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Nissan 3.5 hp has issues!

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Nissan 3.5 hp has issues!
Carb has been cleaned and is all shiny like three times.

Gas is good.

Runs and then just shuts off.

Jet is clear but it is acting like the fuel is shutting off.

Engine is peeing.

It runs nicely and then it shuts off. Sometimes on high speed sometimes at idle but then it shuts off. Get it going and it will run and then die.

Any ideas?

Something electrical maybe? Where would we look for that?

Currently the kill switch assembly is off so it should just run and run and run.
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Re: Nissan 3.5 hp has issues! In reply to
Could possably be something heating up and shorting out but Sounds more like a fuel delivery issue than electrical. Make sure tank vent open to start with.. Check ,tank for debris against pickup screens. Hose for interior collapse. If all good there move to motor. Fuel bowl filter, Fuel pump. Bring up schematics of your motor and basicaly troubleshoot everything delivering fuel. Forgot to ask but will motor keep on running if choked?

Last edited by:

roy brewington: Apr 10, 2022, 1:09 PM
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Re: Nissan 3.5 hp has issues! In reply to
Has internal tank and if you take the top fuel cap off it acts the same as if it is on and the vent is open. Runs a short amount of time and then turns off.

take the drain plug off the bottom of the carb and the gas flows freely. No fuel pump....gravity fed.

Fuel filter not clogged. Fuel line not clogged.

Dies if you keep it choked.
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Re: Nissan 3.5 hp has issues! In reply to
just hunt or fish close to the ramp. :)

As a side note, I wonder how many of us have those. I have one and I know there are others.

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tod osier: Apr 10, 2022, 3:49 PM
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Re: Nissan 3.5 hp has issues! In reply to
Dani, I agree with Roy, sounds like a fuel delivery issue. Had a motor that acted like that....... there was a tiny piece of plastic in the bowl that would jam up the jet. Ran fine after I got it out.


Pete


MOLON LABE [mo 'lon la 've]

Technology has it's place, hunting isn't it.

Life's a blink, never have to say ....... "I should have"!

"That human optimism & goodness that we put our faith in, is in no more danger than the stars in the jaws of the clouds." .................Victor Hugo
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Re: Nissan 3.5 hp has issues! In reply to
My Merc 25 is doing the same sorta thing except it will get up to speed, run fine and then suddenly die back to idle. I have ordering a fuel pump kit on my to-do list.

If yours is completely shutting down, I wonder if its a coil issue?
I read that a cracked/damaged coil will expand and drop spark once it gets hot. Once it cools off & contracts, it run fine until hot & expands again.


Carl
Mobile, AL
DHBP Member since 1998

"Life is too short to drink bad beer."
Disclaimer: This post and/or report is not a substantiation of or reflection on the true accuracy of the present surveying methods. It is only a report on or comment concerning local observation and/or results. Your results and observation may vary based on your location, local water conditions, food supply, weather conditions and migratory patterns "
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does it start right back up or does it have to cool down for several minutes?
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My dad thinks it is something fuel related too. He is trying to figure out the best way to clean the jet other than just spraying stuff into it..maybe a wire could be run through the hole in the jet? The carb itself is squeaky clean and shiny. He doesn't think the float is floating too high or too low but he didn't seem inclined to totally rule that out at this point. We were talking about different ideas last night on why it isn't working cuz it is such a simple system.

It doesn't get hot or even warm enough to need a cool down. Doesn't run long enough that the spark plug even warms up much. It will usually start back up fairly easily once gas from the tank has gotten back in the carb and then it will run until that amount of gas is gone it seems like.

When it runs for that short amount of time, it is running and purring the way it is supposed to. My dad played with the choke some yesterday afternoon and he can force it to run as it is dying by choking it momentarily and then reopening the choke. But even doing that, it still didn't prevent the motor from dying after a bit.
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Re: Nissan 3.5 hp has issues! In reply to
Mine completely shuts down when it "runs out" of gas it seems like. My dad is going to get a new spark plug just to rule that out. The motor just isn't running long enough to get hot so not sure....I had asked about the coil when he started talking about the magnet and how a spark is created. He doesn't "think" it is that but not positive at this point.
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I have noticed with mine that it takes quite a while for the bowl to fill once the fuel valve is opened. It won't start for a minute or two, but it will start one pull if you let it sit for a minute after opening the valve.

Obviously, you have the case opened up and can see any restriction in the line. Have you pulled the fuel line off the carb to see how fast the flow is?
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Re: Nissan 3.5 hp has issues! In reply to
tod osier wrote:
I have noticed with mine that it takes quite a while for the bowl to fill once the fuel valve is opened. It won't start for a minute or two, but it will start one pull if you let it sit for a minute after opening the valve.

Obviously, you have the case opened up and can see any restriction in the line. Have you pulled the fuel line off the carb to see how fast the flow is?


That is essentially how the motor reacts.

We removed the drain plug from the carb and it pees gas quite freely for quite as long as you leave it open. I asked my dad about something being in the hose itself. He took it off and inspected the hose, trimmed one edge off just because it was split a bit. He blew through it with no issues, though I don't recall if he fed something through the line itself just to make sure there wasn't a spider web or something in it that was partially blocking the hose.

He says the fuel filter isn't clogged, but maybe it is so small that it wouldn't be obvious? Maybe? I also asked about the possibility of the fuel shut off valve having something going on with it as the problem...but he thinks that gas wouldn't pee so freely from the carb when you take the drain plug off if either of those two things were an issue. Which makes sense I think.
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I,ve never had the need on a boat motor carb but in the past have cleaned jets in mower carbs with a piece of stranded copper wire unwound from a cut lenght. I,m still thinking clogged jet especially if it can be kept running for a bit by choking. Just because inside of carb bowl is clean doesn,t mean that interior of jet is. A bit of varnish can cause big headaches.
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Dani,
You can clean the jets with a soft wire like Roy said. Just don't use anything made of a hard metal like a steel brush for example. Copper wire is a good choice.

It does sound like its a fuel problem. Is the fuel filter in line? If so you could try by passing it to see if its slowing the flow down to the point the engine is starving. Otherwise I would look for a jet that is clogged or something under a needle valve that you missed.

"UNLESS someone like you cares a whole awful lot, nothing is going to get better. It's not."

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Thanks guys...I'll pass the ideas along.

Brandon, the fuel filter is inside the fuel tank....I didn't take a close look at it but I think it is possible that it could be removed and that test done....
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   Had a similar issue with my 3.5. Turns out the vent on the fuel cap wasn't venting. Would run then suddenly quit. I ended up punching a small hole in the cap gasket.
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Had a similar issue with my snowblower this year. Small motor, gravity fed fuel and so on. took apart the carb and cleaned it good. Put back together and the same thing. Would start and run for awhile and shut down. Took the carb off again and took out the jets. Inside one of the jets was a tiny piece of something (looked like grass but how the heck would that get in there). Got it out, reassembled and the snowblower ran like a champ again. My bet would be a bad or clogged jet. Doesn't take much to disrupt a carb jet.

Just a guess for what it is worth.

Mark
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Re: Nissan 3.5 hp has issues! In reply to
Thanks Mark...