Yamaha 115 4 stroke, starting problem

[Prof Thomas]

Here's a good 1, help ! Went to Change gas tanks, motor IMMEDIATLY won't start, unless in neutral with throttle advanced. Dies when put in neutral to shift into gear. Checked fuel lines, Mechanic reccomended replacing fuel pump. replaced both fuel pumps, hi & low pressure. Motor immediately started, ran. Went out twice. went to change tanks on 2nd trip. Immediately won't start again ! If it was bad gas in 2nd tank, it should have started and run for a little bit before the bad gas got to cylinders. Both times changed back to 1st tank, not starting. It will start in neutral with throttle advanced but dies in neutral before I can put it in gear. Fuel is getting too cylinders, fuel rail has pressure, checked hoses, clamps. Put new fuel in 1st tank & sea foam ? Still can't get in neutral to engage. Is this a vacuum hose ?
Is it electrical ?

 

[99yam40]

Here's a good 1, help ! Went to Change gas tanks, motor IMMEDIATLY won't start, unless in neutral with throttle advanced. Dies when put in neutral to shift into gear. Checked fuel lines, Mechanic reccomended replacing fuel pump. replaced both fuel pumps, hi & low pressure. Motor immediately started, ran. Went out twice. went to change tanks on 2nd trip. Immediately won't start again ! If it was bad gas in 2nd tank, it should have started and run for a little bit before the bad gas got to cylinders. Both times changed back to 1st tank, not starting. It will start in neutral with throttle advanced but dies in neutral before I can put it in gear. Fuel is getting too cylinders, fuel rail has pressure, checked hoses, clamps. Put new fuel in 1st tank & sea foam ? Still can't get in neutral to engage. Is this a vacuum hose ?
Is it electrical ?

if it is already in neutral to start, why are you trying to put it in neutral

 

[Prof Thomas]

if it is already in neutral to start, why are you trying to put it in neutral

It has to be in neutral to start, but will only start with throttle advanced, reved up. Then you put it in neutral, ( at idle) to put it in gear.

 

[CaptnKingfisher]

So this problem occured right after changing tanks? A new fuel pump temporarily fixed the problem, immediately came back after switching tanks and the problem persisted when you switched back.. I'm thinking you had bad fuel or some sort of debris in the gas tank. I'd remove the fuel lines and blow em out with an air compressor but it's likely whatever got in has your carb plugged up now and may need a rebuild. I don't like to jump into a carb rebuild til I eliminate other possibilities so just for the sake of making sure it's not something to do with the ignition circuit I would use an adjustable spark tester to verify strong spark (7/16") on each cylinder. How many rpms when you are at fast idle?

 

[Prof Thomas]

So this problem occured right after changing tanks? A new fuel pump temporarily fixed the problem, immediately came back after switching tanks and the problem persisted when you switched back.. I'm thinking you had bad fuel or some sort of debris in the gas tank. I'd remove the fuel lines and blow em out with an air compressor but it's likely whatever got in has your carb plugged up now and may need a rebuild. I don't like to jump into a carb rebuild til I eliminate other possibilities so just for the sake of making sure it's not something to do with the ignition circuit I would use an adjustable spark tester to verify strong spark (7/16") on each cylinder. How many rpms when you are at fast idle?

After the 1st breakdown, I drained all the fuel lines, they looked good. Changed both fuel pumps. High pressure pump in VST was a beast to get to. Had to remove intake, then refilled original tank. No carb, fuel injected. VST tank wasn't dirty. Changed plugs. When all back together, Motor started, I ran it in neutral at all Rpm ranges, Took it out ran through all RPM's again in gear, or under load. 2nd trip, went to change tanks, dead.
I changed gas tanks lots and it always starts IMMEDIATLY. Neither time here. Runs great at all RPM's, but won't " click " into neutral, or start there. Turns over, almost coughs, just won't start.

 

[Prof Thomas]

After the 1st breakdown, I drained all the fuel lines, they looked good. Changed both fuel pumps. High pressure pump in VST was a beast to get to. Had to remove intake, then refilled original tank. No carb, fuel injected. VST tank wasn't dirty. Changed plugs. When all back together, Motor started, I ran it in neutral at all Rpm ranges, Took it out ran through all RPM's again in gear, or under load. 2nd trip, went to change tanks, dead.
I changed gas tanks lots and it always starts IMMEDIATLY. Neither time here. Runs great at all RPM's, but won't " click " into neutral, or start there. Turns over, almost coughs, just won't start.

I should be more clear, if the gas in first tank was good, there are 2 h2o separators, high pres. Pump is in a tank with 1/2 cup, plus gas in lines, it should start on good gas before dying from bad in 2nd tank. Since I've replaced most of the fuel system, is there an sporadic electrical problem possible here, relay ? Could a vacuum line be sporadic like this ?

 

[CaptnKingfisher]

Vacumn leaks are pretty easy to test for. Plenty of videos on YouTube that can prolly give you a better explanation than I could as I'm not familiar with fuel injection systems but get a can of carb cleaner and spray it around the intake manifold and around hose connections etc while the engine is running. If you hear the engine stumble, rev, or stall while you're spraying one of these locations then you've found a vacuum leak

 

[Prof Thomas]

That's a brilliant hack. When the sun comes up I'm on it. Hope it works. Petty Officer, you're a Gentleman & a Scholar. Thanks

 

[QBhoy]

Hi. Any chance your fuel line from tank to engine is on the wrong direction? The primer bulbs are mostly unidirectional and one way.

 

[Prof Thomas]

Nope, know about the direction and the arrow points to the motor