Not starting...blown head gasket?

[tracy]

Hey, this is my first post so please be gentle. A quick history of current a-4 problems might make this make more sense. Last month I noticed a small leak under my water pump but since it was not noticeably affecting my raw water outflow I ran my engine for about 6 hours (off and on). Of course at the worst possible time my engine decided to overheat and shut down. After letting it cool I had to try again. Short story; 2 overheats for about 5-10 minutes. After 2-3 hours of not trying it started and ran fine (good outflow) for about two hours while I got to dock.Took my water pump off and found a perfect impellar but replaced the seals (a big thanks to moyer marine) After re-assembly I could not start the a-4. When checking the plugs I noticed that #3and #4 had a bit of water on it. replaced plugs and tried again. Same water intrusion. The next day tried again with water off and a tiny bit of either. It still wouldnt start (tiny water intrusion in 3 and 4 probably residual). I did a compression test to see if head gasket blew between #3 and#4. I figured that if 3 and 4 were exactly the same p.s.i. that there was a leak between them. They were 15 lbs different and not out of range of the others. I than discovered the 2 gasket system used on these engines. Finally, my guestions 1)Could water leak into two pistons at once without equallizing pressure between them? 2) Could a bad head gasket prevent the engine from starting? I have spark and a newly cleaned anti-syphon valve Thanks for everything.

[msmith10]

Welcome. There aren't any flamers on this site- just helpful advice. It sounds like you have 2 problems.
1. No start- fix this first, then the overheat problem.
If your plugs are wet with water and the engine won't start are you sure you don't have water in the fuel? Check your water separator. Yes, you could have a warped head from the overheat allowing water into the 3-4 cylinders, but I've never seen any report of that on this forum. I think it's an unusual event with the A4. On the other hand, water in the fuel is very common.
2. Overheat: After getting the engine running I'd start with an acid flush. Search this forum for the procedure.

[Marian Claire]

A second welcome. Along with the above you can remove the drain plug in the bottom of the carb and catch what comes out and check for water/gunk. This will also make sure fuel is getting to the carb. Do the plugs smell of gas? Make sure the plug wires are in proper firing order. It is easy to swap them when pulling plugs. A quick spark check would also help. This may help:http://www.moyermarine.com/faq/11.13.html
The A-4 is known to be very overheat tolerant so you probable did not do any major damage. Dan S/V Marian Claire

[Baltimore Sailor]

The A4 is very overheat tolerant IF it has the two metallic head gaskets in place. The old green paper ones will burn through quickly enough, as I found out when I first got my boat.

If the OP will look at the gap between the head and the block he can tell which type of gasket he has. If it's a barely-visible fibrous looking gasket he's got the old paper type, and may well have a problem. If it's a thickish silvery gasket he's got the metallic gasket, and can probably quit worrying about a burnt or blown head gasket.

[rigspelt]

If you were doing a lot of cranking trying to restart the engine, the water in 3 and 4 could be backflow from an overfull exhaust maybe, and thus a red herring?

[tracy]

Thanks for your suggestions. I finally got back down to the boat to work on engine. I checked spark and had good spark on all wires. I then drained the carb bowl and found water in the gas. By disconnecting the hose from the fuel pump to the carb I determined that water was not coming from the tank.After draining the fuel from the carb bowl several times, and still not getting the engine to run, I figured that the diminishing amount of water in the carb bowl was coming from the manifold. As I was about to tackle removing the carb I grabbed the horizontal part the exhaust pipe and it broke in two. After counting to 10 and removing all heavy blunt objects from my reach, I noticed the carbon (I assume) clogging my exhaust pipe. It was so constricted I couldnt get my pinky in. I plan to take the pipe off the manifold tomorrow. My guestions ...Could a severly clogged exhaust create enough back-pressue to stop the engine from starting, and will the engine be harmed if I turn it over without having the exhaust pipe connected? Thanks again for all your support.

[hanleyclifford]

Sounds like you will be fabricating a new hot section for your boat. If you couldn't even get a finger into the pipe that would explain why the engine won't start. I don't like starting an engine without some sort of exhaust pipe since there is a danger of warping a hot valve after shutting down if cold air rushes in at just the right angle. How about posting a picture and maybe some one on the forum could suggest a plan?

[Marian Claire]

What if he disconnected the old hot section and the water line to the wet/dry connection. Then connected the first few pieces of the new hot section, say to the point just before the wet/dry mixer. Would the pipe give enough protection for a short start up? The water would flow to the bilge or be routed to scupper or overboard but would not be hindered by the old exhaust and there would be no restriction in the dry section. ??? It will be loud. Dan S/V Marian Claire

[hanleyclifford]

Yes, if a temporary pipe with a bend were installed that should protect the valve stems from all but an arctic blast. I would go ahead and get the new black iron pipe pieces and of course the flange will have to be cleared or replaced.This is going to be a bigger job than originally contemplated.

[tracy]

Thanks everyone for your help. I took off exhaust pipe and replaced. I also took off manifold and acid flushed it. While I had a chance I cleaned the carb and blew thru everything. After re-assembly everything worked well except for low idle. Under 1100 rpm the engine dies due to fuel starvation, I think. I'll fool with the Idle screw tomorrow. I'll also check choke. I read in one of your responses to use black iron pipe. Why the black pipe? Is it more heat tolerant than the regular iron pipe? As an aside, while cleaning the manifold I noticed that behind what I assumed was the drain bolt there was metal painted engine gold, as if it was never fully punched out at the factory. Not knowing if this was actually a drain,or a port for some kind of sensor so I left it in. Cheers.

[hanleyclifford]

Black iron is preferred over galvanized pipe because of the poison gas issue. If you have used galvanized avoid breathing fumes until the pipe has burned off the plating. Sounds like you have looked at the manifold drain. Typically they are well plugged with rust from the inside and usually no water comes out unless you break into the chamber with a screwdriver or some such tool.

[ndutton]

Actually more than preferred, check out this thread, post #4

http://www.moyermarine.com/forums/sh...ighlight=redux

[hanleyclifford]

Neil - Thanks for bringing that discussion back to this thread. It's so important maybe it should be listed in our Links of Particular Interest?

[tracy]

I've cleaned the carburetor and the cooling system. I've replaced the pipe. No water was found in the gas or carburetor. Gas is getting into the carburetor bowl. When idling the engine high, at 1800, it is fine. But once it dips down below 1600, the engine dies. Any suggestions?
Thanks again!

[smosher]

What is the idle mix set to ?

When you clean the carb you need to poke wire through all of the vents and passages.
Some of these are so small just blowing carb cleaner through it will not break apart the blockage

[tracy]

I set the idle screw 1 1/2 turns off the seat. I read in a old thread to check for air leaks around manifold and carb flange. Did that with no results. When the engine dies it sounds as if its starved of gas. Its my understanding that the main jet is fixed (unadjustable), but the problem seems to be stalling when the engines r.p.m. falls below about 1600. Any info would be greatly appreciated

[hanleyclifford]

When an engine displays the characteristic you describe the first thing I do is make sure the timing is set at TDC, centrigugal advance springs relaxed on freely moving weights, plugs wired in proper order. Inasmuch as you have had water in the carb I would next suspect the idle system. Look at a diagram of the carb and note the internal passages including the well vent system. As was mentioned earlier there could be something in there left by the water. These parts, especially the jet, can be difficult to remove if water has been in the system for any time period. I like to start with carb cleaner and/or starting fluid (This is the best use of "engine crack"). Even if you cannot completely disassemble the carb you can do a lot of cleaning. Follow up with compressed air making sure your compressor is supplying dry air. If not, end the job with starting fluid. At restart reduce initial setting to 1 full turn off seat for idle screw.