JD 6620 combine - still won't run - Part III

First, thanks for all of the help. Here is what I did this mornng:
1) Ran fuel from tank sediment bulb - good flow
2) Ran fuel from sediment bulb outlet - good flow
3) Ran fuel from pipe going to electric pump - good flow
4) Ran fuel out of electric pump - good flow
5) Ran fuel out of end of pipe at injector pump (note - on inline pump combine, fuel from tank goes to injector pump first/hand pump is on side/also a mechanical pump runs off of injector pump) - pretty good flow - maybe rising 3/8" to 1/2" above pipe. Just a nice slow constant flow - not spraying everywhere. Reminded me of a low pressure drinking water fountain.
6) ONE TIME FUEL WOULD NOT GO THROUGH THE HAND/MECHANICAL PUMP ON THE SIDE OF THE INJECTION PUMP PUSHED BY THE ELECTRIC PUMP. ANOTHER TIME IT DID GO THROUGH THE HAND/MECHANICAL PUMP. I had ran the engine so maybe the piston in the pump was located at a different position and would not allow fuel to go through. Either time when the hand pump was used fuel would go through this item (hand/mechanical pump). I take it that the mechanical pump in this thing charges the filters and fuel rail in the injection pump.
7) Checked for fuel at end of pipe leading to filters. Like I said in #6 above one time it did not go through with the electric pump and one time it did after I had ran the engine. Always went through with hand pump.

Started the engine a few times today and actually I think it runs even less - maybe 30 seconds. Tiny air bubbles can still be seem coming in with the fuel at the bottom of the glass filter. Eventually the top of the filter has an air void exposing the outlet and the fuel stops going to the injector pump.

A couple have mentioned the hand pump plunger. I wonder if that plunger can act like a farm chemical injector in a spray mixing system, except in my case it is injecting air?????? The hand pump works OK - it is pulling and pushing fuel with each stroke. Could be a little loose. Still tightens down fine, which you would think out seal the air off. Looks to be a none repairable plastic plunger.

Could something be wrong in the hand/mechanical pump located on the side of the injector pump???? Remember fuel didn't want to go through and after I rolled the engine over it did go through. Looks to be a little piston in there with a push rod ran off of a cam in the injection pump. What all does that thing do??? Maybe the check valve too??? Someone told me they rarely cause problems.

Electric pump seems to be pushing an adequate supply to the engine. Is 3/8" to 1/2 " rise out of the pipe enough? After all I am not harvesting ... I am just idling. Can't take that much fuel at idle.

Thanks again guys. Eventually it will be figured out.

if you getting air at bottom of fuel filter i say your hand mech. pump is bad ele pump is just to move fuel from tank to and pump you should not have any air at top of fuel filter once you have fuel in filter remove line going into injunction pump turn on key and with hand pump see if you are getting good flow of fuel the hand pump runs on a cam in injunction pump that why some time it pump and some time it wont so you need to make sue your had pump has travel might have to trun engine over. the fuel should squirt from fuel line one other think make sure you fuel shut off has full travel i seen one where it had slip on cable and was not opening all the way

When I get it started and the fuel is flowing properly the engine will purr like a kitten - well for 30 seconds or so. So I don't think it would be the fuel shut off know/cable. When the hand primer pump goes bad does it allow air into the system like it does????????

yes they well . the shut off was just a passing though as i work on lot old machine and have run into lot funny things

This is side story, but I had a similar problem on my GMC diesel PU. Have an after-market fuel filter with a clear globe. After a period of running filter would slowly fill up with air, stalling the engine. Mechanical fuel pump was between tank and filter. I about went nuts finding the source of the air leaking into fuel system. Finally located it... a pinhole in the drop tube IN the fuel tank. Once I got it fixed (soldered it) problem went away. I would be looking for a pinhole in a line somewhere begore fuel pump.

There are two spring loaded check valves in the supply pump, one is under the 19 MM cap and other is under the hand primer. Have those been checked, if they are bad the supply pump can't work correctly. The new style hand primer # is 2 447 010 033 if you want a new one. Bosch changed it to one that does not unscrew to work, just bush down and a spring brings it back up.

YES

Andy, this is NOT rocket surgery.

As I posted before, "T" into the inlet fitting at the transfer pump on the Bosch IP and monitor fuel pressure as it runs and then fails.

Either you have a constant few PSI of fuel being forced up there by the lift pump or you don't.

My GUESS is that you don't.

Bob, monitor the pressure between the electric pump and the transfer pump OR, between the transfer pump and the filter?????

Start by monitoring the fuel pressure at the input of the transfer pump that is supplied/lifted up there by the electric pump.

One stupid guess,You didn't put WIX fuel filters on it by chance.If I have any air or any fuel troubles,it will be with WIX filters.Only wish them on my worst enemy.