those of you with daily driven C4s or just a C4 in general: CHECK to be sure your fuel area drains are clear. I've read a few of these stories in addition to the one I posted. It's a friggin' nightmare that can easily be prevented by taking a coat hanger and running it through the drain tube to be SURE it's clear-clean.

Be sure to give that area a look folks. :cheers:

Mike's 86

Whew! what a ordeal, thank for the heads up, I'm sure we'll all check that drain hose often now. thanks...... :cheers:

Mike's 86

And welcome to the forum :cheers: :cheers:

CentralCoaster

I think I had the same problem. The scary part was, the water never covered the gas cap, it only went up to the level of the gas cap, which tells me it was getting in there. I get a bunch of suction on the gas cap because I think my vapor/canister purge lines are plugged.

Now I always check that drain hole, and blow through it to keep it unclogged.

A question though... let's say there's a half gallon of water in there.... will it ever go away? will it absorb slowly with the gas, and possibly be burned off? I never did drop the tank... but I changed out the filter, and siphoned about a gallon out of the fuel rail, and didn't notice any signs of water in there.

kittmaster

Folks, I have never had this happen, but have you ever purchased the Gordon Killebrew books he sells for 6 bucks apiece? This a big point he makes about keeping the hose line clear especially if you have a gas protector. Just because I'm ****, I always shoot some water (lightly) into the gas cap area to WATCH it drain EVERYTIME I wash the car (twice a week in summer). This ensure that something of this magnitude will never happen. Just a tip IMHO. Most vette owners are **** as I when it comes to cleaning, my question, don't you ever wash under the gas lid? You can watch the results from there......good luck and good points. I like the fuel pump purge idea the most to pump it out of the lines both fast and effective......

kitt


[Modified by kittmaster, 9:15 AM 1/9/2003]

lead foot 85 vet

The samething happened on my 69, so I parked it outside ....let the water freeze and then reached in the tank and removed the ice. :cheers:

grapeknutz

A good way to prevent water buildup is to use "gas line anti freeze" or a simular product such as ethanol ( a cup will do) this will emulsify the water and gas. This will not harm the fuel system or the engine.

allenw@icsgroup.com

My research on 99% Isopropyl Alcohol added to gasoline lead me to use
so much that I got a milky white fluid out the fuel rail with all that water. This stuff actually would run but "run" is subject to inturpitation.
OK - The products for sale at the local auto shop for dealing with
water, moisture, or prevention of freeze all have one thing in common.
They either use Isopropyl or ethanol(or was it methanol) as the active ingredient. These alcohol's are soluble in water and in gas. They can absorbed and or suspend water in the gas fluid. At a small level the suspended water is in small proportion to the gas. Very small, the engine probably runs a little better. O-let's run out and add water to our fuel. I have no clue to what that level is. In the retail delivery process of gas to your tank the gas gets put into many different tanks. These tanks all have a small amount of moisture (water)in them. The fuel absorbs this moisture. This is anticipated by the refinery and is normal. When a gas station has a water in tank problem they are shutdown for 24 hours. Something is done, I forget what it was, but the end result is to delivery you and I a fuel with some, but very little water.
Now in your tank the process starts again. As the tank empties it draws in air. The air has water suspended in it. This is the part that the antifreeze/water products deal with. Or exploit with fear.
It is my guess that once upon a time gas was formulated in a way that it did not absorbed much water as it can now. In the winter months your tank becomes a water plant every time it is allowed to get air and condense the water. (normal usage-what you going to do fill it up every time you use a gallon?)
Back then the water would not suspend and would build up. (accumulate with tank fills)
Then once it sat and got real cold the water would be in some place that would
cause havoc. Like, at bottom of tank next to the pickup tube then in fuel lines or that resevore with a float in it inside the carburetor. (dating myself) I bet fuel rails do not like pure water either. Did I mention that gas floats on water so the water is at the bottom of the tank if not suspended.
Now days with oxygenated formulations the fuel seems to be more water absorbing.
I had read that where methanol gas is used that there is no reason to worry about normal water build up. The small amount of winter condensation is easily absorbed by the methanol and burned with the fuel.
Out here in California, they use a cheep additive called MTBE and not a alcohol.
Crap, we have polluted our water table with this stuff as it leaks and is absorbed by ground water. But that's another story. We have only one vender in the SF bay area the offers methanol instead of MTBE. I have switch to them for moisture control and to protest politics of water pollution.

Answer: Yes, my resent experence and testing would lead me
to not wory about a half gallon if using a gas that has any type
of alcohol additive for Oxygenation. It's going to mix eventually.


Sorry for all the words and indirect answer, but I wanted to get this information down in RAM so I could review it in a few years when I forget and start having water problems. I wrote in a tone that I would understand after forgetting some of the terms I used. ( I seem to forget mistakes and make them over every few years)

None of the information above is heavily researched and is a educated guess
of what I think is true. Fell free to dispel any on my assertions. The truth would be better for all.

allen

Corvette Suzy

​​​​​​ Love it! Sorry, don't mean to giggle but can't help it...I have an '85 too. Went through the same predicament. 🤪