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  #1   IP: 24.5.5.159
Old 07-10-2005, 07:14 PM
Jacob Wenegrat
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Unhappy Engine woes

Hello all,

Your help in diagnosing an engine problem would be greatly appreciated.

Started while motoring the boat, it felt slightly sluggish, and I found myself giving a bit more throttle than usual. It also seemed that the engine temperature was rising faster than normal during the trip out of the marina, but the exhaust seemed to have the normal amount of water.
Then the engine died, in a "just turned off the ignition" manner. Engine wouldn't restart at that point.

Checked compression- found 110 on all cylinders.
Spark seemed good from the coil. Put on new plugs.
Emptied fuel filter.

The engine would then restart, but ran very very rough, needed a lot of throttle to keep it running at even a low rpm, and then died with a loud "ping" noise.

Since then:

Engine will start consistently, but continues to run rough, in the same manner as before. Occasionally a puff of smoke (bluish?) will come out of the blowby tube.

In addition, checked the (new) spark plugs and it seems that the plugs from 1 and 2 have a lot of carbon build up and are very dry. These cylinders, and plugs, are also very hot after running the engine for even short periods. Cylinders 3, 4 are much cooler, and the plugs when removed seem very clean, and damp with a fuel smell.

Any suggestions on which way to proceede with troubleshooting this?

The original shut down of the engine seemed to indicate electrical, but I don't know if the other symptoms are compatible with that.

Thanks so much,

Jacob
Cal 29
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  #2   IP: 38.118.52.61
Old 07-11-2005, 07:08 PM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
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Jacob,

From the last part of your report, it seems clear that the current situation of your engine is that cylinders 3 and 4 are not firing, most likely due to some kind of breakdown within the secondary ignition system. Since you have consistent secondary output from the coil, I would replace the distributor cap, rotor, and spark plug leads, since these are the only secondary ignition components downstream of the coil and coil lead. I don't normally subscribe to the "diagnose by replacement" method of troubleshooting, but it's frequently difficult to differentiate between a faulty rotor, cap, and plug leads, and the cost to replace these components is usually cheaper than a couple hours of labor trying to sort out which item is really at fault.

In the process of replacing these secondary components, be sure to recheck for the proper sequence of the plug leads. The proper sequence of the plug leads around the top of the distributor cap is 1,2,4,3, with the number one spark plug post normally being the one directly away from the engine block.

Best regards,

Don Moyer
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Old 07-13-2005, 01:56 AM
jacob jacob is offline
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Update

Hi Don,

I went back today and looked over what you had suggested.

Embarassingly, I had reversed the spark plug leads for cylinder 3 and 4. Putting these in there rightful place caused the engine to roar back to life, sounding much more healthy.
However, after re-setting the timing, I shut the engine down for about 1 minute, and then tried restarting. The engine cranks on the starter, but does not start up.

I believe that the spark plug mistake occured while trying to sail/troubleshoot and is different from the primary reason that the engine died in the first place, and then did not want to restart after that.

I am particularly confused about what might cause the engine to run strongly one minute, and then, after a brief shutdown, not even startup.

Thanks,
Jacob
________
Z50M

Last edited by jacob; 01-23-2011 at 03:55 PM.
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  #4   IP: 38.118.52.61
Old 07-13-2005, 07:02 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
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Jacob,

Here is a check list for non-starting engines that we prepared in the recent past that might help. It got a bit longer than I intended, but you can zip through it in less time than you might think:

QUICK CHECKS FOR NON-STARTING ENGINES:

Two preliminary items:

1) Close raw water through hull as soon as it is determined that the engine is not starting within the normal time.

2) Be sure the choke is closed completely. If an engine chronically starts hard, but then runs OK after it starts, the hard starting is almost assuredly caused by the choke not closing completely.

An engine requires three basic things to start: Fuel, Ignition, and Compression:

1) FUEL: Remove the flame arrestor and check for the presence of raw fuel. If the choke is closed completely, there should be raw fuel puddled in the bottom of the intake throat within 15 to 20 seconds of cranking (3 or 4 five-second attempts). If the carburetor intake throat is "bone dry", the reason for the non-starting is either a problem in the fuel supply that prevents the fuel from getting to the carburetor, or some problem within the carburetor that prevents the fuel from getting through the carburetor (most likely a blocked main jet).

2) IGNITION: Remove the secondary lead from the center of the distributor cap and hold it approximately 1/4" from the cylinder head while someone cranks the starter. You should see a good arc between the end of the coil lead and the head that can be stretched to 1/2" or even 3/4". If you see no spark, the reason for non-starting is clearly within the ignition system, most likely a breakdown within the primary ignition circuit.

3) COMPRESSION: With all spark plugs removed, hold your thumb over each spark plug hole sequentially to check compression, as someone cranks the engine for a second or two with the starter. An Atomic 4 will usually start
if any two cylinders have normal compression as indicated below.

a. If you can't hold your thumb over the spark plug holes no matter how hard you press, the compression is generally normal (approximately 85 psi or above).

b. If you can hold your thumb against the compression, but not easily, a compression value of approximately 40 to 50 psi would be indicated, and starting could be problematic.

c. If you feel virtually no compression on any cylinder, the problem is likely a stuck valve.

Regards,

Don
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  #5   IP: 24.5.5.159
Old 07-14-2005, 12:17 PM
Jacob Wenegrat Jacob Wenegrat is offline
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No choke?

Hi Don,

Went back over the normal troubleshooting, found that the compression is good and even on all 4 cylinders. Good consistent spark, all plugs/wires relatively new.

After cranking (engine wouldn't start) found some (not a lot) of fuel in the throat of the carb.

Then, on an off chance I cranked the engine without any choke and it immediately fired right up.

Since then I've found that the engine will start right up, usually with just the shortest touch of the ignition switch, as long as there is no choke on.

Does this indicate a problem with the carb?

Thanks again,
Jacob
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  #6   IP: 38.118.52.61
Old 07-14-2005, 09:33 PM
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Jacob,

I have never seen an Atomic 4 on our test stand that would start without choke, so I've never had an opportunity to investigate first hand the condition you're reporting.

Having said that, we do hear of engines every now and then which reportedly start better with no choke. I have no explanation of why this condition might exist, but my instinct is that there is something unusual about a carburetor which allows an engine (particularly a cold one) to start with no choke being applied. I would keep an eye on things for a while, particularly for any indication of a rich running condition. Sootier than normal plugs would be such an indication.

Meanwhile, I'm glad to hear that your engine is back among the living.

Regards,

Don
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