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Engine knock in 225

H

hondatic

Member
Have been working to restore a 225 to top running order. After running well for a four or five hours after launching the boat in Alaska, one of my 225s developed an intermittent but continuous "knock" at idle and wont turn up to full rpm at cruise. I completely drained and replaced fuel with fresh, replaced filter with new racor, drained all settlement bowls on engine. Replaced all spark plugs and started engine, same knock. Suspected perhaps a coil to be at fault so I swapped all six coilsf from starboard engine which runs fine on all cylinders. Same knock after all coils were swapped.

Looking for suggestions on where to go next. How are the coils controlled and is there a way to see if the signal to the coils is not making it short of disconnecting them one at a time to see if the engine runs differently? Is there a knock sensor that could be reset? I have the shop manual but don't see any trouble shooting entry for the symptoms I am seeing here.

Thank anyone in advance for their time, chawk_man and honda_dude in particular have been very helpful thus far. Both units are on and running fine after extension case and bearing replacements.
 
I had a continuous knock in the mercury i use to have a long time ago.I rebuilt the entire engine,and knock was still there,My friends father did something to my lower unit and the knock went away.So make sure everything is adjusted correctly.It sounded like it was comeing from the engine, but it was actually the lower unit.
 
The cylinder drop test is probably the easiest thing to start. Hopefully, it will isolate a cylinder or two. If you can isolate the problem to a couple of cylinders, then the following test only has to be done between a potentially bad cylinder and a probable good cylinder.

You can check the pulses going to the coils if you have an analog volt meter. At each coil, you will have to backprobe the leads. First check to be sure all of the coils have 12v at the yellow/black leads. Then connect the positive side of your meter to a +12v source (the engine battery is ok). Then, with the black lead of the meter, backprobe the other lead (not the yellow/black) going to the coils. Each coil has a different color.
It generally is easier and less destructive if you use a straight pin or safety pin, and connect your meter to the pin with a small jumper lead.

The ECM sends pulsing grounds to each of the coils. Your meter needle should jump in time with each time the cylinder fires. It may not go all the way to zero or all the way to 12v since it is going on and off so fast. Just make sure that all of the cylinders look the same on the meter. If they do, they the coils are getting what they need.

You should also check for a potental location of actual physical clunking. Use a short hose or screwdriver and hold it against various areas of the motor...including lower unit. That might give you more info.

If you do have a couple of cylinders in question, take compression of all your cylinders. See if a low compression is consistant with the failing cyinders.

The other thing that could be cylinder specific would be a plugged fuel injector or two.

That should keep you busy for a while.

Mike
 
Mike,

Thanks for the suggestions. I am still unsure of what the cylinder drop test actually is. Should i unplug the coils one at a time with the engine running to see if there is any change in how the motor runs and when I find the one or more that don't affect the performance look to the coil tests you described on those cylinders?

In an earlier post you alluded to the possibility of damaging the ecm or a coil by doing so, just don't want to create more work for myself.

Also would a bottle of injector cleaner in a 5 gallon portable tank possible clear a plugged injector?

I will listen more carefully tomorrow with a hose, used a 3/8" extension today and definitely heard loudest knocking, almost a puck, puck sound on block where cylinder head joins the block. Lower unit doesn't seem likely as performance is affected by about what one cylinder missing might cause, wot only 5200rpm. I will swap unit with a spare to check anyway.

How hard are injectors to change out?

Thanks for the help, this forum is of great value to me.

Shawn
 
If you do not have an HDS...sometimes you have to do what you have to do...

If you pull the entire coil assembly off of the spark plug, the spark will most likely jump to the inside of the tube. I have never tried it, but that might be better than just disconnecting the connector from the coil.

If someone else has another thought...please jump in.

If the injector is partially gooed up and it passes some fuel, the injector cleaner or Seafoam, would possibly help the injector. It would not hurt it.

Never had to change out an injector on a 225. It looks like you have to take off the intake manifold and fuel rails. It does not look too bad. Just follow the step by step in the Manual.

As you get into all of this, do not forget the basics of doing a compression test. Just one more piece of the puzzle...

Hopefully, you will isolate it to a particular cylinder.

One other potential problem could be a crank bearing. Let's put that off to the side for now.

Mike
 
After spending an hour working with the motor this afternoon I have isolated the knock to the area around the bottom of the cylinder head on cylinder 1. I used my iphone to video/record audio of the knocking and can email it to anyone interested in giving it a listen. It is quite clear as I put the socket extension I was listening with against the phone and it picked it up very well.

I haven't done anything with the coil to test spark but hope to do so on Sunday. I ran the engine with clean gas mixed with stp injector cleaner for 5 minutes today and at one point the knocking became much more intermittent and would go away for a few revs all together but then returned to be fairly steady.

There is no knocking noise from anywhere on the engine but the cylinder head area. I don't hear anything at either side of the crankcase and very little of the knock transfers to the port side of engine. Am I correct to infer that if the knock is not constant it isn't likely to be mechanical? A rod or bearing would knock steadily with each rev at constant rpm?

I pulled the sparkplug for cylinder 1 after running at idle for 10 minutes and it was clean and dry.

Should I pull the valve cover and see if something is loose or tight in the valve train?

The knock started the morning after I ran the boat from Juneau to my hometown. 2 hours at 3800-4000 rpm, easy cruise. There wasn't any knocking at start up when launched or during any of the test runs in Florida where I bought the boat.

Thank in advance for anything else anyone might have to offer.
 
I had the compression tested when I decided to purchase the boat. All cylinders on both motors on the boat were between 205 and 215psi about 6 running hours ago. Should I retest quickly to see if a valve might be to blame?
 
Agree that it is not likely a rod bearing. To me, what you described sounds like a fouled up injector or a valve that has not been set properly. Sure, pull the valve cover and check the gaps per the manual. If that doesn't fix the problem try a strong mixture of SeaFoam or Yamalube Ring Free mixed in an external tank. That may clean out the injectors. The other possibility is a timing problem, but that should not be isolated in a single cylinder.
 
I tested the compression this evening with the engine pretty cool and hadn't read the manual about how to do a proper test before I did it. Just removed all the plugs and cranked over on each cylinder until gauge maxed out. The number one cylinder was 205 psi, #2 182, #3 190, #4 200, #5 190, #6 188 psi. The cylinder with the highest compression is the one knocking. I will try some ring free in the small tank and see what happens. How much should I mix with 3 gallons of gas to give it a good jolt without damaging something?

Doubtful timing would be a factor at idle and all of a sudden like it came on and like you said, seems to be only the one cylinder.
 
It should tell you on the container, but normally it is two ounces per gallon. You will need to change the oil after the shock treatment because of possible oil dilution. Also, remove the plugs after treatment and clean them. They may be fouled. I'd do some searches on this site and others about decarbonizing shock treatments. I think you will find that many folks will shut down the engine about halfway through the treatment to give the decarbonizer a chance to soak into the carbon deposits. Others will likely disagree with that procedure. Either way, you will know when it is working because of all the crap that comes out of the exhaust.
 
Have been doing some thinking on knocking without time for working on it lately. Recorded video/audio of engine running, counted knocks, 340 per minute. If the engine idles at about 650rpm this means knock is every other revolution?

Could this be consistent with a compression or exhaust event in a single cylinder?

Is it possible for the piston to actually contact a valve, I guess the exhaust valve since compression is good in suspect cylinder?

As the plug in suspect cylinder is dry after running either the cylinder is firing or injector is not putting fuel into cylinder?

Is a knock common when a cylinder isn't firing in a Honda?

Could I duplicate the knock in another cylinder by disconnecting the coil to that cylinder?

The knock is loud enough to be audible, though muffled and dispersed through the cowling.

Planning a proper compression test and running a gallon or two of ring free shock treatment through the engine to day to see what happens but am a little concerned about running the engine much more with this knock being so loud.

Thanks for any help or suggestion.
 
A knock every other revelution is likely consistent with a problem in the compression cycle on a 4-stroke engine. It is possible that the cylinder head is striking an exhaust valve, but I think that is unlikely, unless it is way out of adjustment, and if that were the case, you would not get the compression numbers you reported. And, yes, a knock would be consistent with not firing in the cylinder due to fuel starvation or lack of spark. Change the plug and coil with another cylinder and see if the knock moves with the plug and coil. Of course, the other possibility is a worn sleeve bushing or rod bushing, but that is very rare on a Honda engine.
 
chawk_man,

Thanks for the reply, I have swapped all of the coils with those from the other motor and replaced all of the sparkplugs and the problem is unchanged. with fine compression I expect the exhaust valve to be fully shut when expected and not striking the piston.

I will try to disconnect one of the other coils on the other bank of cylinders to see if I can duplicate the knock. I am about to run the motor with ring free for a while to give it a chance to work its magic before I go further.

The motors have less than 300 total hours on them and there are no codes for overheat, overrev, low oil pressure in the computer according to the honda dealer i had read them in Florida before I bought the boat so I hope there isn't anything mechanical worn out save the extension case bushings.

Will three gallons of fuel be sufficient to run through the motor to give the ring free a chance to work?

thanks again for taking part of a sunday to help.

shawn
 
Three gallons should be fine. I assume you are doing this on the water, correct? If so, I would run it up to about 1500 rpm in neutral. That will still take about 2 hours to run through 3 gallons of fuel.
 
The boat is in my yard on its trailer so I will be doing this with a garden hose on the suction cup over the intakes. i've modified the system to have a 3/4 hose split to two 1/2 hoses so there is more water flowing with less pressure than the original plastic hose attachment with a 3/8" inlet.

I have a temp gun and will watch the manifolds for proper temp to avoid overheat. Also will keep track of the indicator stream to see if it is getting warm. Probably will only run at about 1000max but will see. Just doing what I can, relaunch isn't really going to be an option until I can run the boat around a bit.
 
Remeasured compression on all cylinders as per manual, engine at operating temp with throttle full, cylinder 1 230 psi, #2 only 190 which is 9psi below spec. All others 205-210psi.

ran engine and pulled each coil one at a time to see if I could change or create a similar knock in another cylinder, no other noise. Pulling the coil on each cylinder decreased the smoothness of the engine's idle also the smoothness of start-up. All coils would arc strongly to metal tube lining passage to spark plugs so all coils are functional.

The low compression in cylinder 2 and the knock on the exhaust side of cylinder head area near the top of the engine lead me to believe it must be one of the exhaust valves tapping on the top of the piston in cylinder 2. The knock is pretty loud.

I will try to pull the intake manifold and valve cover to see how things look in there. What mechanical causes could there be for the valve going down so far as to touch the piston? Broken spring on rocker arm? broken clip allowing the valve to drop into the cylinder on intake and then slam as it is being pushed into place on compression? At 1000rpm the knock is quieter and seems to be harmonic and cyclical, knock for a few seconds then gone for a few revs then back etc.

Should I expect the valve to be bent at this point as well?

Also wonder why compression is so high on cylinder #1.
 
You are beyond my level of competence at this point. Hopefully Jimmy or Mike will jump in here. Any way you look at it, I think you will need to pull the heads. Did you try decarbonizing?
 
Chawk_man,

Thank you for your time and input. I ran the motor for close to an hour at 1000rpm with the ring free mix but really can't run it anymore until I find the cause of the knock. It didn't change at all and actually has become steadier with time.

I have the intake manifold off and starboard side valve cover and will run the valves next time I get off work.

To check the top dead center exhaust position and feel of the valves do I rotate crankshaft pulley 360 degrees from the position where the cam shaft pulley mark says tdc compression for each cylinder?

I want to turn the engine over and listen to see if I can hear or feel the valve touch the piston. tearing the head off looks pretty daunting considering you have to remove all the belts, and the cam shaft pulley and the exhaust manifolds. Hope I can learn something from looking at the valves as the engine moves through the cycle.
 
I went back over your posts. Pulling the head is certainly beyond my competence level, so I would try to avoid that if at all possible. The one thing you have not eliminated is whether #1 is getting fuel. If you can get to the injectors, I would pull, inspect, and clean both #1 and #2 injectors. I would also thoroughly check the wiring to the injectors. You can test the injectors doing a resistance test, but I'm not sure what the proper resistance is. So, you may want to test all the injector resistances and see if #1 and/or # 2 are out of range. The other mystery in this is that you have above normal compression in #1 and below normal compression in #2. Is it possible that # 1 is not getting fuel (and building up oil) and # 2 is getting too much fuel and diluting the oil, thus lowering compression. Injector problems COULD explain that difference.

Mike - sure wish you would jump in here to help out Hondatic. As you can see, I'm beyond my level of competence.
 
I would also go for the injectors first before pulling the head. Check resistances as Bill said, but I would also pull out one that is assumed good and the other one or two in question.

This is a rather crude test, but should help you zero in whether the injector is clogged or not....

Get a 9 v battery. Then get your self some small jumper wires with allegator clips and clip them on to the injector. Connect one of the wires to one of the terminals on the 9v battery.

Hold the injector vertically and fill with alcohol or some type of non toxic fluid (brake clean is ok). Then tap the second wire on the other terminal of the 9v battery. You should hear the clicking of the injector. If the injector is working, the fluid should come out the bottom. Do it a few times to be sure of your results.

Compare the results of the presumed good one with the questionable ones.

If they all pass the same, then most likely, there is another issue.

To answer your question on valves....

If you turn the cam to tdc for a particular cylinder, both the intake and exhaust valves should be closed.

Mike
 
Mike,

Thanks for the answer to my post. I have adjusted valve clearances, they were all a bit large, all valve stems seem to be making good contact with the seats on the rocker arms through the entire cycle on all cylinders on the bank that is knocking.

I am going to pull the injectors and rail on the 1,2,3 bank and do as you suggested for testing to see if they are all pushing liquid through.

I cranked the engine over with a big drill today for several revs listening and feeling the exhaust valve banks on each cylinder for any sign of mechanical contact with a piston and couldn't get a hint of it so I think the injection may be the right track.

I will let you guys know how things come out.

On another note, any suggestions for a propeller choice for a twin vee 32 catamaran pretty heavy built with new cabin built on it? I'll be hauling six passengers plus myself for whale watching with full fuel on occasion.

I don't seem to be able to find anything on the props on the boat as to their pitch or diameter. Just a series of numbers on the hub. They are also strangely shaped compared to the yamaha props I'm used to seeing. One of the rubber grommets in the hub is cracked and the prop rocks on the shaft.

Thanks again everyone for the input.
 
Honda_dude and Chawk_man,

tested injectors 1,2,3 according to the manual for resistance, all were 11.6, 11.7 ohms, a little above book but my meter isn't expensive.

Filled them all with alcohol and tested with 9v battery. At first 2 and 3 just seemed to let the alcohol dribble through, forming a drop on the injector nozzle, after testing 3, (thought to be most likely to be normal function based on where the knock seemed to come from), then 2, injector 1 shot a nice fine spray out onto the sheet of paper I had under the nozzles in two opposing v patterns as I expect a good injector should.

Retested 2 and 3 with paper and one pulse at a time and was then able to get a pulse spray much the same for these two injectors though without the quality of the resolution of the opposing v pattern of injector 1. All three drained the tiny reservoir of alcohol at about the same rate when pulsed rapidly.

I expect when the system is pressurized the patterns are more distinct and the pulses more of a mist.

I guess I'm looking for some input and perhaps a suggestion to try next. I am going to order o rings for the injectors and put them back in and put the motor back together to see if I can make it run again, that would be a feat at least.
 
If you are still not sure on the injectors...put some seafoam through them a few times before you put them back in.

Also, do not put them back in the sameplace. Put the one most likely to be good in a cylinder that is questionable and see if the trouble follows.

With a rag on the fuel rail, flush the rail before you put them back in. Just has someone cycle the switch a couple of times to operate the fuel pump. Be sure to wear some eye protection in case the fuel splashes your way.

While you are that far...did you pull the valve cover and check the valve clearances and see if anything looks wrong or inconsistant amoung the cylinders.

Mike
 
subscribing........ sounds like the same issue I am having. I am at the point of needing torque specs to put my motor back together and see if I got rid of the knocking/ticking in the valve train. I started a new thread asking for torque specs.... maybe someone could help me out :eek:
 
Wellll...

After cleaning and testing the injectors for cylinders 1,2, and 3 and then moving them around to different holes on reassembly, same knock, same place. I think it must be valve related though in my experience I don't know how a leaky valve makes a "knocking noise." Compression on cylinder 2 is 190, well below what it was 10 running hours ago when tested before purchase so I suspect the problem is there.

I guess the next step is to remove the head and look at the valves. All valves were adjusted to within the specs in the manual, none were wildly out of spec when checked initially. The valves all seem to be touching the rocker arm adjusters fine but a valve not fully closing by a tiny fraction would hardly be noticeable and might be causing the leak I suspect here.

I cannot detect the knock anywhere on the block or near crank, it is definitely coming from the upper part of the engine near the head/block joint. A new head is likely my best quick fix?

In a post earlier Mdoherty suggested that an exhaust leak might sound like a knock or tap. Would this include a leaky exhaust valve or is that what he was referring to?
 
You may be correct in your diagnosis, but I don't think a leaking valve - one that is leaking bad enough to cause a knock - would still give you a 190 PSI. Furthermore, you earlier stated that the knock was every other stroke. Before pulling the head, I would go over the rocker arm assemply with a fine fine tooth comb and make sure you're not dealing with a bent or out-of-alignment rocker arm, or possibly a broken or weak valve spring on that number two cylinder.
 
CHawk,

Thanks for the reply, I am going to stay with it for a while.

I have posted a 3.5mb 30 second, video clip on my website (www.g-wind.com/knock.wmv) if you want to download it and listen, I used my iphone and an extension to touch the engine in the trouble spot but you can hear the knock with the phone held a meter from the engine easily as well.
 
Have done everything short of pulling a head and looking at the cylinders and valves from below. Knock is constant, loud and seems to be coming from top end on 1,2 3 bank.

Removing coils while engine is running has no effect on the knock intensity or loudness, it knocks every other stroke. The engine runs smoother than ever now that injectors are clean and have run a few gallons of ring free mixed with gas from a fresh can through the engine.

With air box off of top of engine sounding on the idler adjustment pully, and side of block at junction with head, exhaust side has loudest knock. Inaudible on port side of engine.

Removed and replaced thermostats, both were operating normally, someone suggested cold running engine could cause extra fuel dump, thin oil then burn up rod bearing. Oil has no gas in it, temp is fine on both manifolds and with less than 300 hours on a honda motor I can't believe a bearing could be out.

If anyone might have another top end suggestion I am waiting happily to hear, otherwise I am going to pull the engine off and put it in the shed til winter. I ordered a new 225 to replace it and hope it runs strong and without problem or this will be the end of Honda for me. Thank you to all that have helped, I will revisit this thread or start another when I find out what it is.
 
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