Deere 6620 combine still only runs for 2 - 3 minutes. Par...

I am still having problems with my combine. For new readers my JD 6620 combine will run for 2 to 3 minutes and then will struggle and die. Not even trying to run the thresher, just move it. Before it dies it will loose power, but continue to run with reduced load. Combine ran perfect through bean harvest under full load. Right rear wheel dropped into a tile hole so it sat in the field while I used another combine to finish. Warmed up last week so I temporarily put the axle back on and was going to run it to the farmstead. In attempting to move it is where I run into the engine problems.

UPDATE - I have changed the two fuel filters. Checked the tank sediment bulb. Checked the injection pump sediment bulb. Fuel has winter additives from supplier. With sediment bulb loose it will run a constant stream - it filled a five gallon bucket half full in a 2 to 3 minutes. Have opened the tank filler cap to check for vacume. With sediment bulb off of the injection pump and the key switch turned on fuel runs out of the sediment bulb housing on the injection pump. Hand pump on injection pump works and will push fuel into the fuel filters forcing air out. Can't seem to get all of the air out - just a little at the top center of the filters. Some one mentioned that the right side countershaft bearing may have went bad and has worn the fuel pipe - no, can slide a finger inbetween the pipe and shaft - also no visable fuel soaked spots on side of machine/no drips.

NEW INFORMATION - a couple of times when the engine has quit or I have pulled the fuel shut off knob and I have walked around the combine near the fuel tank, I could hear diesel apparently running (gurgling/bubbling) back into the fuel tank from the engine compartment I would assume. Should the fuel run back?? Can't really remember hearing that before. I don't think there is a return line from the injection pump.

When the engine is running and you are standing in front of the engine with your head looking over it you can see a stream of tiny bubbles in the fuel flow into the bottom of the glass fuel filter nearest the injection pump.

Just seems like the fuel filter somewhat empties out. Maybe the one I see the stream of tiny bubbles in empties the worst. What should I do next??? I am willing to go back to check things I already have if you feel necessary. Thanks.

if you can see air bubbles, I'd say it is not pumping fuel when running. If it is pumping fuel when the key is on and the engine is not running, it really sounds like the pump isn't pumping when the engine is running.

I mean, it could be sucking air, but, the pump should keep positive pressure on the system from the tank all the way to the injection pump. I'm assuming it is like my 6620 titan II. You said it filled a 5 gallon bucket in a few minutes? How about when it is under pressure?

and yeah, there is a rubber return line...

Where is your fuel pump located? Is it directly on the bottom of the fuel tank? Just not sure how different yours is from mine.

It filled half of a five gallon bucket by gravity out of the fuel tank sediment bulb when I loosened the glass bulb in a few minutes. The flow was way more than an idling engine would use. I guess if I can't find anything I will just start to disassemble everything from the fuel tank forward - one thing at a time - trying the engine between each step. Alot of things back by the tank are related to flow. I just don't think flow to the engine compartment is a problem. I don't think the tiny little bubbles streaming into the fuel filter with the fuel is right.

If you take the fuel filter off, on the engine, then put a bucket under the housing, or a funnel with a tube, going to a bucket(combines are cramped for space) will it fill the bucket the same way? If you see air bubbles appear in the filter, then that means it is not pumping enough fuel to the filter. If there was an air leak into the system, the positive pressure of the fuel pump would push fuel out of the leak, not suck air into the leak. seeing air bubbles means the injector pump is pulling a vacuum on the filter housing.

Andy, your Bosch in-line IP (and injectors) have a return line.

But the return system isn't your problem. (As it can be with a Stanadyne rotary pump).


You have a restriction between the tank outlet and the electric lift pump, or a bad lift pump.

There is NO way for air to get into that fuel system, once it is bled, while the engine is running if there is fuel available to the electric lift pump and it is functioning.

The tank outlet is below the level of the fuel, as is the electric lift pump.

Any leak there and you'd have fuel dripping on the ground.

Once the fuel gets to a properly functioning electric lift pump, it is forced upward to the transfer pump on the Bosch. And any leak between the electric pump and the Bosch will spew fuel under 6 to 8 PSI of pressure.

If you want to get serious about this, rig up a "T" fitting at the input connection to the transfer pump on the Bosch IP and monitor fuel pressure.

I don't have factory specs in front of me, but you want to see positive pressure, even when the engine is "dying" and 6 to 8 PSI is an educated GUESS.

Please post back with the resolution to this!

couldnt you rig up a temporary tank hanging above the engine feeding your injector pump through the filters? would at least let you know everything at the engine is good and get the machine out of the field.

I will go through the components on the tank end tomorrow. I understand the concept that it is not getting enough fuel from the tank (somewhere after the tank sediment bulb) and therefore is pulling air into the system (since the electric fuel pump is not pressurizing the line) possibly between the sediment bulb and the electric fuel pump. If the electric fuel pump is working properly and had adequate fuel and the line had a crack or opening it would shoot fuel out. No fuel is shooting out.

A few years ago I had a wad of chaff that got by the sediment bulb screen and floated up the fuel line to the check valve located on the mechanical transfer pump. This was on a Massey 550. The check valve passage was so small the wad of chaff would just hit the inlet of the opening and plug everything. The engine would stop. The chaff would float down the fuel line. The engine would start. Might run 5 minutes to 15 minutes depending on how fast the chaff floated back up to again plug the opening. Maybe I have something like this going on down at the sediment bulb and electric fuel pump. Thanks for you suggestions.

Have you checked to see if you have good fuel flow at the injection pump. Loosen the line from the fuel filter to the pump at the pump. I'm going on rusty memory and think the line from the filter to the pump is rubber part of the way, I have seen those rubber lines swell internally and plug off the fuel supply. I also think there is an orifice at the fitting on that line end on the pump. Now I'm not talking about the lines at the little hand pump, but the actual filtered fuel into the pump.

Not to be smart ars but Do you have enough fuel in it?

That's probably air bubbles you see. As been mentioned see if you check fuel pressure from the tank pumps. Hal

See if you can install a pressure gauge and measure the pump pressure. Hal

For a quick additional trouble shooting step, remove the outlet fuel line of the electric fuel pump, remove the fuel filters and with an air gun at the fuel filter inlet, blow backwards through it.

Do the same for the line from the sediment bowl, blow backwards through the line/bowl/tank assembly as well. You should hear bubbling in the tank.

This should be a quick check that the lines/assemblies are not plugged.

Oops, not fuel filter inlet but rather lift pump inlet on the Bosch injection pump...