Carb engine choke / starting issues

[illMATTic]

I have a stock 97 merc 454 carbureted engine. It has an electric automatic choke. And like may others it is hard as hell to start.

Cold starts take FOREVER to get it fired up. No matter if I pump the throttle once or 20 times it still takes a real long time to fire.

Warm starts fire quickly but are real weak sounding. There is no "crack" when it starts. It kind of just rolls over.

Have any of you experienced this? Were you able to figure out how to fix it?

Is it a choke issue or is it a lack of fuel issue?

I have read so many threads on this but they are mainly guys asking questions. There are never any answers.

 

[Old Navy]

Since ethanol was added to the fuel, my carbed boat takes longer to start too. I think that it evaporates out of the bowls over a week or two. Once it starts at the ramp its good for the weekend.

 

[Gimme Fuel]

The old man's merc small block is the same way anymore. Does yours stumble then pick right up when you mach the throttle while running? His does, guessing accelerator pump? It doesn't warm up worth a chit either so probably auto choke is bad also.

 

[illMATTic]

Mine runs great otherwise.

There may be something to the idea that the fuel is draining out of the carb causing the hard start.

 

[Old Navy]

The old man's merc small block is the same way anymore. Does yours stumble then pick right up when you mach the throttle while running? His does, guessing accelerator pump? It doesn't warm up worth a chit either so probably auto choke is bad also.

No stumble, it runs good. I also switched to 93 octane Shell only last year and it seems to run better than the past couple years. Same tune all years, only change was brand of fuel.

 

[Blue Mist '97]

Are you running the stock Webber or something different? Mine is 97 also and the carb had never been off the manifold until 2009. It was in sad shape, found internal parts wrong or missing (from the manufacturer), running rich and smokin' up the back of the boat, not a lot of power. When I had it rebuilt my carb guy told me, as mentioned above by Old Navy, most of the hard cold starting is because of the fuel, i.e. ethanol. Said that it does, in fact, dissipate when it sits for a week or three. Have had no issues with it since the rebuild.

He told me when I first try to start it, to just crank it over (no throttle) for about 10 secs to pump fuel up and into the bowls. Then pump the throttle a few times when trying to start it. Usually works with the first 3-4 throttle pumps. Occasionally it takes 6-7 and fires right up.

As far as the electric choke goes, down here we don't really need it, so I think he just set it to be open all the time. We discussed it and I think that was his recommendation. I can't remember for sure, but will check next time I head up to the boat.

Also, I am going to try and run nothing but ethanol free fuel this year and see if that makes a difference, especially with cold starting. My thinking is that E0 won't evaporate in the bowl like E10 and hopefully make the cold starts easier, not to mention no water in the fuel.

 

[RNGRDVE]

Y money is on lack of fuel. Be it fuel evaporating from bowls or the lines bleeding back into the tank. The mechanical fuel pump used needs the engine to turn over a few time to supply a good flow of fuel.

 

[illMATTic]

Its too bad I think of these things in the winter. I don't even know why I posted it. I can't act on anything for 4 months.

I think I have a Rochester carb on mine. I have read that they are notorious for this type of problem both on and off the water.

 

[Jimway]

The next time you go to fire it up after sitting, pull the spark arrestor and operate the throttle while looking down the carb bores to see if the accelerator pump is squirting fuel. Remember too, that the carb sits right there on top of the motor and is subject to all of the heat rising during a 'hot soak' after running, although not as bad as a road driven engine, this sometimes will evaporate fuel from the float chamber. Make sure choke closes completely when setting throttle for cold start. I, too, am not a fan of gasoline with alcohol in it.

 

[wired]

My money would be buying an electric fuel pump and return regulator with return line to the tank. That engine should fire immediately every time.

 

[Kurtster]

I, too, am not a fan of gasoline with alcohol in it.

6 ounces of 104 octane boost added for every 35 gallons of 92 or 93 high test gallons will negate the ethanol/alcohol "running" issues in the carb motas.
If using Sunoco 94 high test, reduce the mix formula down to 5 ounces per..

Don't over mix or you'll be dealing with valve burning.

 

[Wrenchmate]

If it has the Rochester on it and it probably dose theres one easy and really
cheap thing to check. Rochesters have a real small filter in the carb right
where the fuel line screws in and it has a little rubber like check valve on
the end that stops the fuel from draining back in to the tank and keeps it
in the carb. I had those check valves go bad and Ive seen people leave
them out thinking it will get more fuel. It probably needs changed anyway.
One time I myself installed this little filter and I put it in backwards so the
check valve was on the wrong end and had exactly the same problem
you have. Everybody dose the big water fuel filter and forgets about this
one. Worth a try anyway before spending bigger money. Also when you
take the fuel line off sometimes they have a spring in there pushing the
filter up in the carb tightly.

 

[JW]

After listening to my buddy's Boss 429 fire up with an EFI where the 4bbl carb used to be, I'm now a huge fan of fuel injection conversions. Takes $$$$ though...

 

[jazzy]

The mechanical fuel pumps allow the fuel pressure to bleed down. I have pressure gauges on my feed lines, I usually start the motors in the driveway before I leave to go boating. If I haven't used the boat since the previous weekend I can watch the gauges working their way up to pressure. An electric pump will help that situation, you turn the key on for a second before you try to start and it will already have pressure.
But if it doesn't start great when warm then you have more problems, and probably need a tune up. Getting carbs set up just right is an art. My dad does most of the dialing in on the carbs and is teaching me, but he is still better than I am at it. He does it by ear where I have to get out a vacuum gauge. Once I have fuel pressure built up, my motors start at the touch of a key and come on like an explosion. If I don't get the right sound, I'm usually due for plugs, or the idle mixture is off for the humidity and temp.

 

[illMATTic]

Thanks guys.

On warm starts the engine will start much easier. However, it just kind of fizzles and starts. No explosive start. It sure does sound like fuel bleed down.

It would be sweet if all I had to do was replace a check valve.

Its all a guess at this point. Spring has never felt so far away.

 

[RNGRDVE]

Do you have a pressure gauge on your fuel rail?

 

[illMATTic]

I do not. Its all stock.

 

[Old Navy]

The fuel in the bowl starts the engine. If there is not enough, then it has to be pumped to the bowl to start the engine. It might take a few cranks if the bowl is empty. This can be caused by evaporation, or on Qjets, leaking well plugs.

 

[ezstriper]

The 97 should have a weber type carb(now edelbrock) 1st make sure that the choke closed after hitting the throttle the first time, these carbs DO NOT want to start with no choke, if that is working then you are evaporating all the fuel out of the bowl, need spin it over for 15-20 seconds to refill, then pump 2-3 times, if after this does not help, going to have to look at the needle and seats sticking closed not letting the fuel back in..have run into this on these carbs, and as others said, a low pressure elec fuel pump not a bad deal...and you can can that B/S merc $$$$water/fuel pump setup...

 

[Don's89 Senator]

Just throwing this out there. Could it be a weak spark?