Question about air leaks in fuel lines, BX

[cerlawson]

My BX has had nothing but trouble with fuel and stoppages from early on. Plugged fuel filters, tank cap not venting, pump may weak, bad fuel, etc. Now with only 220 hours on it I installed an outboard larger fuel filter to minimize the head ache of changing the filter that sits under the floor. Low and behold it ran great with only a little fuel in tank. So I fill the tank and get some 2.2 hours and it stalls and quits when mowing with just over 1/2 tank level. I dump in fuel and away she goes. At 1/2 tank it needs the pump to run. But, at full tank it will run with pump unhooked (as tested some time ago). That was pointing to weak pump maybe.

Now I am blaming the pump as being weak until today. I have a friend with a diesel engine on his boat. He had all sorts of trouble until he found an air leak in the hose between tank and pump. No fuel leaked out but air came in.

Now that seems to be the main reason for my problems from the word go.

When I had the tank out at one time and did the cleaning as a shop here advised, I noticed the connection of tank to hose is not the most secure thing with no way to adjust it for tightness. I was looking for crap in the tank but found nothing. See boat friend suggestion at end here.

My plan now is to remove the shroud of engine and run it until it quits. Then I will open the plug at the injectors to vent any air. If so, a major job is expected to get the tank out again and work on that and loose fittings if any ahead of the pump.

Now it looks like my boat friend may have hit on my problem. Can anyone comment on checking his BX for air leaks in the fuel lines? I don't think the arrangement there for the level sensor will permit putting pressure on tank and hoses to look for fuel leaking or fuel leak when under pressure.

Comments?

 

[CountryBumkin]

I don't think your friend with the boat has the same fuel setup as the BX, so I don't think his problem is the same as yours. Maybe I'm wrong.

I believe on the boat the fuel tank is below the engine, so the fuel has to be pumped/drawn up. That could meant that a loose fuel line might suck air without leaking (if the fuel line is above the fuel tank height - meaning above the fuel level).

But on the BX the fuel tank is mounted up high and the lines flow downward to the engine. I don't see anywhere where a loose/leaking fuel line would suck air and not also leak. I think on the BX the fuel can gravity flow to the pump.

But I can't explain why your tractor is giving you so much trouble, especially since you had the tank cleaned and changed the filters.

If you install a clear filter at/near the injection pump you should be able to see bubbles (if its sucking air), or if your running out of fuel - you would see the filter go empty.

 

[cerlawson]

When installing the latest round of filters (standard one closer to injectors and the new one at the left outside frame I didn't look at them when purging the first time. I see that I should have loosened the mount of last in line to let air get fully out. However, I doubt that that did it.

Now with shroud off I'll be looking. Both have fuel visible.

If you were fully right about gravity feed from tank, no fuel pump would be needed. When disconnected wire for pump, tractor runs fine with more than 1/2 tank, but not with less. Thanks anyhow, but keep thinking.

 

[North Idaho Wolfman]

Replace the fuel pump!

 

[cerlawson]

Wolfman:

The pump was replaced about 142 hrs. Same problem continued. Old one runs, but have not checked if it pumps. Was thinking of putting two in line. However, at last purge, the fuel really sprayed out before I closed the drain. Interesting that that pump is made in China and is used on many many engines, etc. I'd like to see the innerds.

Do a Google search for HEP-02A

 

[North Idaho Wolfman]

Off of the pump put a clear line on it, run a loop up above the top of the tractor then back to the filter or the injection pump, run it and see if it pumps air up the line of if it will stay full of fuel.

 

[cerlawson]

Sounds like a good idea. My rough calculations show that if the pump can produce 3 psi (which I see is the least they say) that would mean that diesel can be pushed to a pressure head of about 10 feet. I assume diesel weighs about 56 pounds per cubic foot, with then one foot high providing about 0.39psi.

So actually wouldn't almost any loop height show air in that line?

 

[tcrote5516]

Sounds like a good idea. My rough calculations show that if the pump can produce 3 psi (which I see is the least they say) that would mean that diesel can be pushed to a pressure head of about 10 feet. I assume diesel weighs about 56 pounds per cubic foot, with then one foot high providing about 0.39psi.

So actually wouldn't almost any loop height show air in that line?

Yes it would but the higher you make that loop the more of a vacuum test you put on the system. Given your problem, the bigger the vac the better the test IMO.

 

[Grouse Feathers]

When you test run with the electric pump disconnected have you used the tractor and put load on the engine? With the electric pump disconnected and a full fuel tank, will the tractor run pulling a loaded box blade or does it just run setting in the garage doing nothing?

 

[ThisIsNotaStep]

I had the opposite problem on my BX, a fuel leak at one of the screw-in hose barbs. The fuel sensor grommet was also wet, so I changed out the old one. The instructions on that said, if the tank mating surface was "rough" use a liquid gasket, so I did. I also put a bit on the last couple of threads on the hose barb. Problem solved. Thinking your issue sounds more like a blocked/pinched fuel line ...

 

[FishOn]

I have a BX1870 and right from day one the engine would stall after running for a bit. After a couple of filter changes and draining the fuel tank (thinking it was bad fuel - which they put in) the dealer finally found the problem. When the MMM was in the full up position, it would pinch off the fuel line. I never did see this for myself but that is what they told me and it was like this right from the factory. Running like a charm ever since.