Putting gas into air intake! yikes! – moyer marine atomic 4 community – home of the afourians gas vs electric stove top


I tried for days to get my A4 to start for the first time this year. First I put some Marvel oil into the cylinders, let it soak in overnight, and cranked to get the pistons lubricated again after 5 months off. I cleaned the carb, put on new filters and fuel hose, new cap and rotor, new plugs, new coil and EI module. Set the initial timing according to Don’s video. Using the bail next to the mechanical fuel pump, I pressurized the fuel line to the float valve in the carb. It took a while to hand pump gas from the tank, through the filters, and up to the float valve before I no longer felt resistance on the bail, and it went limp. Fuel pressure was 3 and holding. In the past the engine would start once the fuel line pressurized, but not this time. Spark was improved after replacing coil, EI unit and optical trigger. But no sign of it wanting to start. Turning the distributor a bit back and forth made no difference. The choke worked properly. Compression is ok. No water in the oil.

So I called the local boat engine guy, and he had it running in 10 minutes, using a trick that I had not heard of anywhere in the Moyer manual or forum, probably for good reason. It seemed a little scary at the time, but it worked. After checking for spark by holding the coil wire over the block, he pulled a spark plug, and it didn’t smell like gas. Then he asked if I had any starter fluid, but I didn’t. So he actually poured maybe a tablespoon of gas into the air intake, through the flame arrestor. (I turned on the blower.) Then the engine finally sounded like it wanted to start. So we turned the distributor a bit, and bingo, she ran. Once running she could draw fuel in no problem. We turned the distributor to make it sound better, and again under load at cruising rpm. It has been starting well since then.

I don’t know why priming the fuel line with the mechanical bail was not enough to get her to run this time. I thought having good fuel pressure would be enough. There may have been an airlock in the line despite the fuel pressure reading. Maybe the MMO I put in the cylinders was affecting ignition. But apparently, pouring a bit of gas into the air intake enabled the scavenge tube at the bottom of the carb to pull the gas into the intake manifold, bypassing the carburetor. Then the air/fuel mixture became rich enough to fire. Another Atomic 4 educational moment.

Tenders, it occurred to me while replacing all this stuff shotgun-style that it wasn’t a troubleshooting method. I should have tried to start it after each change, to isolate the problem, and to educate myself about the engine. But I wanted to make sure what the problem wasn’t, besides generally upgrading the components. That is a good point about how this non-method creates problems if any one of several things is installed improperly, I guess I was relying too much on my ability to install stuff correctly. In my slap-dash attempt to fix everything at once, I did make the spark stronger with a new coil. Afterwards I discovered that the old coil was leaking oil. The EI may not have needed to be replaced, but it has been upgraded anyway. Lack of fuel seemed to be the problem, because the spark plug didn’t smell of gas, and adding fuel to the carb intake made it at least try to run. Timing was also the problem, because turning the distributor made it actually run. You hit on the big question; how is it possible that fuel was the problem if there was good fuel pressure? That puzzled me too. Apparently timing was the real issue, although I thought I had set initial timing correctly. To me, ‘cleaning the carb’ includes removing jets, inspecting them, and poking out the passages, reaming out the float valve seat with a pointed dowel, replacing gaskets, and seeing that the choke works properly. Also that the idle screw and adjustable main jet are set correctly. And that the floats bracket has the right gap to the float valve.

Joe, I have never used ether to start the engine in 24 years of operation, but there may have been many times when it could have helped start it, and with diagnosis. It starts fine now, but it may be adjusted a little lean, as it doesn’t fire up as vigorously as I would like.

John, I didn’t mention that I serviced the advance also, as part of my non-methodical effort to get it to start. The parts under the breaker plate were rusted and sticking a bit. I took the rust off and oiled the parts well. Did I then try to start it, to be scientific about it, and further isolate the real problem? Nope. I just moved on to the next thing the problem could be. As a result, I don’t know for sure what the actual fix was.

Rom-com, thanks for pointing out that it wasn’t the scavenge tube that made the difference, it was by dumping the fuel in to make the air richer to begin with. Running the bowl dry at lay up is a good idea, and I have done that, but at the end of last season it wouldn’t start to do so, and I put off the diagnostics until spring. That’s why I cleaned the carb before trying to start it this year. Draining the carb by removing the main jet is awkward with the lack of space. It’s hard to put anything underneath the carb to catch the fuel and keep it out of the bilge. So I remove the carb, and then drain it.

John, actually I didn’t try setting the timing until after I put the advance back together. I set the initial timing according to the Moyer video, or so I thought. I had a test light between the terminals of the coil, and the engine at #1 TDC, the rotor pointing away from the block, and the tab on the breaker plate under the rotor. I rotated the distributor counter-clockwise until the light went off, and tightened the hold-down. This has worked in the past to make the engine start, but not this time. I think I had the distributor turned too far to begin with, a quarter turn off. The light was lit, but I guess for another cylinder, either #2 or #3. Thus it wouldn’t start because the firing order was wrong. I think I should have paid more attention to the tab on the breaker plate being under the rotor. I don’t know what else it could have been. Once the gas was dumped into the carb, and I heard the faintest hint of firing, we went straight to turning the distributor, searching for the point it would start at. I don’t know how far or in what direction my friend turned it to get it to start. Looking at the engine now that it’s timed at speed, at #1 TDC the rotor and tab are lined up, pointing directly away from the block. That’s where I thought I had set it.

Yes, and the peace of mind comes from knowing what you did to make the engine reliable. Or course, you never know. You might have done something else wrong, or neglected to do something right, and made the engine less reliable, only you don’t know it yet. Every engine is reliable right up to the time it isn’t. That’s why you learn your engine, practice constant vigilance, and think ahead. You have not doubts, but concerns. Doubt is when you know that you don’t know what you don’t know. Concern is "What could go wrong here?" For instance, right now I’m thinking I should check the zinc in my heat exchanger.

There are lots of people uncomfortable on the water. That doesn’t mean they should stay ashore. You get comfortable by working on what makes you uncomfortable. There is always a little bit of adventure in leaving the dock. That’s why we do it. The most important thing for a sailor to know is when to stay in port. But if I had always waited until I felt that the boat and I were totally ready for whatever might happen, I wouldn’t have accumulated this experience, such as it is. Now I’m more careful. Reliably careful, I hope.