At the end of my rope with this Mercury !!

[99scout1976]

Good day everyone...
Ok here is my issue . I have a 1999 2 stroke 90hp mercury and when i attach the fuel line it dies. Now from reading past post of similar problems i found out it could be a bad fuel pump, stuck carb or even a bad primer bulb. So here's the kicker...
I rebuilt the fuel pump first after doing so i put it on the hose and it fired right up and ran fine, problem solved or so i thought two days later i put it back on the hose and it's the same problem as before runs fine as long as the fuel line is disconnected but as soon as i connect the fuel it dies. So now i rebuild the carbs and boom problem solved starts right up runs fine take it out fishing all day fri. without a problem, it sits for one day and i put it back on the hose and pow... same problem as before..... will only run with fuel line disconnected.... so i replace the primer bulb... and wouldn't you know it runs great again... this time i wait about 30 mins and try and start her back up and once again same problem ...will only run with fuel line disconnected! So i redo the fuel pump redo the carbs and it still currently will only run with the fuel line disconnected.... It acts as if it is flooding out which is why it will only run with fuel line disconnected. I am positive the carbs are good pretty sure about the fuel pump,... i am at the end of my rope. Any help would be great! thanks.

 

[schematic]

Re: At the end of my rope with this Mercury !!

Is it possible your fuel pump has a cracked diaphram or cracked body and is flooding engine? Undo pulse line, and squeeze the primer ball. Watch for fuel escaping pulse line...

 

[bldgengineer]

Re: At the end of my rope with this Mercury !!

did you check the float level on the carbs? I know the manual says to make them even with the float bowl but I like mine slightly lower to keep a good seal. Also, how do the needle valves look? sometimes the rubber can be a little deceiving as well as the seats. If the seats are damaged in any way it will cause a flooding condition. Learned this the hard way on my bike. I know you say you pretty sure they're good but maybe something got overlooked? It's easy to do with a single or dual carb setup. I just did the three 2 barrels on my 200 and didn't realize until the 3rd carb that I was forgetting to put the gasket on my needle seats.

 

[99scout1976]

Re: At the end of my rope with this Mercury !!

Is it possible your fuel pump has a cracked diaphram or cracked body and is flooding engine? Undo pulse line, and squeeze the primer ball. Watch for fuel escaping pulse line...

Replaced the diaphragms with the new ones from the rebuild kit, body is in good shape. Don't think i have a pulse line... one line from the fuel tank in and two going out to top and middle carb with a hole in the fuel pump which meets up to hole when mounted to the engine that goes into the bottom cylinder if i'm not mistaken. Will re-look this to make sure. Thank you for the reply.

 

[99scout1976]

Re: At the end of my rope with this Mercury !!

I did not do anything with the float level ..... i assumed if i put it back together with the rebuild kit same way i took it apart it would be good. the tabs which i would have to bend to adjust float level are on the floats them self's and do not appear to have ever been adjusted. Is this a step i missed? When installed the floats are not level with the carb at all but i assumed because that's how it was when taken apart that that's how it should be... wrong? Needle valves were replaced with new ones from the kit. Thank you for your help .

 

[Texasmark]

Re: At the end of my rope with this Mercury !!

How can you possibly run your engine with the fuel (source) line disconnected? Makes absolutely no sense to me. Like running your engine on thin air.

 

[wired247]

Re: At the end of my rope with this Mercury !!

Your float level is wrong. Only possible explanation.

 

[bldgengineer]

Re: At the end of my rope with this Mercury !!

I did not do anything with the float level ..... i assumed if i put it back together with the rebuild kit same way i took it apart it would be good. the tabs which i would have to bend to adjust float level are on the floats them self's and do not appear to have ever been adjusted. Is this a step i missed? When installed the floats are not level with the carb at all but i assumed because that's how it was when taken apart that that's how it should be... wrong? Needle valves were replaced with new ones from the kit. Thank you for your help .

When you put your fuel bowl back together, you turn it upside down so that the float acts as if its full. Put a straight edge across the bowl and the float should just touch it. I typically keep mine at around a .050 higher than the straight edge. Been doing this forever and never had a problem with fuel after a rebuild.

 

[GA_Boater]

Re: At the end of my rope with this Mercury !!

I did not do anything with the float level ..... i assumed if i put it back together with the rebuild kit same way i took it apart it would be good. the tabs which i would have to bend to adjust float level are on the floats them self's and do not appear to have ever been adjusted. Is this a step i missed? When installed the floats are not level with the carb at all but i assumed because that's how it was when taken apart that that's how it should be... wrong? Needle valves were replaced with new ones from the kit. Thank you for your help .

I wish I had this problem. Never need to fill up again. :lol:

Your motor wasn't running right, so you rebuild the fuel pump. Didn't fix it, so rebuild the carbs and didn't fix it. So replace the bulb and still no fix. And then you say when you did the carbs you put in new needle valves. Of course the float level needs to be adjusted, that's why the instructions in the kit say that. Any other thing you skipped? Like the idle mixture?

 

[99scout1976]

Re: At the end of my rope with this Mercury !!

How can you possibly run your engine with the fuel (source) line disconnected? Makes absolutely no sense to me. Like running your engine on thin air.

With the fuel connected it floods the engine , i then have to disconnect the fuel line and the engine runs burning the fuel already in it. As it is running off the fuel previously put it in from having the fuel line connected, if i reconnect the fuel line it dies.

 

[99scout1976]

Re: At the end of my rope with this Mercury !!

I wish I had this problem. Never need to fill up again. :lol:

Your motor wasn't running right, so you rebuild the fuel pump. Didn't fix it, so rebuild the carbs and didn't fix it. So replace the bulb and still no fix. And then you say when you did the carbs you put in new needle valves. Of course the float level needs to be adjusted, that's why the instructions in the kit say that. Any other thing you skipped? Like the idle mixture?

This is my first time rebuilding anything. I purchased the rebuild kits from a local mercury dealer and while the fuel pump kit did have directions even though they were very vague. The carb kits had no directions with them. I you-tubed how to rebuild them. I would also like to add that for the last year and a half i had no problems with this engine i go out fishing almost every weekend so it never sits for more than 5 days. This problem arose last weekend when i could not get the engine started at the boat ramp. After rebuilding / replacing bulb engine would run but then return to the same problem. Never touched idle mix. Thank you for your replay and sorry if my original post was confusing.

 

[99scout1976]

Re: At the end of my rope with this Mercury !!

When you put your fuel bowl back together, you turn it upside down so that the float acts as if its full. Put a straight edge across the bowl and the float should just touch it. I typically keep mine at around a .050 higher than the straight edge. Been doing this forever and never had a problem with fuel after a rebuild.

Thank you for your input.... i will take the crabs back apart and adjust the floats. I will let you know how it works.

 

[bldgengineer]

Re: At the end of my rope with this Mercury !!

With the fuel connected it floods the engine , i then have to disconnect the fuel line and the engine runs burning the fuel already in it. As it is running off the fuel previously put it in from having the fuel line connected, if i reconnect the fuel line it dies.

This definitely sounds like a float issue. Once you disconnect the fuel line and try to start it, the excess fuel gets sucked in and what's left in the bowls is keeping the motor running. Hope it works out for you!

FYI - start putting Marine Stabil in your fuel at every fill up and hopefully you have a decent filter before and after your fuel pump. Most likely the carbs needed to be cleaned and you had a "slight" flooding issue that was made worse by not readjusting the floats after the needle replacement. I've had everything from a tiny piece of crystallization to a freaking leaf flood out a carb on me....

 

[99scout1976]

Re: At the end of my rope with this Mercury !!

Update:
I went into my local dealer to ask about setting the float levels on the carbs and explained the problem to the mechanic who suggested before i tear apart the cabs for a third time to test the auto choke solenoid. To do so he said to disconnect the fuel line to the solenoid and blow into it, if air passed freely without pressing the little button on the top of the solenoid then it was bad. So i tried this and no air would pass indicating it was working properly. I then decided to try to start it up and it started and ran with the fuel line connected. As it has done this before and then not ran with the fuel line connected i decided to turn it off and let it sit and try again in a few mins. and wouldn't you know right back to the same problem.. I then tested the auto choke solenoid again in the same manner as stated above and sure enough i could blow air threw it without pushing the button indicating the choke solenoid is in fact bad. So my new plan of action is to replace this auto choke solenoid which i am sure is the culprit. After i buy this new part i will have a total of 180 bucks i have sunk into this issue . When compared to what it would have cost to take it in to be worked on i feel im still ahead of the game but i have put money and time into fixing things that probably did not need fixing but that's the DIY tax i suppose. The new auto choke solenoid had to be ordered so it will be a few days before i am able to share the results. I have my fingers crossed and will keep everyone posted. Thanks to everyone for their input.

 

[Texasmark]

Re: At the end of my rope with this Mercury !!

Agree on the floats too. A rough rule of thumb is to install the float in the carb, and turn the carb upside down with the bowl off. The float is usually parallel with the casting that connects to the bowl when properly set.

To test, put the carb(s) back on the engine with fuel lines connected. Hold all three floats gently parallel with the bottom of the carb casting. With the squeeze bulb firm, allow one float at a time to fall. when you do, that carb should squirt fuel.....that would go into the bowl if it were installed.

If you can control the flow with all 3 floats you should be good to go. If you can't then I would suggest that your needle valve that allows fuel into the bowl is defective.

HTH,
Mark

 

[buddybo]

Re: At the end of my rope with this Mercury !!

Agree on the floats too. A rough rule of thumb is to install the float in the carb, and turn the carb upside down with the bowl off. The float is usually parallel with the casting that connects to the bowl when properly set.

To test, put the carb(s) back on the engine with fuel lines connected. Hold all three floats gently parallel with the bottom of the carb casting. With the squeeze bulb firm, allow one float at a time to fall. when you do, that carb should squirt fuel.....that would go into the bowl if it were installed.

If you can control the flow with all 3 floats you should be good to go. If you can't then I would suggest that your needle valve that allows fuel into the bowl is defective.

HTH,
Mark

When I'm working on a engine whether it be a boat motor, lawn mower, motorcycle, atv, or anything that has a carb and I think it has a gas feed issue. I usually start by pulling the carb or carbs and draining the gas from it and with the carb in my hand upright, blow gently into the carb where the gas line connects. This tells me if the needle is stuck. With the carb in my hand turned upside down, blow gently in the carb, this tells me if the needle is sealing or not.

I hardly ever have to buy a carb rebuild kit with the exception of maybe a couple needle and seats because they wouldn't seal. Usually a good cleaning works for me and if someone else has not been screwing with the float level, I hardly ever have to mess with it.

 

[Texasmark]

Re: At the end of my rope with this Mercury !!

Update:
I went into my local dealer to ask about setting the float levels on the carbs and explained the problem to the mechanic who suggested before i tear apart the cabs for a third time to test the auto choke solenoid. To do so he said to disconnect the fuel line to the solenoid and blow into it, if air passed freely without pressing the little button on the top of the solenoid then it was bad. So i tried this and no air would pass indicating it was working properly. I then decided to try to start it up and it started and ran with the fuel line connected. As it has done this before and then not ran with the fuel line connected i decided to turn it off and let it sit and try again in a few mins. and wouldn't you know right back to the same problem.. I then tested the auto choke solenoid again in the same manner as stated above and sure enough i could blow air threw it without pushing the button indicating the choke solenoid is in fact bad. So my new plan of action is to replace this auto choke solenoid which i am sure is the culprit. After i buy this new part i will have a total of 180 bucks i have sunk into this issue . When compared to what it would have cost to take it in to be worked on i feel im still ahead of the game but i have put money and time into fixing things that probably did not need fixing but that's the DIY tax i suppose. The new auto choke solenoid had to be ordered so it will be a few days before i am able to share the results. I have my fingers crossed and will keep everyone posted. Thanks to everyone for their input.

Hope it works for you. I have read where the fuel is injected into the intake manifold even though it is plumbed to the right side of the carb. To me that is a separate circuit from your supply from your bowl, but it makes perfect sense. When you have the fuel source connected, under squeeze bulb pressure, and with the enhancement valve not closing, yes you would flood the engine with excessive fuel. Removing the fuel line removes the fuel source to the enrichment valve but the engine, as you said, still has the carb bowl full of fuel from which it can run till dry.

I think you have your problem nailed and might thank the mechanic that put you onto it.

Mark

 

[99scout1976]

Re: At the end of my rope with this Mercury !!

FINAL UPDATE:
received my new auto choke solenoid yesterday and installed it, took the boat out that evening and she did great. No more problems! So if anyone is having a similar problem and the fuel pump / carb rebuild does not work make sure to check your choke solenoid. All in it cost me under 200 bucks to get back on the water and i'm feeling pretty good about that even if i rebuilt the fuel pump and carbs which while they may not have needed it i'm sure the new seals and gaskets wont hurt in the long run. Thanks to everyone for their input and i hope that this thread helps someone else out down the road.

Scout, Out.