tracking down a diesel fuel leak

[Jim L.]

I see a lot of good advice offered.

While I don't think that I am completely tuned in to the problem, I'll throw this out for consideration.

You could get some vinyl or clear tubing for the return fuel lines. Doesn't have to go in same place as the present return lines. When you substitute it in, it will be empty of fuel. Now you can see if the return fuel goes where it is supposed to go. Then take out the clear tubing.

Or maybe this triggers a better idea.

 

[Tractor Gal]

Maybe I'm all wet. I am not familiar with you specific tractor or engine. I do know that the fuel coming from the injector pump to the injectors is NOT rubber but steel. It is a high pressure like, like 2200 PSI.

The fuel return lines an not high pressure, just fuel draining back to the tank. There is a fitting at the base of the injector that has the hose barb for the return line. One injector will have only one of those hose barbs because it is only going to the next injector. That second injector will have a similar fitting but will have two hose barbs. One for the line coming from the injector in front and going to the injector to the back. The third injector will have a two hose barb fitting. One line coming from the second injector and the other side going to the fuel tank.

You are very patient, D2C an I commend you. I understand what you are saying. My terminology is probably wrong and I'm sure you're right on target. My best way is to go by the diagram. I am certain that blowing a bit of air through that return line will give me an answer and will be a start. I'll do that tomorrow...rest of today is pretty busy. Thanks for taking time. I'll report back.

TG

 

[GreensvilleJay]

This is from the Kubota parts page.....though it appear he excess fuel goes back into the injector pump ? tube 210 kinda between 'A" and 'B' ports of the IP ??

 

[torch]

I don't want to use this tractor much until the leak is repaired. I believe diesel fuel is not combustible but it does burn and I would prefer not
ending up injured!

Diesel is certainly combustible. In fact, some grades are even classed as flammable, although they are at the high end of the range. The difference between "flammable" and "combustible" lies in the flash point (temperature at which it will ignite).

While diesel certainly has a higher flash point than gasoline, and is therefore harder to ignite, once it does get going it releases more heat than the same volume of gasoline. You are wise to be cautious, find the leak and fix it.

Clean things off well then dust lightly with flour, talc or similar. A tiny leak will be more apparent in the powder. Remember that fluid runs downhill, but a pressurized leak can spray in any direction, and a tiny spray could make it appear that whatever else it hits is actually the source of the leak. If you suspect a fine spray or mist, a piece of paper will quickly show the culprit when held in front of the spray.

 

[Tractor Gal]

You are great

This is from the Kubota parts page.....though it appear he excess fuel goes back into the injector pump ? tube 210 kinda between 'A" and 'B' ports of the IP ??

, GreensvilleJay, to try to help. I don't think that is the diagram for my bx23. I have discovered that the rubber tubes I replaced labeled as overflow tubes. There are also overflow tubes that go from the nozzles and those tubes are all in a line. That line ends at the muffler/exhaust area with a larger rubber tube that runs all the way back to the fuel tank. Tomorrow, I am going to run some compressed air into that tube to make sure it is not clogged. Up to that point, everything seems to be freely flowing. But, I don't know for sure, so we'll see. Thanks for the tip! I'll report back when I learn more.

TG

 

[Tractor Gal]

Diesel is certainly combustible. In fact, some grades are even classed as flammable, although they are at the high end of the range. The difference between "flammable" and "combustible" lies in the flash point (temperature at which it will ignite).

While diesel certainly has a higher flash point than gasoline, and is therefore harder to ignite, once it does get going it releases more heat than the same volume of gasoline. You are wise to be cautious, find the leak and fix it.

Clean things off well then dust lightly with flour, talc or similar. A tiny leak will be more apparent in the powder. Remember that fluid runs downhill, but a pressurized leak can spray in any direction, and a tiny spray could make it appear that whatever else it hits is actually the source of the leak. If you suspect a fine spray or mist, a piece of paper will quickly show the culprit when held in front of the spray.

Thanks, Torch. After I try the compressed air to make sure the return line is not plugged, I will try the flour/talc process. The leak that I seem to notice is not in a pressurized area but, as you say, it is hard to see a small leak. I'll report back when I find something. Thanks for helping.

TG

 

[sheepfarmer]

Tractor gal, I don’t have access to the shop manual for your tractor to help directly, but I can tell you how to figure it out by the same method I used to figure out the fuel path on my L3560 which is complicated.

I think D2 and Jay are making good points. The steel lines are more likely to be the input of fuel, and the flexible rubber are returns. Before you start blowing compressed air anywhere, make sure you are not blowing anything into your injection pump! I’d hold off on that experiment until you know exactly where the leak is. You could create an expensive problem.

Do you have a shop manual? mine gave a verbal description of the fuel path with some diagrams. Between those and the Messick’s parts diagrams I could figure out how it was supposed to work. I recommend printing out the relevant parts pages and tracing things out. Colored pencils are really helpful!

The fuel pump may be on a separate page in Messicks, or may be with the engine parts. Print it out and see if there are any little arrows. See where part 210 goes relative to the inside of the fuel pump.

I will be interested in what you find out.

Anyone have the shop manual for her tractor?

edit: tg you were typing your reply while I was working on mine and so parts of my post might not apply. Your description of where you want to blow compressed air makes better sense to me now.

 

[kubotafreak]

I think your on the right track. You need to confirm the to tank rubber line is clear. The bleed back on your model has both metal unison pipe, and rubber vent tubes. The older engines just had the barbs at each injector that looped between each as other have said. These bleed lines have nominal flow if the injectors are in good order. When your injector gets worn, it bleeds back around the main body internally. So whatever doesn’t get pumped in the cylinder ends up in the bleed back line. So added up should have little to no flow to the tank. Where it gets confusing is on that model the T, is from the bleed off from the injection pump bleed. It should only flow lift pump flow when you crack it open. Should have a smaller step hex on the top of it. Now since this usually is closed the T should not be adding any flow. The vent screw I believe is a one way check valve to crankcase, or the fuel bleed off from the injection pump, again shouldn’t have a bunch of flow unless something is worn.

So I think you either have a leaking T.

A blockage in the return to tank(lone end)
Or an injector having major leak back causing too much pressure in the line.
Should have poor engine performance if this is the case bc one or more cylinders would be low on fuel.

 

[GeoHorn]

OK...further investigation results. I am finally getting an understanding of how this fuel system works...at least, in part. The tubing located at the engine left side fuel filter goes into the injection pump which then goes through the rubber tubings I replaced and into the injectors. Excess fuel is then sent back to the tank through the overflow system which exits the injectors through a rubber tubing that is near the exhaust. That tubing runs beside and below the engine, under the chasis and back to the left rear of the tractor where the fuel tank extends.

I have checked and checked to see if fuel is going through all of those tubes from the filter to the injectors, and out to the overflow tubing by the exhaust and it flows freely. My theory at this point is that perhaps that overflow tubing back to the tank is clogged somehow and is creating a diminished flow back. When it gets "full," the flow slows down and the system backs up and begins to leak at the input tubes.

There does not appear to be any hesitation, coughing or sputtering of the engine so it must be getting the fuel?

Here's the plan, if someone could validate is OK...I am going to use the compressor to blow a bit of air through the overflow tube leaving the injectors to see if the air can get back to the tank. I would take the whole tube off but it would be quite an undertaking since it runs over and around lots of other things. I see nothing that would be damaged with a bit of pressure. If there is a clog of some kind, it would go into the tank and eventually into the filters, recently replaced, so nothing lost, as I see it.

The air bleeder screw is only to bleed air from the system and there does not appear to be that problem so that idea didn't work out...but it was a good one! I didn't put any flour/powder to check on the leak (another good idea) because I know the general vicinity which is around the tubing I just replaced and the t-connector, I just don't know why it would leak.

Thanks for listening, all. This time of year people are busy with their projects and work, so if there are no answers, I understand.

TG

TractorGal, ... you are “imagining” or “theorizing” a possible “cause” of a problem (on a return line) you have not-yet proven exists, and have ventured off the main-problem-trail by imagining WHY fuel is leaking from “someplace” you have not yet proven to be the location of that leak.

The FIRST thing to do is discover WHERE it’s leaking.
THEN address WHY that leak is occurring at that location.

 

[GreensvilleJay]

the problem with finding the leak, is it's like a 'leaky roof'..... the liquid can flow far,far away from the actual problem.
OK.....here's the fuel tank and lines drawing... #110 is the 'return hose'(my name) FROM the engine to the tank. It's attached on the FRONT injector. The 3 other hoses you replaced are on the rear injector.
I'd disconnect from the front injector and 1) see if fuel drips out of the hose then 2) blow into it.
2 might be hard as fuel will be in the line, but <5psi shop air or bicycle pump would help !
If possible have someone 'man the pump' while you listen near the tank for 1st some gurgling of fuel(purging the line), then pisss of air(line empty).
IF that doesn't happen then the fitting(follow 110->C->130-> TANK in dwg...) HAS to be plugged. How ? I have no idea but I do KNOW the steps to get to it( 'book' 1/2 day, not hard just a lot to do.....)
Now IF it IS clear, then the only thing I can see would be that an injector is blocking flow in the 'metal rail' section. You could disconnect hose at both ends of the 'rail', lightly blow and air should pass through.

sadly it's a process of elimination, good news is it's NOT the dead of winter and a ice storm.
hope this helps

 

[D2Cat]

I doubt the leak is for a high pressure line or your problem would be OBVIOUS with fuel squirting while the engine was turning over/running.

Do not ever put you hand (fingers) over steel fuel lines trying to determine a leak. The fuel can be injected into your skin...... And the same goes for hyd. hoses.

 

[Tractor Gal]

You, gentlemen, are the best! I so appreciate all the help and suggestions. There has been some good success today...I did blow some compressed air into the return line. Prior to doing it, I had seen it on the diagrams and there was nothing that would prevent doing it. I immediately heard bubbles in the fuel tank so that line is clear.

Then, I put some talc on the block, especially around the t-connector and the air bleed screw. When I started the motor, there was lots of activity around the bleed screw. It turned about 1/4 turn to get it tightened so that's quite a bit for such a small screw.

I ran the tractor for a few minutes to monitor and the problem is certainly far better. There may be just a bit of fuel at the t-connector but I'll have to monitor more closely as I go forward. That connector is not in stock at Messick's so either way, it would be a while before that could be replaced. And, it may be wise to go ahead and order one, just to make sure.

So, thanks for the lessons! There are some good mechanics on this board. It is wonderful that you share what you know to help those who want to know. Thanks again.

Tractor Gal

 

[GreensvilleJay]

It sure sounds like you've finally WON !!!!

 

[Tractor Gal]

It sure sounds like you've finally WON !!!!

I'm looking for the wood to knock!