Starts easily, idles, dies upon acceleration

[GregB]

This is a late model Atomic 4 with the aluminum 5 bolt carb and factory electric pump. I've been having trouble since I replaced the filter with the Racor unit from MMI (my fault, I turned the old unit sideways before removing it).

At first, I had trouble starting, so I watched the d/l video and went through the process of draining the carb and blasting out the jet area with carburetor cleaner. The gas I drained looked yellow and had visible chunks in it. That helped tremendously and I actually had the engine running well - last Monday. Then on Saturday, I couldn't get the engine to run above an idle, although it starts easily and will happily idle if I leave it alone. Actually, it will accelerate for a few seconds before it starts to die. If I can turn the throttle back to idle quickly enough, it will keep running.

I'm considering having the fuel tank drained and cleaned to eliminate that as a problem, but wonder what else I can do? There doesn't seem to be much information on the factory electric fuel pump out there and I'm wondering if there's a way to check it for dirt, like there is with the carb.

Thanks for any help,
Greg
Cal 29 Happy Hour
Marina del Rey

[Dave Neptune]

Soap box again

Greg, first welcome to the MMI Afourian Forum. If you have an electric pump it is "aftermarket" as the stock pump was mechanical. Sounds like you are leaning out as the engine accelerates just before it dies or starts to. You could have some issues in the carb but first some info on the fuel delivery system. A common problem is a loose fitting allowing a bit of air to be sucked in. So first carefully check to be sure all fittings and filters are snug.
Are you using a "second" polishing filter just ahead of the carb? If not I suggest you do. Is the old pump still mounted and if so are the fuel lines running through it?
This would be a good time to just bight the bullet and install a fuel pressure gage and eliminate all the guessing! Your $$$'s though. If you have adequate pressure at the carb and still no "power" then it's time to clean the carb.
I strongly suggest starting at the tank to recheck connections and checking the actual pressure at the carb.

Dave Neptune

[romantic comedy]

Hi Greg,

The first thing i would do, would be to hook up a simple fuel supply to the carb, gravity fed. Just take a gallon jug with a hose, hang it up, and there you go. This way you can check to see if it is the carb, or the fuel supply.

My thoughts are that you definitely need to disassemble the crab, and clean it out. The symptoms that you describe show you are starving for fuel. But since it runs at idle, the fuel supply is probably adequate. There would be fuel enough in the bowl to accelerate, even briefly, if the supply was weak.

Bottom line, I say rebuild the carb. Dont fool with a dirty carb, It really is a simple job.

[yeahjohn]

I would start simple, it seems like your main jet is blocked or you are to lean. It would be strange if your mixture is off but maybe whatever fuel system changes you made gave you better fuel. Get a clear container and put it under the carb main jet. Unscrew the bolt and turn your key to shoot some fuel out, this should clear your main jet, let fuel sit and check for crud. Your best bet would be to break down and go over your carb, but lots of times just flushing out fuel through the main jet can solve your issues (maybe temporarily depending on the crud in your carb).

[GregB]

Thanks to everyone for the replies, they gave me a few things to work on. I'll keep plugging away at it and, if necessary, try rebuilding the carburetor.

Note to Dave Neptune: Take a look at the catalog section of the site; you'll see the factory electric pump there. Apparently it was only installed on the late 70s-early 80s engines and, since my boat was re-engined with one of those, the pump I have is exactly what's pictured. Now if only I could find some information about what seems to be a fairly rare item, it would be great.

[Mo]

..just a few things...hope it helps.

Hi Greg,
You can interchange a new fuel pump with minimal problem if that is the problem. Dave mentioned changing the fuel filters. Also ensure no line leaks.

Also, I understand you had the carb apart...might want to do that again taking care to preserve your gasket. Did you remove the jets and clean them out when you had the carb apart? Combustion chamber cleaner and some fine wire will do it nicely. Remove all jets and lay them to the side on a paper towel. Ensure you use the correct size screw drivers as not to damage housing or jets. Spray all passages and the jets liberally. Run the wire through the jets and hold them up to a light to ensure nice and clear...don't ream the holes larger...the wire is just to clean stuck on debris. Clean out the float needle valve seat as well and remove that piece. Don't bend the float as you take it apart. Remove the idle screw and use a wire brush to clean the threads...they sometimes corrode and cause a problem because it may not be seated properly due to corrosion on threads etc. Now, if you have an air compressor spray every thing again with carb clean (or brake clean as it works perfect as well)...use compressor blow dry and any debris out of there.

Reassemble the carb putting jets back in snug..don't over torque them. Install the needle valve and float carefully then put the halves back together. Ensure all screws are tight. With my air compressor I put carb cleaner in the top and hold my hand and give it a shot of air...if there are leaks around the gasket it is really obvious as it bubbles out there. I sometimes note a leak this way on the old carbs at the forward portion where the new carb has the new screw....anyway...if all is good re-install and see how it goes....new filters and drain the line a bit before you try your now "clean" carb.

Long reply I know...Hope that helps.

PS...I just re-read that...it sounds much harder than it is. Usually takes me about 20 to 40 minutes to do it all and have the boat running...depending on how much I have to clean up on the carb. Sometimes even the screw that hold the halves are full of corrosion.