Another Low Compression Issue

[Triton106]

Hi,

I have always thought I have been keeping my A4 well maintained but I guess everything is relative. Trying to balance the maintenance demands of an 1960 Pearson Triton and an 1970'sh vintage A4 and a reasonable amount of sailing time means that something is getting neglected.

Last Saturday, on the way back from a day sailing trip when Blossom (Triton 106) and I were pounded by winds gusting in 30's and short and steep chops on SF Bay, the A4 quit in the narrow Oakland estruary when Blossom and I were between two huge container freighter ships. Luckly I still had my sail up so although the boat speed drop a knot or two I was able to maintain steerage.

On Sunday I dove into the standard diagonostic routine and found that compressions were low, fuel supply was ok, and no spark. I have yet to further diagnose sparks issue. But what I want to ask here is the low compression issue.

Historically my 1-2-3 cylinders always had compressions in 90-100 range and cylinder 4 always had low compression in th 60-70 range. However, this time 1-2-4 cylinders all had compressions in 60-70 range and cylinder 3 had compression in high 30 to low 40. My friend Rob thinks the low compression in 1-2 (compared to historical range) was due to the fact that the engine was cold and there was no oil in the cylinder. But what could explain the low compression in cylinder 3? It does not look like a stuck value because usually that results in 0 compression. Could it be a sign that the head geskets are wearing out? I checked oil and does not see sign of water.

Thanks in advance for your insight and expertise.

Ray

[Marian Claire]

Pays to have a sail up or at least ready to raise. I would start by figuring out the "no spark" issue. Then when she is running you can get some more telling compression #s. I experienced a big compression drop in one cylinder. http://www.moyermarine.com//forums/s...ead.php?t=2238 Hope this is not your issue. Dan S/V Marian Claire

[smosher]

Hi Ray, How do you measure the compression, all spark plugs out, choke open etc..

I agree with Marian, work on the spark, do you have points or electronic ignition?

How long was the A4 running before it quit, how did it quit? any performance issue prior to the shutdown or did it just shut off like it was turned off.

How do the plugs look ?

Steve

[Dave Neptune]

Compression

Ray, I'd try the spark fix first to get her to run. After you get her to run and it is warmed up a bit be ready to do a compression test again.
Test one with all plugs removed carb at WOT (wide open throttle) and choke open~~do test.
Test two now with everything still set the same spray some penetrating oil or even WD-40 into the cylinder your are checking and check it and so on one cylinder at a time.
Post your numbers.
It may just be that your rings are a bit sticky and they can be worked loose with a bit of top oil (oil in the fuel). You can use MMO or my choice of a good synthetic two stroke racing lubricant mixed at around 100~125:1. It will smoke a tiny bit but the added lubrication from the "top" side can often break loose sticky rings. It is easy for rings to get sticky in a marine environment.
I wouldn't start tearing anything down yet.

Dave Neptune

[Triton106]

This forum is great (and so is owning an A4), thanks for the advice.

Sounds like the consensus is to fix the no spark issue first. I plan to do that this weekend. I plan to follow Moyer's standard routine for troubleshooting a no spark issue. Here is a little more detail on the circumstances around the A4 shut down.

- Late model A4, well maintained.
- New fuel tank, primary fuel filter (Racor), in-line filter.
- Fuel is clean and added recently.
- Recently rebuilt carburetor.
- Recently rebuilt mechanical fuel pump.
- Oil changed once a year.
- Spark plugs in good condition.
- Converted to electronic ignition in 2008.
- New impeller.
- New exhaust hose and waterlift muffler.
- Recent prop shaft realignment.
- New head gesket in 2007.

On Saturday I motored out the Oakland estruary (all upwind about 45 minutes) and sailed in fair rough conditions on the SF Bay with short choppy seas and wind guts in the 30's. The boat pounded more than usual which forced me to cut short my outing. On the way back I sailed in pretty typical light wind condition in the Oakland estruary (downwind) until I ran into heavy container ship traffic. That's when I decided to turn on the A4 again and put it on very low throttle just in case I need to maneuver to avoid the ships. It ran about 15-20 minutes and shut down without any discernable cause. Actually the only reason I noticed it was because I all of sudden felt that the boat was very quite. I turned off the ignition right away and waited for a minute and tried to restart it. The A4 cranked but will not catch. That's when I said "well, it's a sailboat" and I still have steerage so I will sail it back to the marina. Well, you know the rest of the story.

From the feedback so far it looks like the possible causes of low compression are sticky ring or valve. I will follow the advice and add some MMO in the fuel and the spark plug hole to see if the compression improves. I will report back the outcome.

[smosher]

There are a few reports of the coil going bad after changing over to electronic ignition.

Since there's been fuel line work and new filters I would double check the tightness of the lines.

For the compression you could have a bad gauge since all of the cylinders are lower then previously. I would try another gauge after you get the motor running, which you will.

Steve

[Mo]

?? overheat ??

Do the checks as the guys suggest. In the back of my mind I am wondering if the engine overheated then or earlier in the day at some point. I end up in ocean swell and waves more often than not. My greatest concern was always overheating the engine when I push it hard.

[Loki9]

I have an A4 that had 100psi in #1, #2, and #3, and 70psi in #4. Turned out that #4 had a broken exhaust valve spring.

[Triton106]

There are a few reports of the coil going bad after changing over to electronic ignition.

Steve

Steve, I have read about it, although I converted to electronic ignition over a couple of years ago now and never had any problems. The only thing I can think of that is different on this trip is that the pounding was harder than all previous outings which could cause either the distributor or the coil internal parts to move around. Again, I will need to perform the diagnostics this weekend and will report back.

I have an A4 that had 100psi in #1, #2, and #3, and 70psi in #4. Turned out that #4 had a broken exhaust valve spring.

That may be the cause on the 3rd cylinder. I remember replacing several springs the last time (but not every spring) I had a stuck valve in the 4th cylinder.

[JOHN COOKSON]

That's when I decided to turn on the A4 again and put it on very low throttle just in case I need to maneuver to avoid the ships. It ran about 15-20 minutes and shut down without any discernable cause. Actually the only reason I noticed it was because I all of sudden felt that the boat was very quite.

106
Was the shut down a gradual fuel related type of shut down?
Is there any chance your low speed idle is to rich and\or the choke is not opening all the way or some other to rich condition loading up the engine with fuel and causing the shut down?

TRUE GRIT

[Triton106]

Ok, here is the follow up. Today, armed with new coil, points, condensers, distributor cap I was ready to tackle the no spark issue.

First thing I did is to replace the coil with the backup coil I bought from Moyer Marine a couple of years ago (maybe even more than a couple). The reason I suspected that coil was the cause is because I already checked voltage on the coil primary circuit and got 12V last week. In addition, when I cranked the starter I can see the voltage drop to 8/10V.

In any case, I moved the location of the coil from the back of the engine block to the engine room bulkhead to get better access. I hooked up the wirings and turned on the starter. The first try my trusty A4 fired right up. Great, right?

No, after running it for 15 minutes or so the coil got hot (I can still hold it, though, without having to pull my hand back). Is that normal? The old (bad) coil is oil filled (I can hear it when I shake it) and the new Moyer coil is probably epoxy filled. I understand oil filled coils run cool. Should I expect the epoxy filled coils to run a littler hotter?

What troubles me more is that I still don't know what cause the coil to break. I tested for shorts between the secondary terminal and the case and found none. The original coil has been in the boat since I bought it in 2000. Could it be age? What is the expected life of a coil? Could it be due to the electronic ignition that I installed a couple of years ago? Hmmm....

Ok, now the compression report back. I squirted several drops of MMO in each spark plug hole and waited for about 10 minutes. I then ran the engine for 15 minutes (as noted above). I then tested for compression again and this time the compressions are: 90, 85, 80, 85. All lower than they used to be (except for cylinder #4 which has always been lower). Are the compressions deteriorating due to wear? Is it time to overhaul it? I don't know I will probably run it for a couple more tanks of gas with MMO and test the compression again.

In any case, I forgot to take some pictures. So a lot of words, really boring stuff. Sorry

[jpian0923]

Low compression could be stuck rings from carbon build up...keep treating with MMO but leave it in there for as long as you can, hours or days even. Too rich fuel mixture can lead to carbon build up. Lean the mix as much as possible. If you have the adjustable main jet, run the engine, turn it "in" until it is about to stall. Back it off part way til it keeps running on it's own. Carbon should burn off.

Others can weigh in on the hot coil but I think the general consensus on hot coils is too high voltage getting to the coil. Might need external resistor, or an adjustment to the voltage regulator on your alternator.

[Triton106]

Thanks Jim, about the possible cause of compression issue. I have noticed that spark plugs have indication that the fuel mix is a bit rich. I have also had stuck valve issue a couple of times before. I have never adjusted the main jet before so will give your idea a try.

Also, your point on alternator voltage output, I measured it today and it was about 20V. That seems to be on the high end? If so, how do you adjust the regulator? Mine is attached to the alternator unit. I will take some picture next time. Thanks again.

[jpian0923]

Hopefully someone with alternator expertise will weigh in. Mine is not adjustable. 20V does seem high though.

[hanleyclifford]

An alternator putting 20 volts into a (nominal) 12 volt system would explain why the coil got fried. 14.2 volts is the most you should allow unless you have a mutli stage regulator (which can give you "bulk" charging at 14.4 volts for limited periods).