Briggs & Stratton Hard to Start

[WranglerX]

Have JD L120 mower with 20hp Briggs Intek "V" twin and its miserable to try and start....

Did internet search and solution seems to be adjusting valves to .004 for intake and .006 for exhaust.... According to some "compression release" mumbo jumbo with cam...

Well that is not solution. valves are at tight .004 & .006, some people suggest a .003 and .005 but .003 & .005 feeler gauge shows them almost loose... So I believe I'm in the ballpark...

Have gone over engine and its getting fuel, no intake or exhaust leaks, choke seems to work and solenoid on float bowl seems to work....

Runs great, once started....

Any suggestions appreciated...

Dale

 

[RandyT]

Make sure the choke is closing all the way. Just take a few thousands from complete close to make hard starts. Happens a lot with the single throttle/choke control systems. Cable slides in the clamp or gets some wear/slack in the cable and then choke doesn't close properly.

 

[Fuddy1952]

Can you start it easier with starting fluid? Of course air filter off, no choke (open).
New spark plugs? Check spark intensity?
Is it cranking over fast? Of course plugs out it will crank faster...but does it have a good intense spark?

 

[Maxify55]

You didn't mention that you'd moved the motor to TDC on either cylinder for the test.
It's critical that you do it for the gap set

 

[WranglerX]

You didn't mention that you'd moved the motor to TDC on either cylinder for the test.
It's critical that you do it for the gap set

YEs I followed procedure .. Actually procedure say to go to TDC and with SP out put a dowel in spark plug hole and go past TDC till dowel moves in about 1/4 inch...

Good spark, not new plugs but they are burning clean (light tan/brown) and are gapped properly.......

And yes starting fluid (actuall carb cleaner- less volatile than ether) helps...

Dale

 

[Travelover]

Have you taken a compression test? To run, you need adequate compression, fresh fuel and a properly timed spark. The problem is always one of those three, though it is often not obvious which is the problem.

 

[bindian]

Rebuild the carb after giving it a soak in an ultrasonic cleaner. You might have blockage around the idle jet.
hugs, Brandi

 

[Richard001]

YEs I followed procedure .. Actually procedure say to go to TDC and with SP out put a dowel in spark plug hole and go past TDC till dowel moves in about 1/4 inch...

Good spark, not new plugs but they are burning clean (light tan/brown) and are gapped properly.......

And yes starting fluid (actuall carb cleaner- less volatile than ether) helps...

Dale

Does the engine crank well with the starter? As others have implied, if the valves are not set correctly, the compression release will not function properly thus not allowing the engine to crank at a speed needed to start.

 

[WranglerX]

Battery and starter are good, cranks good.... Valves are set buy the book.... Actual starts easy when hot...

Issue with starting is when it has set for a week or two without being run ... Probably should have mentioned this in first post...... Much like carb bowl is dry and won't fill.... Suspect fuel pump, but then once it runs a bit it starts easy...

Dale

 

[Richard001]

DL,
If you don't have the service manual for your engine, go here:
https://www.mytractorforum.com/threads/briggs-statton-repair-manuals.242387/

As someone else said, make sure your choke is working properly.

This engine useis a pulse pump. Could be that it is not working correctly. Check the pulse line.

From the manual:
FUEL PUMP
The fuel pump, mounted on the No. 1 cylinder shield,
allows remote fuel tank installations. The fuel pump will
prime at 12” (30.5 cm) maximum lift. Fuel pump pressure is
1.5 psi (0.1 Bar ). The pump is operated by pulsating
crankcase vacuum from the engine. The vacuum pulse line
is installed on the No. 1 cylinder valve cover, Fig. 33.
Note: Fuel pump is available as an assembly only.
Replace fuel lines and vacuum pulse line if stiff and brittle.
Note: An air leak at the fuel pump pulse line hose
connections will result in improper fuel flow.


Richard

 

[WranglerX]

DL,
If you don't have the service manual for your engine, go here:
https://www.mytractorforum.com/threads/briggs-statton-repair-manuals.242387/

As someone else said, make sure your choke is working properly.

This engine useis a pulse pump. Could be that it is not working correctly. Check the pulse line.

From the manual:
FUEL PUMP
The fuel pump, mounted on the No. 1 cylinder shield,
allows remote fuel tank installations. The fuel pump will
prime at 12” (30.5 cm) maximum lift. Fuel pump pressure is
1.5 psi (0.1 Bar ). The pump is operated by pulsating
crankcase vacuum from the engine. The vacuum pulse line
is installed on the No. 1 cylinder valve cover, Fig. 33.
Note: Fuel pump is available as an assembly only.
Replace fuel lines and vacuum pulse line if stiff and brittle.
Note: An air leak at the fuel pump pulse line hose
connections will result in improper fuel flow.


Richard

Pretty much leaning towards fuel pump, thanks for information.... Though as crosses my mind too if the was a really small (fuel rate) electric pump out there that would replace pulse pump and insure fuel to carb bowl... But it was just a thought...

Think after it sits a few days I will turn key on so solenoid will open flow to bowl and prime carb bowl from fuel line and see if it really is a pump or carb issue, if fuel line is "overflowing" and solenoid open (bowl full), and it starts right away, then it just might be pump....

Dale

 

[RandyT]

Pretty much leaning towards fuel pump, thanks for information.... Though as crosses my mind too if the was a really small (fuel rate) electric pump out there that would replace pulse pump and insure fuel to carb bowl... But it was just a thought...

Think after it sits a few days I will turn key on so solenoid will open flow to bowl and prime carb bowl from fuel line and see if it really is a pump or carb issue, if fuel line is "overflowing" and solenoid open (bowl full), and it starts right away, then it just might be pump....

Dale

That solenoid that you are talking about doesn't have any control over the fuel flow into the carb. That is the float needle that does that. the solenoid has one purpose and that is to try to avoid the bang on shutoff. Like I mentioned earlier sounds like a choke that isn't closing all the way. Have you tried putting a small amount of gas into the intake and then trying to start with a prime fuel, to see what it does. those pulse type pumps don't fail as often as people think they do, and change them out because they suspect that is the problem when it really isn't.

Just for a little background I am a 22 year experience Briggs Master Service Technician.

 

[WranglerX]

That solenoid that you are talking about doesn't have any control over the fuel flow into the carb. That is the float needle that does that. the solenoid has one purpose and that is to try to avoid the bang on shutoff. Like I mentioned earlier sounds like a choke that isn't closing all the way. Have you tried putting a small amount of gas into the intake and then trying to start with a prime fuel, to see what it does. those pulse type pumps don't fail as often as people think they do, and change them out because they suspect that is the problem when it really isn't.

Just for a little background I am a 22 year experience Briggs Master Service Technician.

I may have found issue.... Hose (vacuum) for valve cover to pump is aged and appears it may be partially split.... Would seem to affect pump operation... Also engine was run yesterday, but today fuel filter is empty as if all fuel has drained back to tank... That seems odd to me...

Think I may be onto something here...

I need to order new hose to see if it is issue, maybe local B&S dealer will have hose....

Dale

 

[RandyT]

Split will cause issues. Will cause symptoms similar to a bad fuel pump since it can't get the impulse from the crankcase to actuate the diaphragm. I would worry too much about the fuel filter draining since the impulse line shouldn't have any effect on it. Temp changes can drain the fuel filter due to vapor pressure changes. Just make sure to also check the fuel line from the filter to the pump for any cracking because that can allow drainback.

 

[Richard001]

I'm with RANDYT on this.

Richard

 

[mike48130]

I think these pulse pumps have a check valve in them by design. It should not be completely draining the filter. Make sure the cap on the tank is venting properly, that could add to the hard start and fuel being sucked back to the tank.

 

[WranglerX]

I think these pulse pumps have a check valve in them by design. It should not be completely draining the filter. Make sure the cap on the tank is venting properly, that could add to the hard start and fuel being sucked back to the tank.

I am thinking fuel should not be sucked back out of filter either.... It's sort of contrary to all I know about fuel systems... Will check tank venting just in case...

Got new pulse/vacuum hose and fuel filter yesterday maybe get them on soon and see what happens... Will also inspect rest of lines and such when I have it in shop....

Dale

 

[WranglerX]

Well this is what been done so far..

Replaced faulty vacuum hose to fuel pump.
Replaced fuel filter.
Adjusted choke cable to ensure full choke.
Checked vent in fuel filler cap (clear).
Check all fuel line and they appear good.

Guess it going to be a time thing, probably going to have to sit a few days to see if "hard start" issues are solved....

Dale

 

[radios1]

for some reason, JD had their Briggs engines made with a PLASTIC needle valve, which swells, and sticks closed a rebuild kit contains the proper stainless steel needle valve.. I had this happen on My JD la145!..

 

[WranglerX]

for some reason, JD had their Briggs engines made with a PLASTIC needle valve, which swells, and sticks closed a rebuild kit contains the proper stainless steel needle valve.. I had this happen on My JD la145!..

Yeah... Had issue on another engine that they uses neoprene (or something goofy plastic) for float needle seat and it would swell up... Rather not go into carb If I don't have to...

Dale