Carb Engine Guru's
 

I have a quick question about my carb engine..it's not really a problem, but was wondering if anyone else experiences this..

when starting my carb engine it takes me 5 or 6 different times turning the key before my engine kicks over, but once started it fires one time.. and this is with me pumping the throttles 5 or 6 times before each time i turn the key.....

carb is a holly 4150..when starting i do not use the manual choke, i just pump throttles a few times and turn the key..

again not experiencing any back firing or anything like that, boat runs great except for some tuning issues as far as idling characteristics under load under low rpms.

i'm do to have a compression test, and leak down test before the season, but was wondering if this is normal
thanks again,

Q

Pretty normal without a choke and if the boat has sitting for couple days or more.

Why not use the choke?

Your bowls are probbaly just emptying while it sits. Only way to get fuel to the carb is by cranking the engine over a few times.

Not abnormal with a carbed motor.

thanks, the mechanic that installed the motor made something up to lock it in the open position so that while running hard it doesn't fall and choke the motoor..? cool cause during the winter months i take the boat home from the marina and start once every two weeks..

thanks again,
Q

Try pumping the throttle a few times a minute or 2 before you try cranking it. Like before you back down the ramp or before lowering the boat into the water or whatever you do before going boating.

Works like a champ for me.

The bowls should not empty while sitting for a long long time. Basically the gas would have to evaporate out of the bowls unless there is a leak. If there's a leak it needs to be fixed.

Your mechanic is right, you don't need a choke in Bermuda.

Is it an electric fuel pump with an oil pressure switch?
If it is- then most likley fuel evaporating while sitting for a couple of weeks, then when you crank it you have to wait for oil pressure to build before fuel pump starts and fills bowls.

Thanks, for all the advice...should i use the choke before starting or am i fine doing it the other way..


holly blue electric fuel pump
Thanks

Its fine the way you are doing it.

There's no signs of gas leaking, so i guess it must be evaporating from the bowls..

thanks again for claring it up for me..

Ok try this. After your normal time between cranking the motors days/weeks whatever, before you touch the throttles or turn the starter, take off the flame arrestor and look into the carb. Push on the accelerator pump lever and see if any gas comes out of the accelerator pump nozzle in the top of the carb. Obviously if gas comes out the gas is not evaporating between outings.

I would try changing the plugs and setting the idle.

You'll need to pump the accel pump more than once - the pump holds one shot of gas in a closed area (at least on the stock weber I have), so the second shot will tell you if there is gas in the bowls.

I had the same issue as the OP. Gas evaporated after about a week or so of storage. I always had to crank a bit to start, but then the pump got weak and you could crank until the battery died with no gas coming forth (of course, I learned this on a ramp). Would not prime the pump when cranking. A little gas in the carb throats ran it fast enough to prime the pump. A new pump solved that, but I still have to crank 20 seconds or so after storage.

Your idle mixture screws are set to lean for both cold start and idle causing your problem under light load rpm. The choke automatically enriches the air fuel mixture and holds the throttle plates open until the engine reaches operating temp. When you disable the choke you have to do all this manually. The description of how you are starting your engine is needed for all engine without a choke any time the engine is cold started. Tune idle mixture in gear on the water at operating temp. Then hook the choke back up the next time you do cold start and tune it for you geographic location it will take several time to get it right. If you decide not to use the choke do not reset the idle screws after they are set for idle in gear on water. Compensating for no choke will have to be done by you as the operator until the engine has enough heat to idle on its own. The fact that it idles now is because the mixtures are set half way between cold start and normal operation leaving you with a lean condition under normal operation. If you set the mixture to idle when cold using the idle mixture screws, the exhaust fumes will burn your eyes from being to rich when the engine reaches operating temp. When the engine is tuned right for running it will need the choke to warm up and idle until then. If your mechanic is worried about the choke closing while running its broken, fix it don't disable it, causes more problems in the long run.

Fix the choke. Dunno if you had an electric choke or a thermostatically operated one, but fix it. It's a cheap fix, and will make life easier.

If you have an electric fuel pump, your ground wire should be attached to an oil pressure switch. If so, you have to have oil pressure before the pump will run. If this is the case, then you can install a relay that connects to ground whenever the starter is engaged. This will start the pump a little earlier. I've even seen motors with a primer switch - instead of relay, you just run the ground thru a dash switch. Turn on the key (to provide + voltage to the pump), and thumb the primer switch to fill the float bowl. THEN pump the throttle a couple of times and fire it up.

Several ways to do it.
MC