Up next in 10
Mercury Outboard Fuel Problem
215 views
Aug 16, 2024
Learn More About Your Boats Systems By Joining The Born Again Boating Academy! https://www.bornagainboating.com/ Get Your Born Again Boating Clothing! https://www.bornagainboatingshop.com Get Savings On Boat Parts With BAB Coupons At Partsvu Here: https://shareasale.com/r.cfm?b=1991037&u=3159438&m=119617&urllink=&afftrack= Please Buy Anything From This Link To Amazon & Help Us Keep Bringing You Content!!!! https://www.amazon.com/?&_encoding=UTF8&tag=bornagainboat-20&linkCode=ur2&linkId=97bb1968e1ac47dfc3703d401d95fb5a&camp=1789&creative=9325 Join this channel to get access to perks: https://www.youtube.com/channel/UCWZhbfXDCg7_PvlwvierP1A/join Join this channel to get access to perks: https://www.youtube.com/channel/UCWZhbfXDCg7_PvlwvierP1A/join Subscribe To Our Podcast! The Boater's Podcast: https://www.youtube.com/channel/UC6Y2xnr23ERD2n_t51Jv4-Q?sub_confirmation=1 ------------------------------------------------------------------------------------------------------------------------------------------------------------- PARTS USED: ------------------------------------------------------------------------------------------------------------------------------------------------------------- DONATE
View Video Transcript
0:00
This is a Mercury fuel supply module or FSM
0:03
Now, they have stopped using this system since like 2018 or so
0:07
but they did utilize it for a lot of years from 115 horsepower
0:12
all the way up to like a 275 or even a 300 verado
0:16
depending on the model and year it was made. Now, the new style doesn't have all these floats
0:21
but we have seen a lot of questions about this FSM and how it works with all these floats
0:25
The main one is that we've got a person that's got twin, six-cylinder vera
0:29
of four strokes and they have a critical 207 code can they be reset with a scan tool or do we need to remove the fsm and
0:38
unstick them so the fuel is going to come into this position right here this is going to be low
0:42
pressure and this right here is going to be our low pressure fuel pump that is going to suck the
0:50
fuel from your boat into this fSM it is going to fill up this canister then it is going to
0:56
pressurize that fuel with this pump here being your high pressure pump and that is going to send the fuel out of here to your fuel rail and all of your
1:05
injectors. Now what most people don't realize is there are more parts in this system. So you have this
1:11
right here which is the pressure regulator and that has a hose on it that goes right here. That's
1:18
going to come out of this back hose right here and it's going to go to your intake. This hose can
1:24
break and if that hose breaks the vacuum that is in the intake is usually
1:29
operating this fuel pressure regulator. If this hose breaks, which it can, it will suck fuel from
1:36
this fSM up through this hose into your intake and it will completely load your engine up with fuel
1:42
So if you have an engine that has a crankcase completely full of fuel, most likely this hose right here is
1:49
broken and is filling up your engine with raw fuel. Then we have this item right here. This is the
1:55
float switch. This is what everybody thinks is always the problem, but it isn't always the problem
1:59
This float switch is going to be the fsm float switch This is monitored by the engine computer This flow switch is being monitored by the engine computer So the way it works is whenever the float switch is down at the bottom it will say low and that will signal the computer to turn on the low pressure pump that will suck fuel from the fuel tank and fill up that fSM
2:25
Certain models would have certain ranges. Usually it would turn the pump on for 20 seconds
2:32
There are some older models that would turn it on for longer than that, but generally it is
2:38
20 seconds. Then that float would go to high. As soon as the float hit the high mark, it would tell
2:44
the low pressure pump to turn off. So that's how it would turn on the low pressure pump. When the
2:49
flow went down, it would turn the pump on. When it went to high, it would turn the pump off. If the
2:54
float switch went to low and turn that pump on, and after 20 seconds, the float switch never went to
3:00
high, the computer would automatically turn the low pressure pump off and would throw a code
3:05
for a lift pump timeout, meaning that the lift pump turned on and then timed out because it never
3:11
saw that float switch go too high. So generally, a bad float switch or a stuck float switch
3:18
would cause a problem. Now, if the float switch is stuck in the high position, then the lift pump
3:24
would never turn on, basically, and you would run out of fuel very quickly. And then if it would
3:29
stick at low, it would lift pump timeout, and you would not be able to pull fuel and you'd run out of
3:34
fuel that way too. But there are other failures depending on whether or not it's getting the right
3:40
amount of fuel or if the screen is dirty or if the flow switch is broken in either way. It could
3:46
give you other issues and other codes depending on what it is seeing. Now this float switch is
3:51
normally going to have a red wire on it. If it has red wires, that means it is newer or it is an
3:57
updated flow switch. The old ones were white and black. So if you open up your fSM and you see a white
4:04
or a black wire on that float switch. You need to replace the float switch that is an old
4:09
style and it is getting ready to fail at some point in time if it hasn't already. Also while you're
4:15
in there, that hose that goes to the pressure regulator, you need to squeeze it to make sure
4:20
that it is hard If it is not hard and it is soft that is another problem There is an updated hose for that too though there are probably not too many of these still out there but it still good information to know
4:31
Now, the other problem is that there is another float switch in the system
4:36
And that float switch is going to come out of this hose right here, and it's going to go up to another float switch
4:43
which is going to be over here. So this hose is going to have a hose that comes up off of this, which goes over
4:51
over to here, this one right here, boom, it connects to here, then it's going to come over and up to this hose
4:58
which goes to this item here. This is a float switch that they call a vent canister. It's basically still a
5:06
float switch, but it is a vent canister because there is a float in here, and if you have a
5:11
problem within this fSM, and the lift pump doesn't turn off, and this never changes, and this
5:18
fills up with fuel, it will then vent out of this up through that hose into this canister
5:24
Now, if this canister's float switch goes from low to high, meaning that this right here is full
5:31
it is going to operate this right here, which is called a purge valve. And this purge valve
5:36
if it sees this float switch go to high, it is going to automatically close that because this
5:40
goes over to your intake and it will just dump it into the intake, but it will close that
5:45
because it does not want that to happen. It doesn't want to just be pouring fuel all over the place
5:50
That's why this is so important. So in the event of a problem being with the FSM and it fills up that vent canister
5:56
and moves that float switch to the top, it closes the purge valve so that way you don't have a fuel leak
6:02
Now, this is very important because any one of these issues can throw different codes
6:07
What you see on your gauge might not necessarily be the exact code that you need to be looking at
6:13
because there is only a set number of codes that you will see on a gauge or on your Vessel View mobile
6:18
or any of those other things that display codes because they're all universal codes
6:23
Now, whenever you hook it to a computer, the computer tells you all of the different information
6:28
It's going to tell you exactly what part and how long and all the parameters that you need to see
6:33
in order to separate each one of these components Now in the case of our issue where we have two separate engines giving the same code pertaining to a float switch this is the
6:44
problem that I would most likely be looking at in this situation. Seeing you have
6:49
two engines with only one common denominator being the fuel tank. So generally now
6:55
that you know that the FSMs can fill up with fuel and then the fuel can go up
7:00
to that vent canister and move that float switch to the top which is going to
7:04
close your purge valves and as soon as that closes, I don't think it turns on your lift pumps
7:09
So you'll have a lift pump timeout or you'll have a 207 code or you have any other kind of code
7:14
not exactly sure what you're going to see depending on what gauge you're looking at as far as the
7:19
actual code goes. But most likely, this situation sounds like somebody filled a tank up full of fuel
7:27
and then trailered the boat as you're going around bouncing up and down. So you've got your engines
7:34
trimmed up like this and you're driving around, that fSM and all the fuel that's in the tank
7:39
is going to be forcing its way to the back. It's going to fill the fs and it's going to be
7:43
pushing it up into the engine, which is going to push it up into that vent canister, and that
7:49
vent canister is now going to be all the way up. So most likely, whenever you back down the ramp or
7:55
whatever the case may be, you have taken fuel and it is forced this way up into the vent canisters
8:01
and that is most likely what the problem is. Those float switches are both at high
8:08
not necessarily that both float switches in each individual FSM have gone bad
8:14
That is pretty unlikely for that to happen because it's two separate engines
8:19
You know what I'm saying? It's not like on one engine, if it was only one engine, all right, that could be a problem
8:24
But you've got the same problem on two separate engines. Most likely the fuel tank was completely full of fuel
8:31
It got hot, you were tailoring it. When you were going down a hill or backing down the ramp
8:36
it was able to push that fuel up into the vent canisters, moving that float switch to the top
8:41
which is now giving you that code. But now you understand a lot more about how that system works
8:47
and hopefully you'll be able to diagnose any issue that you have with that FSM system
#Boating
#Boats & Watercraft
#Vehicle Repair & Maintenance