Re: 1980 merc 1 went up to trailer and now wont come back down-can hear pump running
I went through exactly the same thing last week. The folks here walked me through the potential issues. Here's what I learned and what turned out to be the simple solution.
Was told that it's possible for the hydraulics to hold pressure against the valve plate in the trim pump and that this can keep it from coming down. If you hear the pump running it's a good bet your electrically ok (solenoids, pump, etc).
I was told to "bounce" on the drive a bit while engaging the "down" part of the system. I just hooked a remote starter button to the down solenoid so could engage the pump while bouncing the drive up and down some. I'm sure this looked hilarious to anyone who might have been watching. But, alas, it didn't solve the problem.
Then I was told what turned out to be a simple easy solution. Just crack open the hydraulic lines on the cylinders. Just a bit. I lost maybe two ounces of fluid when I just cracked the lines. Have a rag in hand and a pan beneath to catch what drips.
While the lines are cracked push down on the drive a bit. As the pressure/fluid drains a bit the drive goes down. Mine went down a couple inches. Closed the lines and, voila, it all worked fine again.
compresion fittings and put it back togeather. 