Sprayer Hypro pump won't prime

[Tomas]

I have a new Fimco 60 gal. pto sprayer that works great until I run it dry. I then have to remove the discharge hose to get the 6500C pump to reprime. The valve to the boom is open, outflow part of pump is up, tank full. No obvious constriction in any line (unit is only 1 month old.) Is there some secret to getting the roller pump to self prime?
Many thanks.

 

[JohninCT]

Since it seems to prime and work OK when you remove the discharge hose, the only thing I can think of is that with the discharge spray pining connected there is enough backpressure and there is just enough wear in the pump that it just compresses the air past the next roller instead of out the discharge. Can you open an existing valve (bypass or relief) or add another one to make it more convenient to open the discharge rather than disconnecting the hose?

Found a couple of interesting links on these pumps that might help you

http://www.hypropumps.com/FileAttac...rature/OIPMs/L-1488-HydraulicDrivenRoller.pdf

Pump service videos
http://www.hypropumps.com/FileAttac...rature/OIPMs/L-1488-HydraulicDrivenRoller.pdf

 

[Tomas]

Thanks for the links, John. Your suggestion to put a quick relief valve on the supply line is something I will seriously consider.
I sprayed 120 gal. today, and the unit held 27 psi the whole day. I intentionally let it run dry, and had to go through the same routine to get it to prime. May have a defective pump.
Many thanks.
Tom