#4 no workie

[deepthought]

After deciding (at the end of the season) that my A4 was not running as proper as she may have at one time, I did some poking around with my no contact thermometer and discovered that the #4 plug/cylinder (closest to the trannie) was not firing. A visual examination shows that the #1-3 plugs have soot and discoloration from use where as the #4 looks basically brand new, no carbon or discoloration at all but there is presence of fuel (nose test)

The other thing is that I do notice a small trace of either oil or gas in the exhaust water when running

Is this a worn head gasket? A stuck valve? Bad ring? Poor point contact? Bad luck?

What is the easy way to test for spark? I have limited tools, a mutimeter and a bag of hammers...

Would running the engine on only 3 tubes damage the 4th?

I'm going down today and see if switching the plugs around has any effect. I will also see if I can have a peek at the valves from the plug receptacles as well. The boat hauls out in a week which might be a better time to pull the head and check the gasket.

There is no sign of water contamination in the oil. Oil pressure sits at 50 at idle and drops to 40-45 when run at higher RPM. Water is 135 and seems to never ever change. The boat was built in '67 and I have to assume this A4 is original to the boat and I have no history on the engine, this is my 4th year with the boat.

If any of you bright folks have any ideas please let me know..

Cheers

[Dave Neptune]

cheers, welcome to the MMI Afourian Forum.

Don't pull the head until you have done a first dry and then a wet compression test~could save a lot of work.

Post a pic of the plugs if you can. Also sound like she may be running a bit rich too IE the soot. Try opening the IDLE AIR SCREW a bit over a quarter of a turn to see if it helps or the idle improves.

Changing the plugs around is a good idea just be careful not to juggle the wires.

Do you have points ao an electronic ignition?

Dave Neptune

[JOHN COOKSON]

To check for spark at the plug start the engine, pull the wire boot off, put a screwdriver in it and see it you can jump an arc to the plug.
You can see if there is some compression by putting your thumb over the spark plug hole and cranking the engine.
If you still suspect the head gasket a metered compression test is in order. The thumb test will not verify that there is enough compression to drive the piston effectively, only that there is none present. You could compare the thumb test to the feel of a known working cylinder.

A BIG WELCOME TO THE FORUM. HANG AROUND. YOU'LL LEARN A LOT.

TRUE GRIT

[JOHN COOKSON]

. Water is 135 and seems to never ever change. Cheers

I just spotted this in your original post. If the meter always reads 135 the needle may be corroded on 135. Or the needle may be touching 135 then be blocked from moving further by corrosion.
Are you RWC? There may be some KRAP around the sending that is insulating it. Also there may be a mineral deposit on the sending unit that is insulating it. This exact scenario happened to me.
Don't put an open end wrench on the sending unit. It will only round the soft brass. Use a socket or a closed end wrench. I had good luck with a closed end wrench and a hammer. You can start the engine and get it good and hot then while the engine is still running try to loosen the sending unit. The heat + vibration will help loosen it.

TRUE GRIT

[Bratina]

I had the same issue with #4 not firing - the issue followed the plug, so the plug was the problem. I changed plug #4 and it has worked since.

[deepthought]

Wow

Faster response please next time everyone...LOL.

Thanks for all the input folks.

So today was too breezy to drop the mast so I spent a few hours playing spark plug chess.

#1,2 & 3 were reading about 90C abd #4 about 50C. I was taking my readings of the hex part of the plug while the A4 was running after about 30 minutes. The low reading on #4 was what made me think I might have a dead cylinder/plug issue. So thinking that #4 plug might just be a dud, I swapped it with the existing #1 plug and moved the formerly known as #4, to #1. Now my temp readings shift and show #1 as being the cold one about 60C and the rest showing about 90-100C. OK, it's the plug then right? Well I'm not so sure. Taking the now #1 plug out (RJ12C) and swapping with a used (B6S which I am not sure what the difference is..) The cold plug is now #2.

So I can safely check off any ignition from the coil magneto coil etc bla bla bla. And this would now point that my tubes are at least OK.

My thoughts are as such:

Go and get a full set of brand new plugs and run the machine and see what's what. It seems like #2 fouls the worst.

Yes, I don't have too much faith in my temperature sender I never see that needle move, it's pegged at 135. I have a spare/replacement gauge and sender I might install tomorrow just for fun. f it's oil I am ok with that, but if it's gasoline, I am a little concerned, but I have no way to figure out which it may be.

The other school of thought is that I might just be a hypochondriac and that there is no problem at all. However I am still concerned about the oil/gas that comes out of the exhaust.

And yes it's RWC
And yes it's old school ignition (points 'n stuff)
Does anyone know what the difference in spark plugs is? Would 3 of one type and one of another be a poor idea?

Also, is there a way of testing or verifying that all cylinders are actually firing?

Thanks again for all your input, in know my issues are minor but I am dealing with an ancient engine here and am a little intimidated.

Cheers

[deepthought]

NB

I will proof read my post next time before I post. Sorry, cat on the keyboard syndrome.

[sastanley]

DT, even though you are not a newbie to the A-4, welcome to the forum as a n00b.

The way to verify all cylinders are firing is to pull a single spark plug wire at a time while the motor is running..you should notice a difference as you pull and replace each plug wire. A $20 compression gauge from the local auto store is also invaluable in this type of test situation, as Dave recommended above.

So, when my motor was new to me...I had a sticky #4 valve..Since you hopefully have a couple days before haul (winterize), I would liberally squirt some Marvel Mystery Oil (MMO) into the #4 and turn the motor over by hand if you can, or blip the starter to move it around in that #4 and maybe loosen up the offensive valve. This does not always work right away..it took mine several applications and weeks, but i didn't have to pull the head unnecessarily. It will be a bit smokey on fire up, especially if you can get that plug to fire and make some compression.

[deepthought]

test

Thank you Shawn, that was exactly the info I was seeking. I was planing on trying that but lived in fear of burning out the coil or some other part of A4 voodoo.

Cheers

[sastanley]

Nah..if you've been running a while on 3 cyls, it won't get any worse. I ran my motor for several hours before that silly #4 exhaust valve popped loose and started closing. The #4 plug may still in fact be firing, just not burning anything well since there is no compression.

The real check is a compression test, and before you dump oil in it, which can affect the results.

Edit - DT, BTW - alcodiesel posted a great pic of his motor which shows you where the serial number should be stamped. I stole this from his post in another thread.
There should also be a date stamp on the block (6 digit number, mine is 041976, indicating April 19, 1976), underneath the carb, and a little hard to see unless you remove the carb.

[JOHN COOKSON]

Have a look inside the distributor cap to check and be sure there is no arcing or electrical communication between the terminals or any other weird stuff going on. Also check the towers to see if they are bright and shiny. A piece of sandpaper on a pencil will clean the towers up. Be sure the contacts on the wires are bright and shiny also.
How long has it been since you have replaced the distributer cap and rotor?

TRUE GRIT

[tenders]

I'm not sure how reliable these temperatures really are. They're certainly measuring something but I don't know they're measuring what you're interpreting them to be. Do the wire-pull test, and check the compression of each cylinder. It's possible you have several intermittently sticking valves - the prevention of which I'd suggest adding several cups of Marvel Mystery Oil to a full tank of fuel regardless, on an ongoing basis.

If you have questions about the ignition components I'd suggest replacing all the plugs, the wires, the rotor, and the cap now, running the engine between each to make sure nothing is getting boffed up, like the wires getting put on in an order other than 1-2-4-3. (You checked that already, right?) Next spring once she's running again replace the points and condenser, or install electronic ignition for not much more money. And the coil, if you're feeling flush.

[BunnyPlanet169]

running the engine between each to make sure nothing is getting boffed up

This is great advice, often not mentioned. You've got a lot of good suggestions here for troubleshooting. Take them one at a time, and make sure you understand the results before taking the next step. That will help you make sense of it, and help us in diagnosing.

[Vermonstah]

DT - let me echo previous expressions of "welcome aboard" to the forum. As you have already discovered: You have come to the right place, where the experts regularly and liberally dispense their wisdom.

I have no such expertise to dispense, just some experience with sticky valves and the like. So, my recommendations to you are very simple:

1. Get the Moyer maintenance manual, if you don't already possess it. This is your primary reference that you should use to orient yourself to your engine. The Moyer Manual is a treasure trove of info, complete with "hand holding" instructions to troubleshoot your engine. I have found it to be immensely valuable. And by boat bucks standards, it is essentially free.

2. I previously had issue with my water temp gauge - unreliable readings. While I was troubleshooting sticky valves etc, I found the handheld temp gauges like this one https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 to be very useful. You can get a reading on #4 and relate it to each of the other 3 while under operating conditions. Very useful for troubleshooting. Then later, you can take readings for anything you desire, (e.g., your exhaust etc). Like the Moyer manual, this IR thermometer is essentially free. After I got everything sorted out with the valves, and the engine running smoothly, then I followed the specific directions provided here on the forum to replace my sending unit, without issue.

3. Lastly, if you follow the troubleshooting advice provided here and in the Moyer manual, you will not only remedy secondary issues, but you will also identify and resolve root causes. With minimal time and expense, getting you back on the water soonest, with confidence in your beastie.

[Dave Neptune]

Cheers, yes it is somewhat common to run a hotter plug in a cylinder that is low on compression and passing some oil up past the rings otherwise there is no reason. I ran the RJ12C Champions for over 30 years in my old A-4.

As you have a point type ignition taking a look at the "dwell" with a meter is a good idea.

Get the gage replaced then worry about temps.

Sounds like you do have a bad plug and replacing them can only help if not fix.

Dave Neptune