Seems to be running way too lean

[BSquared]

Last season, I couldn't get much power out of my A4, and it would stall if I opened the throttle all the way. I was having trouble with the hand-priming lever on the mechanical fuel pump, so I thought maybe it was pump troubles. I replaced the mechanical with one of Moyer's electric pumps.

I finished the job today and had one helluva time getting the engine started. I finally discovered that it would only start if I cranked with the throttle all the way open and then closed the throttle while still cranking. Even then, it would only keep running if I gave it at least a little choke. Worse, it now runs almost exactly as it did before: kills if I open the throttle too fast or too far and doesn't develop nearly enough power.

I'm guessing that since it has to have some choke on, it must be running too lean. What can cause this: a dirty carb? I rebuilt the carb a couple of years ago, but I didn't have a very good fuel filter (until I installed Moyer's electric fuel-pump kit) so it could certainly be crudded up. Is anything else likely to cause this kind of symptom?

I'm hoping for quick replies, because the boat is essentially unusable. I can imagine trying to reverse to stop in the slip and having the engine give its characteristic "gasp" and quit!

-B2

[BSquared]

PS: If I connect the electric fuel pump directly to the power supply, it never seems to stop. Is that proper behavior? I don't have much experience with electric fuel pumps, but at least one kind I've seen has a pressure switch that turns it off once the system is pressurized (after the float bowl is full and float valve closes). I don't see any gas leaking out, so I guess it's not a serious problem... :confused:

[Don Moyer]

The Facet electric pump is built for continuous duty. It has an internal spring-loaded by-pass valve to re-circulate fuel once the specified pressure is reached.

While the pump doesn't mind being connected to a DC power supply that receives power directly from the ignition switch, the Coast Guard requires that an oil safety switch be installed between the power supply and the pump so that it will only operate while the engine is running.

Regards,

Don

[Don Moyer]

Your symptoms are very consistent with a lean condition. I would start by removing and cleaning the main jet.

Regards,

Don

[BSquared]

Thanks very much for the quick reply, Don! I'm sitting here at work without a carburetor diagram: is it possible to clean the main jet without removing the carb? Wait a minute, let me change that: is it practical to clean it without removing the carb?

-B2

[Don Moyer]

B2,

You can remove the main jet if you have good access to the lower part of the carburetor. The main jet is just behind the passage plug, which is the 1/2" hex-headed plug in the bottom of the bowel chamber. The main passage plug lays horizontal and its hex-head faces aft (away from the flywheel end of the engine). After you remove this plug, you will be able to see the main jet. It is a screwdriver-slotted brass plug.

Best regards,

Don

[BSquared]

OK, I couldn't access the main jet in the boat, so I pulled the carb, removed the plug, and -- ugh what a mess! I rebuilt the carb a couple of years ago, but obviously there's been *serious* crud coming through, because there was black sticky goo all over the float-bowl end of the jet. I quickly ordered one of Moyer's carb rebuild kits and a Racor gas filter, and hose to replace all the existing fuel line.

WHAT ELSE SHOULD I CLEAN? In particular, do I need to have someone flush and clean the fuel tank? Or will the new Racor filter take care of the crud that has obviously built up in there? Is flushing and cleaning the fuel tank something I could tackle myself (with reasonable expectation of not blowing myself up)? If so, is there some kind of solvent I could use to get the persistent crud out?

[Don Moyer]

Hello,

Black sticky goo is not something that I would normally expect to come out of a fuel tank, so before spending too much time and effort on tank maintenance, I'd give the RACOR filter a chance to catch whatever might be coming from the tank.

If the filter remains clean over a reasonable period of time, we'll have to scratch our heads in another direction than the tank. For example, I'm wondering if you might have a restriction in your exhaust system that is creating black sticky residue in your intake manifold that ends up dripping down into the carburetor.

Regards,

Don

[BSquared]

I received my carburetor rebuild kit and Racor fuel filter today -- you guys are good!

The instructions for the Racor filter say not to use Teflon tape with NPT connections, but I've always done that (including when I installed the electric fuel pump a couple of weeks ago). Is it really a bad idea? What do people recommend instead? Should I redo the fuel-pump installation?

[Don Moyer]

The objection to Teflon tape is that small "snippets" of Teflon can break away from the fitting and cause problems in fuel systems (mostly the carburetor). We like old Permatex aviation brand sealer or one of the newer silicone-based Permatex products.

Don Moyer