sudden loss of power

[ndutton]

And possibly rotten fuel hoses (internally).

[SimonP]

now to clean the carb

I got my new facet pump yesterday from MMI and plan to fit it tomorrow. Assuming that a bit of destroyed rubber from the fuel pump is the culprit - where is it ? and how should I approach the carb? I've been looking around for tips here but can't find a 'how to clean your carb' post. (Odd, I'm sure there must be several). Can someone give me a tip or two?

I saw one post about a bit of grit under the float needle valve involving removing the main passage plug and draining, but after that...how should I proceed? Note that for the moment I'm hoping not to remove the carb and that the problem is easy to resolve since it is a relatively new carb.

BTW - I read somewhere that some fuel additives will eat rubber hoses and seals - this would tally with my decaying facet seal, and with stuff I've heard about ie biodiesel eating diesel engine rubber. There's a to of talk about stabil on some threads - but I worry that its got rubber eating solvents - any opinions?

[marthur]

Simon,

Don't be afraid to remove the carb and clean it.

You may find this link helpful: http://home.earthlink.net/~ultratom/...rb_rebuild.htm

[SimonP]

very helpful set of pics
those gloved hands would be yours I take it

[SimonP]

service manual and parts list pdfs

FYI
I just found the complete service manual and parts list online at

http://www.user.firstclass.com/~Eric/Arioso/Manuals/Atomic%204%20Engine/

[Vermonter]

Loss of power

Simon, you don't say how long you were running before you lost power, whether you had recently adjusted anything, or whether you were at higher revs then lost revs but here are a few things to check:
- were your plugs black after the power loss?
- if yes (toss the plugs, don't try to clean them),
- check idle speed mixture screw (1 1/2 turns I think)
- check choke cable - is it opening choke all the way
- if no,
- check for plugged exhaust (will run at idle and causes the throaty sound you mentioned)

If you're like me you will find out the real culprit only after you tear down the carb, replace the points, replace the coil, etc! Good luck!

Bob

[SimonP]

praise be to the gods of old engines

I installed my new fuel pump, pulled main jet plug in carb and sprayed in some carb cleaner, cleaned lines and changed filter canister, pumped up the bulb, and after a couple of stutters, the thing purred like a cat and pulled like a mule. Ran up to 3000 and back, in and out of gear - problem solved I guess. It seems to run stronger and smoother than before so I guess that old fuel pump was the culprit.

BTW- I've got a plastic polishing filter. I know its not safe but I do like the fact that I can see the fuel flow when I pump the bulb. Its before the fuel pump cause I didn't want to cut the nice copper line between the pump and carb. When I change to the metal polishing filter, does anyone have a suggestion for a visual on fuel flow. I guess one could insert a glass tube, but that's not real safe either.

[Marian Claire]

The MC originally had a copper tube from pump to carb. When I installed the polishing filter I removed the copper and fittings. I then used new fittings to adapt to the new flexible fuel line. The smooth copper makes a poor connection. I believe USCG regs require some kind of barbs, rings, threads etc to make a good connection. I believe they also say that if you have an electric fuel pump it must stop when the engine stops. So a low oil pressure switch is needed. If you find a filter that meets regs and has a view let me know. Dan S/V Marian Claire

[Administrator]

I'm not sure whether this adds anything to the conversation, but in contemplating a see-thru polishing filter, it's worth remembering that an A4 operating under load at cruising RPM consumes less than a quarter of a teaspoon of fuel per second (assuming a gallon per hour, which is probably on the rich side). You're not exactly going to see the fuel racing thru the filter, and I don't know how you would discern whether the flow was something lower or higher than it ought to be.

My John Deere lawn tractor has a clear filter of the same general size and type, and it is never more than perhaps a quarter full of gas, even though the engine runs perfectly. I have never understood that, but nevertheless, that's the case.

It seems to me that if you have a properly maintained Racor or similar filter/water separator upstream, the polishing filter shouldn't have much to do. Given what they cost, I would just swap it out every couple of years without much thought.

Bill

[Marian Claire]

I may be totally wrong in this line of logic. If the fuel system from pickup tube to needle valve in the carb is tight then the air bubble in the filter should remain more or less a constant size. The difference in elevation of the in/out ports would determine the bubble size. When used, my clear filter has the in slightly higher than the out. When I have had slow, “fuel related”, shut downs if I could see the filter slowly go from 95% full of fuel to almost empty. To me that suggested an air leak upstream of the filter. If the engine shut down and the filter was still 95% full of fuel I figured that there was a jet clogged in the carb. I am not a mechanic so some times my “logic” is way off. Dan S/V Marian Claire