784 fuel issue

scott2013 · Sep 22, 2016

I need some help. The tractor runs and pulls great until it gets up to temperature then it acts like it isn't getting fuel. I checked for flow from the tank and through the filters and it wasn't the problem. I can mess with the cold start / shut off and it will run ok for a few seconds but goes back to sputtering. Any idea on what might cause this? If its the pump is there a way to check before taking it off and rebuilding it?
Thanks,
Scott

JimB2 · Sep 22, 2016

Hi, when hot if you let the tractor sit for a few minutes does it start and run correctly again?
For fuel flow did you check it all the way to where the fuel line enters the injection pump? From the last fuel filter to the injection pump the fuel
line runs around the front of the engine block, some versions had a completely steel line and others had a section that was braided steel over
rubber and I have heard of problems with the braided section clogging.

Make sure that when the Stop/Start/Run lever is in the Run position that the fuel control lever on the side of the injection pump is full forward
against the power adjustment screw.

JimB

scott2013 · Sep 22, 2016

If the tractor sits for a few minutes it will start but I have to use the cold start position. It will run normally for about 2-3 minutes until the heat comes back. I cracked the fitting going into the pump and fuel flowed at a rate I would expect. The line is steel so no rubber line issues.

Thanks for the reply,

Scott

Al Baker(pumpman) · Sep 23, 2016

Because you stated you put it in the cold start position I will guess you have the Bosch VA CR pump. This pump operates on fuel pressure. There is no mechanical governor to regulate speed. Its all done hydraulically. It doesn't take much for this pump to act funny. Pull the side cover off and peak inside. Do you see rust or a gummy look? Pull the fuel pressure regulator out and see if the piston is free. Also disconnect the return line from your nozzles and see if you have a change in how it runs. A bad nozzle will back feed pressure into the low pressure side. I am old school and type VERY slowly. It is easier for me to explain how to hunt down a problem over the phone. Give me a call if you like and I will try to help you out. Al 231/757/0064

scott2013 · Sep 23, 2016

Thanks Al. I went out today and started it up and it stumbled when cold so this isn't a heat induced issue. I plan on starting at the tank and clean everything I can all the way to the pump. Got to start the process of elimination somewhere. I will also check the pump as you said.

Thanks,

Scott

scott2013 · Oct 3, 2016

Just an update. I drained the tank so I could clean it out. There was about 10 gallons of fuel in the tank which should’ve been plenty. There was some black gunk in the tank but not enough to cause any problems. When I was inspecting the fuel lines I found the equalizing line that runs from side to side had been patched (brazed) in several places. One of the patches had the line almost plugged up restricting fuel flow. I think this is what was happening: If the tractor sat for a couple of days the 2 tank sides would equalize and allow the engine to run for 45 minutes or so. As the fuel was pulled from the right side and returned to the left side the plugged line kept the tank from equalizing and the right side ran out of fuel. I replaced all the fuel lines with hose and ran it hard today for over an hour and it never missed a beat.

Scott

784 fuel issue

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JimB2

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Al Baker(pumpman)

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