Pushing choke key in on cold starts

[Snoopy-2]

What is actually happening when you hold the starter key in for 6 to 8 seconds on a cold start before you engage the starter. Does is electronically push extra gas into the carbs for a richer mixture and if you hold it in to long will it flood the engine? Referring to a 98 Johnson 115 h/p.

 

[F_R]

Re: Pushing choke key in on cold starts

Well, it depends. What it does is open the primer valve. Nothing flows unless there is pressure behind it. If you have a pressure build-up in the tank/lines, etc, it will allow some of that of gas to go into the engine. I suppose if the tank is pressurized (yes, it can) and you hold it pushed, yes it conceivably could flood it. .But the proper use is push & hold while turning to crank. The fuel pump supplies the gas to the primer then.

 

[racerone]

Re: Pushing choke key in on cold starts

Correct and agreed.---Many folks think that the primer is some sort of pump.--All it is is an electric valve.----Holding the key in before cranking does very little.

 

[coolbri70]

Re: Pushing choke key in on cold starts

it activates a solenoid that closes the choke

 

[racerone]

Re: Pushing choke key in on cold starts

The post is about a 1998--115 HP and it does not have choke flappers.

 

[Fed]

Re: Pushing choke key in on cold starts

It's a 1998 model coolbri, no choke butterflies.

I've read that 6-8 second advice & thought urban myth for sure, then I tried it & I have to say it did seem to make my motor fire faster.

That got me thinking maybe I was pressurizing the fuel system too much, rather than just filling the carbies I was also expanding the fuel lines & fuel pump diaphragm.

Either way you'd think after a couple of cranking revolutions the fuel pump would do exactly the same thing.

 

[coolbri70]

Re: Pushing choke key in on cold starts

guess I need to brush up on my newer outboards I will follow to learn about this choke that doesn't choke, is it fuel injected with idle air valve? how does it control airflow with no butterfly? even throttle bodies have one. I will study this as I must know:facepalm: must be like the fuel primer on these new mowers

 

[F_R]

Re: Pushing choke key in on cold starts

It doesn't control airflow. It opens a valve that lets the fuel pump inject some fuel directly into the intake manifold, thereby enriching the mixture for starting. Personally, I liked the choke better. But I suppose the new generation doesn't know about or understand the old carburetors and chokes. Lessee, when did carburetors disappear from cars?

 

[Joe Reeves]

Re: Pushing choke key in on cold starts

Lessee, when did carburetors disappear from cars?

I don't rightly remember, BUT.... I'd prefer the old flathead ford V8 over what's in my truck now!

 

[coolbri70]

Re: Pushing choke key in on cold starts

after looking at a parts diagram and FR's explanation, I think I get it they have a carburetor with a separate throttle body between it and the intake, so there is no way to close it off and create the vacuum that sucks in the fuel needed to start cold so they added a primer. I think I like the old way better too

 

[racerone]

Re: Pushing choke key in on cold starts

No ,---By using this primer set-up the choke flappers are no longer needed.--------This primer has been used for 25 years or so.----This means it is a good and reliable unit !!

 

[iwombat]

Re: Pushing choke key in on cold starts

When I wrote the starting procedures article in the archives, I had to appeal to the hive mind for the later model starting advice (I have real chokes on all mine). There was enough anecdotal evidence that holding the key in for a few seconds worked better that we decided to put it in. It certainly doesn't hurt, so why not.

 

[racerone]

Re: Pushing choke key in on cold starts

The electric primer ( when activated ) only puts fuel into the engine when there is fuel pressure supplied to it.------------This pressure comes from the manual pump or from the motor fuel pump when engine is cranking !!

 

[Joe Reeves]

Re: Pushing choke key in on cold starts

(Proper Starting Method - Fuel Primer Solenoid - Choke Butterflies)
(J. Reeves)

Cold Engine: Pump fuel primer bulb up hard. Increase throttle somewhat with whatever type control you might have UNLESS your engine is equipped with the "Fast Start" feature. Turn key to start position. As engine cranks over, push in key to activate the fuel primer solenoid OR to close the choke butterfly(s). (Fuel is drawn into the crankcase with every upward stroke of the pistons). When engine fires/starts, release the key. Should engine start to die out, push key in (just a tap) as needed to activate primer solenoid OR choke butterfly(s) in order to momentatily increase the fuel flow.

Warm engine: Pump fuel primer bulb up hard. Turn key to start position. When engine fires/starts, release the key. If engine does not fire/start within 6 revolutions, push in key to activate fuel primer solenoid OR choke butterfly(s) as needed.

This is assuming that the engine is as it should be in all respects (Compression, Ignition, Carburetion, Fuel Supply, etc).

NOTE: Many boaters with the engines incorporating the "Fuel Primer Solenoid" use a method to start their "cold" engine(s) whereas they pressurize their fuel primer bulb, then without cranking the engine over (Key ON), they push in the key to energize the fuel primer solenoid. This allows the pressurized fuel line to have fuel flowing directly into the intake manifold area... a puddle of fuel mixture sitting there waiting to be drawn in as soon as the engine cranks over. Many swear by this method... a matter of choice, opinion, whatever. However, what OMC originally recommended is as you see stated above this paragraph... but then again... whatever works for you.

Engines incorporating the older choke butterfly setup..... Of course, with the engine NOT running but with the key in the ON position, pushing the key in to activate the choke results in closing the butterfly (butterflies) but does absolutely nothing other then to verify that the choke assembly is operational. The engine must of course be cranking over to create the needed vacuum to drawn the fuel into the crankcase.

 

[Chris1956]

Re: Pushing choke key in on cold starts

The OP's motor has a vapor separator between the primer bulb and the OMS Fuel pump. The enrichment primer is downstream from the OMS Pump, so priming the motor with the primer bulb simply fills the vapor separator with gasoline. Cranking the motor with the choke button pushed in will allow fuel that had been pumped to the primer to run into the intake manifolds. I doubt you will get much fuel flow unless motor is cranking.