Firing on 2 cylinders and baffled..

[Hooper1819]

Technical Anomaly

Over the years I have been grateful for the great deal of wisdom shared on this site. Now, I write my first post with my first Atomic 4 challenge that I am unable to solve. I have a 1981 Catalina 30 for 23 years. I took Don’s course and rebuilt my late model engine in 1994. I have had flawless performance until the summer of 2009. I stayed in the water for my winter lay up. During the winter my marina conducted an extensive dock and piling replacement.

Upon spring commissioning start-up, the engine immediately started up and after 2 minutes began rumbling and vibrating severely. Fearing that I ingested some lingering construction debris in the intake, I immediately shut the motor off to check the intake, plugs and wires but all was clear and the problem never went away. Cylinders 3 & 4 quit firing.

Currently, I am still firing on only 2 of the 4 cylinders. Cylinders 1 & 2 are fine with 3 & 4 not firing at all. I have better than 100 psi in each cylinder. I have completed the following component replacements.

Ignition: I have replaced the spark plugs, plug wires, points, condenser, ignition coil, distributor cap and button.

Fuel: I replaced the fuel, fuel pump, and re-built the carburetor.

Exhaust: Fearing back pressure, I replaced the hot section of the exhaust, aqua-lift muffler, 3 feet of exhaust hose immediately after the aqua-lift muffler, removed the anti-back flow butterfly valve in between the muffler and the transom and manually bored out the exhaust hose to verify no blockages.

Mechanical: I removed the manifold to adjust the valves and validate the integrity of the valve springs and operation. Nothing is sticking and all valves and timing are exactly adjusted. I have a 2 year old Moyer Marine manifold in perfect condition.

My dear wife is convinced I am obsessed and fearing for my sanity agreed with Don’s suggestion to take a step back and get a second opinion. I asked Dr. Will Sibley of Sibley Marine to examine and comment on this situation. The engine started immediately and Will observed excellent spark at 3 & 4 both direct and indirect with added resistance to the plug. We disconnected the exhaust flange and ran the motor with no exhaust at all. Thankfully, he confirmed all that I state above with 3 & 4 still not firing. Don reminded me that we are still smarter than the engines. I am anxious and grateful for any suggestions you may have.

[jayw]

Hmmm...
Sounds like you've already checked and replaced all the usual suspects. Maybe confirm the firing order and the order of the plug wires out of the distributor cap?

[sastanley]

Hooper..
welcome - Back in my old 1985 Civic, I did a tune up in preparation for a trip. I replaced the spark plugs, changed oil/filter, cleaned carb, etc.etc..The car ran terribly on my trip. So poorly, that I stopped at a Honda dealer enroute and bought new plug wires thinking I had maybe pulled one of the fittings loose, etc.. Although it ran rough, I completed my trip. When I got home, I started checking on things...Turns out the high dollar Bosch spark plugs I bought were no good! $5 worth of new Champion plugs later (which is what I had always run in it...not sure why I changed brands!) and she ran like a champ. That was my first & only set of Bosch plugs.

Also, even though it sounds like you've already done this, the previous poster mentioned the firing order..double check you have the plug wires running correctly (1-2-3-4) from the distributor to cyl #s 1-2-4-3.

Also double check that there is no scarring or burn marks on the inside of the distributor cap, rotor, etc..

Maybe put some of the old parts back on, one by one, to see if a new part is no good.

Good Luck and report back.

[captain kenny]

KISS this is an ignition problem period and as such should be dealt as one. I am a dc electrician and my response is the trouble will be where you find it. Move the plugs around, if not replace the cheap stuff condensor, points check the gap. focus on detail i bet it is something small but it will be were you find it in the ignition system.

[ndutton]

I agree it's probably something simple. Are you sure the dist cap is seated and installed properly??

[Baltimore Sailor]

The engine only needs three things: (1) spark, (2) compression and (3) fuel.

You seem to be getting numbers (1) and (2), but I haven't seen any verification that you're getting number (3) in those cylinders. As Sherlock Holmes said, "when you have eliminated the impossible, whatever remains, however improbable, must be the truth."

Are you SURE you're getting fuel into cylinders #3 & #4?

Do you KNOW????

[ndutton]

Seems you're down to 2 possible issues.

As Balty said, insufficient fuel to #3 & 4 could be the culprit although given your report of the excellent manifold condition it's interesting that 1 & 2 can get good fuel and not 3 & 4. A massive intake leak on #3 & 4 would starve those two yet not show up with a compression test. Spray a little carb cleaner in the area with the engine running and see if there's a change in RPM.

On the other hand, accepting your report of good spark, having good spark to #3 & 4 (or more accurately #4 & #3 in that order) means little if it's not at the right time.

I'm curious, how did you determine #3 & 4 weren't firing? Pull plug wires one at a time?

[thatch]

Hooper,
Since you have tried all of the more obvious cures to no avail I will approach your problem from another direction. What could have happened during the down season? As you stated "your engine started up normally and then developed it's miss". Although you have a relatively new intake/exhaust manifold on your engine a water leak in the intake runner that feeds the #3 and #4 cylinders could create this condition. Compression and ignition tests would show up normal but water could be (under manifold vacuum) sucked into those cylinders killing their ability to fire. Although it is rare defective castings do corode through prematurely and are difficult to detect. The easiest way to confirm this senerio is to start the engine up dry for a brief amount of time after removing as much water from the cooling system as possible and after making sure that you have a clean, dry set of spark plugs installed. It is also a good idea to remove the water pump impeller for this test. If you would rather remove the manifold for it's pressure test, any competant machine can help you with that.
Even if this not the problem it might stir up the mental juices in the rest of the group to hammer on this challenge until it is solved.
Best of luck, Tom

[rheaton]

I like the idea mentioned above, to move around the spark plugs, to see if this also moves the problem to the different cylinder. This would isolate the plugs. Trying a new set of plugs might not be bad. Did you try removeing a plug, connecting it to it's plug wire, and testing that it is indeed giving strong spark. As mentioned about I would also try switching out the distributer cap. Good luck with this.

[Hooper1819]

Thank you for all your suggestions. Over time, I implemented almost each and every one to no avail. I shared my frustrations with Don and Will on frequent occasions resulting in a similar infliction of the "what are we missing syndrome" that I had been living with for so long. It got the best of both gentlemen resulting in me being privileged with their on-water examination of my engine. We remained baffled for the longest period until I left to buy some fresh plugs. Attached below is Don's summary of events that led to identifying the problem and ensuring his position as the Atomic 4's Obi Wan Kenobi.

Here are my observations and assessments:

1) We rather quickly confirmed your earlier reports of good compression, proper ignition timing, and the mechanical integrity of the engine (including checking for a broken crankshaft). While I accept your report of having changed spark plugs numerous times in the past as having no affect on your symptoms, for the sake of accuracy, I must report that your plugs at the time of my visit were in a condition which could have caused symptoms similar to yours (not necessarily only in cylinders 3 and 4).

2) Prior to ever starting the engine, there appeared to be some amount of water emulsion in the oil. This condition was indicated by the color of the oil and the fact that it was approximately 2" over the full mark (you reported that you had filled the crankcase only to the full mark on your last oil change). I didn't make too much of this observation at the time since you hadn't reported any water evidence previously.

3) We started the engine with the exhaust flange removed from the back of the manifold to rule out exhaust back pressure as being a problem.

4) Intermittent operation of the electric fuel pump created some difficulty in starting and keeping the engine running, and in retrospect, I cannot be sure that I ever recall a time when we had a good clean repeat of your earlier symptoms (cylinders 1 and 2 firing cleanly while 3 and 4 were not). That being said, the engine was certainly running poorly enough to support your earlier observations. I simply couldn't duplicate them exactly during my visit.

5) Believing that the current condition of the plugs was complicating our work, you went for a new set. Meanwhile, Will Sibley and I removed the plugs in preparation for replacing them, whereupon we discovered water on each of the plugs from the three back cylinders (2,3,&4). We cranked the starter a bit and observed water spray coming out of each of the these cylinders as well as a trickle out of the rear of the exhaust manifold and carburetor intake. With the appearance of this water, coupled with the observation of water in the oil previously, I believe it's reasonable to conclude that some level of water intrusion had been occurring for some time prior to our visit and most likely contributed to your symptoms by causing plugs to miss-fire.

6) When you returned with the plugs (sorry we never got to use them), we decided to remove the head, hoping to find a small leak in the combustion chamber of cylinder 3 or 4. However, the head appeared sound.

7) The source of the water was eventually found to be from hairline cracks in the two center exhaust ports from which we were able to observe water emerging from the water jacket under gravity pressure alone.

[thatch]

Hooper,
I was truly sorry to hear about the results of Don and Will's troublshooting session on your A4. If there is one part that we collectively fear about having to replace it is our cylinder blocks, and i'm sure the rest of the group will be wishing you well through the repair process. I would also like to apologize to Don for suggesting that the problem might be with the Moyer manifold although I'm sure he would rather it had been that, rather than your block that was defective.
In order to try to find something constructive about your situation I will ask the question, did Don, Will and you come to any conclusion about what caused the cracking? Was it a winter freeze, some other event or just old age that caused the problem? Hopefully the rest of the group will be able to gain some useful knowledge because of your ordeal.
Best Regards, Tom

[Hooper1819]

Tom,

Thanks for your thoughts. You should be pleased knowing that your suggested trouble shooting diagnosis was the closest to the actual problem and didn't go un-noticed by Don and Will. I can only assume at this point what actually caused the crack. Winter freeze and old age are two excellent and pragmatic guesses. I didn't help the situation any by torqueing the manifold to the original 35 foot pounds when in fact it was reduced to 25. I can only look forward to developing another long term relationship with a replacement Atomic much to the chagrin of many slip mates that have grown accustomed to and prefer their diesel infused cabins and salons.

[thatch]

Hooper,
Thank you for giving us your final thoughts regarding your block failure. It is incouraging to me and I'm sure to many others in this forum that you have decided to stay the A4 course rather than straying to one of those noisy, oil burning "D" word engines. Maybe it will make the process a little easier if you think of it as "freshening up" your 1994 rebuild. Please continue to update us with your progress.
Best of luck, Tom