Briggs 18 HP Hard to Start

[Ss4000]

I would try a lighter weight oil if you have not already done so for this extreme cold weather. Also, just use a squirt of starting fluid if that is not a problem for your circumstance. Hope these ideas help.

 

[Ss4000]

Also, any chance fuel line freezing? Just trying to take a guess.

 

[TobyU]

What would I do besides making sure the valves are adjusted properly?

Nothing, because that's not going to be the problem. If you adjusted the valves even close when you did it.....
They don't get tight on these. They get loose

 

[TobyU]

I really appreciate everyone's patience with this. Visually, it looks like the choke is closing. I adjusted the cable back, and it does seem to start easier. Not sure if the easier start was from the cable adjustment or because I started it about 4 hours ago. It is -15 wind chill here in WI! How far back can the cable be adjusted? I'm wondering if this has been adjusted in the past. The cable casing does not protrude beyond the adjuster. The electric fuel pump concept is interesting.

It's not a matter of how far back out can be adjusted. Only rarely will you have one that won't work at buy choke and stop.
Since choke is most important for this situation, you have someone hold the handle control to full choke and then you loosen clamp and move cable outer part until choke is fully closed and tight.
Then tighten clamp.
Then move lever back and forth to make sure it's is still closing fully.
Sometimes you have to have lever like 1mm just a little bit not all the way to choke and do this same procedure so when you push lever all the way it is pushing choke even more toward full closed.

 

[batrater]

This is good info, I have the exact same problem with my 16 hp v-twin cub cadet, (I know the choke works great) I keep a spray bottle with gasoline handy, a quick spray directly into the carburator fires it up on first crank, sounds like I have a vacuum problem from what I'm reading

 

[TobyU]

This is good info, I have the exact same problem with my 16 hp v-twin cub cadet, (I know the choke works great) I keep a spray bottle with gasoline handy, a quick spray directly into the carburator fires it up on first crank, sounds like I have a vacuum problem from what I'm reading

Not necessarily but you should look into it. The only thing you know for certain is it's not getting enough fuel into the intake when you start it unless you spray the gas in there yourself.
You need to get in there and make absolutely certain the choke is shutting all the way because on those newer v twins it's usually a little rod you can reach down with your finger and move up and down. You will often find that when the choke is fully on you can reach down and push the lever rod a little further up which is closing the choke fully. Try that next time.
If you're starting the mower within 5 to 10 days of the last time you started it the vacuum shouldn't even be an issue.
The bowl of the carburetor should still be almost full and most the time it's still completely full because any amount that is evaporated the float has allowed more to come in and there's still more in the fuel line to trickle in as you don't really need gravity pressure or the pump from the fuel pump to let a little bit more like that flow in.
The only time the vacuum comes into play is if the bowl has gotten below let's say half full or even empty because of a slight seepage or leak. In this case the engine has to continue to crank and provide proper vacuum to the pulsator pump until it can fill the bowl back up before it will be able to suck the fuel up the venturi tube and into the intake.
It's also possible, of course a lot of things are possible that aren't supposed to be, that the needle valve in the carb is not actually shutting off properly which is a common problem on older engines.
This allows the throat of the carburetor to puddle or pull up with gas.
On a gravity tank without a fuel pump it will continue to flood and leak and smell up your garage etc and be very hard to start and require no choke to start and then smoke some white puff of smoke when you first fire it up BUT on a fuel pump motor if the tank isn't very full they won't really be any pressure or way for gas to continue to flow into the bowl so it will only half what kind of in the three or four inches of fuel line before the carburetor and it can flood out the carb and kind of act like a siphoning action and then that can evaporate because there's no more fuel to come after it to keep flooding out. So the bowl can be lower than it needs to be or should be when you try to start it next time.
This isn't really common but as I said it is possible.
There's several different types of air filter setups on those and some are easier to do this than others but if you can take the air filter off and put the flat of your hand on the plastic inlet area there to block it off completely and put your throttle to fast or choke, doesn't matter and crank it up and see if it starts quicker this way you will also know that it's probably a choke issue.

 

[nthnwdhs]

Briggs 350777 Replaced plugs, coils, adjusted valves. Have to turn it over for 20-30 seconds to get it to start. Once started runs fantastic. What am I missing? Some kind of fuel problem? Replaced fuel pump a couple of years ago.

Not sure if you've tried this, dismissed it or even if it applies to a BS carbi but I watched this video a while ago on how a carburetor works - it explains the four circuits of a carbi. What you've described here sounds like the starter circuit in the carbi not working but the main circuit working fine.

Here is the video:

and at about 3:12 it shows the 4 circuits. Maybe you just need to clean the carbi?

 

[bk10s]

Thank you for sharing. We are out of town until Sunday, and then I will be back at it!

 

[TobyU]

Not sure if you've tried this, dismissed it or even if it applies to a BS carbi but I watched this video a while ago on how a carburetor works - it explains the four circuits of a carbi. What you've described here sounds like the starter circuit in the carbi not working but the main circuit working fine.

Here is the video:

and at about 3:12 it shows the 4 circuits. Maybe you just need to clean the carbi?

I'm assuming all of that's true without actually watching the video but it's from one of those engineers standpoints.
Technically you could break down the circuits into four circuits of a carb like that but people really don't.
Sometimes for clarification or educational purposes I will tell customers that there's two basic circuits on a carb and I don't mean the ones they're talking about. I mean the air and the fuel because people think sometimes that a dirty air filter or dirty Dusty conditions causes the mower not to start and run after stuff gets in the carburetor and clogs up the jets.
I explained to them that that's not the case and all the clogging internal carburetor passages has to come from what's in the gas tank or from the fuel itself congealing etc or water grease bubbles what have you.
The fuel and air never actually mix at least not until the very very end and only when the engine is running. No matter how much dirt and dust you operate the lawn mower in even if you do it without an air filter, which is bad on the engine especially the rings and cylinder walls etc even though people have gotten by with it for years, you're not going to get dirt into the carburetor bowl and clog up the jets.
But as far as what this video is relating to most people just refer to the running circuit and us old text or younger ones with lots of experience especially with older equipment will refer to the primary and secondary circuits or Jets or the high speed and low speed.
It's a little clearer when you start looking at the two cycle or similar engines with the very small carbs with two separate mixture screws.
One literally controls the gas flow at larger throttle openings and the other one controls the mixture at almost closed throttle idle.
In the old days pretty much all equipment had two mixture screws along with your minimum idle speed. Lots of people confuse idle stop screws for mixture screws.
You had the large one you could operate with your thumb on the bottom of the bowl that screwed the needle up and down and adjusted how much fuel could get sucked through the carburetor from the Venturi effect of the air going down the throat with it running then you had the smaller one up higher on the carb that controlled your idle mixture when the engine was running at idle and much slower speeds.
What they're going to call the choke or starting circuit most people just refer to as a choke or whatever it doesn't really deserve being called its own separate circuit.
Again, in the old days you had a choke that was a butterfly that closed just like putting your hand over the throat of the carb. Then they went to a primer bulb which squirts gas right into the carburetor actually by blowing air into the bowl which displaces the gas up the metering rod tube emulsion tube whatever you want to call it into the throat of the carburetor the exact same way it gets sucked up through his little straw like hole when the air is rushing over it.
There's other ways to do it but that's the two main ways.
Motorcycles have typically used a different approach and some of the small newer handheld blowers and trimmers , especially the last of the two cycle ones used a similar approach to the motorcycles as in an enriching situation which they would call a enriching or riching circuit but like I said most of us don't bother to consider that really its own separate thing.
Most the time you're dealing with a choke and it's not like it can get clogged up or anything. The flat / butterfly either closes all the way or it doesn't.
It is worth noting there has been a couple of tsbs and revisions over the years mainly on Briggs & Stratton but it's probably happened elsewhere where they made the butterfly with not complete coverage of the whole and they left a cutout in the corner. Often on equipment they would be holes drilled in the butterfly too so they could have just enough sealing without flooding it. Some of these I think it was the overhead valve vertical crankshaft ready start Briggs had an improved replacement butterfly that you would replace to make them start better.
It's been a few years now since I've had the situation and it could have actually been on a hot restart issue where it was two complete and the new one had the corner cut out because I think I remember modifying one to like the new style and cutting it out myself instead of having to buy one.
Regardless, pretty much we deal with the high-speed running circuit and the low speed idle circuit which on many things isn't even a concern today because for the vast majority of lawn mowers that are standard 21 and 22 walk behind and push mowers, there is no throttle speed so you're never really going to know if it runs well at idle or not unlike a rider or many of the snow blowers.
The trick is knowing that many of these carburetor designs will not run smoothly and even surge extremely like the Chinese Huayi carburetor.
It's common procedure for those of us who actually keep the original carburetors and clean them which is a very good day because most shops and most people throw away a perfectly good carburetor and often replace it with an inferior quality no name carburetor because the factory one is quite good. It doesn't go bad, it just gets clogged up.
The main jet for the primary high speed running circuit is the one that gets it to run but if the secondary or idle circuit is still restricted or clogged it will surge up and down and it will not run at idle..
The old tecumseh's were similar but not as extreme. When they ran but surged about 15 or 20% you could pretty much guarantee you needed to take out the secondary idol circuit jet and run a wire through it and blow it out well with car cleaner and compressed air. Then they would almost always smooth out to 100%.
These are the tricky circuits that you have to worry about and that's probably why that's almost of us are concerned with. The choke is fully mechanical and easy to inspect and observe correct operation or not.
Air is also obvious as I do get a number of mowers in every year that will not start and run or run properly and the only reason is the air filter is so clogged up they cannot breathe..

 

[NeilH]

Hello B. I have read the thread of your difficulties and suggestions. I'm not a mechanic but am old enough to have had experience. It reads to me as fuel supply trouble. Pardon me for asking simple questions. Do you have that inline fuel filter installed correctly? If not, it may have a check valve that is preventing fuel flow in the right direction. If you have spark while you turn the engine over with the spark plug(s) out, try spraying in some gas into the cylinder(s), replace the plug (even finger tight for now) and see if the engine fires. If it fires right away, then you likely confirmed that fuel supply is the issue. I recently had a grain auger engine that needed choke to run and then eventually would die. In checking the fuel system and taking off the fuel tank to check for debris, I found that the shut-off valve at the bottom of the fuel tank had vibrated to almost be closed. That had been an undiscovered problem for a few times in using that engine.

Regarding spark, your posts sound like you would know this, but check for spark and spark quality. Spark should be good because you replaced the spark plugs and coils. Your engine may not have a set of points but, if it does, check the points. Timing being off can be a problem also. I have a Tecumseh mower engine that has a key in the flywheel that, over time and use, becomes bent enough that the engine won't start or run well so I have needed to replace that key.