Flooded engine. Running out of ideas....

[Gabe]

After fixing a fuel problem with a new tank and a cleaned carb, I was testing the engine. Started right up but ran rough. Determined that there was 0 compression on cylinder 3. Used ATF+Acetone and got the valve unstuck. Still running rough. After a few days of tinkering with idle adjustments and reading this site, I decided to check compression again...decent compression on 1,2,3 (78,78,80) but now cylinder 4 shows no compression. Gave it an ATF/Acetone soak and started it up. After throttling up a few times it died when returning to idle. I tried to restart but it wouldn't. I didn't think I tried excessively, but I must have because sure enough when I checked compression again water came shooting out of the cylinders.

I closed the through-hull, turned the engine over until no more water was shooting out, cleaned the plugs and tried to restart with no luck. Water shooting out of plug holes again. Cranked until it seemed to be gone, but ran out of daylight, so I added MMO to all 4 cylinders and left. Went back and cranked until MMO was clear and then tried to start again with no luck. More water in cylinders (Through-hull has been closed since it flooded). I removed the flame arrestor from the carb and the carb is full of a water/what-I-assume-to-be-MMO mix (looks like a lighter version of the milkshake look of regular oil with water in it). It seems as water flowed into the carb and I have just been sucking it back and forth from the engine to the carb every time I try to start? I removed the carb and cleaned it out. Hooked it back up and tried to start....surprise...no start. After a few tries I check the carb again and sure enough the water/oil mix is back....where is this coming from?? I'm pretty much completely out of ideas. I've been battling this engine for a month now and will be out of town next week...I'd really like to get it started before I leave to make sure ALL the water is gone.

Note: after flooding I did discover that there was probably about a quart of water added to the oil. I pumped out as much as possible and refilled until it read full....this was before discovering the mess in the carb.

Also, I still have compression reading of 80 80 75 and 0.

[ndutton]

There are only two possible avenues for water to enter the carb: contaminated fuel or the manifold. Taking your description in total, I don't think it's contaminated fuel BUT good troubleshooting protocol dictates it should be positively eliminated rather than assumed good. Those assumptions will get you every time.

However, the first thing I'd do is a manifold pressure test. It's easy to do and can be done in place. In a few minutes this test will either confirm or condemn the manifold. I'd eliminate this possibility before looking elsewhere. There are certainly other possibilities, one step at a time though.

Here's a post that describes the testing procedure pretty well.

http://www.moyermarine.com/forums/showpost.php?p=66592&postcount=14

[sastanley]

Gabe, let's hope it is not a compromised manifold, but once you have the carb & cooling lines off, the manifold comes off with three studs. (been there done that)

i would follow Neil's suggestions and report back before anything else.

I know you NOW already know this, but always remember to close the thru-hull when you have trouble starting. I am so anal, I am about 5-10 seconds of crank/no-start and the thru-hull is closed, since I know my boat was back flooded thru the manifold more than once before I owned her.

[Gabe]

It's funny because I have always been super paranoid about starting with the through-hull open. Guess I got careless when I was frustrated. I will pressure test when I can. I guess what I'm wondering now is...where is the water coming from now since the through-hull is closed? Have I just not cleared it all out? Is there something that I am not doing to help it clear that I could be doing?

thanks.

[romantic comedy]

You can eliminate the water in the fuel possibility, but hooking up a separate tank. Gravity feed.

[CalebD]

Exhaust/Muffler backflow into manifold

Maybe I'm alone in left field on this one. I'm going to guess that maybe there is a restriction in the exhaust OR the hot section of this A4 may be poorly plumbed.
A water lift muffler or a stand pipe muffler setup will hold a certain amount of water once the engine is shut off. Depending on how the rest of the exhaust is plumbed can affect how much residual water is in the system.
If the water lift muffler is full then it may not take so much cranking without starting to start getting water back flowing into the manifold, where you do not want it to be.

I don't do this religiously, just sometimes. Once we are tied up and the engine, gas and water are off I will start up the motor again for, say 10 - 20 seconds to help purge the water in the exhaust/cooling system. The exhaust gases help push water through the exhaust system. Then again, with our raw water/exhaust system set up we have never found water in the cylinders (knocks wood).

[Mo]

thinking manifold as well.

Hi Gabe,

First I am in agreement with a pressure test your manifold but there is a quick check you can do if you are close to the boat.
-You remove the hose off both ends of the manifold,
-Remove all spark plugs
-cover the far hose end of manifold with your thumb and blow into the close end...blow in to build pressure.
-if you hear air coming from the spark plug holes the manifold is shot.

Typically, if the hole is big enough to cause the engine to run poorly and dump water into the oil...it's big enough to test this way. If for some reason the manifold seems OK via this simple test it will STILL require a more definite leak-down test.

As Caleb mentioned ... exhaust. Pics would be helpful but unless something changed drastically from a good running boat I'd be thinking it less likely an exhaust issue beyond the manifold.

Need a bit of engine history as well. When was it last run, how did it run, any overheating issues, any motor sailing or rough seas...small things sometimes matter as well.

Good luck with it...and a manifold is a better alternative that some scenarios.

[T27_478]

easy exhaust check

I've found an easy exhaust check is to simply disconnect at the exhaust flange and blow into it. You will get a nasty ring around your lips in the process but if you can't fairly easily blow air neither can your a4. you may feel some resistance at first while the water clears but once dry you should have almost no resistance to blow air out the back.

[Gabe]

update

Got the engine running today. The stuff in the carb was definitely MMO mixed with water. When I cranked with the plugs in and the carb removed while holding a rag over the carb intake, the MMO/water mix just came pouring out. After cranking a few times it cleared. So I reattached the carb and started it up (with the thru-hull closed!) Ran for a bit and no sign of anymore water so I'm pretty sure the manifold is good.

My theory is that I still had MMO in the cylinders (from trying to fix a stuck valve) when I flooded it and the seawater washed the MMO through an intake valve and into the manifold and from there down the throat of the carb.

So now I'm finally back to a point where I can fight the original problem...stuck valve in cylinder #4.

I'm just glad I got it running so I don't come back in a week to a seized engine. Thanks to everyone who responded.