DPS-b drive lifts in reverse

[NoXcuse]

Hello,
I have a DPS-b drive (s/n A204006) that lifts slowly when I rev in reverse above about 900 rpm. I pulled the boat from the water and checked the fluid level and added about 2 oz. Replaced the o ring in the cap (cap hissed when I originally removed it which makes me think it was sealed) and could not find any leaks around the lines or cylinders. I could life the drive by hand with a decent amount of force. Cycled the drive up and down and checked level again but it still occurs.

It doesn't seem this drive has a reverse lock mechanism to keep the drive down? A friend thinks that maybe it could be the cylinders have some sort of internal limiters to keep the drive down when in reverse. Is there any way to test this as each cylinder is almost 600 and the trim pump which seems to be working fine is about 1200. I would prefer to not have to open any lines and replace if possible due to potential leaks that are not already there.

Any help would be appreciated!
Thank you!

 

[kenny nunez]

To me if you had a internal ram leak the drive would not hold a trimmed position. Where is the trim pump located? Can you post a picture of the pump?

 

[NoXcuse]

That is a good point. The drive holds wherever I trim it in forward at any speed. Just reverse pulls the drive up.

Here is a picture for reference.

 

[kenny nunez]

The best I can think of is that Volvo refers to this as a “Non Serviceable “ item. The pump body has a system like the Mercruiser style. There is a “trail out” valve which is also used to hold the drive down for reversing.
The only thing you could try is to remove the lines from the rams, run the pump in both directions to purge it and manually raise and lower the drive to do the same. Fill the pump with diesel fuel and run it in both directions which may clean it out. Refill it with power steering or the $Volvo fluid, refill it and reconnect the lines and cross your fingers.

 

[NoXcuse]

The best I can think of is that Volvo refers to this as a “Non Serviceable “ item. The pump body has a system like the Mercruiser style. There is a “trail out” valve which is also used to hold the drive down for reversing.
The only thing you could try is to remove the lines from the rams, run the pump in both directions to purge it and manually raise and lower the drive to do the same. Fill the pump with diesel fuel and run it in both directions which may clean it out. Refill it with power steering or the $Volvo fluid, refill it and reconnect the lines and cross your fingers.

So in this scenario, there is something broken inside the pump? Almost like a one way valve?

 

[kenny nunez]

So in this scenario, there is something broken inside the pump? Almost like a one way valve?

There is probably a check ball and spring that may have something stuck in it. The older Mercruiser Prestolite systems were adjustable, I had a test manifold that resembled a Freon charging manifold. Too bad Volvo likes the “throw away” and pay system.
Flushing it out is worth a try.

 

[Nashville]

So in this scenario, there is something broken inside the pump? Almost like a one way valve?

Something else to rule out, is the pump operating when in reverse. If so, the root cause is electrical not hydraulic. The -B is heavy, and fairly “aerodynamic”. 900-RPM in reverse may not be enough to lift it. Just food for thought.

 

[NoXcuse]

Something else to rule out, is the pump operating when in reverse. If so, the root cause is electrical not hydraulic. The -B is heavy, and fairly “aerodynamic”. 900-RPM in reverse may not be enough to lift it. Just food for thought.

It is not operating by itself. If the drive starts lifting and I hold the trim down, it stops it from lifting but does not have the power to bring it down while in reverse.

 

[Nashville]

It is not operating by itself. If the drive starts lifting and I hold the trim down, it stops it from lifting but does not have the power to bring it down while in reverse.

Thank you. In reverse though, going backward at 900 RPM, force from the water acting on the drive is perpendicular to the drive and pushing towards the transom. Would this not hold it down? Perhaps when the button is pushed, whatever is causing it to activate (short, contact) is interrupted. Food for thought. Interesting issue for sure. (There is a kick-up/impact circuit, but not a reverse lock/lockout.)

 

[bruceb58]

Thank you. In reverse though, going backward at 900 RPM, force from the water acting on the drive is perpendicular to the drive and pushing towards the transom. Would this not hold it down? Perhaps when the button is pushed, whatever is causing it to activate (short, contact) is interrupted. Food for thought. Interesting issue for sure. (There is a kick-up/impact circuit, but not a reverse lock/lockout.)

No...in reverse, the drive pulls itself up.

 

[QBhoy]

Hi. You definitely do have a reverse locking mechanism. Well known to fail, when they can wear away slightly. See picture. Each side with next to springs there is a catch that engages on the stainless bar

 

[bruceb58]

Hi. You definitely do have a reverse locking mechanism. Well known to fail, when they can wear away slightly. See picture. Each side with next to springs there is a catch that engages on the stainless bar

He has a DPS-B drive. No idea what part you are showing. Possibly a 270 drive from 40 years earlier.

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[QBhoy]

He has a DPS-B drive. No idea what part you are showing. Possibly a 270 drive from 40 years earlier.

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It’s a 290 apologies. Thought he said DPb

 

[NoXcuse]

I just wanted to update this thread. Bit the bullet and purchased a new pump and trim motor thinking there is a one way valve within the unit that has failed. Just put the drives on today and filled it up with fluid. Purged the system by going up and down a few times and refilling. Tightened the full cap and... It still does it!

So now I'm thinking the rams are the next likely cause of the issue. Five Star Marine offers a ram rebuild service for $400 for both rams. Not sure if I should send them off a d get them rebuilt. I'm out of ideas as I would have figured this has happened to someone else in the past?

 

[QBhoy]

I just wanted to update this thread. Bit the bullet and purchased a new pump and trim motor thinking there is a one way valve within the unit that has failed. Just put the drives on today and filled it up with fluid. Purged the system by going up and down a few times and refilling. Tightened the full cap and... It still does it!

So now I'm thinking the rams are the next likely cause of the issue. Five Star Marine offers a ram rebuild service for $400 for both rams. Not sure if I should send them off a d get them rebuilt. I'm out of ideas as I would have figured this has happened to someone else in the past?

Did you check the reverse latch for wear ? Common issue.

 

[NoXcuse]

Did you check the reverse latch for wear ? Common issue.

The DPS drives don't have a reverse latch.

 

[dubs283]

IME these style Volvo pumps, colloquially known a SX-A drives have a high rate of failure on both the trim pump/line assy and the rams. Most common failure is the pump or rams fail to keep the drive up/out when trailered/stored. For a while Volvo was giving the pumps to customers as warranty and now I believe that time has passed. Yep, they are expensive and sadly no guarantee they will not fail again.

Can't confirm your issue over the internet but seeing as how you replaced the pump and lines and still have the same exact problem then new/rebuilt rams are next. Only strange item you mention is how the drive will stay trimmed up in fwd gear under a load however I'm not privy to the internal workings of the rams

 

[QBhoy]

The DPS drives don't have a reverse latch.

Ah. Forgot about what drive you had…once again. Apologies.

 

[NoXcuse]

IME these style Volvo pumps, colloquially known a SX-A drives have a high rate of failure on both the trim pump/line assy and the rams. Most common failure is the pump or rams fail to keep the drive up/out when trailered/stored. For a while Volvo was giving the pumps to customers as warranty and now I believe that time has passed. Yep, they are expensive and sadly no guarantee they will not fail again.

Can't confirm your issue over the internet but seeing as how you replaced the pump and lines and still have the same exact problem then new/rebuilt rams are next. Only strange item you mention is how the drive will stay trimmed up in fwd gear under a load however I'm not privy to the internal workings of the rams

I actually only replaced the pump and not the lines. I didn't see how the lines could be a failure point in this scenario as they weren't leaking at all and seemed in good shape. My drive is a bit newer so it already had the new style pump cover that has been prone to failure.

 

[dubs283]

You replaced just the pump not the cover? In any case, if the cover isn't leaking and lines are sound the issue is most likely the rams