Perplexed - loss of power during day, more power at night.

[RancherGuy]

I have a 4 cylinder JD 5425 - 65 PTO hp utility tractor by definition.

For two years, this has demonstrated power loss when I use it at full power when cutting hay. The crop is consistent density and I cut for hours. Power starts off great but can start to decline after 20 to 30 minutes. I shift gears when power declines to keep the PTO RPM up. I might downshift from gears 9 to 8, 7, or 6. My intuition is that the decline is fuel related.

I've changed the fuel filter twice, but I think the power revival is because the tractor was off for a while when changing. I've cleaned out the air filter, but again I think revival was because of the time while cleaning. Power losses resumed within 30 minutes after those rest periods.

This year I found something peculiar one day - started in 9th gear but had to slow down to 7th. Air temp at start was 94 degrees, but after sunset, temp was 88 degrees and power loss seemed to stop declining. Air temp kept dropping and I found that I could kick back up to 8th gear. What a revelation!

Today it got down to 7th gear, but a thunderhead appeared and there was a cool air blast. The engine was power revitalized! I bumped it up to 8th.

Here's the big question: there has to be a means to meter the fuel based on air density, right? To compensate for temperature and turbo pressure? Is there a Mass Airflow Sensor? I've looked at JD parts and can't find something that seems to fit the bill. I'm thinking that whatever the sensor is, it has become temperature sensitive. And at 16 years old, needs to be replaced. Any information? Any ideas?

 

[jdinfo]

If it is a fuel temperature issue, we have had good luck purchasing an automotive transmission cooler from an auto parts store and running the return fuel through the cooler in front of the tractor cooling package, then back to the fuel tank. The transmission coolers are small enough that you can attach it in front of the radiator with zip ties.

Just reroute the hot fuel coming off of the injectors & fuel pump to the cooler and then to the fuel tank. It should drop the return fuel temps by 30°F going back to the fuel tank.

 

[5030]

Turbocharged? Could be the compressor side of the turbo is failing. Air is denser in the evening than during the heat of the day.

 

[workinonit]

Check your fuel tank screen/strainer. I bet it is getting clogged. I just had to do it on my 5090. I actually just removed mine.

 

[workinonit]

I'm not sure the 5425 was a turbo. I know th 5420 was not.

 

[RancherGuy]

Turbocharged? Could be the compressor side of the turbo is failing. Air is denser in the evening than during the heat of the day.

Yes, turbo. Can you explain more about what you know of failure? In my mind, I'm thinking the thing is spinning or it is not. I have read that turbo failure is a thing.

 

[RancherGuy]

Check your fuel tank screen/strainer. I bet it is getting clogged. I just had to do it on my 5090. I actually just removed mine.

Maybe ... but I'm not inclined to take any action to find out. Very clearly, my issue seems to change with either ambient air temp or "final" engine operating teimp. Clogging would not tend to improve if running constant but the air temp drops.

 

[RancherGuy]

If it is a fuel temperature issue, we have had good luck purchasing an automotive transmission cooler from an auto parts store and running the return fuel through the cooler in front of the tractor cooling package, then back to the fuel tank. The transmission coolers are small enough that you can attach it in front of the radiator with zip ties.

Just reroute the hot fuel coming off of the injectors & fuel pump to the cooler and then to the fuel tank. It should drop the return fuel temps by 30°F going back to the fuel tank.

Good point. I'll have to check out my setup to see if it has a cooler already. If so, I'll try to ensure it is cleaned.

Related to that, the other day I got down to 1/4 tank and was thinking that the entire volume was circulating too often to allow time to cool. I stopped and filled fuel to full. Because of the rest period, power was revitalized, but after 30-40 minutes, it was loosing power again even with a full tank.

 

[LouNY]

If your tractor is a common rail injected unit it will have numerous sensors that feed info to the computer for the fuel injection.
I have not researched it but do you have an intercooler on that unit. Some of the sensors will be looking at intercooler temp, water temp, possibly oil temp as well as intake air temp and barometric pressure and boost pressure.

If your tractor is mechanically injected it will not have all those sensors.
I wouldn't be that concerned with fuel temp.

 

[5030]

Like Lou says, ot all depends on age and emissions level. If it's a pre 4 tractor, it's much less complex but either way it's easy to determine if the turbo os the issue. Take the intake off the turbo so you can see inside and grab and spin the compressor wheel. If it rotates freely with no radial slop or back and forth slop (play), then it's fine. If there is play in either direction it needs replaced. Conversely, if you can see where the compressor wheel is cutting onto housing (scroll), it needs replaced. The bearings on the hot side (the side you cannot see, exhaust side) are ceramic and they can wear out. If the turbo has radial or end play, the compressor wheel is hanging up and you aren't getting proper boost. time to renew it.


Rule of thumb with any turbocharged engine is, after working it (up on boost), you should always idle the engine for a couple minutes prior to shutting it off to allow the hot side ceramic bearings to cool off and allow the lubrication oil (they are lubricated with engine oil) to circulate in the turbo tp aid that cooling off.

If it's charge air cooled, rarely would there be an issue with the inter cooler so long as the air filter was doing it's job.