Accelerator pump

[pigeon laker]

I own a merc 115 2+2 and have a quick question about the acceleator pump.Is this thing actually a pump or just a switch.It has a fuel line in from the carbs and the fuel line out to a filter and to the bottom 2 cylinders.I know the theory as to what it does(adds fuel directly into cylinder 3 and 4 once opened by throttle position)What powers it?It seems just like an open or closed switch and if it was removed and the fuel line from the carbs connected directly to the cylinders you would have full time operation of #3 and #4.As well the high speed jets on #3and #4 carbs are smaller than #1 and #2 to compensate for the injectors connected to the cylinders from the accelerator pump.Seems simple but very confusing at the same time

 

[racerone]

Re: Accelerator pump

You have me confused with what you are trying to achieve here.

 

[pigeon laker]

Re: Accelerator pump

To eliminate the acceleator pump(if it is really just a switch)and run full time 4 cylinders using the injectors connected to the accel pump as the low speed jets.

 

[Faztbullet]

Re: Accelerator pump

The accelerator pump is a pump, it squirts when its pressed in. The pressure is needed to unseat needles in injectors and its only a couple of cc's injected. If you bypassed accelerator pump like your saying the bottom cylinders would flood all the time as theres no way to meter fuel/pressure from fuel pump. Also they wont idle on all 4 as they idle like s**t and shake themselves to pieces.That why this is set up like this...

 

[wired247]

Re: Accelerator pump

If you want to run it as a full time 4 cylinder you will need to replace the 2 lower carbs .

 

[pigeon laker]

Re: Accelerator pump

What powers the pump?Isn't a pulse line needed to move a diaphram or something.If it just squirts a small amount of fuel when activated isn't just a metering switch?Won't the injectors on the cylinders meter the fuel?Less RPM's , = less fuel pressure,means less fuel pumped.
I hope it doesn't seem like I'm being difficult.I'm just very curious as to how this pump actually is useful.I'm pretty sure that I'll try it and see what happens.Also,any idea why these motors will"shake themselves apart" if idling on four cylinders.

 

[Faztbullet]

Re: Accelerator pump

What powers the pump?

The accelerator pump is depressed by cam and it squirts a high pressure fuel charge to the injectors, its like a syringe as nothing happens til plunger is depressed.

If it just squirts a small amount of fuel when activated isn't just a metering switch

No as it only holds a set amount of fuel, once its depressed all the fuel in chamber is gone and it will not refill till throttle is brought back to idle

Won't the injectors on the cylinders meter the fuel?

No as they are not a jet and really not a injector per say, more like a check valve.

.I'm pretty sure that I'll try it and see what happens

If you go bypaasing like you stated all your going to do is possible damage motor as you will be dumping raw fuel in cylinder which can :1) wash cylinder and cause seizing 2)hydraulically lock engine damaging pistons & rods. The engine does not run on wet fuel but atomized fuel charge and the reason they shake apart as told by Merc rep is you cannot get idle rpm low enough with 4 carbs(think of it as 4 independent 1 cyl engines) and timing has to be retarded so much they load up and shake like dog crapping a peach seed..

 

[racerone]

Re: Accelerator pump

Outboard motors rarely get a chance to wear out.----They are usually thrown in the scrap pile because the owner made mistakes !!

 

[wired247]

Re: Accelerator pump

retarded so much they load up and shake like dog crapping a peach seed..

Thank you for that visual and the phrase to yell at my kids .

 

[pigeon laker]

Re: Accelerator pump

The accelerator pump is depressed by cam and it squirts a high pressure fuel charge to the injectors, its like a syringe as nothing happens til plunger is depressed.

No as it only holds a set amount of fuel, once its depressed all the fuel in chamber is gone and it will not refill till throttle is brought back to idle

No as they are not a jet and really not a injector per say, more like a check valve.

If you go bypaasing like you stated all your going to do is possible damage motor as you will be dumping raw fuel in cylinder which can :1) wash cylinder and cause seizing 2)hydraulically lock engine damaging pistons & rods. The engine does not run on wet fuel but atomized fuel charge and the reason they shake apart as told by Merc rep is you cannot get idle rpm low enough with 4 carbs(think of it as 4 independent 1 cyl engines) and timing has to be retarded so much they load up and shake like dog crapping a peach seed..

Thank you for your help.I was unaware that the pump only gives a shot of fuel and thought it was supplying it the whole time it was activated.So much for that idea.