water in gas?

Inertia 500 · 10-24-05, 12:41 PM

I've noticed that after almost every time I wash my 86 coupe, the engine will run poorly for a while. It will stumble and cut out on deceleration and then set a code 33 (MAF too high). I've gone through the troubleshooting sections in the shop manual for the MAF and can find no problems with it but I think what is really happening is that I'm getting some water in the gas from around the gas cap. This throws off the fuel injection system during deceleration because the oxygen sensor goes very lean. The ECM thinks the MAF is bad because the mixture is too lean even though the injectors are passing the right amount of fuel. Of course, since some of the "fuel" is water, the mixture is too lean but not because there is too much air.

After I drive for a while (40+/- miles) everything goes back to normal. The check engine light usually does not come back on the next time I drive the car.

I changed the MAF relays after the first time the car did this but I don't think that changed anything.

Two questions:

Has anyone else had problems with water getting into their gas tanks? I always tighten the lid until it ratchets. The drain hose is clear. However, when washing the car the gas cap will become submerged momentarily.

Does anyone have any comments on my theory as to why the code 33 is set?

vetteboy86 · 10-24-05, 12:55 PM

Why does your gas cap get submerged in water momentarily?? That doens't sound right to me at all. Anyways I wouldn't think that water could actually get in with the cap on. Another thing to think about is that water is heavier then gas, and water will go to the bottom of the tank. I am not sure where the fuel sender is but I woudln't think you would pull water unless you are running the tank really low.

You might have some other issues here, but I can't be for sure.

Good Luck

Barrier · 10-24-05, 01:20 PM

I have had a similar problem when I let the gas run low. Try putting a siphon down the filler and drain out from lowest part of the tank. Make sure you get the bottom of the siphon as deep into the tank as possible. I drained it into a clear container, you could see the water, (cloudy). I got almost 1 quart out, this was when I first got the car at 85k miles. Since then I put dry gas in periodically, and change filter at least yearly and make sure not to let the fuel level get low.
By the way my 1968 427 Coupe had this problem when new. The car would stall when nailed, just like you turned it off. Solution by the Dealer Vette mechanic was to cut slits around the perimeter of the boot to let the water out faster. That Corvette spent much of the first two months I owned it at the Dealer with the problem, until their aforementioned Vette Expert returned from Vacation. I even spoke with Zora Argus Duntov by phone when I got nowhere with the dealer. They eventually enlarged the drain tube diameter as a permanent cure.
Barrier

Tuna · 10-24-05, 03:23 PM

Check and clean the drain hose by the gas cap and make sure the gas cap has a good seal. If water sits by the gas cap for very long, the drain is probably plugged or partially plugged. A small and flexible bottle bush should do the trick (aquarium shop stuff).

The next time you wash the car, pay attention to this area and dry it out with a towel if need be. This should help track down the problem if it still happens.

vett boy · 10-24-05, 07:04 PM

I agree with vetteboy 86.I'd bet that water in the gas is not the problem.Your probably one of those purest that have never driven in the rain.But that might give you the right track.Good luck.

Inertia 500 · 10-25-05, 12:11 PM

Thanks for the replys. I will definitely try siphoning the dregs out of the bottom of the tank.

jmccloud · 10-26-05, 08:58 AM

Clearing up after only 40 or so miles after a wash sounds like ignition dampness.
Water in the gas will persist and poor runnability will show up more with low level (like it may not run at all).

vetteboy86 · 10-26-05, 12:51 PM

I agree with that, however I have never had a problem on an L98 engine. I have degreased the motor several times with no problems.

74bigblock · 10-26-05, 12:54 PM

If you are concerned that there is water in your gas... go get some "Heat" from the store and dump it in your tank.

gmjunkie · 10-26-05, 01:32 PM

Quote:

Originally Posted by 74bigblock

If you are concerned that there is water in your gas... go get some "Heat" from the store and dump it in your tank.

Yes Sir !! Heet Is the Best Thay Make!! It Will Thaw out a Frozen Gas Line in 10 min!!

junk!!

jiangtao · 10-26-05, 01:46 PM

You might also want to check the wiring to the MAF relays. I know that my '86 has some wire shrink. Maybe that when you wash the car there is some water getting on the wiring. If they have shrunk, then you would definately be getting a problem. By the way, does anyone know what would be the best thing to correct the wire shrink issue? I know you can buy the liquid type insulation, but how could you get the wires back inside the harness really good?

Inertia 500 · 10-26-05, 03:59 PM

Quote:

Originally Posted by jiangtao

You might also want to check the wiring to the MAF relays. I know that my '86 has some wire shrink. Maybe that when you wash the car there is some water getting on the wiring. If they have shrunk, then you would definately be getting a problem. By the way, does anyone know what would be the best thing to correct the wire shrink issue? I know you can buy the liquid type insulation, but how could you get the wires back inside the harness really good?

Thanks for the suggestion jiangtao. My harness also has insulation shrink at the MAF relays. I'd like to know how others have repaired this problem. I tried heat shrink tubing but I didn't have any that was large enough to fit over the pins (terminals?) on the individual wires and would still shrink down securely onto the wire.

I will take a look at these wires next time I wash the car to see if they are getting wet.

jiangtao · 10-28-05, 01:33 AM

If you do have the wire shrink issue, then that's where I would start. I looked at the place where my hood meets the door today and noticed that there is a chance that water can get sprayed in there and probably hit the MAF realys. When I wash my '86 I always use the "sprinkle" part of the nozzle.{I have one of those multi spray nozzles} That way when you are rinsing the car off water is less likely to get sprayed into that spot where the hood meets the driver {or passenger} door.

Inertia 500 · 10-29-05, 12:20 PM

Quote:

Originally Posted by Barrier

I have had a similar problem when I let the gas run low. Try putting a siphon down the filler and drain out from lowest part of the tank. Make sure you get the bottom of the siphon as deep into the tank as possible. I drained it into a clear container, you could see the water, (cloudy). I got almost 1 quart out, this was when I first got the car at 85k miles. Since then I put dry gas in periodically, and change filter at least yearly and make sure not to let the fuel level get low.
By the way my 1968 427 Coupe had this problem when new. The car would stall when nailed, just like you turned it off. Solution by the Dealer Vette mechanic was to cut slits around the perimeter of the boot to let the water out faster. That Corvette spent much of the first two months I owned it at the Dealer with the problem, until their aforementioned Vette Expert returned from Vacation. I even spoke with Zora Argus Duntov by phone when I got nowhere with the dealer. They eventually enlarged the drain tube diameter as a permanent cure.
Barrier

I siphoned out a few gallons of gas like you suggested. A few tablespoons of brown water out came out with the gas. It is pretty hard to get anything down into the tank with the fuel pump and everything in the way. I used a piece of aluminum tubing attached to a flexible hose. I put the aluminum tube into the filler hole and pushed it down to the tank bottom and moved it around as much as possible to try and "vacuum" the bottom of the tank.