B&S 5HP engine runs for a minute then stalls
cano...@telecom-digest.zzn.com
Recently acquired an air compressor equipped with a B&S 5HP motor.
When cold motor starts on 2nd pull and runs fine for the first minute
then
gradually slows down over the next 30 seconds till it quits.
Googling revealed people with similar problems. So I've:
--loosened cap on fuel tank
---------- no difference
--replaced spark plug with new plug
---------- no difference
--replaced air filter
---------- no difference
--rebuilt carb, complete disassembly + soaking in carb cleaner
overnight, resent needle to 1-1/2 turns.
---------- no difference
--double-checked there is no gunk in bottom of gas tank clogging the
tiny screen at the tip of the fuel inlet
---------- no difference
OOoooooOOOOooo this make me SO frustrated!!!
Any more ideas to try? Help!!
TIA,
Steve
John Gilmer
If you use the choke to start you should take out the choke within one
minute. A hot engine will just not run on full or even half choke.
You might have some restrictions in the fuel supply. The most reliable
small engines have a gravity feed to the fuel bowl. It doesn't take much
to clog the needle valve in the float.
Other small engines have a "fuel pump" which is a diaphram that's part of
the carb. If you truly rebuilt the carb this should have all new sealing
and moving parts.
There is an oddball possibility that when the engine starts to heat up the
ignition system fails.
<cano...@telecom-digest.zzn.com> wrote in message
news:1158917528....@b28g2000cwb.googlegroups.com...
nobody
have a shipping plug in the gas tank, under the cap.
I got a great deal on a leaf vacuum that a guy returned to the store with
you exact symptoms and one I removed that blue gas plug, it ran great.
But generally you definitely have a fuel problem, having a partial vacuum in
the tank would do it, a constriction preventing the fuel bowl from filling
properly would do it. As it sits over a minute or too enough air/fuel seeps
through to allow a re-start .
Good luck.
<cano...@telecom-digest.zzn.com> wrote in message
news:1158917528....@b28g2000cwb.googlegroups.com...
m Ransley
its the fuel system, if nothing see if you get spark after it dies, it
could be the ignition system,
Ether Jones
cano...@telecom-digest.zzn.com wrote:
> Recently acquired an air compressor equipped with a B&S 5HP motor.
> When cold motor starts on 2nd pull and runs fine for the first minute
> then
> gradually slows down over the next 30 seconds till it quits.
The choke cable may have come loose, and the choke is closed. Pull the
air filter off and check it out.
There's a small tool that you attach between the spark plug and the
spark plug wire that allows you to see the spark as the engine is
running. Briggs tool #19368 or similar.
You could hook this up, start the engine, and watch as it stalls to see
if there is still a strong spark.
Stubby
cano...@telecom-digest.zzn.com wrote:
> Hi all,
>
> Recently acquired an air compressor equipped with a B&S 5HP motor.
> When cold motor starts on 2nd pull and runs fine for the first minute
> then
> gradually slows down over the next 30 seconds till it quits.
>
> Googling revealed people with similar problems. So I've:
> --loosened cap on fuel tank
> ---------- no difference
> --replaced spark plug with new plug
> ---------- no difference
> --replaced air filter
> ---------- no difference
> --rebuilt carb, complete disassembly + soaking in carb cleaner
> overnight, resent needle to 1-1/2 turns.
> ---------- no difference
> --double-checked there is no gunk in bottom of gas tank clogging the
> tiny screen at the tip of the fuel inlet
> ---------- no difference
Check that the RPM governor is free to move.
Chris Lewis
> Hi all,
>
> Recently acquired an air compressor equipped with a B&S 5HP motor.
> When cold motor starts on 2nd pull and runs fine for the first minute
> then gradually slows down over the next 30 seconds till it quits.
I've seen this happen on a Stihl two stroke weed wacker.
Turned out that the spark arrester screen was fouled and was
retricting exhaust gasses thru the muffler.
If the engine easily restarts after quitting on you, that may be the
cause.
Check the muffler for restrictions.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
Stubby
heat fins. Last Spring that happened to a small mower we had -- B&S. I
was mystified and paid $65 for a "tune up" that didn't do anything. It
took 3 more trips to the shop and screaming at the owner to get him to
fix it. The high school kids working for him would need help falling
off a ladder.
cano...@telecom-digest.zzn.com
can't be a vacuum problem, I've tried it with the gascap completely
off.
can't be the choke, I move it to "run" right after cold-starting
can't be any sort of exhaust restriction
can't be clogged cooling fins
carb is a suction-feed. There's a long stem that goes to the bottom of
the fuel tank. This has a fine-mesh metal screen for a filter, which is
clean. There's another stem, shorter with what in a Holley automotive
carb would be called a 'jet' staked into the end - this goes into a
shallow pan tack-welded to the inside of the gas tank. There's no
moving parts in any of this except for the throttle and choke plates. I
can't figure out what the purpose of this short stem/shallow pan is or
how fuel gets into the pan to cover the jet, but it'd make sense that
once the shallow pan ran dry the engine would quit.
I don't think the engine runs long enough to get hot enough to cause
the ignition system to fail. Where it the system located?
I don't think it's the RPM governor but could check it - where is it
located and how can I check it?
Grrrrrrr. I'll make a call to the local small-engine repair shop, maybe
they can give me a straight answer.
Steve
DK
It is a bad fuel cap.
new caps have a tiny air vent that lets the tank breath and the
hole prevents vacuums.
Yours is defective and the tank is creating a vacuum.
.
Ether Jones
cano...@telecom-digest.zzn.com wrote:
> can't be the choke, I move it to "run" right after cold-starting
Yes, but did you actually look at the choke plate in the carb to make
sure it is opening?
If the choke cable got loose, you could have full choke even with the
choke lever in the "off" position.
Does this engine have a primer bulb? What happens if you pump that a
couple of times when the engine starts to stall?
Oren
wrote:
>
>cano...@telecom-digest.zzn.com wrote:
>
>> can't be the choke, I move it to "run" right after cold-starting
>
>Yes, but did you actually look at the choke plate in the carb to make
>sure it is opening?
Yes the "butterfly" valve could just be sticking.
>
>If the choke cable got loose, you could have full choke even with the
>choke lever in the "off" position.
Like you said, you gotta look at the "choke plate".
--
Oren
"Well, it doesn't happen all the time, but when it happens, it happens constantly."
Oren
>Thx so far to all who've replied...
>
>can't be a vacuum problem, I've tried it with the gascap completely
>off.
A vacuum problem can be as simple as a misaligned or a damaged gasket.
>can't be the choke, I move it to "run" right after cold-starting
Before you re-mounted the carb, did you check for easy operation, like
moving the parts....is something "binding", resulting in poor
operation?
Husky
> Thx so far to all who've replied...
>
> can't be a vacuum problem, I've tried it with the gascap completely
> off.
> can't be the choke, I move it to "run" right after cold-starting
> can't be any sort of exhaust restriction
> can't be clogged cooling fins
>
> carb is a suction-feed. There's a long stem that goes to the bottom of
> the fuel tank. This has a fine-mesh metal screen for a filter, which is
> clean. There's another stem, shorter with what in a Holley automotive
> carb would be called a 'jet' staked into the end - this goes into a
> shallow pan tack-welded to the inside of the gas tank. There's no
The shallow pan welded into the top of the tank is the carburetor bowl.
The long tube is the fuel pump pick up, and the short one is the
carburetor venturi tube. The fuel pump is under the side cover, the
rubber gasket with the spring and protector ring. The two little flaps
are the "reeds" for the check valves.
> moving parts in any of this except for the throttle and choke plates. I
> can't figure out what the purpose of this short stem/shallow pan is or
> how fuel gets into the pan to cover the jet, but it'd make sense that
> once the shallow pan ran dry the engine would quit.
>
> I don't think the engine runs long enough to get hot enough to cause
> the ignition system to fail. Where it the system located?
> I don't think it's the RPM governor but could check it - where is it
> located and how can I check it?
>
> Grrrrrrr. I'll make a call to the local small-engine repair shop, maybe
> they can give me a straight answer.
>
>
> Steve
>
Try taking the belt off the engine and compressor pulleys and see if it
runs okay. It could be a siezing compressor head.
Husky
Husky
Depending on how old the engine is, it may not have any vent in the cap
at all. Most of the newer B&S engines vent the tank through the threads
themselves, to reduce splash spilling and evaporative emissions... Won't
be long and they'll have to do away with that and add a vapor canister...
Husky
marad...@unlisted.com
torch and turn on the propane. Dont light the torch, just hold the
torch over the intake on the carburetor (remove the air cleaner
first). If you are not getting enough gas, the propane will keep the
engine running (not the smoothest, but it will run). You can vary the
valve on the torch and move closer or further from the carb to adjust
the engine speed. If this keeps it running, you have a fuel problem.
If not, it's ignition. Do be sure the choke butterfly is staying
open. Look at it, not the lever for it.
If it's ignition, replace the entire magneto. That IS your ignition
system all built into one. (unless you got an old engine with points
and condenser).
Mark
On 22 Sep 2006 12:24:59 -0700, cano...@telecom-digest.zzn.com wrote:
cano...@telecom-digest.zzn.com
> at all. Most of the newer B&S engines vent the tank through the threads
> themselves, to reduce splash spilling and evaporative emissions... Won't
> be long and they'll have to do away with that and add a vapor canister...
hmmmm ... I get the same symptom with the cap completely removed. So
it can't be a problem with the cap, venting/non-venting/loose
threads/etc
I can verify that the choke cable is connected and working correctly.
I did replace the gasket that contains the reed valves as part of the
carb-rebuild. I made sure to install the spring against the carb inself
pressing outward against the gasket towards the tiny plate that bolts
onto the carb - this is the way the spring was oriented when I first
opened it up. Sure looked correct - the inside of the tiny plate did
not have a machined area for a spring to reside whereas the
corrosponding area within the carb itself was machined. And yet - no
fuel pumping would surely explain the symptoms I'm experiencing. How
does this pumping occur in a carb with no moving parts?
Tomorrow I'll try filling the gas tank -extremely- full i.e. enough to
make sure some gas is sloughing into the shallow pan.
Thanx for everyone help so far!
Steve
Stormin Mormon
the fuel tank. This has a fine-mesh metal screen for a filter, which
is
clean. There's another stem, shorter with what in a Holley automotive
carb would be called a 'jet' staked into the end - this goes into a
shallow pan tack-welded to the inside of the gas tank. There's no
moving parts in any of this except for the throttle and choke plates.
I
can't figure out what the purpose of this short stem/shallow pan is or
how fuel gets into the pan to cover the jet, but it'd make sense that
once the shallow pan ran dry the engine would quit.
describing is a Vacu-Jet. When the piston goes towards the spark plug,
it creates a slight vacuum in the crankcase. This slight vacuum goes
to the carb in a silver tube about 3/8 diameter. Which moves a
diaphragm, and pumps a bit of gas into the small pan. The air flow
through the carb body creates a slight vacuum (venturi effect) which
lifts the gas into the combustion air. On the other side of the motor
is a cover over the bottom of the valves. The cover is abotu 1 inch
wide, and 3 inches tall. You'll need a 5/16 nut driver, it is held on
with two screws. This cover has a gasket, and contains a check valve.
When you get the cover off, you'll see a hole in the inside surface of
the cover. It is possible this cover is dirty, and not allowing the
crankcase vacuum. Gently remove the gasket, and clean out the valve
cover with brake cleaner, soak in gasoline, etc.
I don't think the engine runs long enough to get hot enough to cause
the ignition system to fail. Where it the system located?
CY: Under the motor cover. Next to the flywheel. If it's an older
motor, it has a points and condensor setup under the flywheel.
I don't think it's the RPM governor but could check it - where is it
located and how can I check it?
CY: On top of the carb, there is a spring. And a short rod. the rod
goes to what looks like the rudder of a small plane. This rudder
(can't remember he name of it) is under the motor cover, and is blown
by the airflow coming off the flywheel). These parts should move
gently and easily when you try to move them.
Grrrrrrr. I'll make a call to the local small-engine repair shop,
maybe
they can give me a straight answer.
CY: Please keep us posted.
Steve
DK
>> Depending on how old the engine is, it may not have any vent in the cap
>> at all. Most of the newer B&S engines vent the tank through the threads
>> themselves, to reduce splash spilling and evaporative emissions... Won't
>> be long and they'll have to do away with that and add a vapor canister...
>
>hmmmm ... I get the same symptom with the cap completely removed. So
>it can't be a problem with the cap, venting/non-venting/loose
>threads/etc
>
>I can verify that the choke cable is connected and working correctly.
>
>I did replace the gasket that contains the reed valves as part of the
>carb-rebuild. I made sure to install the spring against the carb inself
>pressing outward against the gasket towards the tiny plate that bolts
>onto the carb - this is the way the spring was oriented when I first
>opened it up. Sure looked correct - the inside of the tiny plate did
>not have a machined area for a spring to reside whereas the
>corrosponding area within the carb itself was machined. And yet - no
>fuel pumping would surely explain the symptoms I'm experiencing. How
>does this pumping occur in a carb with no moving parts?
The cylinder piston pulls a vacuum and the pressures as the air flows
past the jets suck the fuel from the jets into the air stream.
Might be time to put a pressure gauge on the spark plug.
Gary Dyrkacz
A relatively unusual possibility that can also have symptons like this
is a leaking head gasket. The engine can start and run fine and then
as it heats up, the gasket begins to leak.
Gary
George
the carbon off the screen over the exhaust outlet.
George
On 22 Sep 2006 02:32:08 -0700, cano...@telecom-digest.zzn.com wrote:
Husky
Wrong! The vacu-jet only had ONE pick-up tube, and is a "suction" system
where the entire fuel tank ACTS as the carburetor bowl. Two tubes
indicate the carb is a PULSA-JET, which uses the short tube as the
venturi nozzle and the long tube as the fuel pump pick-up. The 3/8"
aluminum tube connecting the crankcase breather to the carburetor is the
CLOSED CRANKCASE VENTILATION "hose", and the breather and tube combined
are the equivalent to your car's POSITIVE CRANKCASE VENTILATION (PCV)
where the breater itself is the valve. The fuel pump is operated
entirely by the intake vacuum pulses directly from the inside of the
carburetor throat. On horizontal shaft engines, the diaphragm is open
directly to the throat between the throttle plate and the mounting
flange; on verticle shaft engines it is ported to the same area by a
drilled passage. Some verticle shaft engines also include a vacuum choke
control ("pull off") on the same diaphragm, and vacu-jet carbs only use
a diaphragm to provide the choke pull-off. A newer version of the
Pulsa-Jet, called the Pulsa-Prime, replaces the choke and choke pull-off
with a bulb operated primer, which is basically just an extra fuel pump
jetted directly into the throat of the carburetor. This should not be
confused with the primer installed on B&S/Walbro carburetors, which
pressurize the bowl with air to force fuel up the nozzle.
The reason for the Pulsa-Jet carbs is that the fuel level in the bowl
affects the mixture at which the carburetor operates. The higher the
fuel level, the richer the mix it provides. To more closely control the
mixture, the Pulsa-Jet maintains the inner bowl at a full to overflowing
level by the operation of the fuel pump and the opening at the top of
the inner cup which spills back into the fuel tank. The Vacu-Jet carbs
change their mixture as the fuel level drops, requiring the specific
instruction in the service manual that they are only to be adjusted at
the half-tank level.
>
>
> I don't think the engine runs long enough to get hot enough to cause
> the ignition system to fail. Where it the system located?
> CY: Under the motor cover. Next to the flywheel. If it's an older
> motor, it has a points and condensor setup under the flywheel.
>
> I don't think it's the RPM governor but could check it - where is it
> located and how can I check it?
> CY: On top of the carb, there is a spring. And a short rod. the rod
> goes to what looks like the rudder of a small plane. This rudder
> (can't remember he name of it) is under the motor cover, and is blown
> by the airflow coming off the flywheel). These parts should move
> gently and easily when you try to move them.
Five horsepower engines can be equiped with EITHER an air-vane governor
OR a mechanical flyweight internal governor. Both will have the spring
and linkage however, and should move such that the throttle plate can
travel from fully closed to fully open.
>
> Grrrrrrr. I'll make a call to the local small-engine repair shop,
> maybe
> they can give me a straight answer.
> CY: Please keep us posted.
>
> Steve
>
>
One thing I "missed" the first time is the "Jet" staked into the end of
the short tube. This indicates the engine is a late model, and is
probably pollution "controlled". There should have also been a fine
metal screen sock over that short tube. Everything I posted earlier
still applies, but due to the leaner operating environment of an E.P.A.
or C.A.R.B. engine, it may have to be started two or three times before
it will stay running, or it may have to be "warmed up" for as much as a
minute on part choke. The other thing to suspect is the "jet" may be
partially blocked. The shallow pan can only get fuel from the fuel pump,
if it isn't working, you would never start the engine in the first
place, as the only way to get fuel into the "bowl" would be to
completely "overfill" the tank, which, I suspect is impossible due to
the angled fuel fill cap the fits into the cut off corner of the tank.
The older tanks had a raised neck, onto which the cap threaded, but the
"jet" you describe in the short tube was introduced about the same time
as the new tank with no neck and a quarter turn, non-vented cap like the
old cars. The vent is through the carburetor on these models. It is
possible, if your problem with stall occured only after the carb had
been taken apart, that the gasket may be installed incorrectly, or be
the wrong part altogether, and is blocking the vent. That would make the
engine "run out of gas", as the pump would be unable to suck fuel up.
But, IIRC, you said you ran it without the cap and it did the same thing?
Stormin Mormon
owner to see. I learned a bit, thank you.
That's some seriously interesting information. I got out my old, dusty
Briggs and Stratton book. turns out that it says that suction from the
intake stroke powers the diaphragm which moves fuel. Essentially what
you said.
And you're right that I got pulsa and vacu backwards. Ah, well.
Thanks for the advice, it' someone else's engine, I'm just a
spectator.
moder...@worldnet.att.net
cano...@telecom-digest.zzn.com wrote:
> I did replace the gasket that contains the reed valves as part of the
> carb-rebuild. I made sure to install the spring against the carb inself
> pressing outward against the gasket towards the tiny plate that bolts
> onto the carb - this is the way the spring was oriented when I first
> opened it up. Sure looked correct - the inside of the tiny plate did
> not have a machined area for a spring to reside whereas the
> corrosponding area within the carb itself was machined. And yet - no
> fuel pumping would surely explain the symptoms I'm experiencing. How
> does this pumping occur in a carb with no moving parts?
The suction to draw gas from the bowl into the carb venturi nozzle is
the Bernoulli effect.
Perhaps you're asking how the fuel pump works? Part of that thing you
called a "the gasket that contains the reed valves" is actually a pump
diaphragm. Those little flaps are the check valves, and they do act
like reed valves. A pulse of intake vacuum pulls the diaphragm one
direction while compressing the spring, and this draws the liquid
through the foot valve flap, up via the pick-up tube. Then the spring
ejects the liquid through the other valve and into the bowl.
A similar type of pump is used on 2-stroke outboard motors, chainsaws
etc. In that case, the crankcase supplies pulses of both vacuum and
pressure to operate the diaphragm both ways, so the spring is typically
not necessary.
> Tomorrow I'll try filling the gas tank -extremely- full i.e. enough to
> make sure some gas is sloughing into the shallow pan.
The design of the tank may make this difficult. You might be able to
snake a tube into the bowl through the filler opening and squirt some
gas in that way. If the engine can be revived by filling the bowl
directly, suspect the pump. Confirm your suspicion by checking the
level in the bowl after a nuisance shutdown. The bowl should be full to
the point of overflowing back into the tank proper. If this requires
tank removal to confirm, be careful not to affect your reading by
sloshing fuel out of the bowl as you do it.
A weak pump might be able to supply enough fuel when the engine is not
loaded, but as the throttle opens and consumption increases, the level
in the bowl drops and leans the mixture, or just plain starves the
engine if the level drops sufficiently. Running lean under load can
cause overheating, which may cause the engine to seize or shutdown
after a few minutes.
A weak pump might work OK when the tank is full but not so well as the
tank level drops. If the pump cover doesn't mate with the carb casting
(almost) perfectly, air can leak into the wrong part of the pump and
decrease its effectiveness.
If the diaphram has a pinhole, it can play heck with the mixture,
making it very throttle-dependent and hard to set reliably with the
needle. Did the pump spring have a little "ring" that fit over it to
protect the diaphragm from the sharp end of the spring wire?
%MOD%
moder...@worldnet.att.net
Husky wrote:
> The older tanks had a raised neck, onto which the cap threaded, but the
> "jet" you describe in the short tube was introduced about the same time
> as the new tank with no neck and a quarter turn, non-vented cap like the
> old cars.
I have/had some horizontal shaft B&S engines from the 1960s with
PulsaJet (pump and bowl) carbs and screwcap tanks. Friggin stamped caps
were not knurled very well and not so easy to grip with a gloved hand,
as I recall. I don't remember the 1/4 turn plastic caps showing up till
the '80s, but there's a lot I don't remember.
I just now remembered that I have a 5 hp horizontal B&S (screwcap
pulsajet) in the far corner of the shed, in an old dishpan, on a bottom
shelf, hidden behind some outboard motor gas cans. Haven't used it
since I switched to a 12V water pump. I may have to make a go-kart just
so it doesn't go to waste :-)
%MOD%
cano...@telecom-digest.zzn.com
I'm back from a brief vacation and ready to tackle this issue again,
thx
for keeping the thread alive.
> A weak pump might be able to supply enough fuel when the engine is not
> loaded, but as the throttle opens and consumption increases, the level
> in the bowl drops and leans the mixture, or just plain starves the
> engine if the level drops sufficiently. Running lean under load can
> cause overheating, which may cause the engine to seize or shutdown
> after a few minutes.
Ah, most interesting. The engine doesn't seem overly hot once it
stalls.
> Did the pump spring have a little "ring" that fit over it to
> protect the diaphragm from the sharp end of the spring wire?
Yes.
Someone suggested I remove the load from the engine (remove fanbelt
connecting engine to compressor) to see what difference that makes -
good idea, I'll try that as well.
Steve
kent.m...@gmail.com
cano...@telecom-digest.zzn.com wrote:
>
> carb is a suction-feed. There's a long stem that goes to the bottom of
> the fuel tank. This has a fine-mesh metal screen for a filter, which is
> clean. There's another stem, shorter with what in a Holley automotive
> carb would be called a 'jet' staked into the end - this goes into a
> shallow pan tack-welded to the inside of the gas tank.
> Steve
I had a B&S 5 hp generator that had similar symptoms. Discovered that
the suction tube from carb to tank had developed a split, preventing
gas from being drawn up into the carb. A little JB Weld on the tube
cured it.
vanderb...@gmail.com
vanderb...@gmail.com
Diesel Dan
when it starts to slow down, I'd try feeding the carb air inlet with some propane from an unlit torch.
trader_4
see if fuel flows freely. Make sure you're prepared to deal with whatever
amount is in the tank.
