|
|
JimS88
Novice
Jul 17, 2012, 3:55 PM
Post #1 of 14
(1584 views)
|
|
Compression Mystery
|
Sign In
|
|
Here is a problem I don't understand. My 4 cylinder volvo penta AQ151C engine quit running the other day. (It's the same basic Engine used on countless Older Volvo cars through the years} I thought the problem was the head so I got a rebuilt one and put it back together. It seems to be doing the same thing:
The motor won't start. I did a compression test and When I turn it over it it makes compression for about 5 or 6 revolutions, then for about another 6 revolutions it makes zero compression. This make no sense to me whatsoever but I suspect the problem is in the lower end due to the head rebuild.
Anyone have any ideas what is wrong?
Thanks,
Jim
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 4:31 PM
Post #2 of 14
(1560 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
Your testing procedure is making no sense to me.
What exactly do you mean it makes compression for about 5 or 6 revolutions, then for about another 6 revolutions it makes zero compression.
Are you relieving compression and starting over?
Does your compression tester not hold pressure with a schrader valve?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
|
|
| |
|
|
JimS88
Novice
Jul 17, 2012, 4:43 PM
Post #3 of 14
(1547 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
It does it on all 4 cylinders although #4 has lower compression. All plugs were removed for the test. I turned the engine over about 15 revolutions on each test attempt. I frequently hit the button to release the pressure on the gauge when it built up. and when it was in the group of revolutions where it made compression the needle would climb but then after about 5 or 6 revolutions the engine would spin faster and the needle would stay at zero for about 5 or 6 more revolutions then it would repeat the process.
Also, and this may be a key clue, when it is making compression air blows out the spark plug holes (obviously) But when it isn't making compression, air blows out of the carburetors, which seems odd to me.
I can't understand how any engine could alternately make compression
then make none. I've done compression tests before on this and other
engines and always the needle rises with each revolution until about the
fourth time where it hit maximum.
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 4:47 PM
Post #4 of 14
(1544 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
It was probably just collapsing the lifters from cranking it too long with no oil pressure. You only need about 3-4 revolutions for a compression test. You car has compression, you're done.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
|
|
| |
|
|
JimS88
Novice
Jul 17, 2012, 4:49 PM
Post #5 of 14
(1537 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
No Lifters, Overhead Cam.
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 4:51 PM
Post #6 of 14
(1533 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
Overhead cams have lifters too.
edit, I see this one has solid lifters.
Why are you checking this? What problem are you having?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jul 17, 2012, 5:03 PM)
|
|
| |
|
|
JimS88
Novice
Jul 17, 2012, 5:10 PM
Post #7 of 14
(1526 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
Sorry, I was thinking pushrods.
The engine won't start so I need to find out why. If it ran fine I wouldn't mess with it further which is what I was hoping for when I put it back together. Now I have to diagnose the problem so I can fix it.
Are you suggesting that it is normal for an engine not to have compression intermittently? I've had this engine (actually twins) for about 22 years now and it never made this sound or had this problem before.
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 5:16 PM
Post #8 of 14
(1521 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
If you say you can hear it through the intake, that means you're losing it through the intake valve for some reason. Pull the valve cover off and observe the valves and see if they are continuing to close on time.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
|
|
| |
|
|
Discretesignals
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 6:14 PM
Post #9 of 14
(1508 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
What is the year and model of your Volvo?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 6:18 PM
Post #10 of 14
(1502 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
I believe this is a marine application.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
|
|
| |
|
|
Discretesignals
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 6:23 PM
Post #11 of 14
(1496 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
Just wondering because cylinder wash out can cause those symptoms. Especially if it is using EFI.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 6:26 PM
Post #12 of 14
(1491 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
I seriously doubt they are injected. he stated he's had them 22 years. Boats started using injection in last 10 years.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
|
|
| |
|
|
JimS88
Novice
Jul 17, 2012, 9:30 PM
Post #13 of 14
(1475 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
I figured it out. the timing belt slipped. Still dunno why it had compression some of the time. Doesn't matter now.
Thanks for your help.
Jim
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Jul 18, 2012, 3:05 AM
Post #14 of 14
(1460 views)
|
|
Re: Compression Mystery
|
Sign In
|
|
Yep, that makes no sense at all. Once it's out of time, the compression should be gone permanently.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
|
|
| |
|
Auto Repair Home
SEARCH
WHO'S 
LOG 
Strut spring orientation and strut mount tension nut
Please Help - Knock sound & engine fail
Brake Seals Bulging
