check valve ?

[Snoopy11 5,714]

Just now, lynnmor said:

 

I never timed it but it seems like in a month they will be dry.  I'm sure that temperature and winter grade fuel changes things.

Valid statement.

 

Take a generator for instance.

 

I could run it for an hour. Shut it off. Then close the fuel valve.

 

Fuel should still be in the bowl... no?

 

Wait a month, crank the engine over without opening that fuel valve...

 

Won't start.

 

Open the fuel valve.

 

BOOM SHACKA LACKA.

 

Fire.

 

'nuff said.

 

I've tested this theory in the past with my 3 generators... so ask me how I know.

 

Don

[lynnmor 7,308]

8 minutes ago, Snoopy11 said:

 

Because of their input, I will be installing primer bulbs.

 

I mentioned primer bulbs on here about 7 years ago, even had some poke fun at me about having a boat. 

[peter lena 8,637]

@Snoopy11  as you know you have to experiment with a change , transition from what was there , then  do some tweaking to that change , to dial it in , then its happy time , when it  regularly works like it should / or better .  love doing that , and its  often a simple change , jumped over the fence a long time ago , pete

[Snoopy11 5,714]

1 minute ago, lynnmor said:

 

I mentioned primer bulbs on here about 7 years ago, even had some poke fun at me about having a boat. 

Well, I for one appreciate it.

 

If a certain small, inexpensive part solves a problem that multiple people have, that is a good thing, something that should be celebrated.

 

Don

[peter lena 8,637]

@lynnmor  always looked at a chronic problem as an opportunity to really go step by stem to eliminate that problem .  we have all probably been there on something , and of course while you are there doing brain surgery , the other  PIA  problem related to that , dares to exposé itself !  not done everything , but just enjoy wallowing  in the used to be  problem area  total function . pete

[RED-Z06 2,221]

On 11/27/2022 at 12:36 PM, Jeff-C175 said:

 

I know they exist, but perhaps only older pumps?

 

All mine have pressed in check valves and no screw.  All early 80s vintage.

 

 

All diaphragm pumps have some kind of check valve by design, be it a flap (think flathead briggs) or spring and disc, because they are opposite one another, fuel can freely flow in, but not back...when the diaphragm retracts, the outlet valve shuts and the inlet valve opens, fuel is drawn in and the chamber fills...when the diaphragm pulls in, pressurized fuel pushes the outlet valve open and the inlet valve shut..pushing fuel out the outlet

Edited November 30, 2022 by RED-Z06

[Snoopy11 5,714]

Truth is @peter lena ...without the knowledge that the older guys on this forum share... many people would be lost as to how to improve their machines and keep them going.

 

So many guys on here share their valuable time and experience on... even the smallest issues.

 

This is what makes Redsquare rock.

 

Don

[Jeff-C175 7,202]

1 hour ago, RED-Z06 said:

the bowls should hold fuel for a couple months

 

Don't forget that the bowls are not airtight.  There is an atmospheric vent.

 

Put a few ounces of petrol in a cup and see how long it takes to evaporate.

 

 

[Jeff-C175 7,202]

3 minutes ago, RED-Z06 said:

All diaphragm pumps have some kind of check valve by design, be it a flap (think flathead briggs) or spring and disc, because they are opposite one another, fuel can freely flow in, but not back...when the diaphragm retracts, the outlet valve shuts and the inlet valve opens, fuel is drawn in and the chamber fills...when the diaphragm pulls in, pressurized fuel pushes the outlet valve open and the inlet valve shut..pushing fuel out the outlet

 

Yes, of course, but that was not the point.

 

What I said was that the NEWER pumps that I have on all my machines do not have the removable check valve assemblies that you can take out a screw and the springs go flying.

 

The newer pumps have pressed in check valves that are, for all intents and purposes, not serviceable.

 

And those two check valves are exactly the same principle that the primer valves use.  The bulb is the diaphragm, your hand the lever.  There are check valves at the inlet and the outlet.

 

 

[Handy Don 12,237]

When putting small engines away for seasonal rest, I try to shut off the fuel valve and run the engine (adding choke as needed) until it stalls from lack of fuel. This takes nearly all of the fuel out of the bowl. On my Techcumseh's and the Briggs Vantage, I use their bowl drains. I expect to do more cranking for these on their first start next season. 

That said, I'll likely add a primer bulb when next messing with the camp tractor as it spends the longest time hibernating!

[RED-Z06 2,221]

2 minutes ago, Jeff-C175 said:

 

Don't forget that the bowls are not airtight.  There is an atmospheric vent.

 

Put a few ounces of petrol in a cup and see how long it takes to evaporate.

 

 

Im aware of the bowl vent but also remember that the vent is not "open air" in a cup and its not subject to rapid evaporation. A quart of gas will evaporate down to its solids in a couple days but a carb can hold fuel for quite a while, otherwise you would have solids in your carb in a couple weeks.

[peter lena 8,637]

@Snoopy11  so glad  I  passed on / interest  on mechanical anything to my son , in todays world  he is a rare bird indeed , he can ask  anything and we can  understand each other  , and have the same interests in many things . my grandsons  have the  definite gap , growing up in the tech world , you really have to break down and   detail interests , and possibilities ,  but they pick it up fast ,  grampa

[RED-Z06 2,221]

1 minute ago, Handy Don said:

When putting small engines away for seasonal rest, I try to shut off the fuel valve and run the engine (adding choke as needed) until it stalls from lack of fuel. This takes nearly all of the fuel out of the bowl. On my Techcumseh's and the Briggs Vantage, I use their bowl drains. I expect to do more cranking for these on their first start next season. 

That said, I'll likely add a primer bulb when next messing with the camp tractor as it spends the longest time hibernating!

Its the best method, run it dry...tank, lines, carb...stuff can sit years bone dry and fire right up out of hibernation...thats how we do it in the south with generators when we dont need them for 8 years then suddenly need them to run for a couple weeks straight

[RED-Z06 2,221]

3 minutes ago, RED-Z06 said:

Its the best method, run it dry...tank, lines, carb...stuff can sit years bone dry and fire right up out of hibernation...thats how we do it in the south with generators when we dont need them for 8 years then suddenly need them to run for a couple weeks straight

I ran this dry in 2020, didnt need it this year or last so i rolled it out to out a pint in it and exercise it.  Cranked up on 2 or 3 seconds of cranking...ran a few minutes on a pint...shes a thirsty girl

[Snoopy11 5,714]

 

Mmmkay...

 

I didn't really want to 'go there' ...but...

 

So... what... are the guys who say that their tractor engines crank for extended periods of time after sitting with ZERO fuel leaks or other fuel system related issues... imagining this phenomenon...?

 

Is that what you are arguing?

 

If not, what is the solution that you are offering...? You got a better idea? I haven't seen anything helpful that you have posted in this thread...? 

 

Don

[RED-Z06 2,221]

1 hour ago, Snoopy11 said:

 

Mmmkay...

 

I didn't really want to 'go there' ...but...

 

So... what... are the guys who say that their tractor engines crank for extended periods of time after sitting with ZERO fuel leaks or other fuel system related issues... imagining this phenomenon...?

 

Is that what you are arguing?

 

If not, what is the solution that you are offering...? You got a better idea? I haven't seen anything helpful that you have posted in this thread...? 

 

Don

Im trying to figure that out, im asking questions, trying to go through possible scenarios where there could be a reason for long crank times, because from the point of view of someone who gets paid to work on this stuff every day, if the crank time is long...its not working right.  Its my job, to make sure stuff cranks like its supposed to.

 

But one constant is..if the bowl is full, the fuel cannot physically go back up the inlet needle and back into the fuel line...its not possible.  So, we also dont necessarily have a finite level of fuel in the carb...thermal expansion in the fuel tank can, gently push fuel through the check valves and into the carb but because of the tank vent that's not likely to be a factor.  

 

So we have a bowl of fuel, atmospheric vent, how quickly does that fuel evaporate...knowing that if it evaporates, its going to leave behind solids and its not going to start anyways.  An onan keeps the carb pretty cool, its enclosed, kohler K/M is more open..but again i get quick starting on my Kohlers, always have and ive had probably 20 K/M singles.  The bowls can seep on them though, ive attributed it to the splash baffle, people under or over tighten the nut and as the baffle ages the bowl will take on a yellowish gunky color from slow fuel evaporation.

 

Its like your carb is flooding, so you put a fuel shut off valve on it...its not fixed.

 

Edited November 30, 2022 by RED-Z06

[rick 233]

I can tell you my WheeHorses had a long crank time after a week setting in the shed.  Electric fuel pump cured them.  The fuel runs back into the tank overnight, and the carb bowl hasn't enough fuel to start until the pump fills it back.  I'm in South Central Virginia, halfway between the glaciated zone and Florida.   

[Handy Don 12,237]

1 hour ago, RED-Z06 said:

So we have a bowl of fuel, atmospheric vent, how quickly does that fuel evaporate...knowing that if it evaporates, its going to leave behind solids and its not going to start anyways

You are definitely questioning the right leg of the triad (fuel, oxygen, spark). 

 

I've never seen or read a tested, engineered explanation for why it takes x seconds for sufficient fuel to vaporize and get "inhaled' for ignition under different conditions.

 

A couple of factors I've always thought relevant:

- we use choke to enrich the fuel/air mixture by reducing the air flow. BUT, it's the velocity of the air through the venturi of the carb that causes the low pressure that draws the fuel out of the bowl and vaporizes it so, in a way, choking is counter productive as it can suck too much fuel and make the vapor to dense for combustion. Other systems (like primer bulbs built into carbs) find ways to increase the amount of fuel temporarily without reducing airflow.

 

- fuel vapor will condense even on warm-ish surfaces -- so does some of the first vaporized fuel out of the carb condense on its way into and through the combustion chamber initially leaving an inadequate concentration of fuel for combustion? Once there is a film of fuel on the passages, does the later vapor pass through at a concentration good for ignition? Does that film evaporate as the engine warms up? Onans (and, in fact all opposed twins) have longish intake manifolds. They are much shorter on single cylinder Kohlers.

 

- the potential for carb icing in the right climactic conditions (high relative humidity in near-freezing air temps)

Edited November 30, 2022 by Handy Don

[RED-Z06 2,221]

4 minutes ago, Handy Don said:

You are definitely questioning the right leg of the triad (fuel, oxygen, spark). 

 

I've never seen or read a tested, engineered explanation for why it takes x seconds for sufficient fuel to vaporize and get "inhaled' for ignition under different conditions.

 

A couple of factors I've always thought relevant:

- we use choke to enrich the fuel/air mixture by reducing the air flow. BUT, it's the velocity of the air through the venturi of the carb that causes the low pressure that draws the fuel out of the bowl and vaporizes it so, in a way, choking is counter productive as it can suck too much fuel and make the vapor to dense for combustion. Other systems (like primer bulbs built into carbs) find ways to increase the amount of fuel temporarily without reducing airflow.

 

- fuel vapor will condense even on warm-ish surfaces -- so does some of the first vaporized fuel out of the carb condense on its way into and through the combustion chamber initially leaving an inadequate concentration of fuel for combustion? Once there is a film of fuel on the passages, does the later vapor pass through at a concentration good for ignition? Does that film evaporate as the engine warms up? Onans (and, in fact all opposed twins) have longish intake manifolds. They are much shorter on single cylinder Kohlers.

 

- the potential for carb icing in the right climactic conditions (high relative humidity in near-freezing air temps)

A cold engine lacks compression, its not as efficient as far as ring seal..the oil has largely drained back, off the top end, we also have low speed compression release to further hinder cold efficiency as well as the low cranking speed.

 

Without choke you'll eventually start..but the engine really needs that initial burst of fuel from choke, to enrich the mixture briefly.  Some outboards didnt have a choke, they had a solenoid that pushed the float down on one of the carbs to flood it, to aid in cold starting...much like a small engine primer (not purge) bulb..that blows air through the bowl vent to push fuel up and out of the main jet to flood the carb.

 

Once warmed up, everything seals a bit better and choke is usually not needed.

 

Remember that most governors open the throttle when the engine dies, and when cranking, you would be on the main jet and there's just not enough velocity to draw gas up at cranking speed.  you'll find older engines will close the throttle at engine shut down at idke and sometimes will start without choke in the summer because they are able to utilize the idle circuit which is behind the throttle butterfly so it can draft fuel up without choke.

[Jeff-C175 7,202]

23 minutes ago, RED-Z06 said:

cold engine lacks compression

 

It does?  I've measured cold and hot engines and they've always been the same within tolerance of the measuring tool.

 

I think you're just making stuff up now.

 

What's to understand?  Tens of people have said the primer bulb gives instant start after setting a spell.  My machines included.  My 175 I would have to crank the snot out of it after it set a week or so.  Couple squeezes on that little black booby and instant start.

 

Why are you in disbelief?

 

Oh.. ok, so you think the atmospheric vent isn't enough to cause evaporation?  So put a few ounces of Gaza Lean in a cup and put a cover with a 1/4" hole in it and see how long it takes.  While you're doing that, measure the amount of "solids" it leaves behind.  Report back with your findings.  And pics... We need pics or it didn't happen.

 

.

 

[Handy Don 12,237]

32 minutes ago, RED-Z06 said:

Once warmed up

Yep, another good set of relevant points (and more variables added to the equation )

 

Any specifics on the compression for a cold vs. warm engine?

[Snoopy11 5,714]

13 minutes ago, Jeff-C175 said:

It does? 

Generally, there is a 10% difference between the compression of a cold engine vs. a warm engine.

 

Basically, not enough that you would actually notice a difference or MAKE a difference... particularly in the conversation we are having...

 

Cold engines have compression... that digresses from this thread to a point I haven't seen in a long time.

 

18 minutes ago, Jeff-C175 said:

I think you're just making stuff up now.

 

 

We are talking about fuel getting to the engine. If a primer bulb or an electric fuel pump solves the problem... then what does that have to do with compression or choke or...????

 

Don

[Ed Kennell 38,230]

I think all will agree, the slow start problem came when the fuel tanks were relocated under the seat.    

Primer bulbs ended all my slow start problems. 

 

   Could the answer be one of the three rules of plumbing ?

1.  Don't chew your fingernails

2. S@#t doesn't run uphill

3. Payday is on Friday.

 

[Snoopy11 5,714]

4 minutes ago, Ed Kennell said:

Could the answer be one of the three rules of plumbing ?

Option 1... duh....

 

That certainly cracked me up...

 

Problem:

 

7 minutes ago, Ed Kennell said:

S@#t doesn't run uphill

 

Solution:

 

7 minutes ago, Ed Kennell said:

Primer bulbs ended all my slow start problems

 

Plain, simple, case closed.

 

Don

[RED-Z06 2,221]

1 hour ago, Jeff-C175 said:

 

It does?  I've measured cold and hot engines and they've always been the same within tolerance of the measuring tool.

 

I think you're just making stuff up now.

 

What's to understand?  Tens of people have said the primer bulb gives instant start after setting a spell.  My machines included.  My 175 I would have to crank the snot out of it after it set a week or so.  Couple squeezes on that little black booby and instant start.

 

Why are you in disbelief?

 

Oh.. ok, so you think the atmospheric vent isn't enough to cause evaporation?  So put a few ounces of Gaza Lean in a cup and put a cover with a 1/4" hole in it and see how long it takes.  While you're doing that, measure the amount of "solids" it leaves behind.  Report back with your findings.  And pics... We need pics or it didn't happen.

 

.

 

You're probably thinking of Static cylinder pressure, that shouldn't change much unless something is broken, because compressing 9 volumes of air into a 1 volume chamber is going to be a 9:1 compression ratio and the cylinder pressure will usually exist within a range.  But dynamic compression factors in valve overlap, intake velocity, temperature, ignition timing, engine speed, cumbustabilty of the fuel and engine efficiency.  You cant physically test dynamic compression without measuring the cylinder pressure while its running or attempting to run.  A cold engine is less efficient when it comes to igniting fuel.

 

Off the topic but on subject of compression,  they have a variable compression engine now, it uses these linkages on the rods to pivot the pistons into a longer or shorter stroke...high compression for taking off then lower compression once the turbo spools so it can safely run higher boost without detonating.