My M8540 has about 3,000 hours. Recently it has been idling very rough at start-up for about 10-15 seconds. It even died once. After that, it runs fine. Is this likely a position sensor going bad? Other ideas?
Rough idle at start-up
- Thread starter Jolly Rancher
- Start date
I would be suspecting the glow plug controller.
Try this trick. this is a paste from another post but will give you some ideas. It relates to a M7040
but the M8540 is the same generation I think.
Kubota glow plug operation
In very cold weather, with the block heater plugged in, the glow plug sensor will lock out the glow plugs as it senses a warm engine.
However, starting, in these circumstances can be rough and worrisome.
The trick is to put the shuttle shift lever in forward and turn the key to the start position.
You will hear a relay click on. I count to 10, put the shuttle back into the neutral position and start the engine.
Makes an amazing difference.
Dave
Jim How this came up was I was at the dealer on a reasonably cold day and noticed the staff moving around a large number of tractors for snow removal. These are machines that could have been sitting for months. The mechanic said they used to have problems getting all machines started in spite of using the glow plugs as allowed by the tractors electronics until the service rep told them how to get another cycle out of the glow plugs which was the shuttle shift in forward and turning the key to start. The electronics wont give you a second round of glow plugs even if you wanted them. Without this trick, when you turn the key to on, if the tractor is cold enough to need the glow plugs, a symbol lights up on the dash and you just leave the key in the on position until the symbol goes out and then turn the key to start. If the tractor does not start you are screwed. I am certain the system re sets itself after a while but I don't know how long. When using this trick, the dash symbol does not light up and all you hear is a relay click once when you hold the key in the start position. I count to 10 holding the key in start to not overheat the glow plugs as this seems to be how long they stay on under the controller in the coldest conditions. When you return the shuttle shift to neutral and turn the key to start there is no doubt that the glow plugs have heated up. This is a long answer to your question. Yes it overrides the thermostat and other limiting features on the glow plug controller. Dave
Try this trick. this is a paste from another post but will give you some ideas. It relates to a M7040
but the M8540 is the same generation I think.
Kubota glow plug operation
In very cold weather, with the block heater plugged in, the glow plug sensor will lock out the glow plugs as it senses a warm engine.
However, starting, in these circumstances can be rough and worrisome.
The trick is to put the shuttle shift lever in forward and turn the key to the start position.
You will hear a relay click on. I count to 10, put the shuttle back into the neutral position and start the engine.
Makes an amazing difference.
Dave
Jim How this came up was I was at the dealer on a reasonably cold day and noticed the staff moving around a large number of tractors for snow removal. These are machines that could have been sitting for months. The mechanic said they used to have problems getting all machines started in spite of using the glow plugs as allowed by the tractors electronics until the service rep told them how to get another cycle out of the glow plugs which was the shuttle shift in forward and turning the key to start. The electronics wont give you a second round of glow plugs even if you wanted them. Without this trick, when you turn the key to on, if the tractor is cold enough to need the glow plugs, a symbol lights up on the dash and you just leave the key in the on position until the symbol goes out and then turn the key to start. If the tractor does not start you are screwed. I am certain the system re sets itself after a while but I don't know how long. When using this trick, the dash symbol does not light up and all you hear is a relay click once when you hold the key in the start position. I count to 10 holding the key in start to not overheat the glow plugs as this seems to be how long they stay on under the controller in the coldest conditions. When you return the shuttle shift to neutral and turn the key to start there is no doubt that the glow plugs have heated up. This is a long answer to your question. Yes it overrides the thermostat and other limiting features on the glow plug controller. Dave
dvcochran
Active member
Equipment
Kubota M9000, New Holland TN90, Deere 2640, Vermeer 504N, Vermeer 504SI, more
I tried that, and it did not help for this case, but I appreciate you sharing that "trick." That is certainly a good one to have up one's sleeve!
I have experienced this issue when the temps are in the mid 70s. Plus, the tractor starts immediately, at first bump of the starter. It just begins running rough almost immediately. After experiencing it again, I am inclined to think it is getting air in the fuel line. It's like it is losing its prime. Is there something like a check valve in the system? I plan to change out the fuel filter now, even though it is pretty new. I dumped the separator bowl, and it looked like it had only clean fuel, no water.
I have experienced this issue when the temps are in the mid 70s. Plus, the tractor starts immediately, at first bump of the starter. It just begins running rough almost immediately. After experiencing it again, I am inclined to think it is getting air in the fuel line. It's like it is losing its prime. Is there something like a check valve in the system? I plan to change out the fuel filter now, even though it is pretty new. I dumped the separator bowl, and it looked like it had only clean fuel, no water.
The rough running sounds like a symptom of a tiny bit of air in the HP lines.
My *guess*, because that's a common symptom after you bleed the HP lines of a diesel, caused by residual air in the lines.
I would suspect some kind of leakdown happening in a high pressure line, between the injector pump and the injectors. Check the nuts that clamp the lines at each end for leaks and tightness. Could be a tiny crack somewhere. The HP lines must be thoroughly clamped, so that they're not subject to vibration and consequent stress to the metal. These lines need to handle >2000PSI, so they're not very forgiving of metal stress or wear due to rubbing somewhere.
-Paul
My *guess*, because that's a common symptom after you bleed the HP lines of a diesel, caused by residual air in the lines.
I would suspect some kind of leakdown happening in a high pressure line, between the injector pump and the injectors. Check the nuts that clamp the lines at each end for leaks and tightness. Could be a tiny crack somewhere. The HP lines must be thoroughly clamped, so that they're not subject to vibration and consequent stress to the metal. These lines need to handle >2000PSI, so they're not very forgiving of metal stress or wear due to rubbing somewhere.
-Paul
3,000 hrs on the machine…. could be the beginnings of lower compressions on a couple cylinders…until they warm-up and rpm settles-down…??
Not to worry over it… it happens to all of us… My knees don’t like to work after a nights’ sleep… until I take a few steps.
Not to worry over it… it happens to all of us… My knees don’t like to work after a nights’ sleep… until I take a few steps.
I have had good success identifying specific cylinders not outputting their share using an infra red temp gun pointed at each exhaust port on the head. It may be that your issue is too brief to produce a difference in temp but for the cost of the guns these days and the other uses for them it might be a tool to add to your collection.
Dave
Dave