perkins 354 loosing prime

is there a check ball in a cav injection pump? been fighting a hard start. found several lines loose, fixed those. last night combine just shut down. went to change filters and they were low on fuel. thought maybe lift pump went bad. put on an electric and bypassed lift pump. gave it a shot of ether and it started. ran fine about 5 minutes and i shut it off. tried to start right away and would not start. little shot of ether and off we go. seems like pump looses prime. pump was rebuilt before i bought the combine.
Gary

No check valve in pump.The only way air can get into this system is through the low pressure side. It can suck the filters dry if there is a full restriction somewhere. The little rubber sleeves at each end of the fuel lines is the first place to start. When you pull the line they almost always stay in the fitting so most guys dont even know they are there. I use a dental pick to fish them out. Newer CAV injection systems use brass compression sleeves, but the older ones all had the rubber . Al

Most Perkins engines will have a constant air bleed fitting on top of the final filter base, some MF combines had two on the double filter base assembly. Smaller MF tractors the constant bleed orifice is a banjo bolt fitting line that connects to the top injector return line. On most six cylinder engines the orifice is a straight fitting with the line on top, goes to an injector top return line bolt. The job of the orifice is to bleed any trapped air out of the filter base top so NO air goes into the injection pump inlet. The CAV DPA pump will not handle ANY air at the inlet, and WILL shut down every time an air bubble gets in. Remove and clean the banjo bolt side orifice, or if you have the straight fitting orifice it can be checked quickly by removing the line on top and operating the hand primer. Fuel will shoot out if open, no fuel, it needs cleaned. First ran into this years ago on my brothers MF 1105, would die, then restart after bleeding and run maybe an hour, or ten minutes. After cleaning the plugged fitting the problem stopped. Also if NAPA/WIX filters are used MAKE SURE there's NO O ring in the filter top outer groove, that's the fuel INLET on those filters. Made lots of service calls to correct that mistake..

the check is (or was)in the mechanical lift pump on the engine, I had the same problem, most elect. pumps don't have a check valve, you will need to add one into the line

thanks guys for the help. I have a drain back valve to put in but since I put the electric pump on it seems better. took a little bit to get it to start yesterday morning, was 27 degrees here but at least while spinning it over had smoke out of stack. did not have that before. I think the big issue was the loose connection at the mechanical pump.
Gary