Mercruiser 5.0L Carb issue

[achris]

Re: Mercruiser 5.0L Carb issue

thanks joe and chris, I really appreicate your guys help. Everyone has been great on this forum.

You need to pull the whole valve out, or pull the hose and plug it.... (So your talking about the PCV tube? if so plug it up?)

If you just pull the tube off, then you are creating a massive vacuum leak, hence the engine stalls. You need to plug the whole so the engine can draw through the carb....

Turn the carb upside down. You should NOT be able to blow low pressure air into the fuel inlet. If you can, you have a leaky n&s... -(So do i have to take the whole carb out? if so do i need to put a new gasket?

If you didn't use sealer on the gasket (and you shouldn't have) then you should be able to remove the carb carefully enough to not need to replace the gasket....

 

[slixxster]

Re: Mercruiser 5.0L Carb issue

No i didnt use any sealer. But I'm a bit confuse.. on the Turn the carb upside down. You should NOT be able to blow low pressure air into the fuel inlet. If you can, you have a leaky n&s... ---(so i should plug the PCV tube then flip the carb over and blow air thru the fuel inlet?) sorry for not understanding.

 

[joewithaboat]

Re: Mercruiser 5.0L Carb issue

Disconnecting the and plugging pcv line to the carb is something you try with the engine running.

Obviously testing the N&S by removing and flipping the carb is different test all together. If air is getting past the N&S so will fuel.

good luck

 

[CharlieB]

Re: Mercruiser 5.0L Carb issue

I don't see any mention of his idle mixture setting, hopefully he did remove the idle mixture needle and cleaned the passages, then initial adjustment of 1 and 1.2 turns out from lightly seated, start the motor then readjust to 'best' idle while on the water.

 

[achris]

Re: Mercruiser 5.0L Carb issue

.... then initial adjustment of 1 and 1.2 turns out from lightly seated, start the motor then readjust to 'best' idle while on the water.

On a 'standard' carb yes. But the TKS spec is for either 2-1/2 (gen 1) or 2-1/4 (gen 2).

 

[starsnstripers]

Re: Mercruiser 5.0L Carb issue

Maybe i can clarify what Chris meant by flipping the carb over for ya. If you take the carb off turn it upside down and blow into the fuel inlet, you shouldn't be able to blow any air through because by having the carb upside down it makes the float shut the needle and seat as if the bowl was full of fuel to shut off excess fuel. This test will determine if your needle and seat are faulty and bypassing fuel when it should be closed.

 

[starsnstripers]

Re: Mercruiser 5.0L Carb issue

Make sure you take some cleaner and air to your flame arrestor also it needs to be clean. I've seen them all carboned up causing air flow restriction.

 

[slixxster]

Re: Mercruiser 5.0L Carb issue

My idle/mixture screw setting did help if i made it rich, it went from idling about 2k rpm to about 1k without dying. But the Idle/mixture didnt help the dying. So you guys are indicating to take off the top piece of the carb, flip it upside down(closing the needle) and blow air into the fuel inlet and I shouldnt be getting any air flow coming out of the needle correct?

 

[starsnstripers]

Re: Mercruiser 5.0L Carb issue

Dont need to split the carb apart no, take the whole carb off to do it.

 

[slixxster]

Once I flip it how do I determine if it's leakin, while blowing air in it?

 

[starsnstripers]

Re: Mercruiser 5.0L Carb issue

Yes, blow into the fuel inlet. If you can blow through it's leaking by. If you can not then the needle and seat are ok.

 

[slixxster]

Re: Mercruiser 5.0L Carb issue

Another question, Will this be the same test if i just take off the fuel inlet and blow air into there, since the bowl should be full of fuel indicating it's close? My confusion is if I blow air into the fuel inlet, Should i be feeling air anywhere, maybe a vent or something, since I cant see/feel the needle/seat?

Also what I notice is, After the motor runs to normal temperature, motor will not start unless I pump it with gas? That shouldnt be normal correct? Doesn't the TKS thing control that?

 

[slixxster]

Re: Mercruiser 5.0L Carb issue

sorry for all the noobie questions.

 

[achris]

Re: Mercruiser 5.0L Carb issue

Another question, Will this be the same test if i just take off the fuel inlet and blow air into there, since the bowl should be full of fuel indicating it's close?

In essence yes, but the needle may be hang open just a tiny amount and the result would be invalid.

My confusion is if I blow air into the fuel inlet, Should i be feeling air anywhere, maybe a vent or something, since I cant see/feel the needle/seat?

If you blow high pressure air in it will push the needle off the seat and indicate a leak, so only use about 5 psi of air pressure when you have the fully assembled carb upside down for the test. You might feel air somewhere, but don't make that the indicator. I just put a piece of tubing on the fuel inlet and blow with my mouth, that's about 2 psi. If it holds, it's fine...

Also what I notice is, After the motor runs to normal temperature, motor will not start unless I pump it with gas? That shouldnt be normal correct? Doesn't the TKS thing control that?

That's not normal. Drag out the multimeter and start checking things like the resistance of the TKS module as per the manual. The diagnostic section of the TKS manual is excellent and you should be able to check out the module with ease following it.

With the engine not idling below about 1000rpm, I suspect you still have dirt clogging one of the idle or progression holes, or something is very badly out of adjustment.

 

[slixxster]

Re: Mercruiser 5.0L Carb issue

I'll be taking it apart this weekend to do the testing. Do you have any suggestions since I'm taking the carb off to see what idle hole you are thinking that is clog? I can try spraying air and carb cleaner in every spot i can again? But if you had something in mind for me to double check, let me know.

Also I've read that there is this anti-valve shiphon(however you spell it) in the gas tank? Does every boat have it? Is there an easy way to get the fuel tank? I cant even see my fuel tank, followed the fuel line and it goes under the deck.

I'll run thru the TKS test carefully again and see what i find. I also did the Diode test from Mercury Bulletin regarding the Engine hard to start when warm up and diode came back fine reading at 900ohm 1 way and the other way didnt have any reading.

Also is it require to change the spark plug wires and coil? I know for cars, they last pretty long but not too sure how boat handles it.