#1
IP: 71.204.217.107
|
||||
|
||||
Pressure Drop All Cylinders?
I asked this in a facebook forum and got some interesting answers but want your input:
Any ideas why all four cylinders would drop in pressure when tested cold? Previously had a solid 120 but now all cylinders read right around 60. I brought the boat out of winter with great success but the other day on a long sail coming out of an inlet it started dying as the boat pitched with the waves. I suspected back pressure since the exhaust was plunged under the water with those waves. Had a few runs where the engine died with little indication of why. Dying when at idle was particularly repeatable. The next morning, the engine had a lot of difficulty starting. Cleaned off some very sooty spark plugs when it sounded like I had a misfire. Compression test of all cylinders and spark test sat but the pressure in all four was about 60psi. Fuel level was almost full. Eventually I got her running and got out of the marina confidently on flat water with throttle. Thoughts? |
#2
IP: 68.99.97.14
|
|||
|
|||
Dirty Fuel
Pitching in big waves brings to mind stirring up muck lying in the bottom of your fuel tank. Take a look at your in line fuel filter and also drain the carb bowl and see what comes out. If there is a lot of foreign debris, a thorough carb cleaning is in order.
Tom |
#3
IP: 71.204.217.107
|
||||
|
||||
Quote:
Is there a way to check the polishing filter? |
#4
IP: 172.58.79.159
|
||||
|
||||
What kind of fuel filtering do you have inline? (Tank to Carb)
What kind of fuel pump? (Manual or Electric) Do you have a fuel pressure gauge by chance? Agree it could easily be stirred up crud. As Tom said a quick look at what comes out of the carb would help tell you. Lastly, might be worth taking a look at your oil and see if it's milky or the level has gotten higher. Is the engine running well now or still hard starting/running?
__________________
-Jerry 'Lone Ranger' 1978 RANGER 30 |
#5
IP: 32.211.28.40
|
||||
|
||||
I take it you're talking about cylinder compression. Before you get excited, try it with a different gauge.
|
The Following 2 Users Say Thank You to Al Schober For This Useful Post: | ||
Dave Neptune (11-13-2021), Sam (11-13-2021) |
#6
IP: 71.204.217.107
|
||||
|
||||
Quote:
I haven't been able to troubleshoot further because it's been hauled out and the marina isn't big on running the engine. I can disconnect the fuel pump and dry start to get the pressure at some point so I'll try and do the alternate pressure gauge. |
#7
IP: 47.142.140.12
|
|||
|
|||
Yes, it would be great if the polishing filter stopped the (alleged) crud from entering the carb.
The only way to "check" the polishing filter if you don't have a fuel pressure gauge after it before the carb is to remove it. ex TRUE GRIT |
The Following User Says Thank You to JOHN COOKSON For This Useful Post: | ||
Sam (11-13-2021) |
#8
IP: 162.245.50.232
|
|||
|
|||
How did you conduct the 2 compression tests?
The test should be done first dry and then with some oil sprayed into the cylinder the wet test. When conducting the tests the throttle and choke should be set at wide open, all plugs removed and the batteries topped off. Use the same gage and you are looking for how close the values are to each other from cylinder to cylinder. Did you adjust the valves and double check for "crank position" to be sure you were on the heel of the cam? Dave Neptune |
#9
IP: 24.61.95.61
|
|||
|
|||
Quote:
presents little problem with back pressure. Of course it has the Tartan standpipe exhaust which prevents waves enterng the exhaust. best Art |
#10
IP: 32.211.28.40
|
||||
|
||||
The standpipe with the side exhaust works so well on the T30 and T34 that I'm surprised other boats aren't converting to it.
|
#11
IP: 104.174.83.118
|
||||
|
||||
Quote:
https://www.moyermarineforum.com/for...17&postcount=8
__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#12
IP: 71.204.217.107
|
||||
|
||||
I think it's the head gasket
After a few more surveys I'm thinking it's a blown head gasket where there's opening between the cylinders. That would make sense for the common 60 psi pressure between the cylinders. If I remember right, I checked the pressure with a single spark plug removed at a time which would prevent it from going to zero. I'll try and verify that the next time I'm out there but I have a feeling it's going to be a long hard battle of getting that thing replaced.
Ugh... Thoughts? |
#13
IP: 138.207.177.95
|
||||
|
||||
I always do compression tests with all 4 plugs out.
|
#14
IP: 71.204.217.107
|
||||
|
||||
New Head Studs?
I just noticed Moyer's been sold out for a while. Any thoughts on buying replacements for the studs when I pull the head off?
|
#15
IP: 71.204.217.107
|
||||
|
||||
Alright, here she is.
So, I'm all good with the head. Came off no problems.
Going to start scraping off the old head and cleaning everything. The manual says wood chisel? Is that a good idea? Currently soaking in PB Blaster and I'm going to get a scraper. Moyer Marine is out of head studs and I would like to replace them since the stud puller does a number on the threads. Can someone either point me to a comparable source or give me the specifications to simply have them made? Any other pointers welcome. Thanks, ya'll. |
#16
IP: 138.207.177.95
|
||||
|
||||
I have got studs before at auto parts stores and hardware stores.
|
#18
IP: 69.250.111.245
|
||||
|
||||
Jo, I think I saw this same post over on the C-30 or A4 FB forum. It reminded me I have a nice plastic "chisel" I would start with, and personally, I would shift to metal razor blades after that, or even the plastic razor blades I've come to appreciate in recent years.
Sorry, no input on the studs except that let's hope you are getting them reliably enough to equal what Moyer's offered. My only comment here being that Moyer always makes sure the stuff they sell fits. Unfortunately, it seems like the global supply chain issues have crept into our little niche motor. -edit - another option is to remove the old studs to see if they fit the bill for re-use. You can put two nuts on a stud and cinch them together with two wrenches, and then try to remove the stud cleanly with one wrench, and inspect it for re-use. I have a project A4 in my little shop that only turns about 130° rotation, and I suspect I will need to employ this technique after I pull the head to unfreeze the crank.
__________________
-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) Last edited by sastanley; 12-15-2021 at 10:49 PM. |
#19
IP: 71.204.217.107
|
||||
|
||||
Valve seating?
Thanks for y'all's input. I'm making headway.
I'm looking at my valves now that I've cleaned things up and I don't get the warm fuzzy feeling that they're seating correctly. There is definitely buildup visible when they raise and I'm afraid to touch them because of all the warnings about being careful scraping near them. Any thoughts on what to do here to make sure there's a good seal and not too much buildup? |
#20
IP: 165.225.20.168
|
||||
|
||||
Quote:
There are a few tricks to be able to do a valve removal in 10 minutes rather than 3 hours, do not ask me how I know this (https://www.moyermarineforum.com/for...t=11241&page=3) Good luck. By the way, it is a very satisfaying job to do...
__________________
Surcouf A nostalgic PO - Previously "Almost There" - Catalina 27 (1979) |
#21
IP: 71.204.217.107
|
||||
|
||||
Oh boy...
Man, I really do not want to do that... there is not a lot of room between the valve galley and the wall. I agree, I've done almost everything that would be required to prep but... ugh...
I need a better tutorial before I'm confident enough to do that. Where's the best spot to get one of those tools? |
#22
IP: 71.204.217.107
|
||||
|
||||
Alright, I'm going for it.
So, my inner demons got the better of me and I'm going to pull the valves and clean/lap them.
Ordering the tool from Moyer. I've got the overhaul manual in the boat (not in front of me) so forgive me if these questions are answered in there but: I've heard replacing springs may be required but I'm not sure how to tell if they need it. Are the valve keepers something I should anticipate replacing? What is the valve reamer tool for? If my valves are operating correctly it doesn't seem like the path is a problem and therefore I don't need it, right? - Jo |
#23
IP: 104.174.83.118
|
||||
|
||||
OK, I've been watching the progression in this thread for over a month so here are a few observations:
edit: Reasoning for the above For the compression loss to be even across all four cylinders due to either the head gasket or valves, all cylinders would have to be affected exactly the same. That just doesn't happen with valves and for such a total head gasket failure to occur with no water in the cylinders or oil, no way.
__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 12-19-2021 at 12:03 PM. |
The Following 2 Users Say Thank You to ndutton For This Useful Post: | ||
Dave Neptune (12-19-2021), sastanley (12-19-2021) |
#24
IP: 71.204.217.107
|
||||
|
||||
Spot on
You're not wrong on any count.
I'm hauled out and they are pretty adamant about not running the engine on the hard so I did what I could on the water in short time. I agree at this point that the head gasket was not the culprit, but these valves are worryingly blocked, whether that lends to the compression issues or not. As for the fuel, it's a very likely cause. The main separator had considerable sediment in the bottom. I'm not sure how to go about checking the fuel tank yet but the churn we were in that led to the rough running would definitely have stirred up the bottom. We went through a few cans so in my mind we were running on fully fresh fuel. Also, all of this carbon buildup makes me think I'm perhaps running lean? Carb is getting a cleaning and I'll check for sediment in there too. Last edited by Jo Ross; 12-20-2021 at 07:46 AM. Reason: Add photo |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
oil pressure revisited (slow drop) | Kelly | Troubleshooting | 8 | 08-23-2011 05:13 AM |
Oil Pressure Drop | rpowers | Troubleshooting | 8 | 06-13-2010 02:55 PM |
drop in oil pressure | MikeB.330 | Troubleshooting | 6 | 07-14-2009 01:11 PM |
Information about information and oil pressure issues | Don Moyer | Announcements | 0 | 04-14-2009 08:30 AM |
Carburetor Internal Pressure Regulation | Don Moyer | Fuel System | 2 | 04-12-2005 09:30 AM |