New issue, now loses prime after sitting

[fruitcakesa]

After I thought I had solved my no start/no fuel issue, I now find that after sitting for just a little while, it loses prime.
It will chuggingly restart after a few 10 second cranks and then smooth out and run fine.
I went back over all of the hoses that I pulled off and then reinstalled during the earlier problem troubleshooting to ensure they were seated and clamped.
No obvious fuel leaks so I might assume there is an air leak somewhere.
How would you go about tracking this down?

 

[North Idaho Wolfman]

Follow all lines supply and return and look for wet spots.
It helps sometimes to wash everything down with brake parts cleaner.
If nothing pops out at ya, replace lines with clear lines to be able to see where your getting air from.
Most common are the fuel lines, separator / sediment bowl gaskets, fuel filter gaskets.

Putting air into the tank can also help find a leak, but use that as a last resort as it's risky!

 

[fruitcakesa]

Follow all lines supply and return and look for wet spots.
It helps sometimes to wash everything down with brake parts cleaner.
If nothing pops out at ya, replace lines with clear lines to be able to see where your getting air from.
Most common are the fuel lines, separator / sediment bowl gaskets, fuel filter gaskets.

Putting air into the tank can also help find a leak, but use that as a last resort as it's risky!

Thanks.

 

[kubotafreak]

Brake/carb cleaner works well but use cautiously. It will burn paint dull, and ruin stickers. A good degreasing will help too. You can also dust some light talcom/flour around joints once wash dry. The wetness will be easily seen. Sometimes the leaks suck in and don't leak out much.

 

[fruitcakesa]

Brake/carb cleaner works well but use cautiously. It will burn paint dull, and ruin stickers. A good degreasing will help too. You can also dust some light talcom/flour around joints once wash dry. The wetness will be easily seen. Sometimes the leaks suck in and don't leak out much.

It must be sucking as there is no wetness at any of the hose connections I handled earliert

 

[kubotafreak]

It must be sucking as there is no wetness at any of the hose connections I handled earliert

Does it smoke profusely for a few moments when started? Puff is ok, but a good solid black would indicate a injector issue. Try just leaving the ignition on (if electric lift pump)not started so the lift pump keeps pressure in the system. See if that shows anything.

 

[fruitcakesa]

Does it smoke profusely for a few moments when started? Puff is ok, but a good solid black would indicate a injector issue. Try just leaving the ignition on not started so the lift pump keeps pressure in the system. See if that shows anything.

No noticeable smoke, I will try the key on.

 

[PoTreeBoy]

I was going to suggest this earlier.
I'm thinking you have a pin hole in a suction line. I've looked at the WSM and the parts diagram, but I haven't quite figured out the line between the tank and separator. The parts diagram shows a tee but it's not clear why and where those two lines connect to the tank.
I'm not sure how to diagnose this. I suppose you could pressure them. But I think this area is inaccessible, so it might be easier to just replace them. There's not a dip tube in the tank, is there?

 

[kubotafreak]

I was going to suggest this earlier.
I'm thinking you have a pin hole in a suction line. I've looked at the WSM and the parts diagram, but I haven't quite figured out the line between the tank and separator. The parts diagram shows a tee but it's not clear why and where those two lines connect to the tank.
I'm not sure how to diagnose this. I suppose you could pressure them. But I think this area is inaccessible, so it might be easier to just replace them. There's not a dip tube in the tank, is there?

Many times the T is to allow lift pump fuel to vent. Usually only when the vent screw is opened up at filter service.

 

[fruitcakesa]

I was going to suggest this earlier.
I'm thinking you have a pin hole in a suction line. I've looked at the WSM and the parts diagram, but I haven't quite figured out the line between the tank and separator. The parts diagram shows a tee but it's not clear why and where those two lines connect to the tank.
I'm not sure how to diagnose this. I suppose you could pressure them. But I think this area is inaccessible, so it might be easier to just replace them. There's not a dip tube in the tank, is there?

I suspected the same considering the age of the hoses and it is quite possible just removing and reseating the hoses may have damaged one or more of them.
When I pressurized the tank to clear the outlet, I disconnected the supply line from the tank at the filter inlet.
That line runs behind the engine and under the tractor to the tank which is under the cab on the left side. There is little if any access to those hoses.
I had the tank out last year to reseat what I think was the return line but did not look to see if there was a dip tube.

 

[PoTreeBoy]

Many times the T is to allow lift pump fuel to vent. Usually only when the vent screw is opened up at filter service.

I think you're talking about the line that tees into the return from the injectors.
I'm talking about the one circled in blue.

There may be some differences depending on OP's exact model.

 

[RCW]

fruitcakes - - As before, I have no knowledge of your tractor series. Just trying to help.

My grandfather always said if you come up with another problem while fixing something, look back to what you touched just before that.

I recall several/many folks saying they did not reassemble separator and/or fuel filters correctly after having them apart. Caused air problems. Was very simple stuff, but they missed it at reassembly. Some seemed to be in circumstances similar to yours.

Usually was just a matter of taking them apart, then putting them back together correctly. There was something about a spring in the fuel filter, but maybe that was an L?

I know you had one or both apart. May be worth re-checking.

Again - - wish I was of more help.

 

[fruitcakesa]

fruitcakes - - As before, I have no knowledge of your tractor series. Just trying to help.

My grandfather always said if you come up with another problem while fixing something, look back to what you touched just before that.

I recall several/many folks saying they did not reassemble separator and/or fuel filters correctly after having them apart. Caused air problems. Was very simple stuff, but they missed it at reassembly. Some seemed to be in circumstances similar to yours.

Usually was just a matter of taking them apart, then putting them back together correctly. There was something about a spring in the fuel filter, but maybe that was an L?

I know you had one or both apart. May be worth re-checking.

Again - - wish I was of more help.

I subscribe to your GF's philosophy and will be checking everything again.
There is a spring in the separator and it was replaced in the correct orientation.

 

[fruitcakesa]

Rather than working on the fuel lines just before the storm hits [which is what started this whole issue last time I did some work],
Yesterday I tried a test where I shut off the fuel lever at the water separator right after I shut it down .
This morning, I figured it would need a prime so I pumped up the filter, and could hear what I thought was air bubbling, till it got noticeably hard to pump. This is the first time either of those things have occurred.
I switched on, cranked and it turned over maybe 1 or 2 revolutions then fired right up and settled into a clean idle.
No pumping, cranking and stuttering and then do it 4 more times to get it to start.
So what can I deduce from this new behavior?

 

[North Idaho Wolfman]

You have a air leak somewhere between the input of the separator and output of the fuel filter.
I would replace those three line sections, (separator to lift pump and lift pump to fuel filter and fuel filter to injection pump).
Then with the separator valve closed and the line removed from the input of the injection pump, use air about 5PSI on the output line of the fuel filter, check for leaks.
Then remove the line on the input to the Fuel filter and pressure test back to the separator again.

I have seen lift pumps leak air into the system, any slight fuel will leak back into the crank case.
Check your oil level, it will only rise slightly.

 

[Daren Todd]

X2 on the air leak between the fuel tank and the off valve you closed. I would check the hose clamps if it has some. If you can twist the hose at the clamps, then you issue is there. Check the fuel lines as well. If they are hard, replace them.

 

[kubotafreak]

m6040 right? Machine is a few years old. You may just need a new oring behind the shut off valve. Should be a Philips screw, retainer plate, and pull the lever out.

 

[fruitcakesa]

Thanks guys, I plan on replacing those lines after this coming snow storm has passed.

 

[fruitcakesa]

m6040 right? Machine is a few years old. You may just need a new oring behind the shut off valve. Should be a Philips screw, retainer plate, and pull the lever out.

Yes it is. But the lever on the fuel separator has no retainer plate or screw. It just seems to be pressed into the base with no obvious external retention device.

 

[kubotafreak]

Yes it is. But the lever on the fuel separator has no retainer plate or screw. It just seems to be pressed into the base with no obvious external retention device.

Is it like this one? Make sure if it has the pressed in elbow, that it is not loose. Seen that happen as well.

single screw version,

The manual prime pumps can allow air too. I try to not be overly vigorous with them, they cant take much abuse. I've replaced many. Most are that bosch style. Pump only till resistance, any more, and it just overworks the seals. Running the engine gets the small bubbles of air out. Over pumping can make the small bubbles.

Only after you exhaust all other options. I would suspect the cam driven lift pump. They can leak/vent inside crankcase. Most have an external weep hole though. Could have been the problem the whole time.