Another B&S Engine mystery.

[SARG]

I have a Husqvarna 2354GXLS tractor with a B&S engine. Yesterday I changed out the transparent in-line fuel filter. Today I used the machine for about an hour without any issues. Before I put the machine away I lifted the hood from the seat to double check that the new filter was not leaking.
I was surprised to notice that the fuel within the transparent filter looked like it was boiling ......... a multitude of "air bubbles" were entering from the tank side.
I have never noticed this before and now I wonder if there is an issue I should address.
Has anyone else noted this on their engines ?
I'm suspicious it might be heat related.

 

[LittleBill21]

if your not having a issue leave it alone. My mower has the gas tank above the engine. I have literally seen the gas boil on a hot hard load day, that was 8 years ago and I still haven't needed to do anything.

 

[SARG]

I just got back into the house. I can never leave anything I don't understand alone.
I replaced the spring action clamps with some worm drive to eliminate possible air intake and also wrapped the fuel line were it is near the engine components with a length of split ¾" pipe insulation.
Time will tell.

 

[oldnslo]

Was the engine running when you looked at the filter as saw the bubbles?

Where is fuel tank in relation to filter and fuel pump?

Reason for asking is that some of the lower cost filters I have seen had a pretty large seam from mold process that could allow air to leak past especially if pump is lifting or drawing fuel through the filter. Your worm clamp could solve that problem.

 

[SARG]

Machine was running & the fuel tank is in the rear over the tires.
Lots of mowing required tomorrow so that should tell if I've made any change.

 

[sd455dan]

I have a Husqvarna 2354GXLS tractor with a B&S engine. Yesterday I changed out the transparent in-line fuel filter. Today I used the machine for about an hour without any issues. Before I put the machine away I lifted the hood from the seat to double check that the new filter was not leaking.
I was surprised to notice that the fuel within the transparent filter looked like it was boiling ......... a multitude of "air bubbles" were entering from the tank side.
I have never noticed this before and now I wonder if there is an issue I should address.
Has anyone else noted this on their engines ?
I'm suspicious it might be heat related.
View attachment 810649

I had a Volvo Penta Boat engine do that but it was caused by aged fuel line,

The engine used a mechanical diaphragm style pump but had to draw through the tank one way valve which was in the front of the boat.
Boat ran great for a few years but started seeing bubbles in the clear test filter I put on when the boat started needing extended cranking to start.

I started looking very close at the 16 foot fuel line which was pushed up against the carpet under the gunnels. and noticed "dark" spots every few inches in the carpet.

At that point I did a vacuum test on the line itself and sure enough it would not hold a vacuum.

Installed new marine fuel line and the bubbles disappeared as did the extended engine cranking then reinstalled a metal cased filter.
Just another way the fuel can appear to boil- but is not a heat related boiling of the fuel.

 

[WranglerX]

I has similar "bubbles" while engine was running (B&S powered mower) .... Engine was also miserably hard to start.... Found bad fuel line between tank and filter... It had microscopic holes that would allow air into system but were not large enough to show as a fuel leak.... It was all about the size of the molecules of fuel vs air....

 

[tomplum]

You should really replace those barbless filters. Doom, despair and agony they will bring. Trim the line to get a good seal.

 

[Egon]

Chances are a vacuum is lowering pressure and gas is evaporating.

 

[SARG]

You should really replace those barbless filters. Doom, despair and agony they will bring. Trim the line to get a good seal.

Perhaps ....... But I've been using them on five machines without issue for a couple decades until this mystery.

 

[LittleBill21]

Perhaps ....... But I've been using them on five machines without issue for a couple decades until this mystery.

I also have never had a single issue with them

 

[SARG]

So I just mowed with the Husky for almost three hours and when I observed the filter there was still what appeared to be air bubbles entering with the fuel feed. They were very much smaller than what I noted yesterday and the situation does not appear to effect the machine operation in any way I can note.
I'll have to study on how difficult it would be to replace the fuel line to the tank ........ I do have a couple boxes of line in stock.

 

[ning]

You should really replace those barbless filters.
Doom, despair and agony they will bring

 

[SARG]

I will certainly give that consideration .... if I live long enough to use up the twenty-plus I have in stock ..... which is doubtful.

 

[sd455dan]

So I just mowed with the Husky for almost three hours and when I observed the filter there was still what appeared to be air bubbles entering with the fuel feed. They were very much smaller than what I noted yesterday and the situation does not appear to effect the machine operation in any way I can note.
I'll have to study on how difficult it would be to replace the fuel line to the tank ........ I do have a couple boxes of line in stock.

So are the air bubbles present when a "cold" engine start up takes place?

If so then yeah sounds like a bad fuel line.

My boat and that fuel line never smelled like gas but the line had to have microscopic perforations allowing air to enter guessing from old age.

I have also noticed a drop in the quality of some bulk fuel line I purchased recently for chainsaws. This unbranded yellow stuff did not last much over a year.
I bought some Gates black line in various sizes and so far so good .

 

[SARG]

So are the air bubbles present when a "cold" engine start up takes place?

If so then yeah sounds like a bad fuel line.

At start up there was minimal "bubbling" noted....... the filter filled with fuel with a slight air gap at the upper most portion. After mowing & the machine was hot the "bubbling" within the fuel flow was much more notable.

 

[tomplum]

Fuel lines seem to be one of those neglected things. IE folks that jam a bigger fuel filter and ruin the line for the proper filter. Deteriorated, hard lines too. These barbless went around a few years back. I had leakers, lines that came off. I feel that the barb is more apt to seal and of course resist a push off. On a decent line, on your own stuff- good with me. Not so much for retail service. There's a better way to go.

 

[WranglerX]

At start up there was minimal "bubbling" noted....... the filter filled with fuel with a slight air gap at the upper most portion. After mowing & the machine was hot the "bubbling" within the fuel flow was much more notable.

Again, replace fuel line....

@#$%&* B&S. Hard Starting....

OK,,, Its a B&S Intec twin 22HP in a JD L120 mower and it has to be the most miserable starting engine ever... IF it sits 6-8 days It just does not want to start (dry fuel bowl in carb?)... When it finally starts ( resorting to jump box and prime) I can see air bubbles coming in inlet side of...

www.tractorbynet.com

 

[jaxs]

Rather than watching bubbles and trying to eliminate them spend time washing deck or something else productive. It isn't atmospheric air you are seeing, it's liquid turning into gas as result of heat. Same principle as bubbles forming on floor of pan on the stove then ultimately breaking water surface as it comes to rolling boil. Before automobile carburetors had vent tubes in bowl engines would "vapor loc" as result of gases displacing liquid in bowl.

 

[two_bit_score]

Rather than watching bubbles and trying to eliminate them spend time washing deck or something else productive. It isn't atmospheric air you are seeing, it's liquid turning into gas as result of heat. Same principle as bubbles forming on floor of pan on the stove then ultimately breaking water surface as it comes to rolling boil. Before automobile carburetors had vent tubes in bowl engines would "vapor loc" as result of gases displacing liquid in bowl.

Sounds right.