Logo
FULL SITE MENU

Compression Test Issue M440

wh1278

wh1278

Member
Hard running M440 at start so I decided to start with compression test. Removed all plugs and dist coil and went to first cylinder. Instead of a cranking, I got a constant "eeeeeeee" from the starter. No cranking. Checked the juice coming to the starter and it was just under 13 volts (not under load). So I put the plugs back in (except the dist coil) and it cranks. Pulled them all again and got the steady "eeeeeeee" sound. Why doesnt it crank with all the plugs out? Any ideas? Do I need to ground the dist coil? Could a bad cylinder cause this?
 
Re: Compression Test Issue

Sounds like it. At first I thought it was a starter problem, or a battery problem. But it seems I have enough juice, and it cracked fine when I put the plugs back in. Why would is spin and not crank with all the plugs out? Haven't had this before. My knowledge level is surface...timing, plugs, pumps, manifolds.... Initially I thought it was a leaking exhaust manifold causing the rough running at start. I had my port engine do the same thing and it was a small fresh water leak in the exhaust manifold. Swapped the manifold and runs fine now, so I was headed that direction...but first wanted to check the compression. Both engines were rebuilt in '08, so I dind't expect any cylinder problems (except maybe a little water). Any ideas would be appreciated. Thanks
 
Re: Compression Test Issue

Could it be just a coincedence that it happens with the plugs out and that the real problem is an intermitent starter issue? That's what I'm getting from your description ("eeeeee").
 
Re: Compression Test Issue

what your hearing is the engine turning over a lot faster, with the plugs removed you have taken away the compression, thats what makes the engine sound as though its working a lot harder, no plugs=no compression..the " eeeeee" noise is the starter & engine spinning freely,
 
Re: Compression Test Issue

when the plugs are out it makes totally different sound,monotone if you will
because what pete said

you dont have a problem thats the way it goes

never hurts to do a compression test and read the plugs

see whatchu got!!
 
Re: Compression Test Issue

Thanks, so can I still do compression checks on each cylinder without the crank...using the single, constant monotone "crank"? Will it give me accurate readings? Why hasn't it happened this way before? I have always had a standard crank-crank-crank, and stepped compression build with each crank before. Will I still get the top reading? I'm concerned the rough running and knock I had at start up before I removed the plugs may be effecting the ability to get the crank... And I just did the same process with my port engine just a month ago (good compression, but leaking exhaust manifold). Also, is it an all or nothing proposition with the spark plugs while compression testing...meaning you need to remove all of them to test a single cylinder? Wont removing just one, or a side and leaving the rest in mess up your readings?
 
Re: Compression Test Issue

the best way to do compression checks

cold test
hot test
wet test with teaspoon of oil

a leakdown test is what you always use for 4 stroke motors
 
Re: Compression Test Issue

"Also, is it an all or nothing proposition with the spark plugs while compression testing...meaning you need to remove all of them to test a single cylinder? Wont removing just one, or a side and leaving the rest in mess up your readings?"

So the engine cranks with plugs in and the starter just spins with the plugs out?
Sounds like starter solenoid to me.
Will it crank the engine with only 1/2 the plugs in? Try your test one bank at a time.
 
Re: Compression Test Issue

you take all plugs out
because if you have a leaking headgasket, 1 cylinder can make the other cylinder lie
 
Re: Compression Test Issue

"take all plugs out
because if you have a leaking headgasket, 1 cylinder can make the other cylinder lie"

That is why you test one bank at a time, so adjacent cylinders have no effect on the read. I doubt cylinder 1 can leak into cylinder 2!
 
Re: Compression Test Issue

yep odd cant leak into even

but pulling all the plugs out always helps not wearing out the starter!!!!
 
Re: Compression Test Issue

thanks guys. I had tried to pull plugs on only one side yesterday. That worked when I did one side, but not the other. It does seem like it could be an intermittant starter or solenoid problem. When I thought about it, I do remember last summer having a couple times when I would start that engine and the starter would "hang on" a split second after the engine started. So, while I have the exhaust manifolds off and can get to the starter, should I attempt to trouble shoot the starter? Could it be the solenoid? Any way to troubleshoot without replacing the noid, or pulling the starter? Pulling the starter would be a first for me...but this site, and you guys, have given me the courage to do things on those engines (m440's) that I would never dare before.
 
Re: Compression Test Issue

It sounds to me like you have a loose or corroded battery cable connection somewhere. I assume the same morons who left out the t-stats also installed your engines?

Jeff
 
So I changed all the fluids and plugs and started it up again. Bad knocking sound so I shut down. The next day the antifreeze was low and the oil level was high. There was also the dreaded moisture and a little white paste on the value cap. So I drained the oil and replaced, then tried another compression test. Did the "eeee" again with all plugs out, but by turning the key back and forth three or four times for each cylinder I was able to get compression readings. All were a little lower than I expected (103 to 120), but i had one that read absolutely no compression. Would I get a dead cylinder reading with a head gasket leak? Something deeper maybe.... uuughhhhh!
 
your screwed

you need to pop off the heads

sounds like you had a half azz shop work on your boat

better call around and fine a better shop
 
you can pull that one side only
but if you re-do heads, you do both not 1

there is a place in Washington state that manufactures heads for cheap
i think this site sells them also from sierra also
 
So if I dig in the one side that I have identified (cylinder 3), what would cause me to have to replace the head...only if its warped or cracked right? Would a value issue or some other component break in that cylinder require head replacement?
 
no you replace the head because it is cheaper then getting a valve job these days

it is either
bad rings
blown head gasket
bent valve
 
Pulled the head off today (with help of mechanic). Turned out to be an exhaust valve that was stuck open slightly. Head is off to the shop. Cylinders were fine. Hand crank the pistons up and down and put fist pressure on them at all points. Also checked the walls. All's good. Gasket was good too. I think the zero compression reading on that number 3 cylinder was because of the valve stuck open, and it was just a coincidence that I had water in my oil from those darn lower elbow to exhaust manifold gaskets. I had just put on new risers when I had the knock begin (knock was actually right before the riser change). I think I need to take FastJeff's suggestion and get blockoff plates made. I'm thinking exhaust manifold, gasket, blockoff plate, gasket, lower riser elbow. Nothings going to get thru that. If not that, what about those hard composite gaskets by Thermoseal...the green ones. Would one of those without the plate be enough? Definitely not using the black felt types ones that came with the lower elbow again. In the meantime, while head is off, I've obviously drained the coolant, and changed the oil once. Planning on changing the oil again at least once more before firing her back up. Is that enough to wash out any residual antifreeze? Anything else I can do to "de-moisturize"....additives...?
 
Thanks. Did the wd40 on the exposed metal, especially the pistons, and covered up with towel while head in shop . Probably a good idea to go after other head since I have the intake mani off. Strange thing about the intake mani...it only had the valley pan as a gasket. The valley pan has the aluminum ridges around the exhaust ports, but it seemed a little oily on the intake manifold side. I understand some mechanics just use that pan for a gasket with some sealant, but i think i should use a gasket also. Shouldn't i have a regular gasket too...maybe even one on each side of the pan template, with plenty of silicon around the edges and under the clamp down bars to keep oil in. I'm thinking that is why I am seeing some oil on the valley pan on my port engine (different thread). I'm thinking that the oil is getting up around the valley pan from below, past the intake manifold and dripping to the middle. Can't be good if it's getting into the exhaust ports on the head. right?
 
If the heads haven't been milled then the valley pan metal gasket is correct. I you try to install it along with paper gaskets it won't sit deep enough and seal properly. Just put a little sealant on the passages when you install it. Clean out all the heat risor passages while you have it apart.

Dan
 
There seems to be alot of carbon buildup on the cylinder heads, exhaust ports... The head is out to get the stuck value fixed (maybe the cause is all the carbon?). It ran REAL cool for two years, barely getting above 7 knots...without a thermostat. The comment above from Dan about cleaning it out made me think about what I can clean and how. I dont want anything to drop down into the rings. What is the best way to clean this up...pistons, intake manifold...? What should I use?
 
I'm coming in very late on this, but here is an unsolicited FYI, if I may:

The advantage of removing ALL spark plugs (in addition to post #10), is to reduce the load on the starter motor, so that max cranking rpm can be achieved.
The question now becomes, why would you NOT remove all of them for this test?

The dry/wet test can be valuable to determine if the piston rings were to be the primary cause of low cylinder pressures. The oil will temporarily bring cylinder pressure UP, by momentarily aiding in this seal, if the rings seal is not adequate to begin with.

Now.... here's the rub with the wet test, IMO.
The wet test works fairly well on vertical cylinder in-line engines. These pistons are relatively level, and if not dished, will allow the oil to form around the cylinder walls, where it will help with poor piston ring sealing..... and does so momentarily until the oil makes it past the ring set.
If pressue increases during this, then our rings are likely one cause of low cylinder pressure.

A "V" engine piston is not level! Add to this dished pistons (if applicable), and the oil will very likely pool at the low side of the cylinder, and perhaps primarily in the dished area.
If so, the test becomes ineffective as for the results hoped for!

If each cylinder were to have the same volume of oil added, and forced in via compressed air....., our chances of an effective "wet" test increase.
However, there is no perfect science to this, that I am aware of!

I think that it's a common misnomer that the wet test is effective! If this is not taken into account, it's only as good as the amount of oil that can actually reach the ring landings, and in a fairly even means.
What we may see, is a slight increase, due to the volume of oil now taking up space within the cylinder. This is also why we may want to add an equal amount of oil to each cylinder, during a wet test. I think that one of you touched on this!

To the OP here.... good luck! I hope that you get this resolved! :D


.
 
wh1278 said:
There seems to be alot of carbon buildup on the cylinder heads, exhaust ports... The head is out to get the stuck value fixed (maybe the cause is all the carbon?). It ran REAL cool for two years, barely getting above 7 knots...without a thermostat. The comment above from Dan about cleaning it out made me think about what I can clean and how. I dont want anything to drop down into the rings. What is the best way to clean this up...pistons, intake manifold...? What should I use?
Click to expand...

I like to use a wire wheel on a drill to clean the pistons and intake, turn the engine over with a socket and clean each piston at top dead center then vacuum up the mess. Use a drill bit to clean up the heat riser passages in the intake if plugged. In the future you need to run the engine up to cruise RPM for 5 minutes of every hour going slow. I cruise from Seattle to British Coulmbia like you at 7-8 knots to save fuel, you are right about not being to get the engines warm at this speed and they really carbon up but running them at 3000 rpm for 5 minutes every hour has worked good for me. For long distance cruising I have run on one engine at 8 knots and this seems to work better, I switch engines every hour, you really need an auto pilot to do this. First thing to check when running again is the mechanical timing advance, that is the #1 problem in marine engines.

Dan
 
Dan,

Those heat riser passages which Im bout to clean out with a 1/4 inch or so drill bit.

What is there purpose ?To get the choke opened up

Is it okay to dump some sea foam in there to loosen up the gunk

Thanks

Dan:)
 
Back
Top