Cylinders Low In PSI ? (HELP)

Fun Times

Fun Times

Moderator
Staff member
Joined
May 16, 2009
Messages
9,151
Re: Cylinders Low In PSI ? (HELP)

tpenfield said:
Is the actual cause of the low compression known at this point?
Click to expand...
It is undetermined at this point. He his scheduled to work on the boat sometime this weekend. Until then, lets let this thread die down for now until we see what he comes up with after doing the things recommended above. Hang tight on this one! Thanks guys.
 
Last edited:
B

BigDog98

Chief Petty Officer
Joined
Nov 12, 2013
Messages
525
Re: Cylinders Low In PSI ? (HELP)

WIMUSKY said:
Why not just get rid of it and use your 2004 Baha
Click to expand...
I dont own it. The dad does. But since he does not have a account on hear then decided to post that boat up here because if any time in the future the boat also has an issue then you guys would know what i am talking about. And that boat is strictly for business and not pleasure!
 
Last edited by a moderator:
L

littlebookworm

Chief Petty Officer
Joined
Nov 30, 2007
Messages
574
Re: Cylinders Low In PSI ? (HELP)

I've just been reading this thread for the first time. I agree that we should back off and see what develops. BigDog has gotten good advice, but seems to have his plan of action set. Full diagnosis should be done first before even considering pulling the engine and shipping the block to Canada. Frankly, if that engine hasn't ever been winterized, I'm surprised it's been running at all. Let's wait and see how this develops. Good luck, BigDog. Hy
 
H

harleyman1975

Ensign
Joined
May 12, 2003
Messages
959
Re: Cylinders Low In PSI ? (HELP)

Sounds to me like you have a good set of tools and are ready to start.
 
B

BigDog98

Chief Petty Officer
Joined
Nov 12, 2013
Messages
525
Re: Cylinders Low In PSI ? (HELP)

Ok guys. So i have went to my boat today and made my video of the compression test on the engine and the video is uploading right and i will post here in a hour or 2 !!!
 
B

BigDog98

Chief Petty Officer
Joined
Nov 12, 2013
Messages
525
Re: Cylinders Low In PSI ? (HELP)

Here is the video of the compression test. Towards the middle of the video i started to narrate and my voice was so low i dont know what happend with the mic so just turn up your volume. Sorry just bare with me.:D
 
achris

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Cylinders Low In PSI ? (HELP)

So, you have some still low on the wet test, which may indicate valves or a head gasket. Any cylinder that rises to near normal wet, is an indication of ring problems.

What I'd ask you to do (as I did have trouble following what you did) is to fill in a table like this one.... That will help us see at a glance what is going on.

attachment.php


BTW. We didn't doubt you had a 5.7 engine, we just were sure it was NOT the one in the photo you posted claiming it was yours.... ;)
 

Attachments

  • pressure table.jpg
    pressure table.jpg
    16.5 KB · Views: 0
Last edited:
B

BigDog98

Chief Petty Officer
Joined
Nov 12, 2013
Messages
525
Re: Cylinders Low In PSI ? (HELP)

Ignore this one. I messed up on it ! The correct one is down below !!!!!!!!!!!!!!
 

Attachments

  • pressure table.jpg
    pressure table.jpg
    28.8 KB · Views: 0
Last edited:
B

banshee owner

Petty Officer 1st Class
Joined
Sep 4, 2013
Messages
227
Re: Cylinders Low In PSI ? (HELP)

So none means no change right and looks as if one cylinder on each bank have dropped and both are third back. Only thing common to both cylinders is the cam but you would think more cylinders would be affected. If the cam broke or lobes were wore off.you would think more than two cylinders would lose lobes. I would say you may lifter problems or extremly seized piston rings(not sure abiut that one)
 
Last edited:
B

BigDog98

Chief Petty Officer
Joined
Nov 12, 2013
Messages
525
Re: Cylinders Low In PSI ? (HELP)

No it means i did not do the wet test on them. They where way above 150 or they were in the ball park so i did not bother. I did the wet test on only the weak psi cylinders.
 
achris

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Cylinders Low In PSI ? (HELP)

Doesn't look like a ring problem... If you have access to a leakdown tester, do a leakdown test on your low cylinders... That will be conclusive on where the pressure's going. You may be lucky and just need the heads worked on...

Chris.....
 
8

84EdH

Chief Petty Officer
Joined
Apr 30, 2011
Messages
575
Re: Cylinders Low In PSI ? (HELP)

Big dog I think you can rent a leakdown test kit from advance auto or autozone or buy an inexpensive one from Harbor Freight Tools.
 
tpenfield

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
18,224
Re: Cylinders Low In PSI ? (HELP)

Just comparing this to your original test at the beginning of the thread, and sorry if I missed any details . . .

Is this the same gauge? (readings are generally 30 + psi higher), but not in all cylinders . . . not sure opening the throttle would make such a big difference. My experience is that it would add 10-15 psi.

Engine was cold the first time around, . . . is the engine warm or cold the second time?

#2 went down . . . - 30 psi ???

#4 went up +65 psi ???

#7 went up +50 psi ???

Just wondering if there is any test oil (or perhaps water) accumulated in the cylinders from the previous tests, if you did not run the engine prior to the 'dry test?

This engine would normally be in the 170 psi range (right ?)

Anyway as Chris has stated, not looking like a ring issue, so perhaps no need to send the engine off to a machine shop. The more likely things would be head gasket and/or valve job, which could be done locally.
 
B

BigDog98

Chief Petty Officer
Joined
Nov 12, 2013
Messages
525
Re: Cylinders Low In PSI ? (HELP)

The engine was run to running temperature before doing the test (160F-170F). Yes that is exactly what changed in the psi numbers when I opened the throttle. Yes its the same gauge. No first I flushed the engine with fresh water and then I did the test. I saw a little oil residue on the ends of the spark plugs. (The 2 that i previously did the test on only). It says that the psi in all cylinders should be in the 150psi range and generally 10% more or less from it. So I will rent the tester or purchase one buy my question is why are the rest of the cylinders so high? Its like 200psi and up! Can that be fixed. And can I replace the head gasket or do a valve job on my own with the proper tools and parts? And what is included in a valve job. What needs to be done in a valve job. Thanks !
 
tpenfield

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
18,224
Re: Cylinders Low In PSI ? (HELP)

OK, thanks. A leak test requires a compressor and a leak test gauge. You probably can rent these things, but you will need a source of electrical power near the boat to run the compressor. Also, be careful when doing a leak test. . . If you don't get the cylinders at their top dead center (TDC) location, the engine could rotate violently when you apply pressure to the cylinder. Also, if you forget to relieve the pressure prior to rotating the engine to the next cylinder's top TDC the engine will rotate violently as well (I've done that :eek: )

Valve jobs usually involve grinding the valve edges and the valve seats to get a nice fresh and properly angled surface on each. This type of work is pretty straight forward for any machine shop.

The high psi numbers can mean that there is fluid of some sort in the cylinders . . . Or the gauge itself is inaccurate. Anyway, best to proceed with the leak test at this point.
 
Last edited:
B

banshee owner

Petty Officer 1st Class
Joined
Sep 4, 2013
Messages
227
Re: Cylinders Low In PSI ? (HELP)

before tearing into heads and gaskets, valves etc i would pull the valve covers and make sure all the rockers are moving properly and opening the valves properly. you may just get lucky and need adjustments if they are adjustable i don't if they are but higher than normal compression may indicate there out of adjustment just my opinion and remember i am not a marine mechanic just an automotive mechanic but all engines run on the same principles.

someone who knows these particular engines maybe able to direct in the right direction.
 
8

84EdH

Chief Petty Officer
Joined
Apr 30, 2011
Messages
575
Re: Cylinders Low In PSI ? (HELP)

How do you adjust valves to get higher compression?
Valves closed at TDC is most compression you can get. Water in cyl can increase compression. I am suspect of bigdog compression guage/technique due to variable readings.

Bigdog: consider getting a mechanic to do leakdown test. Maybe $100 ? Most important to get correct diagnosis at this point. TPenfield is right you could get hurt trying leakdown yourself. in long run, this will save you money by not chasing wrong problem. Just my opinion.
 
O

ONEGA

Petty Officer 2nd Class
Joined
Feb 18, 2012
Messages
141
Re: Cylinders Low In PSI ? (HELP)

Before you do a leak down test yourself if you do, search for threads on the subject and have some reading. It might be confusing if not done before.
 
B

banshee owner

Petty Officer 1st Class
Joined
Sep 4, 2013
Messages
227
Re: Cylinders Low In PSI ? (HELP)

we dont know the history of this engine (maintenance ect.) if valves are out of adjustment and not opening all way (exhaust side ) could potenially lead to elevated compression readings.

im just looking at the basics before tearing down and i am buy no means asaying anyone is wrong.

low compression could be anything

i agree a leak down test would definatly be a good next step also may want to try another gauge as was stated before.

also fluid entering cylinder could drive the compression up as was stated earlier

was the fuel disconnected before the test i dont recall if it was.

If im way out lunch and let me know and ill back off

sorry if im causing confusion here
 
You must log in or register to reply here.
Top