Problem started with water in the fuel tank

BARBARA NYHUS

MEMBER
1985 CHEVROLET CORVETTE
75,000 MILES

Due to the design of where the gas fill neck is located, I got rain water in the gas. This happened once before and my mechanic and I drained the tank, refilled it and it was fine.
This time, my husband said "oh, there's no water in the gas, that's not the problem" and tried to start the car several times before saying "oh, there must be water in the gas"
He siphoned the tank. I put fresh fuel and it still wouldn't start. So we tried letting gas out of the fuel rail and it still had water in it.
We siphoned the tank again, and drained the fuel line via the fuel rail. Refilled the car and after several tries, got it started. But it ran really rough. After a few minutes, when it started to warm up, one of the coolant lines blew off (the clamp broke) of it spilling coolant all over the place. We replaced the clamp, and refilled the coolant. And basically let it sit overnight.

I figured the plugs were fouled, so today my son, who is in the auto program at school, took it to school and changed the plugs. It is still misfiring like crazy. Sounds like it's missing on at least 2 cylinders. Backfiring like crazy. I felt like I was going to get arrested driving it near a school. Sounded like I was shooting at people. Not Good!

The auto teacher is saying he thinks the next step is to change the wires but I don't agree. I think it's still a fuel problem. I thinking I should change the gas filter. But what happens if watered down gas got into the cylinders? That's really bad, right? Water doesn't burn. It cant evaporate from there, so what does it do? Just take up space in the cylinder?

What do you think the problem is and any idea what I do next to try and fix it? Your input would be appreciated.

2 Replies

KASEKENNY

MECHANIC
18,907 POSTS

At this point, the engine runs but runs poorly? If this is the case and it is backfiring then we may have a larger issue then just water in the fuel. Water is not going to cause a backfire. It will cause poor running until the water is gone. It doesn't stay in the combustion chamber, it just gets expelled out through the exhaust but is not burned and takes the place of fuel in the air fuel mixture. This means it runs on less fuel and doesn't run properly.

The most common cause of a misfire is a timing issue allowing unburned fuel to ignite in the intake due to the intake valve remaining open during ignition or it opens to soon and allows the ignited fuel to escape back into the intake.

Your vehicle should have a distributor correct? If so, I would start with checking the timing.

After this we need to inspect for vacuum leaks. With all that happened we could very easily have created a vacuum leak. Lastly we need to check compression. All of this is to verify base engine and go from there.

https://www.2carpros.com/articles/engine-backfires-while-running

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/how-to-test-engine-compression

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