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Old 10-25-2022, 09:40 AM
dleedvmCNY dleedvmCNY is offline
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A4 not getting fuel

Hi everyone!
I used to be very active here but haven't posted in awhile. My email has changed so I had to change my screen name a bit. I have a 1974 Sabre 28 with an A4. In recent years, I replaced the carburetor and the mechanical fuel pump through Moyer. The engine was running well but we moved, the boat was shipped to our new home, the engine doesn't get used as much and short staffing in the new boat yard has made it almost impossible to get work done. So, I'm rolling up my sleeves again to get reacquainted with my A4!

This Spring we had a tough time getting the engine started. There was a great deal of water in the separator, likely due to a leaky gasket at the tank filler cap (located in the cockpit floor and underwater when the scuppers get clogged...). After flushing that out, the engine still wouldn't start. The shop said it wasn't getting fuel, despite a new fuel filter, and insisted in installing a small portable auxiliary tank to get the boat out of the yard. That didn't really help and it created a lot of gas fumes inside the boat. I have since disconnected the fuel line and can siphon fuel out of the main tank with no obvious problem. I reconnected the line to the original tank. I do use the inline squeeze bulb to prime the carb and it starts great. But it only runs for a few minutes and seems to run out of fuel again.

Maybe there is still junk in the tank but the fuel in the separator looks fine. The fuel pump hasn't had much use but I bought the rebuild kit from MM (just can't remember how to get the pump off now!). What else could it be? If the carb is clogged, would it be running at all? Thanks everyone!
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Old 10-25-2022, 10:17 AM
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joe_db joe_db is online now
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First off, those squeeze bulbs are VERY dangerous. That needs to go once the engine is fixed. I have had them get tiny cracks and leak or just totally split, they are not designed for below decks use.

What really is needed here is a fuel pressure gauge, that will show you right away if you are or are not getting fuel. While you wait for that to arrive, the easy test here is to keep squeezing the bulb. When the engine has run a bit, give it a few more squeezes*. If that works, it is fairly obvious the fuel pump is not pumping.

There is one more danger area to check on, the mechanical pump can leak gas into the crankcase. Check your oil and make sure it doesn't smell like gas.

* We once made a three hour trip with the dinghy fuel tank connected to the engine when the electric fuel pump died. The tank was in the cockpit and we had to squeeze every few minutes for about 18 miles.
Joe Della Barba
C&C 35 MK I
Maryland USA
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Old 10-25-2022, 02:35 PM
dleedvmCNY dleedvmCNY is offline
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Thanks for the awesome post! I agree that the squeeze bulb seemed like a rather janky way to deal with this problem as a permanent fix! I hadn't really considered it being dangerous but that makes total sense. The gas smell in the cabin didn't completely resolve when I removed the portable tank and I am wondering if the hose is leaking somewhere. The hoses on those tanks are much softer than the thick permanent hoses, so I wonder if a hose clamp has split through. I will also check the smell of the oil though, because that also seems pretty likely. Does anyone know where I can get some details on removing the fuel pump? I'm sure I got detailed instructions when I bought the replacement pump. I remember that job being fairly easy. I have all the Moyer videos (on DVD, so not sure I can still watch them). Maybe it was covered there. It isn't in the MM rebuild/maintenance manual. Oh, I also ordered the fuel pressure gauge! Thanks again!

Last edited by dleedvmCNY; 10-25-2022 at 02:38 PM.
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Old 10-25-2022, 09:02 PM
Dave Neptune Dave Neptune is offline
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If you have any question as to the integrity of the fuel lines REPLACE them. A loose fitting, clamp or hose will also keep the pump from pumping by allowing air to be sucked in.

The crud in the tank could also get into the check valves in the pump also reducing pumping action. Some tanks will have access to "snake" a tube into the tank "below" the pick-up tube to suck out the crud.

The carb sounds like it may be OK as it starts when primed.

Dave Neptune
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Old 10-26-2022, 02:33 AM
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A Carb cleaning is in your future.

I'm confused. I have a mechanical fuel pump which has a hand bail underneath that you can use to prime the carburetor. Thus, there is no need for a squeeze bulb, which is dangerous and highly discouraged by the Coast Guard. Maybe you have a different kind of mechanical fuel pump. Mine is the one available from Moyer. I rebuilt my pump over 20 years and many thousands of hours ago and am still waiting for it to leak into the crankcase, as so many warn about. My theory is that using non ethanol fuel with Marvel Oil keeps the rubber parts inside the pump from degrading. With a fuel pressure gauge, you can see when the pump has pressurized the fuel line all the way to the float valve in the carb. You can also feel the resistance in the pump bail go away when that happens.
A clogged carb can definitely run for a while on the gas you pump into it manually past the clog with either the pump bail lever or a squeeze bulb. After that it won't run. Either your carb is clogged, or filters are clogged, the pick-up tube at the bottom of the tank is clogged, or your fuel lines leak. A small leak in the hose won't necessarily leak fuel but it can still take in enough air to reduce fuel flow to the carb. But I doubt that is your problem, because the mechanical pumps create enough suction to overcome a small air leak. Once you shut down, however, gas can leak there. Disassembling and cleaning the jets in the carb is something all A4 owners should be ready to do. I do it every spring to be sure. I replace filters at the same time. In my experience a clogged idle jet or main jet is the usual problem with these engines. If your mechanical pump is a few years old, it is probably fine, unless a lot of crud got into the check valves. That hasn't happened to me, but my tank was cleaned many years ago when the fuel dock mistakenly filled it with diesel and pumped it all out. (When they asked, I said I wanted gasoline, but was ignored. Then the guy after filling said, "You said diesel, right?". Since then, I pump my own darn gas.) I now think they did me a favor.
Much more likely than a clogged pump is a clogged jet. Be sure to remove it, hold it up to a bright light and look through it. The obstruction may be barely visible. I had a tiny clog in the idle jet that kept the engine from running except at high rpm, and then not well. It stalled when reducing throttle. The clog was maybe 1/4 the size of the jet opening. Run a thin wire around in the jet, as compressed air or spray may not be aggressive enough.
You said there was a great deal of water in the separator, but the fuel in it looked good. You did not mention replacing it. The separator could still have water in the filter part, and it can't absorb any more, so it passes water through it into the carb. I also have two inline fuel filters, one before and one after the pump. Unless yours are new, they may be clogged as well.
It is often said that spark, compression, timing and fuel all have to be good, but the fuel part is the most problematic. Clean fuel in the tank is step 1. If you smell even a little gas, you have to check all hoses and fittings to find where it is leaking and fix it. If you have an adjustable main jet, turning it in all the way to the seat and back out 1.5 or 2 turns may clear an obstruction, but the crud will be pushed inside the carb, and end up in a smaller jet.
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