"Priming"The Carb After Period of Non-Use

[TyeeMan]

1995 Volvo 4.3 GS.

I'm sure anybody that has a carburated boat has this same issue. It's either the first start up of the year, or your boat sits for a few weeks, the float bowl in the carb goes dry, so the next time you get to the lake you need to crank the engine for a number of seconds to run the fuel pump to fill the float bowl. Then pump it and then go to start.

Question: My boat has an elecric fuel pump, has any body ever wired in a push button that you could push to run the fuel pump for a number of seconds to fill the float bowl in the carb prior to starting? Then I could just pump it, hit the key and the engine would turn over about 1 revolution and she'd be off and running.

My boat runs great, it just bugs me when I have to crank it for a while just to run the fuel pump to fill the float bowl.

Anyway, does anybody see any potential problems with this?

Thanks for your input.

 

[Don S]

Re: "Priming"The Carb After Period of Non-Use

It could be done, but you would have to splice into a very expensive wiring harness. Are you ready to go there for 5 seconds of cranking time?

 

[TyeeMan]

Re: "Priming"The Carb After Period of Non-Use

I haven't really looked at how everything is wired, but my initial thought was to mount 2 wire weatherproof push button somewhere out of the way on the dash, run two wires back to the fuel pump relay, connect one wire to a hot or hot when the key is on, and connect the other wire to whatever pole on the relay that would run the relay and the pump.

Or something like that. . . . Again, it's just been floating around in my head for a couple years.

 

[jerryjerry05]

Re: "Priming"The Carb After Period of Non-Use

If it's electric it should run till it fills???
Turning over an older motor would activate the mechanical pump and fill the bowl then start.
But an electric should fill itself.
Get back at motor and have some one turn the key on.
Hold the pump and see if it works as soon as the key is turned on. Not the start position,just on.

 

[Maclin]

Re: "Priming"The Carb After Period of Non-Use

Jerry, I'm thinking that if the engine is wired OEM and all components are in working order that the electric fuel pump will not run with just the key in Run/On. The electric fuel pump will only get power if 1.) The engine is running (alternator turning and power supplied from it to the pump) OR 2.) engine is cranking and fuel pump is fed power via the cranking bypass circuit.

It reads like the fuel pump does fill the carb fine, but just needs a couple of 10 second cranking bursts to have enough time to draw the fuel thru the filter from the tank then on up to the carb bowl.

 

[Maclin]

Re: "Priming"The Carb After Period of Non-Use

Tyeeman, I know some have done just what you describe. I am not recommending it, but if you go that route make sure it is good quality and correct gauge wire, and fused, and the push button or lever switch is a spring loaded momentary type.

 

[TyeeMan]

Re: "Priming"The Carb After Period of Non-Use

Jerry, Maclin is correct. The system is designed to run the fuel pump ONLY if the engine is being cranked over, AND obviously when the engine is running. As far as that goes everything works as it should. As far as I can tell the pump runs continually once the engine started, it does not shut off once the bowl is filled. It's a super low psi pump, , 2-6 psi or something like that so it doesn't overcome the needle and seat.

The only reason I'm going after this is more of a personal thing. It would be really cool if I could drop the boat in the water after a couple weeks of down time, pump the throttle and the engine would start after about a 1/2 revolution, , , just the way it does if I use it consecutively for a few days or if it sits just for a couple days.

And yes using a quality, weatherproof, momentary push button or paddle switch with correct wire size would deffinately be done.

Again, just playing with the idea. Thanks for the input though.

 

[dennis461]

Re: "Priming"The Carb After Period of Non-Use

1995 Volvo 4.3 GS Then I could just pump it, hit the key and the engine would turn over about 1 revolution and she'd be off and running.
Anyway, does anybody see any potential problems with this?

.

One big problem, first start after winter, the bowl dried out, the needle is stuck open, you turn on the fuel pump, the engine or bilge gets raw gas in it. :-0

Not worth the risk. IMHO Keep a good battery in the boat, stop worrying about a long crank.
My engine bay is wide open, so I sometimes use spray starting fluid.
For my first ride after sitting; Start fans, one shot into the air cleaner, put the spray can back in the tool box. Turn the key.

 

[ewenm]

Re: "Priming"The Carb After Period of Non-Use

problem i saw with a mercruiser 4.3lx was that the electric fuel pump would NOT run unless there was oil pressure, so that required a lot of engine cranking to get oil pressure and then more cranking to get fuel pumped. what a pain

i dont know if the VP is the same maybe worth a look.

 

[Don S]

Re: "Priming"The Carb After Period of Non-Use

problem i saw with a mercruiser 4.3lx was that the electric fuel pump would NOT run unless there was oil pressure, so that required a lot of engine cranking to get oil pressure and then more cranking to get fuel pumped. what a pain

i dont know if the VP is the same maybe worth a look.

Merc does not use the same system as Volvo, so no, oil pressure or an oil pressure switch has nothing to do with it.

Here is how and when a Volvo electric fuel pump system works from a previous post.

The relay will NOT be energized with just the key on and the engine not running. As soon as you turn the key to start, the relay is energized from the ignition switch from the yellow/red wire. Once the engine starts, power is delivered to the relay via the green wire from the alternator.
There are diodes in the system to prevent back feeding the wires.
Here is the wiring diagram for the relay and pump, should make it a bit clearer.

 

[Grub54891]

Re: "Priming"The Carb After Period of Non-Use

Yeah starting fluid....:facepalm: Really?
Grub

 

[TyeeMan]

Re: "Priming"The Carb After Period of Non-Use

Don, thanks for the wiring diagram and description of what wire does what and when. This looks a little easier than I thougt. Still thinking if I want to do it or not.

 

[Greebo]

Re: "Priming"The Carb After Period of Non-Use

I went a slightly different route. I purchased an outboard 'squeeze' type hand pump as fitted to all outboard motor tanks and fitted this in the fuel line between the tank and the mootor.
Before starting after a time off the water I squeeze the bulb until it's hard (means the fuel lines are full) and then start the motor.
While my boat is out of the water for a period and in my garage, I occassionaly squeeze the bulb and keep the fuel lines (and the carbi) full of fuel.
Of course, I have a much older motor with a mechanical (rather than electric) fuel pump.
Works well for me, and there is no need for any electric wiring.

 

[Don S]

Re: "Priming"The Carb After Period of Non-Use

I went a slightly different route. I purchased an outboard 'squeeze' type hand pump as fitted to all outboard motor tanks and fitted this in the fuel line between the tank and the mootor.

I would strongly recommend you remove that from the system. They are not approved for being in the engine compartment due to fire hazard. They will not pass the fire tests.

 

[aerobat]

Re: "Priming"The Carb After Period of Non-Use

i must say i have no issues on this - even after winter i pump 3-4 times the throttle before cranking and my volvo fires up.

a buddy at our marina installed ( i helped him ) an electric hardy pump on his mercruiser 5.7 ( older model, mechanical fuel pump ) which is pressure regulated so it pumps and primes the carb on ignition on and stops if pressure is reached and you do not crank- when the engine starts it continiously runs. it seems fine on idle, we have to wait for sea trails since he has to sort out drive problems.

is there any serious downside on such a electric pressure regulated pump ? ( flow is +100 litres, so it should be ok even at WOT )

 

[Don S]

Re: "Priming"The Carb After Period of Non-Use

a buddy at our marina installed ( i helped him ) an electric hardy pump on his mercruiser 5.7 ( older model, mechanical fuel pump ) which is pressure regulated so it pumps and primes the carb on ignition on and stops if pressure is reached and you do not crank- when the engine starts it continiously runs. it seems fine on idle, we have to wait for sea trails since he has to sort out drive problems.

is there any serious downside on such a electric pressure regulated pump ? ( flow is +100 litres, so it should be ok even at WOT )

Sounds like his pump is set up to shut off when pressure builds up. But there is nothing to shut it off when the engine is not running, and your float needle is stuck open and the fuel pump keeps pumping fuel on the fire because the pressure hasn't built up.

Volvo uses diodes, and Mercruiser uses an oil pressure switch to keep things like that from happening.

 

[Greebo]

Re: "Priming"The Carb After Period of Non-Use

Thanks Don S for the advice.
I will do so.
I didn't think having the fuel bulb would be a problem.
Expert advice is always appreciated.
Thanks again.