new carb good fuel and spark same proglem

[chiron]

This is a new (50 year old) boat to me and am rapidly learning all about the Atomic 4. Thanks everyone for this wonderful site to help me along. Since I purchased my h-28 6 months ago I have had a common problem of the engine dying on me in the fuel related sort of way after 40 minutes or so.

I have clean fuel with the both fuel filters.
My mechanical fuel pump works fine.
No known fuel or air leaks.
Spark at the coil and plugs.
I just rebuilt the carb and installed the indigo crankcase ventilation kit.

After rebuilding the carb and a little difficulty getting it started it ran like never before. purred like a kitten had great throttle response and more power than ever. Then like before after 40 minutes of motoring it bogged down and eventually died. Usually I could just shift to neutral and let it run for a bit and continue motoring but this time I had to get towed. Now she wont start at all. I pulled the carb and everything checked out. Good clean fuel and spark. You could probably guess where my love and hate relationship is right now. Anything ells I should look for.

Thanks
Chad

[ndutton]

Except that you report good spark and up until the point where she won't start at all I was thinking coil all the way. We've seen time and time again where the coil fails with heat and the symptoms mimic fuel starvation. The time required for sufficient heat to build is usually around 30 - 45 minutes, then after 15 minutes or so of non operation it cools enough to start again only to repeat the cycle.

[sastanley]

Chad, are you sure you have good spark after the 40 minute failures episodes? I thought I had a fuel related shutdown too, but it turned out to be a dying coil...letting it cool off would give me 60 more minutes of run time, but eventually it would get hot and stop running again until cool. edit - oops, ha ha, Neil beat me to it...

Since you just cleaned the carb I might assume it is in good shape for now...Just something else to check...

The real check for a fuel related shut down is to install a fuel pressure gauge inline just before the carb...that will instantly eliminate everything before the gauge if it reads good pressure during a shut down. Dave Neptune is the fuel pressure expert around here. Another way to check during your no-start condition is to see if fuel is puddling in the bottom of the carb throat (near the choke butterfly I think) - you'd need to remove the flame arrestor to observe this area.

[chiron]

Wow such quick responses. Thanks.
I should probably clarify when I said good spark all I really saw was that I had spark. And I did pull off the flame arrestor and had some fuel puddling at the bottom of the carb. Is this an issue? I assumed it was from me turning over the engine so much without it firing up and the unburned fuel just collected there. I was told that the engine had been rebuild a couple of years before I acquired it as indicated by lots of new cool stuff that did not come with the early model like fuel and oil filters electric ignition fresh water cooling and a late model carb which barely fits once I installed the spacer for the crankcase ventilation. I guess I shall try new coil and plugs.

[ndutton]

Yeah, big difference between a good, hot spark and any spark. With electronic ignition be sure to get a coil with the proper resistance, 3 - 4 ohms as I recall. Buy one from Moyer and you can't go wrong.

[Baltimore Sailor]

I'll throw in my 2¢ and hope that the raw water through-hull is closed during all this cranking to try to get the engine started. Don't need to add water in the cylinders to any other problems.

[sastanley]

chad, fuel puddling probably indicates the carb is getting fuel. Another reason I may move that one down the list & check in on good spark.

A coil ranges in price from $30-40...they often last for years and years (mine lasted 31), but if you do not know when it was last replaced, it probably won't hurt. Keep the old one as a 'limp home spare' since you know it will go for 40 minutes at a stretch.

Champion RJ8 (original Universal recommendation) or RJ12C (slightly hotter plugs) are the most common. If I remember my numbers, I also think Autolite 303's & 437's are OK to use too.

BS's comment is a good one too..during prolonged cranking (& non-running) events there is no exhaust gases to expel the raw water accumulating in the muffler/exhaust system..it is common for it to back up the hot pipe while cranking and then dump into the cylinders. The time it takes for this to happen varies with each system, but I know mine was flooded this way twice before I owned the boat. I usually close my raw water thru-hull until the engine starts if I've done 15-20 seconds of cranking.

One more check, while you have the flame arrestor off, double check that the choke butterfly closes ALL the way when the choke cable is pulled..even a slight mis-adjustment here makes starting these old engines difficult.

[Dave Neptune]

Hmmm!

Chad, since you said you could let her idle for a bit and then you could power back up makes me think fuel delivery. Usually if a coil cuts out it does so completely and will through a spark again after it cools a bit.
You can check the spark when the power drops but you would need a fuel preassure gage to check the fuel delivery. Are you a mechanical or electric pump?

Dave Neptune

[sailhog]

I had a problem that was very very similar, and it took me a looooooong time to figure out what it was.

This is what it turned out to be: I had changed my Racor when I bought my boat, and she consistently died with all the symptoms of fuel starvation. Eventually someone (Ken at MM) told me to install a priming bulb between the tank and the Racor. After pumping it a few times to fill the line with a CONTIGUOS column of fuel, the siphoning affect allowed for the consistent flow of fuel to the pump. The problem was magically solved.... Hope this works for you.

[roadnsky]

I had a problem that was very very similar, and it took me a looooooong time to figure out what it was.

This is what it turned out to be: I had changed my Racor when I bought my boat, and she consistently died with all the symptoms of fuel starvation. Eventually someone (Ken at MM) told me to install a priming bulb between the tank and the Racor. After pumping it a few times to fill the line with a CONTIGUOS column of fuel, the siphoning affect allowed for the consistent flow of fuel to the pump. The problem was magically solved.... Hope this works for you.

Chad-
What Dave said...
"Are you a mechanical or electric FUEL PUMP?"

[tenders]

He said in the initial post that he's got a mechanical fuel pump. A possible source of the problem, but seems unlikely if he's getting fuel pooling in the intake.

Chad, with all the futzing you've done with the carb and the crankcase ventilation kit you might want to check all those fittings again for poor sealing.

I have a pretty good feeling about your prospects here. This is going to be one little thing and you'll be off to the races again.

[chiron]

Thanks again everyone. And especially thanks for the reminder to close the water inlet. I keep forgetting that one. So I did buy a new coil and plugs although with a broken hand it took me the entire afternoon just to get the carb back on. That extra spacer supplied with the crankcase ventilation kit puts the bottom of the carb (fuel return line) pinched on the mounting plates of the engine, and can be (I mean is) a pain one handed in 20 deg weather working blind. But I did get it started, it did take a shot of starter fluid. It idled great and in neutral had great throttle response. Oil pressure was 30 and temp was 145. Tomorrow I hope to get a chance to install the coil and new plugs. Worst case I will have an extra set of each just in case.

You guys are great.
Chad

[chiron]

Well I made it back out to the boat and replaced the coil and plugs. It took a bit for her to fire up but that may be from the mystery oil I put in the cylinders while the plugs were out. So she sat there idling fine at 700 rpm temp never getting over 145 and oil pressure between 30 and 40 psi. Then after 30 minutes or so the rpms began to drop and it eventually shut down. I had to run to get home for a dinner party so I did not get a chance to diagnose the problem. My gut is telling me this has to be fuel related. The polishing fuel filter I recently installed does have air in it but I can observe fuel being pumped through it. The fuel is clean with no water. What am I missing. I have a feeling that I will end up dumping a couple hundred into fixing a 25 cent problem.

Thanks
Chad

[CapeCodPiper]

My A-4 sometimes acted like this before I replaced the distributor points with an Indigo/Electronic system. With the old point system, it is rather hard to set them up "just right". And then, when they look good on the dwell meter, the setting does not account for the fact that the engine warms up and slightly changes the metalurgy of the points which changes the gap.

Of course if you have changed over to Electronic points, this is all moot. However, might there be a way that the gradual warming of the engine changes something else for the worse, like allowing a leak in a fuel line to get worse which lets air in so you lose prime?

Just thinking...

[hanleyclifford]

Do you have the electronic ignition or do you have points and condenser?