Hello all, new owner of an old 721d2 here. My first diesel of any kind so excuse my ignorance on how to work on them. I am having trouble with the mower cutting out and then shutting off when I give it throttle. Won’t do it every time, just intermittently. When I first bought the mower it was puffing black smoke and not much power. Would bog when put under a little bit of load. Changed both fuel filters and air filter, then I realized the system needed bled when it wouldn’t start. So I did that, hopefully correctly, and now I’m having this problem. I thought I had it fixed when I blew the fuel pickup line out and a seed blew out of the line, but it came back after a time or two mowing. This last time I noticed the second filter on 1/4 the way full and air bubbles in the return line, and what looks like some black stuff in the in line filter. Could this all be from a dirty tank. I’m hoping it’s not something more, which is maybe why the guy sold it? He did come down in price by 1k. Any help would be appreciated.
Air in fuel
- Thread starter Skrat
- Start date
Yes. Clean and flush the ENTIRE fuel system. Blow out all hard lines with shop air.
Any horizontal hard lines that make a 90 degree bend going up or vertical can form dirt blockages IN the 90 degree bend. Obviously restrict the flow of Diesel TO the injectors in your case.
Make sure your fuel pump is flowing like it has a purpose.
Drop a USB cam into the tank and check for dirt and trash in the bottom.
I did see a feather on the bottom of the tank. A farmer owned it before me. I forgot to mention in the last post the reason for why it was blowing black smoke. The owner before me turned up the fuel to try and get it more power he said. So I turned it down a turn or two and it doesn’t smoke hardly at all, only at startup.
Auto Doc's
Lawn Addict
Sounds like the fuel tank needs to be drained and flushed.
Get some diesel fuel conditioner in that fuel tank quick. People that don't use a good fuel additive will have problems.
Modern diesel has bio diesel mixed in it (read the pump at the station). And you will not do any better with AG diesel because there is nothing special about it except, they add a red dye to identify it. The dye keeps people from trying to run it in their regular vehicles.
The newer diesel tends to gel much quicker in cold weather and that can cost you an injection pump and possibly the injectors. (I've had it happen before)
Make sure to clear out the return line and fittings because that will create problems if there is any blockage.
Get some diesel fuel conditioner in that fuel tank quick. People that don't use a good fuel additive will have problems.
Modern diesel has bio diesel mixed in it (read the pump at the station). And you will not do any better with AG diesel because there is nothing special about it except, they add a red dye to identify it. The dye keeps people from trying to run it in their regular vehicles.
The newer diesel tends to gel much quicker in cold weather and that can cost you an injection pump and possibly the injectors. (I've had it happen before)
Make sure to clear out the return line and fittings because that will create problems if there is any blockage.
What an idiot.
Tell me about it. Well removed tank and cleaned it out. Replaced first in line filter. Second filter I replaced a few months ago and still looks clean. I could see the gunk in the first filter. Ran it for 20-30 minutes and no hiccups! However my second filter is only 40% full. Is that normal? Should that be 100% full? Is there air in the system from replacing the first filter and having the return line off?
Auto Doc's
Lawn Addict
A return line filter? That is odd to me. Yes, the return can have air in it because it is returning the fuel that the injectors did not put into the cylinders back to the fuel tank. Never expect a return line to be full of fuel.
This machine may take multiple filter changes before the systems clears up.
Diesel is a naturally "dirty" fuel that will actually build algae in it if the proper additives are not used and it is left sitting in the tank for long periods of time
This machine may take multiple filter changes before the systems clears up.
Diesel is a naturally "dirty" fuel that will actually build algae in it if the proper additives are not used and it is left sitting in the tank for long periods of time
Auto Doc's
Lawn Addict
This is always a subject of discussion because people are misled to believe that a filter should appear "full". They do not understand the physics involved with fuels.