50 hour service: air in fuel line?

lc12 · Apr 8, 2019

I just completed my 50 hour service on my L4701 HST.
Part of that service was to replace the fuel filter.
I did so and filled the new filter with diesel fuel prior to installation in hopes of minimzing getting air in the lines.
Now, when I start the tractor it seems to crank longer before firing up.
It runs great and no hiccups.
Am I just "imagining" things or can air be the cause?
Thanks in advance for your help.

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mike paulson · Apr 8, 2019

lc12 said:
I just completed my 50 hour service on my L4701 HST.
Part of that service was to replace the fuel filter.
I did so and filled the new filter with diesel fuel prior to installation in hopes of minimzing getting air in the lines.
Now, when I start the tractor it seems to crank longer before firing up.
It runs great and no hiccups.
Am I just "imagining" things or can air be the cause?
Thanks in advance for your help.

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Air in the lines would cause misfire. And either pass or not. Cracking injector lines is a method mechanics use to bleed air. I don't think you have air. Just run it a few days.

lc12 · Apr 8, 2019

Thanks Mike.
Kind of what I was thinking.

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North Idaho Wolfman · Apr 8, 2019

lc12 said:
I just completed my 50 hour service on my L4701 HST.
Part of that service was to replace the fuel filter.
I did so and filled the new filter with diesel fuel prior to installation in hopes of minimzing getting air in the lines.
Now, when I start the tractor it seems to crank longer before firing up.
It runs great and no hiccups.
Am I just "imagining" things or can air be the cause?
Thanks in advance for your help.

Sent from my LG-G710 using Tapatalk

Never prefill the fuel filter, you have now defeated the filters purpose and run unfilter fuel straight to the system.

Get the WSM and or OPS manuals and follow the procedure for changing the filters, all models have different procedures for doing this.

Captain13 · Apr 8, 2019

Is the engine "loping" at all after it cranks?

If so, it's probably sucking some air, but you said no hiccups so I assume the idle is steady.

Check the filter and make sure it's all tight and look and make sure there are no wet spots around the hard and soft fuel lines. The engine may be losing prime causing the harder starting. Since you just changed the fuel filter, I would start there checking to make sure that you have everything nice and snug on the filter and that the lines are seeping fuel. With 50 hours, I wouldn't think you have an injector bleeding down unless some trash got to it.

lc12 · Apr 8, 2019

Captain13 said:
Is the engine "loping" at all after it cranks?

If so, it's probably sucking some air, but you said no hiccups so I assume the idle is steady.

Check the filter and make sure it's all tight and look and make sure there are no wet spots around the hard and soft fuel lines. The engine may be losing prime causing the harder starting. Since you just changed the fuel filter, I would start there checking to make sure that you have everything nice and snug on the filter and that the lines are seeping fuel. With 50 hours, I wouldn't think you have an injector bleeding down unless some trash got to it.

On the first attempt after changing the filter there was some diesel coming out of the top of the filter. I did not want to tighten it too much at first.
I tightened the filter and no more fuel was leaking.
No wet spots, and everything looked good.
It just seems like I am having to crank a bit longer than before the change.
And it is really not that much longer. It just seemed to fire almost instantly before the change.
BUT, once it fires it runs good, so I am thinking it is just me.
I just thought I would ask here as I would rather be safe than sorry!
Thank you for your reply.

lc12 · Apr 8, 2019

North Idaho Wolfman said:
Never prefill the fuel filter, you have now defeated the filters purpose and run unfilter fuel straight to the system.

Get the WSM and or OPS manuals and follow the procedure for changing the filters, all models have different procedures for doing this.

I am not sure what you mean.
The filter was prefilled with clean diesel as would be the case as if coming from the fuel tank.
Am I missing something here?
Maybe I was being to careful, but it seemed like there have been a lot of posts related to air getting in the lines and I was just trying to eliminate that possibility.
I did read the OPS manual, and have to say that it is not the most clearly written document, for me anyway, especially when it came to the HST filter versus the transmission filter, etc., and I know I am not the only one that has this problem with the manual.
Edit:
I just checked both the WSM and the OPS manual regarding the fuel filter change and there was NO mention of NOT prefilling the fuel filter before installation. Granted, it did not suggest filling it prior to installation either.
But I do not see where I did anything wrong.
On the plus side I did find out how to bleed air out of the system and it is not as difficult as I was thinking.

lc12 · Apr 8, 2019

Captain13 said:
Is the engine "loping" at all after it cranks?

If so, it's probably sucking some air, but you said no hiccups so I assume the idle is steady.

Check the filter and make sure it's all tight and look and make sure there are no wet spots around the hard and soft fuel lines. The engine may be losing prime causing the harder starting. Since you just changed the fuel filter, I would start there checking to make sure that you have everything nice and snug on the filter and that the lines are seeping fuel. With 50 hours, I wouldn't think you have an injector bleeding down unless some trash got to it.

Everything is tight and it does not seem to be sucking air.
I just think I was being overly concerned with doing things right and was being a "Nervous Nellie".
I am just happy that it is running!
The only thing left to do is change the transmission filter.
I changed out the HST filter and used the "vacuum trick" and it worked GREAT!
The only spilled hydraulic oil is what was in the old filter.
The dealer did not sell me the transmission filter as he said it was not necessary to change it out for the 50 hour service, yet my manual says to do so.
I am thinking the "vacuum trick" should work just as well on this side. I am interested in getting the metal shavings out of the system that everyone speaks of.
Thanks for the reply.

rjcorazza · Apr 8, 2019

My L4060 fuel filter interval is 400h, and the separator is check for water daily, remove and clean at also 400h. 50h seems like an early fuel filter service...
Anyway, with either filter (the water separator is also a coarse pre filter) it is bad practice to pre fill the filter with diesel. Pre filling will put fuel in the post filter path, resulting in unfiltered fuel moving forward in the system.

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AllDodge · Apr 8, 2019

lc12 said:
I am not sure what you mean.
The filter was prefilled with clean diesel as would be the case as if coming from the fuel tank.
Am I missing something here?
Maybe I was being to careful, but it seemed like there have been a lot of posts related to air getting in the lines and I was just trying to eliminate that possibility.
I did read the OPS manual, and have to say that it is not the most clearly written document, for me anyway, especially when it came to the HST filter versus the transmission filter, etc., and I know I am not the only one that has this problem with the manual.

A diesel uses injector nozzles which have very "very" small holes at the tip. These holes can be smaller then a human hair. It only takes a very small particle to clog the nozzle.

Changing a fuel filter should have the area cleaned, remove old filter, clean sealing surface, put small amount of oil on gasket and install. The motor will either have a hand primer pump or electric pump, but once the filter is installed, fuel is manually pump into the filter.

Once filter is full and air is bleed out, then the motor is started. This way no particle which can not be seen by the naked eye will not make it to the injectors

rjcorazza · Apr 8, 2019

lc12 said:
Everything is tight and it does not seem to be sucking air.

I just think I was being overly concerned with doing things right and was being a "Nervous Nellie".

I am just happy that it is running!

The only thing left to do is change the transmission filter.

I changed out the HST filter and used the "vacuum trick" and it worked GREAT!

The only spilled hydraulic oil is what was in the old filter.

The dealer did not sell me the transmission filter as he said it was not necessary to change it out for the 50 hour service, yet my manual says to do so.

I am thinking the "vacuum trick" should work just as well on this side. I am interested in getting the metal shavings out of the system that everyone speaks of.

Thanks for the reply.

There is frequently confusion regarding the Transmission Filter (HST), and Hydraulic Filter.
The L4701 document I just looked at shows the Transmission Filter (HST) gets changed at the initial 50h service and every 200h thereafter.
The Hydraulic Filter is changed at 400h, and every 400h thereafter.

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lc12 · Apr 8, 2019

AllDodge said:
A diesel uses injector nozzles which have very "very" small holes at the tip. These holes can be smaller then a human hair. It only takes a very small particle to clog the nozzle.

Changing a fuel filter should have the area cleaned, remove old filter, clean sealing surface, put small amount of oil on gasket and install. The motor will either have a hand primer pump or electric pump, but once the filter is installed, fuel is manually pump into the filter.

Once filter is full and air is bleed out, then the motor is started. This way no particle which can not be seen by the naked eye will not make it to the injectors

Thank you for the explanation.

lc12 · Apr 8, 2019

rjcorazza said:
There is frequently confusion regarding the Transmission Filter (HST), and Hydraulic Filter.
The L4701 document I just looked at shows the Transmission Filter (HST) gets changed at the initial 50h service and every 200h thereafter.
The Hydraulic Filter is changed at 400h, and every 400h thereafter.

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Yes, I just saw that myself.
I do not know where I got it in my head that the transmission filter had to be changed at 50 hours.
Maybe a posting from someone more nervous than me about being careful with their tractor! lol
But I do know that there are those that think the transmission filter should be changed out at 50 hours to remove the metal particles that stick to the magnet.
I will follow the OPS manual and do the transmission oil filter change at 400 hours.
At least I know that I can not be held accountable for trouble since I am following the Kubota Manuals directions!
And I always log all services and keep all of my receipts and buy ONLY Kubota brand filters and oils.

Thanks for the help!

rjcorazza · Apr 8, 2019

lc12 said:
Yes, I just saw that myself.

I do not know where I got it in my head that the transmission filter had to be changed at 50 hours.

Maybe a posting from someone more nervous than me about being careful with their tractor! lol

But I do know that there are those that think the transmission filter should be changed out at 50 hours to remove the metal particles that stick to the magnet.

I will follow the OPS manual and do the transmission oil filter change at 400 hours.

At least I know that I can not be held accountable for trouble since I am following the Kubota Manuals directions!

And I always log all services and keep all of my receipts and buy ONLY Kubota brand filters and oils.

Thanks for the help!

Your manual should have the Transmission Filter interval at the first 50h, then every 200h. The Hydraulic Filter is every 400h. If your manual states otherwise, I would confirm with a second source (not me!).

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lc12 · Apr 8, 2019

rjcorazza said:
Your manual should have the Transmission Filter interval at the first 50h, then every 200h. The Hydraulic Filter is every 400h. If your manual states otherwise, I would confirm with a second source (not me!).

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Yes, you are correct!
I thought I had read it on this forum, the idea of changing the transmission filter early.
I can see where someone would be worried when there is talk about METAL FRAGMENTS being found in your oil filter!
But again, I will follow the manual and change that filter at 400 hours.
NOW, this is where there appears to be another debate even within this forum.
My understanding is that the HST filter, which is what the dealer sold me for the 50 Hour Service, is the one located under the step on the LEFT side of the tractor.
The transmission oil filter, which has the magnet, is the one located on the RIGHT side of the tractor.

rjcorazza · Apr 8, 2019

lc12 said:
Yes, you are correct!

I thought I had read it on this forum, the idea of changing the transmission filter early.

I can see where someone would be worried when there is talk about METAL FRAGMENTS being found in your oil filter!

But again, I will follow the manual and change that filter at 400 hours.

NOW, this is where there appears to be another debate even within this forum.

My understanding is that the HST filter, which is what the dealer sold me for the 50 Hour Service, is the one located under the step on the LEFT side of the tractor.

The transmission oil filter, which has the magnet, is the one located on the RIGHT side of the tractor.

The dealer sold you the correct filter based upon what you have written.

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whitetiger · Apr 8, 2019

lc12 said:
Yes, you are correct!
I thought I had read it on this forum, the idea of changing the transmission filter early.
I can see where someone would be worried when there is talk about METAL FRAGMENTS being found in your oil filter!
But again, I will follow the manual and change that filter at 400 hours.
NOW, this is where there appears to be another debate even within this forum.
My understanding is that the HST filter, which is what the dealer sold me for the 50 Hour Service, is the one located under the step on the LEFT side of the tractor.
The transmission oil filter, which has the magnet, is the one located on the RIGHT side of the tractor.[/QUOTE]

The filter on the right-hand side with a magnet is actually the hydraulic pump suction filter. It only filters the hydraulic oil going to the hydraulic pump.
Some models call them Suction filter and the LH an HST filter.
A lot of times the translation of manuals from Japanese to English makes things confusing. Better known as "Jinglish".

lc12 · Apr 12, 2019

Update:
I followed the instructions on bleeding the lines and all is perfect again.
Turn the key on and starts right up!
No cranking.
And it was just a very SMALL amount of air.
I loosened the vent bolt on top of fuel filter.
Set throttle to MINIMUM speed
Turnd the key to ON for a minute.
Tightened the "bleed" bolt on top of filter.
Turned key to start, and YAY! Fired right up!

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