Fuel Pump Assumption

[islandhopper]

Would I be correct to assume that if the motor runs good at low cruising speed ----the lower fuel pump is good.

But when you throttle up and it basiclly shuts you down -----the high pressure fuel filter is probably bad.

Good fuel ----good batteries ----fuel filter new -----trying to figure out next step.

 

[JB]

Re: Fuel Pump Assumption

What engine?

 

[Big Keepers]

Re: Fuel Pump Assumption

If you're talking about an EFI outboard there is pretty much no way it will start at all if the high pressure fuel pump is not operating. The fuel rail needs to be pressurized so that when the injectors are told to open, pressurized fuel is injected. If the filter is new I can't imagine how it can be bad. A fuel line may be crimped or pinched or maybe an electrical connection is loose.

If you're talking about a Yamaha 2 stroke like mine ('87 200hp) then my guess is the second fuel pump is needed to deliver enough fuel to the carbs for high rpm needs. I am curious myself as to why I have two fuel pumps. Maybe I'll get an answer here.

Anyhoo as was mentioned we need to know what kind of motor you're talking about.

 

[islandhopper]

engine

engine

Sorry ------2003 Suzuki 140df 4 stroke
I know there is one fuel pump that is easily accessable ---been told that there is another one and that it has a screen/filter that could be the problem.
Just ran it again ---same thing 3400 is all I can get --with a little (very little) sputtering. @ 2600 ist's like nothing is wrong. One of fuel gauges doesn't work -----that wouldn't have anything to do with it ---would it?

 

[Big Keepers]

Re: Fuel Pump Assumption

Okay,
#1, make sure there is gas in tank(s).
#2 Is the tach flashing code lights at you?
#3 When was the VST last serviced?
#4 When was oil last changed?

Sounds like engine is in safety mode or something.

Why do you have more than one fuel gauge?

Unfortunately a motor like that really needs a mechanic certified for Suzuki who can hook it up to the laptop and see if any codes exist, if any sensors are bad, etc. Some things you can do yourself with this motor, some you can't.

 

[clanton]

Re: Fuel Pump Assumption

The first pump, pulls from boat tank, and pushes to engine vapor seperator where the high pressure pump is located, which puts pressure on the fuel rail and injectors.Fuel system failure does not set any codes. You have to check it with a guage. Check at idle and full throttle under load.

 

[islandhopper]

Re: Fuel Pump Assumption

Thanks Guys,

Pretty simple boat. Custom pontoom. 2 20 gal tanks, gas line to valve (to switch between the 2) -----that run into my water separator then to the engine. I run one fuel tank at a time. So I have 2 separate fuel gauges.

No lights flashing.

Oil was changed last week. Couldn't get to the filter --so just changed the oil

Stupid question here -----what is a VST?

When I run the bulb stays firm. Squezing the bulb while cutting out does not help.

Would I be wasting money to replace the low pressure fuel pump?

I'm afraid this is going to be over my head. Just hate to be without boat for so long. Pretty much a novice at engines but want to try what I can first.

 

[rodbolt]

Re: Fuel Pump Assumption

by pumping the primer bulb you effectivly bypased the lift pump, tells me the lift pump is working.
most likly the screen inside the VST,the VST pump or an injector screen is clogged,
now you will HAVE to check the fuel rail pressure.
most automotive EFI testers will work. prices range from 60 or so to my snap-on one at 260.
just depends on how much you use it.
suzuki electronics are very similar in reliability to Yamaha, they simply rarely fail.
most my work is fuel related.

 

[islandhopper]

Re: Fuel Pump Assumption

What is the VST? Is that the same as the Fuel Vapor Separator?

Thanks

 

[clanton]

Re: Fuel Pump Assumption

Yes, inside the housing is a filter, pressure regulator, and fuel pump, high pressure side should be 36 pounds.

 

[Big Keepers]

Re: Fuel Pump Assumption

Also as an FYI you should always prime the engine even if it was running but sat for a few hours or so. At least a squeeze or two. If you don't have enough fuel near the high pressure pump you can burn it out. The vapor separating tank filters gas yet again and also is just that, a vapor separating tank. Pumps cannot pump vapor only liquid, so fuel that vaporizes on a hot day is recirculated back into the bottom of the tank. Some VST's even have cooling lines where cool water will run along the bottom of the housing to keep the fuel in liquid form. Colder fuel is emulsified better because it is more dense.

I asked about flashing lights because if a sensor is bad or something else is out of whack, the ECM puts the boat into safety mode and usually you can only get about 2500 rpm. Enough to get you home, not enough to damage the motor in most cases.

 

[islandhopper]

All Good

All Good

Thank,s for the help -----since the VST ---was buried under the intake ----I took the easier route and it worked out.

Cleaned the fuel injectors ------2 of them had a black looking substance. Piece of cake to take off -----sprayed a little throttle body cleaner on injectors. Engine running better now than it ever has.

Whew -------I was thinking big $$$$$$$$$$$.

Thanks for the info

 

[Big Keepers]

Re: Fuel Pump Assumption

Welcome to ethanol! That black looking garbage was something that ethanol was kind enough to clean off of where ever it originally was and deposit it on your injector. Do you have fiberglass gas tanks? Hope not. Ethanol will dissolve the fiberglass resins and leave them on places like injectors, valve stems, etc., when the engine cools down. Plenty of info on that in other threads here.

In the fall you should have that VST serviced when you winterize the motors this way its ready to go in the spring. VST service is pretty much an every fall type of thing.

 

[islandhopper]

Re: Fuel Pump Assumption

Ran great for about 45 minutes ---then starting the same thing. Pulled over --cleaned them againg and was good for another 45 minutes.

Have new ones on the way ----hopefully they'll last longer.

I have aluminum tanks --thank goodness.

Thanks for the guidance

 

[Big Keepers]

Re: Fuel Pump Assumption

I'd hold off on installing the new injectors until you figure out why the old ones are getting dirty after you clean them. It sounds to me like you have some bad fuel or dirty fuel in the tank. Don't ruin new injectors until you figure out what is causing the old ones to continually get dirty and black. Do you have a fuel/water separator somewhere in your set up between the tank and the motor? Are any other filters clogging or dirty perhaps?

 

[islandhopper]

Re: Fuel Pump Assumption

Good idea. I have a racor with the clear bottom. It's new and no water in it. Then the one fuel filter on the engine. The only thing I haven't changed is the filter within the Fuel Vapor Sepator. I did drain it though. Very slow drain ---just drops ----got enough out to tell that it didn't have any water in it either.