Temporary loss of oil pressure in 502...
09-28-2002, 09:54 AM
#1
Registered
Thread Starter
Temporary loss of oil pressure in 502...
Last week ran the boat for 5 minutes at 4600 rpm. Came off plane and warning buzzer went off. Checked gauges and saw 0 psi. on oil pressure gauge, temp and voltage OK. Shut off immediately. Checked oil level and looked for leaks. Stick was not hot, started it back up and oil pressure was normal. Ran it on plane and all was fine. Took a few WOT passes and still fine. Pressure was about 20 at low idle, 40 at fast idle and is usually around 55 on plane and 60 at WOT. I have a large Eddie Marine oil cooler so temp is not an issue.
Several days later I cut the oil filter open no water or metal in filter. Oil filter was NAPA Gold with silicone anti-drain back valve. I will replace it with a non-drain back type. I looked at the schematics for the warning buzzer and oil pressure gauge. It looks like the buzzer circuit completes a ground for low pressure and the sender varies ground. The buzzer and gauge are all sourced from the same 12v wire so it is unlikely there was an electrical malfunction that caused two separate failures ( temp, fuel and volts showed OK). One is on pin 4 and other is on pin 8 of harness. Since the buzzer went off and gauge showed zero I suspect that they were correct.
What could have caused this? 1999 502 crate engine with 200 hundred hours. No previous trouble with this engine. I did start it and run on the hose prior to cutting filter open. 50 PSI idle cold. I suspect the pressure relief spring in the oil pump. Is this reasonable or could something else have caused this? It is an intermittent problem since I ran it right after it occurred and on the hose.
Here is my plan, change filter, hook up mechanical gauge where I can see and monitor oil temp. The oil temp sender is in the filter housing. By keeping an eye on it I can tell if the bypass in the block is being engaged. Temps should go high if the block bypass was engaged. Oil is and has always been very clean. Any other thoughts on what could have caused it or things I should check? Anyone hear of a pump acting this way and how common for a relatively new pump to have these symptons?
Tim T.
Several days later I cut the oil filter open no water or metal in filter. Oil filter was NAPA Gold with silicone anti-drain back valve. I will replace it with a non-drain back type. I looked at the schematics for the warning buzzer and oil pressure gauge. It looks like the buzzer circuit completes a ground for low pressure and the sender varies ground. The buzzer and gauge are all sourced from the same 12v wire so it is unlikely there was an electrical malfunction that caused two separate failures ( temp, fuel and volts showed OK). One is on pin 4 and other is on pin 8 of harness. Since the buzzer went off and gauge showed zero I suspect that they were correct.
What could have caused this? 1999 502 crate engine with 200 hundred hours. No previous trouble with this engine. I did start it and run on the hose prior to cutting filter open. 50 PSI idle cold. I suspect the pressure relief spring in the oil pump. Is this reasonable or could something else have caused this? It is an intermittent problem since I ran it right after it occurred and on the hose.
Here is my plan, change filter, hook up mechanical gauge where I can see and monitor oil temp. The oil temp sender is in the filter housing. By keeping an eye on it I can tell if the bypass in the block is being engaged. Temps should go high if the block bypass was engaged. Oil is and has always been very clean. Any other thoughts on what could have caused it or things I should check? Anyone hear of a pump acting this way and how common for a relatively new pump to have these symptons?
Tim T.
Last edited by BadDog; 09-28-2002 at 10:02 AM.
09-28-2002, 10:33 AM
#2
Guest
Posts: n/a
Re: Temporary loss of oil pressure in 502...
Originally posted by cpqtim
Last week ran the boat for 5 minutes at 4600 rpm. Came off plane and warning buzzer went off. Checked gauges and saw 0 psi. on oil pressure gauge, temp and voltage OK. Shut off immediately. Checked oil level and looked for leaks. Stick was not hot, started it back up and oil pressure was normal. Ran it on plane and all was fine. Took a few WOT passes and still fine. Pressure was about 20 at low idle, 40 at fast idle and is usually around 55 on plane and 60 at WOT. I have a large Eddie Marine oil cooler so temp is not an issue.
Several days later I cut the oil filter open no water or metal in filter. Oil filter was NAPA Gold with silicone anti-drain back valve. I will replace it with a non-drain back type. I looked at the schematics for the warning buzzer and oil pressure gauge. It looks like the buzzer circuit completes a ground for low pressure and the sender varies ground. The buzzer and gauge are all sourced from the same 12v wire so it is unlikely there was an electrical malfunction that caused two separate failures ( temp, fuel and volts showed OK). One is on pin 4 and other is on pin 8 of harness. Since the buzzer went off and gauge showed zero I suspect that they were correct.
What could have caused this? 1999 502 crate engine with 200 hundred hours. No previous trouble with this engine. I did start it and run on the hose prior to cutting filter open. 50 PSI idle cold. I suspect the pressure relief spring in the oil pump. Is this reasonable or could something else have caused this? It is an intermittent problem since I ran it right after it occurred and on the hose.
Here is my plan, change filter, hook up mechanical gauge where I can see and monitor oil temp. The oil temp sender is in the filter housing. By keeping an eye on it I can tell if the bypass in the block is being engaged. Temps should go high if the block bypass was engaged. Oil is and has always been very clean. Any other thoughts on what could have caused it or things I should check? Anyone hear of a pump acting this way and how common for a relatively new pump to have these symptons?
Tim T.
Last week ran the boat for 5 minutes at 4600 rpm. Came off plane and warning buzzer went off. Checked gauges and saw 0 psi. on oil pressure gauge, temp and voltage OK. Shut off immediately. Checked oil level and looked for leaks. Stick was not hot, started it back up and oil pressure was normal. Ran it on plane and all was fine. Took a few WOT passes and still fine. Pressure was about 20 at low idle, 40 at fast idle and is usually around 55 on plane and 60 at WOT. I have a large Eddie Marine oil cooler so temp is not an issue.
Several days later I cut the oil filter open no water or metal in filter. Oil filter was NAPA Gold with silicone anti-drain back valve. I will replace it with a non-drain back type. I looked at the schematics for the warning buzzer and oil pressure gauge. It looks like the buzzer circuit completes a ground for low pressure and the sender varies ground. The buzzer and gauge are all sourced from the same 12v wire so it is unlikely there was an electrical malfunction that caused two separate failures ( temp, fuel and volts showed OK). One is on pin 4 and other is on pin 8 of harness. Since the buzzer went off and gauge showed zero I suspect that they were correct.
What could have caused this? 1999 502 crate engine with 200 hundred hours. No previous trouble with this engine. I did start it and run on the hose prior to cutting filter open. 50 PSI idle cold. I suspect the pressure relief spring in the oil pump. Is this reasonable or could something else have caused this? It is an intermittent problem since I ran it right after it occurred and on the hose.
Here is my plan, change filter, hook up mechanical gauge where I can see and monitor oil temp. The oil temp sender is in the filter housing. By keeping an eye on it I can tell if the bypass in the block is being engaged. Temps should go high if the block bypass was engaged. Oil is and has always been very clean. Any other thoughts on what could have caused it or things I should check? Anyone hear of a pump acting this way and how common for a relatively new pump to have these symptons?
Tim T.
09-28-2002, 10:38 AM
#4
Registered
Thread Starter
I could see that but I have been running this boat with the 502 for two years and this never happened before. Maybe I just chopped it too fast. I seldom just cut the throttle from WOT, usually just back out easy to let everything stabilize. Maybe I did not that time but I still suspect SOMETHING was amiss.
Tim T.
Tim T.
09-28-2002, 06:09 PM
#5
I hate the winter!!
Platinum Member
Join Date: Jul 2001
Location: long island, new york
Posts: 2,707
Likes: 0
Received 0 Likes
on
0 Posts
cpqtim;
You are doing just as I would do. Check the electric guage with a mechanical guage. I had a similar problem with my motor. After checking the pressure with a mechanical guage, I saw a big difference in the readings. It turned out that the stock Merc. sending unit was bad. I replaced it with a Gaffrig sender that matchs my guage.
You are doing just as I would do. Check the electric guage with a mechanical guage. I had a similar problem with my motor. After checking the pressure with a mechanical guage, I saw a big difference in the readings. It turned out that the stock Merc. sending unit was bad. I replaced it with a Gaffrig sender that matchs my guage.
