Need help diagnosing my Accusump Accumulator

[frankym]

Hey guys, need help figuring out what's going on. I have the accusump 3 quart accumulator with the solenoid valve. I usually turn the key, flip the switch on the dash and the oil pressure builds to about 40 psi (on the dash), then i start the engine, and turn the solenoid switch off. Today, I went to flip the solenoid switch on the dash. I believe i saw the pressure guage on the dash move to 15 psi and then back down to 0. I added a little air pressure to the accumulator (brought it from 45psi to 60 psi).

So now the large accumulator guage is registering 60 psi after going for a ride, but when i go to stop / start the motor and flip the dash switch, my dash pressure guage does nothing. Everytime i flip the dash switch, the light indicator comes on. I don't hear anything in the engine compartment but i never noticed if that happens anyways. I can't tell if i lost the prime and need to add oil or if i should be hearing the valve open, maybe i blew a fuse? Looking for help completing the diagnosis.

[Turbonut48]

The accumulator pressure needs to be less than the engine oil pressure at start up. If you have more than 60 than you should be good with 60 psi. Otherwise reduce to 40.
Maybe the valve is leaking and not holding your pressure between runs.

The Nut

[Tommy]

frankym,
I'm not assuming you don't understand how the accumulator works, but I want to be sure we are seeing it the same way. Inside the accumulator is a piston like device with a trapped pocket of air on one side and oil that is plumbed into the engine oil system on the other. When the engine is running and the accumulator valve is open, the pressurized oil will push into the accumulator, moving the piston toward the air side until the pressure on the compressed air side matches the pressure of the running engine. If the oil pressure rises (e.g., higher RPM), more oil will be forced into the accumulator until the air pressure matches the new higher oil pressure. If the oil pressure drops (e.g., lower RPM or heavy braking sloshes oil away from the pickup) the higher pressure air will force the piston out, pushing oil back toward the engine's oil system.

When you initially install and prep the accumulator, the goal is to add just the right amount of air to the air side. If you put in too little air, the accumulator will hold a lot of oil, but it will only be able to push a little of it back out before the air pressure drops so low it can't push any more. If you put too much air in, the accumulator will only take a little oil before the air pressure gets so high no more oil can enter.

If you put 60 PSI of air into the empty accumulator (engine off and valve open), it pushed the piston all the way out. The only way oil can get back into the accumulator is for the engine oil pressure to exceed 60 PSI. Unless your engine oil pressure is a lot higher than 60 PSI, there is likely very little oil in your accumulator for the air to push back out. I suggest you look up the instructions for setting up a new accumulator and reset yours to match those instructions.

The last matter is why your accumulator earlier provided less pressure than you were used to seeing. Keep in mind that the accumulator will match the pressure in your oil system at the moment the valve is closed. Perhaps you had been in the habit of closing the valve when the oil pressure was higher, and later closed the valve when it was lower.

If resetting the air pressure to the manufacturers specs doesn't solve the problem, then it is possible you have one of the other problems you mentioned. Let us know how it works.

[frankym]

Thanks guys. Tommy, i didnt understand the mechanics of the air/oil sides and it makes sense to balance pressure at both ends. Its like compression and rebound. I let somebair out and will play around with it in the daylight. It would be cool if there was a glass pane to see where the piston is.

[Legless]

Why are you turning off the solenoid? If you have it turned off it can't provide oil when its needed at low pressure, except for pre oiling at start up and that's assuming its had a chance to fill with oil. You probably should only have about 5psi maximum when the system is purged of oil. Open the solenoid and apply say 60 psi and wait while the oil is purged from the accusump repeat a few times until all the oil has been purged from the accusump (it may have become hydraulically locked, ie filled with oil with no air space). After purging the accusump of oil turn off the solenoid and bleed the air valve until you have about 5psi on the accusump guage. Start the motor then turn on the solenoid and run for a while till the accusump fills with oil and your pressure guage on the accusump should display your engine oil pressure. Turn the solenoid off before turning the engine off. Without starting the motor check over the next few days to make sure the accusump maintains a constant pressure because any leak and loss of pressure will cause you issues.

[Tommy]

Setting the air in the accumulator is a balancing act. If you put too much in, you'll have plenty of air pressure to push oil back to the engine when needed, but there won't be as much oil to push. If you put too little air in, there will be plenty of oil to push back, but the pressure to push it will bleed off very quickly.

I just reread the Accusump instructions for setting the precharge. It says to open the valve with the engine off and put 60 PSI in the accumulator. That will push the piston all the way out. Then bleed the air pressure down to 7-10 PSI. That is the correct precharge. ... If you do the math for an engine running at 50 PSI of oil pressure, that will result in the accumulator holding about 80% oil and 20% air. It also means the air pressure will have dropped by half by the time 1/4th of that oil has been pushed back into the engine in a low oil pressure situation. I set my 3 quart accumulator up with a precharge of about 15 PSI. That means my accumulator has about 2 quarts of oil in it at about 50 PSI and it will push one quart of that back before the air pressure drops to 25 PSI. If the engine oil pressure fails completely, the accumulator will push the last of its oil back out at about 15 PSI.

[Gaz64]

Originally Posted by Tommy

frankym,
I'm not assuming you don't understand how the accumulator works, but I want to be sure we are seeing it the same way. Inside the accumulator is a piston like device with a trapped pocket of air on one side and oil that is plumbed into the engine oil system on the other. When the engine is running and the accumulator valve is open, the pressurized oil will push into the accumulator, moving the piston toward the air side until the pressure on the compressed air side matches the pressure of the running engine. If the oil pressure rises (e.g., higher RPM), more oil will be forced into the accumulator until the air pressure matches the new higher oil pressure. If the oil pressure drops (e.g., lower RPM or heavy braking sloshes oil away from the pickup) the higher pressure air will force the piston out, pushing oil back toward the engine's oil system.

When you initially install and prep the accumulator, the goal is to add just the right amount of air to the air side. If you put in too little air, the accumulator will hold a lot of oil, but it will only be able to push a little of it back out before the air pressure drops so low it can't push any more. If you put too much air in, the accumulator will only take a little oil before the air pressure gets so high no more oil can enter.

If you put 60 PSI of air into the empty accumulator (engine off and valve open), it pushed the piston all the way out. The only way oil can get back into the accumulator is for the engine oil pressure to exceed 60 PSI. Unless your engine oil pressure is a lot higher than 60 PSI, there is likely very little oil in your accumulator for the air to push back out. I suggest you look up the instructions for setting up a new accumulator and reset yours to match those instructions.

The last matter is why your accumulator earlier provided less pressure than you were used to seeing. Keep in mind that the accumulator will match the pressure in your oil system at the moment the valve is closed. Perhaps you had been in the habit of closing the valve when the oil pressure was higher, and later closed the valve when it was lower.

If resetting the air pressure to the manufacturers specs doesn't solve the problem, then it is possible you have one of the other problems you mentioned. Let us know how it works.

Originally Posted by Legless

Why are you turning off the solenoid? If you have it turned off it can't provide oil when its needed at low pressure, except for pre oiling at start up and that's assuming its had a chance to fill with oil. You probably should only have about 5psi maximum when the system is purged of oil. Open the solenoid and apply say 60 psi and wait while the oil is purged from the accusump repeat a few times until all the oil has been purged from the accusump (it may have become hydraulically locked, ie filled with oil with no air space). After purging the accusump of oil turn off the solenoid and bleed the air valve until you have about 5psi on the accusump guage. Start the motor then turn on the solenoid and run for a while till the accusump fills with oil and your pressure guage on the accusump should display your engine oil pressure. Turn the solenoid off before turning the engine off. Without starting the motor check over the next few days to make sure the accusump maintains a constant pressure because any leak and loss of pressure will cause you issues.

You boys have done an excellent job of explaining theory of operation.
Keep up the good work.

[Tommy]

Thanks Gary. I was a flight instructor for many years for an aircraft that had an accumulator system. I've explained how it works many times.

[RICK LAKE]

Tommy I have no problem with my system except for refilling the unit after startup. I understand there is a new control valve that controls flow back into the accusump without a large oil pressure drop to the motor. When racing I have a 70-85 psi range and had 50 psi in the system when full of oil on the air side. Have always worried about long sweeping turns and no way to control oil back into the tank. Do you have any new info on this? My last motor is going dry sump. Rick L. I have not damaged a motor yet. bearing check has come out perfect. No blueing or discolor.

[Tommy]

Rick, I've not before thought about the situation and valve you describe. Sorry I can't be of help.