Engine's first start a hard start after sitting about a week. (No Fuel)

Mercruiser 898 with 2 BBL carb.

After sitting about a week I need to run the starter longer than I am comfortable with to get fuel back into the carb. Maybe about 5-10 seconds. The engine will fire up almost instantly when I pump the throttle once, but it almost immediately dies since there seems to be no fuel in the carb bowl after that one squirt from the accelerator pump. I don't know if the fuel is evaporating or flowing back through the lines and into the tank. There is no evidence of a leak anywhere. What should I look for to resolve this problem? An old check valve in the fuel pump? I have a spare fuel pump if this is the case.

I've read somewhere that some carbs are more prone to this problem than others and the only sure fire way to resolve this problem is to install an electric fuel pump.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Maybe this is normal for a carb'd boat engine?

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

cecho said:

Maybe this is normal for a carb'd boat engine?

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Ayuh,... Some carbs leak off into the intake,...

My Merc/ Weber does,...

Gas can't flow Backwards,... It's Uphill through dead air outa the carb, 'n the fuel pump is nothin' but check-valves....
'n the anti-siphon valve at the tank to boot....

5/ 10 seconds ain't much of a crank,... 40/ 50 seconds is a long crank...

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Not to jump on someone else's posting, but I have the same issue on my 454 and the cranks is 50 sec or more. I wasn't sure if it was a carb thing or not. What could cause this long of a crank?

Sorry OP

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Same issue in my 228. I do ave an electric boost pump which 'sounds' like it fills the carb bowl, but still it takes a good 10-15 seconds to get it to fire. Once it does fire a few times it then starts, idles and runs 100%. I'll be interested to see what solution you come up with.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Mine has this problem after the winter storage. What I do is poor a little fuel down the throat and fire it up. That is usually enough to get the fuel flowing without having to use the starter too much.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Same here......after it sits awhile. A week or so..... I pump it once, crank about 5 sec.....pump again and back off to almost 1/4 throttle, crank and it fires up.

Sometimes double pump it... After that its good to go.......it's a carb

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Thanks for the info. I guess it's just one of those quirks of owning a carb'd engine. When it comes time to repower her with a 350 I may put an electric fuel pump in with an oil pressure switch.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

cecho said:

Thanks for the info. I guess it's just one of those quirks of owning a carb'd engine. When it comes time to repower her with a 350 I may put an electric fuel pump in with an oil pressure switch.

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Yeah, but would you put up with it if it was your car that had this same issue? Why should it be hard to start just because its in a boat? There must be a solution to all these hard-starting engines?

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Cresco750 said:

Yeah, but would you put up with it if it was your car that had this same issue? Why should it be hard to start just because its in a boat? There must be a solution to all these hard-starting engines?

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No, I would not put up with it if this was a car. A boat or airplane's a bit different though. (Starting an old and hot mechanical fuel injected aircraft engine is a PITA) I still would prefer it not to happen on any vehicle though.

I've done some more reading on it. I keeps seeing people talk about bad needle valve/seats in car carbs, I'm not sure why that would cause the problem though since the fuel would have to go up through air to get back through the needle valve inlet passage, like Bond-o said.

I've also read getting an electric pump solves the problem since it runs at close to full power at all times so the carb bowl fills back up while cranking much quicker than a mechanical pump at cranking speeds can. Assuming this is correct, if I ever repower the boat I'd replace the mechanical pump with an electrical one.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

My boat is similar . . . has to crank a while if it has not been run in a week or so. I think the fuel siphons down over a few days and needs 15-20 seconds of good cranking to pump it all back up to the engine.

An interesting thing is that during the spring start-up the engines kicked right over, after sitting all winter. I think that is because I had to fog the engines with a fuel mix (MPI cocktail) from a separate container. Therefore, the siphon back to the tank was broken and the fuel up in the fuel rails, etc stayed there.

Now that I am running off the main tank, it siphons down.

Just my theory of course . . .

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

I must have got lucky with my MC120....Rebuilt the carb this past winter and with a bit of tunin,she fires with the bump of the key and idles like a kitten,even after sitting a weekend or two.Pretty amazing since the last carb I tried(years ago)I threw it in the trash can.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

After a week+ sitting,......I pump the throttle 3-4 time, leave the trottle open maybe 1/8, turn the key and it fires on the first turn!

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

cecho said:

(Starting an old and hot mechanical fuel injected aircraft engine is a PITA)

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Yup, been there, done that. At one stage I flew a C206 on floats that used to be a bit temperamental with its starting procedure. One day it just would not start and began drifting faster and faster down the river. I jumped in the water, middle of winter, with rope in hand, cell phone in pocket and had to swim to the shore and pull the bl@&#y thing back in! That really made my passengers day!

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Carburetors mix the fuel and air up on top of the motor, so it won't usually fire right off cold til the mixture gets into the combustion chambers and gets spark. If you want a quick start experiment with how many pumps gets it. I'd try 3 or even 4 pumps, then set the lever at 1/8 open or so while you crank the starter. Then when it runs set a warmup speed that you choose.
You are supposed to pump a carbureted motor before starting or you are not sending enough fuel down.
Fuel injection sensors tell the system how much gas to send and it is introduced to the air mix just before or just inside the entry to the combustion chamber. You never pump fuel injection, it does nothing anyway. When operating the throttle in a fuel injection motor while the motor isn't running all you do is open and close an air tract.

With a carb it actually shoots a dose of fuel each time you pump. The cold engine needs the extra fuel to start. Once your boat motor is running the carburetor continues to send extra fuel down by blocking part of the air supply. That's the choke, which gradually disengages as the motor warms.

The fuel in the intake tract evaporates while the motor is off, so it's normal to need a few squirts if the motor hasn't been run for a longer period. If you have a TKS (turn key start) engine there is a provision to enrich the fuel, that's part of the carb. I am not completely familiar with them, but I understand they are quick starting. They may not require any pumping at all.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

Cresco750 said:

Yeah, but would you put up with it if it was your car that had this same issue? Why should it be hard to start just because its in a boat? There must be a solution to all these hard-starting engines?

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Have you ever had a 70's car? My 1977 f150 an be stubborn. The boat tech stuff is slower than the car stuff.

Re: Engine's first start a hard start after sitting about a week. (No Fuel)

I've owned 3 carb'd cars. None of them had this problem that I can recall, none of them ever sat for more than a day or two though.