Air/Hydraulic or hand pump issue?

[TomTime]

I got my M1083A1 I found that the cab lock latch was leaking. After sometime I got the correct latch repair kit and fixed the leaking cab latch. I wanted to rebuild the air/hydraulic power unit but have been unable to find a rebuild kit as of this thread.

I filled the manual hand pump and the air/hydraulic power unit up with the correct fluid to the correct level. When pumping the manual pump to lift the cab I noticed that the hand pump emptied out and I refilled the pump thinking that it was because of air in the system. I found that the air/hydraulic power unit was leaking fluid out of the refill hole. When I removed the refill plug, fluid came running out all over. It appears that the manual pump will pump the fluid out but there is no fluid returning back to the pump.
I removed fluid from the air/hydraulic power unit until it was at it's max fill point, check the vent and it was clear and filled the manual pump up again. I removed both lines to the air/hydraulic power unit and when I pump the manual pump fluid comes out of the rear or back line only, that is as far as I have got to this point. I have looked at the TM's but I couldn't find anything that helps with this issue. Trying to figure out.

Without going blindly into trying to fix this, I am looking for some help and direction with this issue and I hope that someone will be able to do so.

Is this a air/hydraulic power unit issue which would require a rebuild? Is this a manual pump issue? Or could it be a blocked line, or a combo of all three?

Still looking for a rebuild kit for the air/hydraulic power unit. I have been offered to purchase an already rebuilt power unit but I would like to rebuild mine so I can learn. If you know of any let me know.

Also, can you rebuild the manual hand pump, and if so, is there a rebuild kit out there? I've only seen people replace them and not rebuild them.

Any help would be greatly appreciated!

Thanks.

 

[NDT]

What is wrong with your air/hydraulic unit?

 

[TomTime]

What is wrong with your air/hydraulic unit?

That's it, I don't know. Engine not running yet so I have only used the manual hand pump and with no fluid returning to the hand pump, is it a air/hydraulic issue, hand pump issue or?

With it being almost 20 years old I'm sure it is probably gummed up. The fluid coming out was nasty.

 

[Ronmar]

The output of both pumps are tied together. But check valves in the pumps are supposed to keep one pump from back-feeding the other. Since there are 2 check valves inline in each pump, I don’t see that being a problem, so one of two things could be happening.
1. One of the pumps might be connected backwards in which case the output of one would feed right into the return of the other, causing it to overflow.
2. Something is wrong in the control valve allowing the pressure side to feed into the return side.
since you say no fluid appears to be returning to the hand pump, it mig be as simple as the first one, one pump is connected backwards...

do you have an air compressor? You can charge the truck air system by connecting a compressor to the front red emergency gladhand. This will charge the air system and allow you to try the AOP. You want to also chock the wheels as applying air at the emer gladhand releases the park brake just like if the vehicle was being towed...

 

[htxol]

FWIW purchased the SPX kit 300140 and rebuilt by air/hydraulic pump. Cant remember from where.

It had all the parts I needed and some better left alone. There are less inclusive/expensive approaches, but it can drag out the process if you get in it and find you need other parts. I've definitely burned an afternoon or two driving around to different auto parts stores looking for that odd o-ring, gasket, or spring.

 

[NDT]

That's it, I don't know. Engine not running yet so I have only used the manual hand pump and with no fluid returning to the hand pump, is it a air/hydraulic issue, hand pump issue or?

With it being almost 20 years old I/m sure it is probably gummed up. The fluid coming out was nasty.

Do you need help with using this forum to find part numbers and sources?

 

[TomTime]

Do you need help with using this forum to find part numbers and sources?

No, on finding part numbers, I have the TM parts manual. Sources, maybe another issue. I also have the TM to rebuild the unit. I'm starting to get use to the TM's but it will take me some time, a lot of pages!!!

With trying to do several project on the truck at the same time and trying to find other parts for it , I figure that If I can find a kit it will save me time on trying to find each little part for the unit one piece at a time. With that said, I have to balance out, time vs. money, I fine line!

DP Equipment makes a really good kit, (per several videos I watched) but have been out of stock for awhile now. Memphis Equipment has a smaller kit and is available. Just checking to see if anyone knows of another source for a kit. When taking this unit apart I would rather have a complete kit in case of any surprises, do the job once and done, and move on.

I'm not a person that will shy away from work, but if I can find a less time consuming, easier or better way of doing things, I'll go that direction.

I thought I would ask SS members if someone would have them before I purchase the one from Memphis Equipment. I have observed that some SS members are a great source for parts and help.

So far, having fun and learning a lot.

Thanks for getting back to me!

 

[NDT]

Does your air/hydraulic pump have a cover over it? That cover keeps the rain out of the muffler. If your system has sat for years full of rain, there is no telling what might be rusted up and stuck inside. You said the fluid was "nasty". Back to your parts issue on the air hydraulic pump, why don't you do as Ronmar suggests and determine if your pump even NEEDS rebuilding or not. The 1990's FMTVs almost always do but you have a A1 which is from the 2000s.

 

[TomTime]

Does your air/hydraulic pump have a cover over it? That cover keeps the rain out of the muffler. If your system has sat for years full of rain, there is no telling what might be rusted up and stuck inside. You said the fluid was "nasty". Back to your parts issue on the air hydraulic pump, why don't you do as Ronmar suggests and determine if your pump even NEEDS rebuilding or not. The 1990's FMTVs almost always do but you have a A1 which is from the 2000s.

Pump has cover over it.

I ran all the lines and they are connected up correctly.

Won't be able to get back to it until Friday and I will do what Ronmar suggested and see what I can find.

Thanks again to you and Ronmar!!!