Excessive smoke, hard idling, and electronic pumps runs constantly after alotted time

[OceanContender25]

I have a 2000 2stroke LX150hpTXRY. The engine has been running very rich, which causes it to smoke and idle rough. I looked this problem up in my yamaha outboard shop manual. It says that there is excess fuel getting into the chamber through the vapor seperator tank vent line and to inspect the components in the vapor seperator tank.

While I was troubleshooting this problem I found out that my electronic fuel pump is not shutting off after, an alotted time, you turn the ignition key to the on position.

That being said, How does the electronic fuel pump know when to shut off? I know it shuts off via the CPU, but does that get an electronic signal from some other source. How is the pressure regulator, on top of the VST, incorporated into all of this? Does the float inside the VST have any reason to contribute to this problem?

[rodbolt17]

at key on the ECU powers up the main relay AND applies a ground on the fuel pump for 3 to 5 seconds.
pressure above about 45 PSI will make it run rich, a blown lift pump diaphram will make it rich and a leaking float needle will flood the lower cylinders via the chamber vent line to the intake manifold.,

[jb123]

unbolt the 2 pumps , leave hoses intact and pump ball,see if any fuel comes out of vac port, if so replace...post results

[OceanContender25]

If I understand correctly the ECU is not cycling properly and the problem is in the ECU. The problem of the pump running continuously is because of the ECU.

[jb123]

have you tested fuel rail pressure? sounds like it never reached full pressure, so it keeps running/trying
cleaned or replaced vst filter?
whats the fuel level of the onboard filter when the issue occurs?

[OceanContender25]

jb123,

I replaced the vst filter 3 months ago. The level of the onboard fuel filter is full. Tomorrow I am going to switch my vst tank out from the other engine to try and pin point the issue. I will also take the diaphragm pumps off and test those.

rodbolt17,

If the other tank runs fine it should pin point it to the components with in the vst tank. Then I will inspect them to see what may be the problem. I will post results afterwards.

Thank you both for the suggestions.

[OceanContender25]

I switched out the vst tank on the motors and the electric fuel pump is still running constantly. My next move is too switch out the ECU to see if thus is the problem.

I checked the diaphragm pumps and they are not leaking. I did not check to see if the vst was overfilling due to time. I'll keep you posted.

[Tucker]

I did not check to see if the vst was overfilling due to time. I'll keep you posted.

How do you check? Remove the vent line from the silencer and see if gas is coming out?

[OceanContender25]

Tucker,

You can check to see if it is overfilling by removing the vent hose on top of the vst. When the engine is running it will come out of the vent line outlet atop of the tank.

When I check this one, I will install the bad vst and I will not reconnect the vent line. When removing the vst tank from the engine you will notice that the vent lines, ontop of the vst, branch into a single hose behind the vst. I disconnected the vent line here. When installing it will be easier.

[OceanContender25]

Just wanted to let everyone know I have been at sea for the last 3 weeks and will not be able to get back to this problem until I get back in about another 3 weeks. Thank you for all of your suggestions thus far.

[OceanContender25]

Same Problems.

Due to irritation I decided to not look at the engine for a while and am now revisiting it.

I ran the engine and am experiencing the same problems. I thought I had fixed it and the problem has come back. I ran it last month and it ran great in a heavy sea. Afterwards, I went inside to and went down the intercoastal to open the engine up. It seemed to be fine then too. After I throttled down and turned around it completely bogged down and wouldn't even start. Since then:

I have pulled the injectors and cleaned along with their filters. Injectors where tested with a 12 volt battery and are operating. I have pulled the diaphram fuel pumps and inspected plus rebuilt spares. I have Sea Foamed the block on the plug and injector side. I have pulled and cleaned the filter on the VST tank and cleaned. I have checked for spark and all seems to be ok.

It should be noted that the plugs are wet. I don't know if an injector isn't seating properly or not. I would have to check the pressure on the rail before I can determine if this is the cause. I'm just having a hard time rigging a gauge to the fitting near the vst tank it looks similar to a tire air fitting.

I am at a dead end and was wondering if anyone has any suggestions?

[BaileysBoat]

at key on the ECU powers up the main relay AND applies a ground on the fuel pump for 3 to 5 seconds.
pressure above about 45 PSI will make it run rich, a blown lift pump diaphram will make it rich and a leaking float needle will flood the lower cylinders via the chamber vent line to the intake manifold.,

Also, a bad fuel pressure regulator will leak at the vacuum port allowing fuel to be sucked into the motor. Pull the vacuum line and check for fuel, should be none. A vaccum tester should not leak down. The pressure regulator dumps fuel back into the VST in response to engine load (Vacuum),

To test the fuel pressure use an automotive fuel pressure tester with a GM adapter.

Next I would check the HP ground circuit. A short to ground would cause the pump to run any time the key is on.

I wish I could offer more but my expertise is 4 stroke.

Good luck

[Tucker]

Bailey's Boat certainly shed good light on this. I've had 2-HP pump test gauges and both had the wrong fittings on the end, didn't know it was a GM schrader valve. Also, good info on a regulator failure, Did you check the regulator screen? If the HP pump screen and inj screens were clean, chances are good the regulator screen is clean. Pressure above spec=clogged reg screen. Pressure below spec=clogged HP pump screen.

[OceanContender25]

Results so far

Thank you baileysboat for the advise on the pressure gauge. I went out today and purchased one. I tested both engines for a comparison. Results are:

Port - Key turned to on = 50 psi. Engine Running - Idle = 44 psi. Engine Running around 2k rpm = 58 psi.
Starboard (the one with problems): Key Turned to on = 38 psi. Engine Running - Idle = 40 psi. Engine Running at 2k RPM = 40 psi.

I had no leaking on the vacuum line. I also switched injectors from the port to the starboard engine and experienced the same pressures.

My next move is to switch VST tank, fuel rail, and hoses between engines to try and narrow this down. If I still have an issue I know that it has to do with the electrical operating the HP pump(ground) as stated before. Gremlins can't ever get rid of em!!!!!!

[rodbolt17]

why not clean the pressure regulator screen?
thats the issue.
50 psi makes it run very rich.