Fuel pump failure - Now have knocking

[esteym]

Just posted this 10 min ago and my post disappeared - sorry if there are two now....

Just heard from the shop and they said there is a knocking in my engine. The upper fuel pump was bad so I assume that this is the cause because I have had no alarms. So I'm going to check the compression, but im not hopeful. They told me it would be the wrist pin or the bearing on the wrist pin.

Do I have to rebuild or can I just replace the wrist pin and bearings on the two upper cylinders? I know i'll need to pull the heads and look inside to see if there is any scoring or obvious wear. If there isn't can I just fix the bearing and pin?

And as to the heads and reinstalling them. Can I just scrape them and use perfect seal or do I need to get them finished?

thanks

Mike

 

[rodbolt]

Re: Fuel pump failure - Now have knocking

first a compression test wont show a bearing failure, yes a blown pump diaphram can take out a crank,rods and wristpins and the occasional piston.
to test remove the plugs,rotate the motor by hand until a piston comes to TDC then rotate about 30 degrees more, then insert a metal rod or phillips screw driver and while holding the flywheel push on the piston, if any motion is felt or heard that is the problem cylinder.
however it will require a complete tear down to inspect for damage.
and that my friends is why I harp on replacing the low pressure pumps on precision blend yamaha's every 3rd season. if they fail it can take the motor out with it if you run it long that way.

 

[esteym]

Re: Fuel pump failure - Now have knocking

Thanks Rodbolt

I hope to start the disassembly today. It is just a matter of the shop getting done with the work they were suppose to get to last tuesday.

So how often do cranks go and what should I look for? If I have bad bearings do I replace the rod, wrist pin and bearings? or just the wrist pin and bearings? I have a micrometer would that be able to measure the wear or would I need to take it to a shop?

I hope it is not the crank because they are REALLY expensive

Thanks much!

Mike

 

[rodbolt]

Re: Fuel pump failure - Now have knocking

depends on what broke, if it took out a rod bearing odds are high the rod and crank went with it, they mostly only go bad due to lack of maint or a serious malfunction.
what motor are we dealing with ?
if a wristpin failed it may or may not take the rod with it, any pitting large enough to interfere with the needle bearing rolling will cause another failure.

 

[esteym]

Re: Fuel pump failure - Now have knocking

Rodbolt,

Just got the boat back from the shop. I'll start on it tomorrow and do the test you said to do on your first post. The engine is a 150 2 stroke carbed yam (sorry I didn't mention that earlier). It was recently rebuilt (about 40 hours on it maybe) so I'm hoping that the crank is fine. Who knows though.

Its funny, I thought the noise was more of a chirping noise before, but they are the experts and I didn't take the cowling off to listen. I'm not going to pull anything apart until I'm sure it is a bearing though. The motor ran fine before except for an intermittant loss of power (due to the failing fuel pump). I searched for "chirping" and found a few explanations. They said the noise was coming from the top of the engine. :/

Anyway, I"ll let you know how it goes. Thanks for all the help.

Mike

 

[esteym]

Re: Fuel pump failure - Now have knocking

It turned out to be the crankshaft. The number 2 piston crank position was severely eroded. I think i got shafted on my rebuild, no pun intended. No other damage anywhere in the engine. 110 on all cylinders. That seems low but since it they are all the same and crosshatch is still visable on I'm fine with it.

I'm looking for a used crank right now. Wish me luck.

Any advice on assembly? Tear down took 3 hours, lots of pics to work from, lots of labeling.

How do you press the bearings on each end of the crank shaft? They talk about a tool in the book, but is there another way?

Thanks

Mike

 

[rodbolt]

Re: Fuel pump failure - Now have knocking

if you remove the upper or lower bearings they are not reusable.
find a remanufactured crank or have yours rebuilt. Outboard Crank Shaft company does it.
as do a few other specialty places.
there are some places that sell used cranks.
if the crank is eaten then carefully inspect the rod for damage.
always use NEW rodbolts at reassembly.
unless they are damaged the mains,except the lower, are normally reusable.
the bottom bearing I always replace anytime the crank is out. its the only main that has to accept a radial and axial load.
beswt advice is clean everything and carefully follow the service manual.
110 PSI is acceptable.

 

[esteym]

Re: Fuel pump failure - Now have knocking

What should the PSI be brand new?

Thanks for all of the advice. I'll let you know how it turns out.

Mike

 

[esteym]

Re: Fuel pump failure - Now have knocking

Would this require a break in period again? I thought break-ins were for the rings and walls of the cylinders, but my bro said that he thought it might.

Thoughts?

Mike

 

[esteym]

Re: Fuel pump failure - Now have knocking

AAAAAhhhhhh.... She lives again!!

Like I said before tore the engine down to the crank, pulled the bearings and the oil pump gear (that was not fun). Installed new bearing and old gear, oil seals, mid bearings and bottom seals and bearings. Put it in the crank housing and snaped a seal. Bugger! got new one, installed pistons in correct order and way, installed cover, heads, put it on the upper housing thing, put all the other crap back on with new fuel pumps and...... discover I've inadvertantly attached a ground wire on a positive terminal...... pop goes the tilt trim relays. 150 bucks gone. Grumble grumble grumble....

end result:

compression test 115 + - 3
after minor adjustments to carbs ... she purrs like a kitten.

Thanks for all the help ..... tuna fishing tomorrow off of chatham!!!

d