Fuel (carb?) problems ...

[sastanley]

Laker, I had an unexplained shut down after running the motor for 9 hours as I came into the dock. I also managed to land without drama, but the shut down was puzzling. I second the recommendation from Al to simply drain the carb bowl and collect the drainings to see if there is some junk in there. I am running a Racor filter and the Moyer secondary in-line, and sometimes I still have some junk in the carb bowl.

While I have the carb drain plug open, I squirt a few bits of gas using the mech fuel pump bale to flush things out..you can try the more thorough cleaning and try to wire out the jet if you think it is needed. After the shut down (and flush) I've been out running the boat with no troubles for the last several weekends.

1/2" wrench and about 5 minutes. Don't forget to run the blower after you put it back together while you examine the catch can.

[Laker]

Thanks Shawn , I will try that. CK

[BunnyPlanet169]

Another thought -

We've had a report here that the inline filter can rust on the inside. I can't speak for everyone's experience, nor do I want to malign an MMI product that many rely on. It's hard to argue about too much filtering unless it causes vacuum issues.

That said, I did not replace my inline filter having also found rust in mine during the rebuild. Maybe annual replacement would avoid this, I don't know.

The specs on the MMI polishing filter are not that great - 7-10 microns. It's not doing much polishing after the 10 micron Racor, so I took it out.

I added a secondary Racor at 2 microns.

[Laker]

Quick fixes were ineffective , so I pulled the carb today. (Not fun --- need to get shorter wrenches.) I will have access to a parts cleaner Monday.
Questions:

1)What is the purpose of the skinny brass tube which runs from the carb intake to the intake manifold?

2) When I tried the fuel pump primer while everything was still assembled , it allowed one stroke , then felt tight. With the fuel line open ended fuel shot out generously with each stroke of the primer. So I know that the pump diaphragm is working , right? Since I ran the engine a week back for 30-40 minutes with gradually reduced choke settings I deduced that the pump is functioning. Do I still need to test the pump by cranking the engine briefly with the fuel line open , which will be messy , or do I have sufficient evidence that the pump is ok?


3) Since the carb will be disassembled , what parts should I order from Moyer , or is there an entire kit I should get , given the opportunity?

Not sailing tomorrow , Laker

[capnward]

Laker;
1. that tube is to vacuum gas from the carb air inlet into the intake manifold, keeping gas from leaking into the bilge while engine is running. It is called a scavenger tube.
2. You are right, your pump is working. If the bail becomes tight, the fuel line is pressurized up to the float valve in the carb. At that point, watch your fuel pressure gauge, if you have one, to see if it holds its prime for a while. If pressure goes down quickly, you have a leak somewhere, maybe in the pump diaphragm, the float valve, or hose connections. No need to otherwise test the pump.
3. Get the rebuilding kit which has all the jets, just to have it. The jets and other parts last a long time. The tapered wooden dowel used for dressing the seat in the float valve is used a lot. File down a screwdriver to fit the idle jet so you don't damage the threads in the aluminum when you remove it to clean it. Get lots of gaskets, especially the one between the carb halves. Get the long idle screw for easier adjustment.
An adjustable main jet is also useful. Take care to not over tighten it with a wrench and damage the washer, they are not sold separately.
Anecdote: After I stopped using ethanol fuel, the tan-colored jelly-like crud collecting in the bottom of my Racor Filter and in the carb bowl hasn't returned. That may have been what clogged my idle jet. I also use the engine a lot during the season, use biocide and MMO in the fuel, and leave the tank close to full in the winter, to keep water from condensing out of the air in the tank. Also, I like to keep the tank full just to keep whatever stuff is a the bottom of the tank from mixing into the gas when the boat is tossed around. I try to not operate the motor much in a chop if I can avoid it.
Nice that you have access to a parts cleaner. You can probably do an adequate job without one, using carb cleaner spray can with a straw attachment. I bet cleaning the carb will do the trick, until the next bit of junk comes out of your tank. Hopefully the filters will stop it before it gets into your carb.

[roadnsky]

Laker-
I think you would benefit greatly by downloading and watching Don's CARB video.
12 bucks well spent...

http://www.moyermarine.com/cgi-bin/shopper.cgi?search=action&category=CLIP&keywords=all&template=Templates/B000_storebuilder.html

[BunnyPlanet169]

Everything Capnward said.

If you use carb cleaner or compressed air, wear goggles. See how big these eyes are? The carb is like a crazy dribble glass that shoots fluid backwards at you when you blow it out.

If you go with the rebuild kit, it's mechanically very simple. Take out the old parts, put in the new ones. BUT, do take the time to find the perfect, correct fit screwdrivers, especially on removal.

[Laker]

Update:
Carb kit ordered and received. Working largely out of town this week I had no time to work on the boat , so I turned the project over to a local trusted mechanic. He reported that the carb was loaded with a particulate gunk which became gelatinous when wetted with gas. Now all is clean and shiny , all jets replaced.

Question : I ordered a replacement for the U shaped copper fuel line which connects the pump to the carb. I received rubber fuel line and filter ; instructions say that the filter is to be installed between the pump and carb. Is this what is referred to as a "polishing filter"?

Plan is to reinstall carb this afternoon.....

[BunnyPlanet169]

Is this what is referred to as a "polishing filter"?

Correct. Depending on what else you have before it, 'polishing' is a bit optimistic. It's rated 7-10 microns, really just about the same as the 10 micron Racor many of us have installed. But as a 'last chance before the tiny spaces' it can't hurt.

That sounds great! Let us know...

[JOHN COOKSON]

While you are at it get (and install) a fuel pressure gauge after the filter before the carburetor. You can plumb it with solid nipples right to the carb.

TRUE GRIT

[capnward]

He reported that the carb was loaded with a particulate gunk which became gelatinous when wetted with gas.

This sounds like the stuff I used to get in my carb before I changed to non-ethanol gas. How long have you been using non-ethanol fuel, and when was the last time the carb was cleaned? Since you use non-ethanol exclusively, and have not cleaned the carb in a while, this stuff may be left over from when ethanol fuel was used. Either that, or my theory about ethanol causing the gelatinous gunk is bogus. If I am right, you should not have that problem in the future.

[ndutton]

I think this is a chicken or egg thing. The popular belief is ethanol causes the krud but some of us think the krud was residual from years of stale gas, varnish, contaminants from any number of sources, worn deck plate O rings and questionable fuel dock gas to name two. Once ethanol is introduced it acts as a solvent returning the krud to the mix and delivering it downstream to show up in filters and carburetors.

When the krud was glommed to the bottom of the tank and held there no one was the wiser.

[capnward]

ignorance is bliss

Thanks Neil, for the clarification. It's probable that Ethanol (the chicken?) does not cause the crud (the egg?), just delivers it downstream. Either way you get egg where it doesn't belong. The rooster would be the corn farmer lobby. I prefer to keep any crud in the tank, and out of the engine as much as possible. Maybe I should just use ethanol gas like you and many others, and clean gunk out of the carb and replace filters until the solvent has done its job. Maybe it already has, I don't know. It's just that I need to not have engine problems from sudden fuel blockages while waiting for the tank to become clean.
Maybe the solution is to run the tank dry, or until the crud at the bottom clogs something and it shuts down, then clean the carb and replace filters, put in more ethanol gas,then repeat. Sailing the boat in 3 foot waves with a low fuel level in the tank, then hoping I can motor to the slip before the crud reaches the carb, would probably help clean the tank. Or I could pump the tank dry with the bail on the pump and dispose of the fuel, and repeat. Or remove the tank so it can be cleaned professionally. Or buy a new tank, but the one I have is stainless steel and I like it.
I once had a guy who cleans tanks in place take a look at my boat, and he said he couldn't get his hose thru the fuel intake. But the guy who removed the diesel fuel that was put in by mistake was able to evacuate the tank no problem. Maybe that cleaned it.
I am kinda lazy, so I will continue to use non-ethanol, and hope the crud (if any) at the bottom of the tank stays there. So far it's working. Like the guy with the "Wolverines Stay Out" sign on his fence. Not a single wolverine in his yard.

[Peter]

+1 on the fuel pressure gauge.

i had almost exactly the same problem - engine suddenly became choke dependant although mine still produced good power but needed full choke.

installed a fuel pressure gage and discovered poor and erratic pressure.

changed fuel filter and ran engine from an auxillary tank and all was well.

therefore dirty fuel tank.

Without the fuel pressure gauge it would have been impossible to quickly and effectively diagnose.

they are very inexpensive.

only drawback i see to them is they do add in a few more joints in the fuel system if you leave it installed.

Good luck,

Peter

[capnward]

Peter,
What is your plan of attack for the dirty fuel tank?