Troubleshooting 91 Force 90HP Tilt/Trim System

[tfowler111]

System with shock absorber, tilt cylinder and trim cylinder. Actuating it up and down to try to refill system since motor/reservoir was replaced (not by me, new to me). Have to lift up engine to get to up position, trim cylinder stays retracted but if I then push the motor down with motor off the trim cylinder pushes out as tilt cylinder retracts. Then I lift engine again and try to get as much fluid in with tilt cylinders fully extended, then cannot push engine down, so I don't think there is a leak and the engine stays tilted up? Then actuating down lets the engine down through tilt range rather quickly and and trim retracts in more controlled manner, but then will get no lift when trying to go up, have to manually lift engine. Am I bleeding this correctly or should I be thinking about rebuilding pump/cylinder?

https://imgur.com/a/eVWAwXM

 

[Jiggz]

Bleeding the system requires running full trim and tile and then going back down and doing this for at least three times. As for filling in the fluid, you should fill it up to the fill up hole with both trim and tilt at full down position.

If the trim (bigger piston) would not go up (from full down position), that is an indication the trim cylinder is leaking or it could just be leaking from the valve body. The only way to find out is to do more testing. There's a sticky post on how to do this. If you ever decide to work on the valve body, always remember DO NOT OPEN THE PUMP SECTION.

 

[tfowler111]

Thanks for reply, I cycle it up down 3-5 times before trying to try to add some fluid, but have to lift each time by hand, so I think I have it bled. I found your sticky it seems to be similar/the same to factory procedure, I was trying to avoid breaking into the lines if it was just air but will try once I get cap and plug. Thanks again.

 

[Jiggz]

Thanks for reply, I cycle it up down 3-5 times before trying to try to add some fluid, but have to lift each time by hand, so I think I have it bled. I found your sticky it seems to be similar/the same to factory procedure, I was trying to avoid breaking into the lines if it was just air but will try once I get cap and plug. Thanks again.

Unfortunately, to repair the T&T requires breaking the hydraulic line connection even with just the testing itself. Those hydraulic lines are really tough and made of stainless tubing. However, the valve body itself is not quite as tough. And it's really very easy to cross thread the fittings when putting them back in. The secret is to always get the fittings (on both ends) started by hand for about three turns and then make sure the other end is also loose enough to get some leeway to properly align. As soon as both ends are threaded at least three turns, that is the only time to tighten each end.
I would surmise and I'm not exacting on this one, most likely the problem is with the valve body's spool valve worn out gasket ring which is exactly the same as the 398188 (available at Amzn) carb needle seat ring on Briggs & Stratton small engines. Or Tecumseh 631021B. However, to do the repair correctly, a proper diagnosis is required.

Finally, if you decide to work on the valve body, you shouldn't have to dismount the entire motor and pump unit itself. With hyd lines disconnected, just dismount the valve body from the four screws. NEVER EVER DISASSEMBLE THE PUMP SECTION AT ANYTIME. THERE'S NOTHING IN THERE THAT IS BROKE (ALL IT IS ARE CHECK BALLS AND SPRINGS) BUT DOING SO CAN BE A NIGHTMARE TO PUT IT BACK TOGETHER.

 

[tfowler111]

Followed factory test did not pass the "up or down" test in the factory test so I am going to attempt to rebuild valve, or get a new assembly. The test is a little confusing as when I capped each line nothing lifted the engine at all? The factory test assumes the engine will lift with the opposite actuator that is capped then leak down, I have to lift it by hand up and then it does not leak down. I have also read that sometimes installing the motor the wrong length driveshaft is used so it doesn't actually engage the pump, so I'm going to check that as well first. The valve/pump body has all 4 lines coming out the bottom vs one bottom 3 side, not sure if same valve rebuild will apply...

 

[jerryjerry05]

The pic you posted shows a new or fairly new pump??
If it 's new it might be the dreaded CHINEESE JUNK??
Lots of them come defective right out of the box.

 

[Jiggz]

As Jerry mentioned, the OEM T&T unit will virtually last forever except for those tiny oil seals in the spool valves. But if you have a new China made one, you'd be better off investing in an old OEM and just fixing it.

Technically, during testing, the capping of the lower line to trim cylinder (which is the line that connects on the top of the tilt cylinder) and plugging on the valve body, isolates the tilt cylinder up circuit. When T&T is operated in up position, the trim cylinder should go up since it is by itself in the up circuit. If trim cylinder fails to go up, most likely the valve body is defective or not working. The trim cylinder could also be faulty but with very few moving parts, the fault is likely at the valve body. It is a process of elimination and from experience, the valve body is most always the culprit.

You can also test isolate the trim cylinder and just have the tilt cylinder in the up circuit and do the same test. Again if tilt cylinder fails to do up, valve body is the common denominator. However, when testing the tilt cylinder you would need to initially raise the motor by hand and support it with a 2 X 4 wood. And when the tilt cylinder is all the way up stop operating the T&T and slowly put down the motor. If tilt cylinder goes down, valve body is bad.