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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Gas > Atomic 4
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  #11  
Old 09-16-2011
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First of all I should say she's a 1976 (Housed in a great C&C 27 Mark II).
I should also mention I don't get out there enough and she sits for over a month at atime sometimes (two little kids).

I had a fuel pump replace at the beginning of the season and, after a subsequent throttle adjustment, she was running great.

Two weeks a go she stalled while idling (I was re-rigging after hurricane Irene). I was able to get her started once or twice for less than a minute. The only non working gauge on the boat is the fuel gauge. I optimistically thought Maybe I was out of fuel. A few days later I filled her up (I was not on E after all). Also got her started a couple of times, but if I did not rev the throttle she stalled. Eventually she wouldn't start at all and I asked the marina to check it out as they had done the Spring tune up and the fuel pump replacement in June.

They told me I had varying degrees of compression loss in all four cylinders.
Trying to get anything else out of them is like pulling teeth.

This is my first full season, and it has been a tough one!
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Old 09-16-2011
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Several things to check:

Carburetor fouled ... typically dirt/gum deposits on the carburetors 'emulsion tube'. The emulsion tube is a thin hollow tube with teeny holes. The emulsion tube controls the air/fuel ratio. Any dirt in or on the 'holes' will cause the air/fuel ratio to vary - very common ailment with this updraft carburetor; easy fix - just disassemble and inspect/clean. A gasoline filter housing that is supplying fuel to the carburetor and is 'rusting' in the bottom of the bowl section will usually be the cause of dirt, etc. catching on/in the small 'holes' in the emulsion tube. The emulsion tube is a quite precision device and needs to be 'perfectly clean'.

The A4 is a quite low compression ratio engine and will run adequately at idle even with compression issues and will 'run' with only 2 or 3 cylinders 'operating'. However, ......
A. Head gasket leakage. The usual leak occurs between cylinders #3 & #4 and involves cross cylinder leakage as well as water leakage. The head should be periodically retorqued. One of the symptoms of a head gasket being 'blown' is the engine will idle quite well but as soon as throttle/load is applied, the engine stalls out.
B. Sticky exhaust valves ... depending on the configuration of the wet exhaust system, high humidity in the exhaust circuit can cause the stems of the exhaust valves to begin to rust; the rusts causing friction which leaves the exhaust valve either non-moving or partly closing (reduced compression value/reading). Easy assay and 'fix': open the valve cover on the side of the engine, disconnect the main high tension wire between the ignition coil and the distributor cap to insure that the engine will not 'start', spin the starter as you WATCH the exhaust valves go 'up and down'. If a valve is fopund to be sticking - remove spark plug, 'go into' the combustion chamber with a 'bent' screwdriver (the valves are on the portside of cylinders) and PUSH the offending valve down so that its fully seated ... then spray the valve stem with an anti-rust compound such as "PB
Blaster", etc. let soak a bit, then spin the starter and spray the valve stem until 'repolished' and free of rust .... and the valve 'reliably' returns to 'full stroke'. Sticky exhaust valves are quite common on A4s that 'sit' for long periods ... the cause is usually a pin hole that develops between the gas and water side of the exhaust manifold. A pressure check by blocking one 'end' of the water port or the manifold and applying 40-60 psi water pressure on the water circuit will prove/disprove any 'pin holes': apply water pressure, close the water supply and look for a drop in a gage pressure that is applied to the water supply, etc. Such can be 'brazed' closed.

Get Moyer's "Rebuild and Maintenance Manual" ... and visit the Moyer forum. A4s simply dont 'wear out' they can run almost forever ... the usual thing that kills an A4 is internal rusting of the block and Moyers Manual will describe simple testing that will determine if there is enough 'meat' still left on the inside of the engine. Usually if there enough meat / wall thickness left then the engine can be easily rebuilt, repaired etc.

Last edited by RichH; 09-16-2011 at 11:16 AM.
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Old 09-16-2011
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A 1976 Atomic four is a relatively new engine by A4 standards. Mine is from 1967 and still works reasonably well but needs TLC now and again.
I know of a good mechanic near Annapolis, MD but so far I only know you were hiding from hurricane Irene like the rest of us on the east coast from NC to ME.
Your starting and idling problems could be related to a number of causes: distributor timing, incorrect plug sequence to sparks, corroded spark plugs, stuck float valve in carburetor etc. If the new fuel pump they installed was electric there could be a bad oil pressure cutoff switch which would not allow the pump to pump fuel.
What you can do now is to inspect your spark plugs. Once the plugs are out you can squirt or spray some Marvel Mystery Oil in each cylinder (< 1 oz). The MMO should help lubricate the piston rings and valves.
What was wrong with the old fuel pump that was replaced in June and was the old pump the mechanical or electric kind?
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Old 09-16-2011
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mmmmmm new elec. fuel pump .......
With an electronic fuel pump, there is usually (and should be) a fuel safety cut-off switch that monitors the OIL PRESSURE. If (due to accident, etc.) the oil pressure drops or the engine stops ... the drop in oil pressure will de-energize the 'switch' and automatically shut off the fuel pump.
If there is insufficient oil pressure to open the safety switch with the starter engaged and thus allow the fuel pump to begin 'pumping' ..... the fuel pump will not deliver fuel and the engine will not start. There should be a 'jumper' switch across the safety switch so that you can energize the fuel pump during/before starting and the engine is not delivering sufficient oil pressure.
BTW if you use a double pole (STDP) switch, this becomes a good anti-theft device ..... center tap = 12vdc, one end tap - fuel pump 'jumper', other end tap - not connected (open short) thus 0 volts to pump.

Last edited by RichH; 09-16-2011 at 12:47 PM.
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Old 09-16-2011
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Lots of good info in this thread. Definitely go to the Moyer forum and discuss this.

But first of all, the A-4 is a low compression engine to begin with, and everything about it is heavy duty. That's what makes them so robust.

The stalling symptoms you describe don't seem to be compression related. An engine with relatively even compression across all cylinders, will run even if the compression isn't optimal. It sounds to me like the marina did a dry compression test and stopped investigating.

Your symptoms seem more fuel or electrical related. It could be a variety of inexpensive, and simple things:

Ignition points worn out, and/or mis-adjusted.
Condensor worn and failing.
Primary ignition coil failing.
Primary high tension wire from coil to distributor cap failing.
Distributor cap worn, or cracked.
Electric fuel pump not pumping (loose wire?)
Clogged fuel filter.
Clogged water/fuel separator.
Clogged carburator idle jets or main jets.

I've had several old cars (old Volkswagens and such) and when the ignition points get badly pitted or the gap slips closed, the symptom is exactly as you describe. Running fine, then quits, then fails to start or barely starts and dies.

Check your ignition point gap and file the points smooth if necessary, or just replace them, and check your distributor cap.
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My money is on a fuel delivery problem. Possible it's either clogging or the switch mentioned. I will bet the compressions have been in their current state for years.
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Old 09-16-2011
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I'll second fuel delivery. Easy to find out. Just spray some go juice in the carb and see if it kicks.
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Quote:
Originally Posted by apogee1mars View Post
I'll second fuel delivery. Easy to find out. Just spray some go juice in the carb and see if it kicks.
Warning: the A4 has an UPdraft carburetor and its next to impossible to 'spray' into the carb. The updraft carb has a 'suction port' in the entrance throat of the 'flame arrestor' to prevent 'explosions' if this carb 'dribbles' fuel out of the carb and into the 'flame arrestor'.
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Quote:
Originally Posted by Hackettsan View Post
......This is my first full season, and it has been a tough one!
Unfortunately, you will become very jaded about the quality and honesty of many, if not most, marine maintenance facilities. If you ever find a good one that you really trust, pay them whatever they want.
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Old 09-17-2011
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Quote:
Originally Posted by RichH View Post
Warning: the A4 has an UPdraft carburetor and its next to impossible to 'spray' into the carb. The updraft carb has a 'suction port' in the entrance throat of the 'flame arrestor' to prevent 'explosions' if this carb 'dribbles' fuel out of the carb and into the 'flame arrestor'.
I am pretty sure that spraying some starting fluid into the updraft carburetor will not create a significant hazard. I know that the infernal combustion engine can be a confusing item for many, but that is certainly not the case for all. If you would wish to dis assemble the intake system to apply some go juice, head on, but not necessary.
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