I’ve not had this happen before today—mowed several acres of pasture, no issues-as normal. Stopped to put in some fuel—about 6 gallons—and within minutes, when going uphill with my Bush Hog, my tractor began dropping RPM’s. Pushed the fuel handle full forward, no change. So, I lifted the mower and shut it off—went up the same hill again, no issues (and it’s really not a hill, just a gentle slope). It continued to drop RPM’s with the mower running—parked it for the day. I’m thinking maybe the fuel I added was contaminated. The diesel was maybe 3-4 months old and stored in a sealed metal can. Any help with this would be much appreciated, Thanks!
Power drops off “under load” on my M4900 Utility
- Thread starter RickandBecky
- Start date
To develop power, the engine needs fuel at the right time, air to oxidize the fuel and compression to ignite the fuel. When is the last time you changed the fuel filter? Do you have a lift pump and is it working? Is your air filter clear? Engines that ran at low load and then quit under high load generally have restricted fuel delivery and compression is not an issue.
I would start by checking the fuel filter outlet line. Get a container to catch that $5/gallon fuel and remove the line at the outlet side of the filter. Make sure the tank valve, if you have one is full open. The fuel should gush out like a cow peein' on a flat rock. If it dribbles or is intermittent, repeat the process on the upstream side of the filter. If you have good fuel flow there than the tank outlet is not clogged and the problem is in the filter or the filter housing. If you have good flow at that point, hook the lines back up, bleed the fuel filter to remove any air, and move on to the lift pump, if you have one.
Some lift pumps have a screen under a removable top cover. Some have mechanical primer pumps, some are electric. If you have one, remove the line from the pump that goes to the Injection Pump (IP). Crank the engine and check the mechanical pump for output. If you have an electric pump, turn on the key and it should pump. If that checks out, connect everything and open the bleeder screw on the IP, turn on the key and attempt to start the engine. Bubble free fuel should come out of the bleeder. Crank in short bursts until air free fuel comes out then close the bleeder.
Finally bleed the injectors by loosening the nut where the fuel from the IP enters the injector. Crank until bubble free fuel comes out of the loosened fitting. Do Not remove the fitting.
Checking the air filter means the filter should not be clogged not any intake passages blocked.
With engine operating check fuel level in water separator bowl. If bowl isn't full your tractor engine is not being supplied sufficient fuel. My guess there's blockage in water separator galley's. I once owned a M4900 that acted similar & I was advised to check screen in water separator fuel cut-off valve. I found screen was clogged. Cleaned screen & my engine operating problem was solved.
Thanks for the suggestions to help fix my issue! Will run through these today and hopefully be back in business soon.