Bogging After Heavy Rain: Water Getting into the Gas Tank?

SE MX-3 · Post by **SE MX-3** » October 20th, 2005, 12:35 pm

Heres the deal. About 2 weeks ago, my area suffered from some heavy rain. It rained steadily for 2 days straight. On my way to work, after the storm, I noticed that I was bogging heavily. The idle was rough, and it felt like the car was only running on 3 or 4 cylinders. I immediately thought it was the spark plugs, wires, or distributor because I have an invader style carbon fiber hood, which would allow water to drain right on top of the front valve cover area. I checked those and everything seemed fine. Next, I checked the couplings on my intake for leaks, and again found nothing wrong. After checking all the simple stuff, I was stumped.

A few days later, when the weather cleared up, and it was bright and sunny again, I started the car and everything seemed ok. Once it warmed up though, the problem started again. I then remembered driving through a big puddle during the storm, but thought nothing of it at the time, because my only fear was hydrolock, and that didn't happen. My next thought was that maybe some water got into my gas tank driving through this puddle. The car ran fine on the first half of the tank, but halfway through, and just after the rain, the problem started. I was already low on gas, so my plan was to run the car as far as I could on that tank. I filled it up, and bingo...the car was running perfectly again.

Now, my question is, should I assume this was a bad tank of gas, and a big coincidence with the rain? Or could there be a leak allowing water into my gas tank, or somewhere else along the line that I should look for? Any other ideas as to what could cause this? I've learned alot reading through the message board over the past couple of years, but this seems to be beyond my knowledge. Any help and or ideas are greatly appreciated.

Cliff Notes: Heavy bogging after a big rain storm. Checked intake, plugs, wires, and disty, and found nothing wrong. Is it possible that water leaked into my gas tank causing problems?

GQ084 · Post by **GQ084** » October 20th, 2005, 1:02 pm

Before we start jumping to conclusions, have you tried driving again on half tank...What happens then?

Grants · Post by **Grants** » October 20th, 2005, 4:37 pm

Yes I'd agree, see how it goes over the next couple of tanks.

Rather than water in the fuel I'd suggest something more like condensation from the rain / high humidity in the electricals.

You say you checked the leads, what about moisure down the plug holes or in the dizzy? If it happens again you may be able to check at night in the pitch black for any arcing.

Or then it may have been just a bad tank of fuel too.... Hope you find the problem ok, or better yet I hope it doesn't happen again.

hgallegos915 · Post by **hgallegos915** » October 20th, 2005, 6:23 pm

hmmhave you checked for water iknside the disty cap?
that gasket tends to wear out wit heat..i had that problem at car washes with my old disty.

mazdababe · Post by **mazdababe** » October 20th, 2005, 6:29 pm

when was the last time u changed plugs and wires...it dosent take much moistur to cause a missfire,the only way water would get in the tank would be if u had a leak...then u would consantly smell the fuel vapors if the hole was on the top...if hole on bottom...well..u would see the fuel on the ground, right?......

Rick Johnson · Post by **Rick Johnson** » October 21st, 2005, 12:07 am

Same thing happened to me when it was really wet out, it was the distributor in my case, it had a very small hairline crack and moisture was getting in.

slimmyslim1420 · Post by **slimmyslim1420** » October 22nd, 2005, 12:27 pm

do you have a cold air or short ram, if so is it possible water got through it. that happened to my car because i have a ram-air hood, if thats the case it will bog down until all the water is out of your engine

jschrauwen · Post by **jschrauwen** » October 23rd, 2005, 11:42 am

I think Grant caught it wrt water in the spark plug holes. Those rubber caps are not perfect sealers and with the Invader hood you're going to have excess amounts of water running onto the front VC. Sure it'll appear that it's all running off, but an inspection by pulling the plug caps should reveal the truth. Try re-creating the same circumstances using a garden hose over your Invader hood to confirm. If water in fact did get into a couple of plug holes you also run the risk of creating a short betwen the plug cap insulator and the VC recess. That'll definitely give you the impression of cylinder missing. As far as water in the gas tank, I believe in time that if we have not changed gas tanks or done a purge, then there will be an accumulation of moisture in the gas tank. Older cars remember and it's bound to happen. Of course it will settle to the bottom of the tank so those that consistantly run their cars til near bone dry may experience some performance issues by sucking in that 13 year (or less) accumulation of crap. Of course there are variables that come into play - dry and wet climate area, outside parking or garage, extreme differences in seasonal temps, all will also generate moisture to some degree. Has a pressure check been done on the gas cap?

Nd4SpdSe · Post by **Nd4SpdSe** » October 23rd, 2005, 11:49 am

Mine would do that on either rain or heavy humid days. I replaced the disty cap to fix that.

PATDIESEL · Post by **PATDIESEL** » October 24th, 2005, 1:59 am

Just a note. I read above that you knew it wasn't hydolocked b/c it still runs...
A car can hydrolock and still run, I know that it doesn't sound like that with the name hydroLOCK, but it is true.
What happens is that water gets in the combustion chamber by being sucked through the intake (aftermarket or custom ones with cone or other type aftermarket filters are much more prone to suck up water, but a stock sysyem will also if you run through a large enough puddel) Water is not very compressable and thus when the pistons come up to compress the air/gas mixture they are also trying to squeeze the water (that isn't going to squeeze). The water will not squeeze and it has to go somewhere so it usually blows through the piston rings and down into the bottom of the motor. After it falls down (and you quit running through the lake) the car will still run albiet on very low compression since the piston rings are now crap. So it will fire, crank, and run, just very poorly. Sadly enough this happened to one of our MOCA members just after a KF swap.

I don't want to scare you b/c your car should run rough all the time if it had gotten water into the combustion chamber, not just when warm. I just wanted to clear up your misconception.
I'd agree that you might have water in the disty cap and need totake it off and dry it out. Then if it is still running rough replace the cap and plugs too.