Mercruiser 5.0LX Rochester 4MV carburetor over fueling. ESN OF066511

[Uncle Whitey]

The boat was bought, not knowing much about it, I’m thinking it sat for over 4 yrs. Got the engine running in the driveway, brought out to the cold water, it didn’t want to run. Over fueling and dumping fuel. Removed the carburetor and cleaned and reassembled. Engine ran fine, noticed a **** ton of fuel in the oil, changed the oil. Didn’t run it for a week. I had the outdrive off, changing the impeller. Tried to start today, carburetor started over fueling again. Not sure where to go from here? Tear it back down and clean again? Help please

 

[Fun Times]

Maybe a needle and seat issue inside the carb or too much fuel pressure coming from the fuel pump...Check fuel psi.

 

[nola mike]

Yes, take the carb apart. Did you replace needle and seat? Did you verify that they sealed correctly? Double check float? Check fuel pressure next if all is the above checks out

 

[Scott Danforth]

+1 on checking fuel pressure
+1 on pulling the carb and going thru it.

 

[dubs283]

Agree with others, sounds like a stuck float/needle not seating. Good idea to check fuel pressure as well

 

[Lou C]

Also might check float to see if it absorbed fuel. If you’re buying a rebuild kit get one from Cliffs High Performance Quadrajets. He has better quality parts esp the accel pumps. When installing the float make sure to get the little clip in the right place (do not put the hook in the holes on the float arm) that will jam the needle valve & cause problems.

 

[Scott06]

Also might check float to see if it absorbed fuel. If you’re buying a rebuild kit get one from Cliffs High Performance Quadrajets. He has better quality parts esp the accel pumps. When installing the float make sure to get the little clip in the right place (do not put the hook in the holes on the float arm) that will jam the needle valve & cause problems.

Agreed- had a float with a small split on it couldn't tell it was leaking ...

To OP -These could be your issues

Float being gas logged or hanging up
needle and seat
too high fuel pressure
I assume you have a mechanical fuel pump - there should be a clear tube coming of it and going to carb - if pump diaphragm ruptures it will spit fuel down carb

 

[Lou C]

if you look at the bottom of this pic you can see what I'm talking about...that little hook on the wire for the needle valve does not go in either of the two holes, it just gets clipped on the side of the float arm.

 

[todhunter]

The clip orientation on the needle valve is super important. Some people (including Cliff) say you can ditch the clip altogether. I'd rather have no clip than an improperly oriented clip.

If you're buying a rebuild kit from Cliff's (which I do recommend), you should also buy his book. Also, this thread is a good reference. I recommend pulling the idle tubes so you can clean under them if you haven't done so before. Trash builds up there and can cause issues. You can buy new idle tubes from Cliff if needed. If you're a glutton for reading carburetor manuals, Rochester Carburetors by Doug Roe is very detailed also.

I'm actually going through the same exact thing right now with my QJ - flooding at idle. I'm adding a fuel pressure gauge to check out the pump, and also doing another rebuild with Cliff's parts.

 

[Uncle Whitey]

+1 on checking fuel pressure
+1 on pulling the carb and going thru it.

I did pull the carburetor off and double checked since I cleaned it last. Looks like the needle is sticking just moving up and down by hand?

 

[Uncle Whitey]

Agreed- had a float with a small split on it couldn't tell it was leaking ...

To OP -These could be your issues

Float being gas logged or hanging up
needle and seat
too high fuel pressure
I assume you have a mechanical fuel pump - there should be a clear tube coming of it and going to carb - if pump diaphragm ruptures it will spit fuel down carb

I do have the clear hose, I do see fuel moving through the hose, lol. I’ve asked around to other mechanics, no one knows what the hose is for? Should I have fuel in it or not?

 

[dubs283]

I do have the clear hose, I do see fuel moving through the hose, lol. I’ve asked around to other mechanics, no one knows what the hose is for? Should I have fuel in it or not?

That clear/yellow line is in place as a safety measure to allow fuel spilled from a ruptured fuel pump diaphragm to be routed to the carburetor instead of spilling into the bilge and creating a fire hazard.

If you indeed have fuel present in the line that is why excess fuel is entering the carburetor. Time for a new fuel pump, the current one is defective

 

[Uncle Whitey]

That clear/yellow line is in place as a safety measure to allow fuel spilled from a ruptured fuel pump diaphragm to be routed to the carburetor instead of spilling into the bilge and creating a fire hazard.

If you indeed have fuel present in the line that is why excess fuel is entering the carburetor. Time for a new fuel pump, the current one is defective

 

[Uncle Whitey]

I tried to upload a video I took, but it wouldn’t load. But I certainly have fuel moving through the line. Awesome man! Glad someone was able to tell me about that line. Lol

 

[Uncle Whitey]

The clip orientation on the needle valve is super important. Some people (including Cliff) say you can ditch the clip altogether. I'd rather have no clip than an improperly oriented clip.

If you're buying a rebuild kit from Cliff's (which I do recommend), you should also buy his book. Also, this thread is a good reference. I recommend pulling the idle tubes so you can clean under them if you haven't done so before. Trash builds up there and can cause issues. You can buy new idle tubes from Cliff if needed. If you're a glutton for reading carburetor manuals, Rochester Carburetors by Doug Roe is very detailed also.

I'm actually going through the same exact thing right now with my QJ - flooding at idle. I'm adding a fuel pressure gauge to check out the pump, and also doing another rebuild with Cliff's parts.

That’s good info, I try to self teach myself about this kind of stuff.

 

[Scott06]

I do have the clear hose, I do see fuel moving through the hose, lol. I’ve asked around to other mechanics, no one knows what the hose is for? Should I have fuel in it or not?

If there is fuel present in the tube your mechanical fuel pump needs replacement. as mentioned this will be pushing fuel from a ruptured fuel pump diaphragm into the carb bores… better than the fuel going into the bilge though. Get a marine replacement pump and you should be good.
may be other issues but take care of this one first

 

[Uncle Whitey]

Yes, take the carb apart. Did you replace needle and seat? Did you verify that they sealed correctly? Double check float? Check fuel pressure next if all is the above checks out

I did replace the seat and needle, didn’t verify that it we seating, ooops. Checked the float height, supposed to be 1/4” I was just a tad over, which would mean not as much fuel in the bowl.

 

[Scott Danforth]

new mechanical fuel pump is less than $50 from Summit Racing

 

[Uncle Whitey]

Hopefully I can get the carburetor and fuel pump issues taken care of tonight? It’s my wife’s birthday today, so she comes first. I’ll post with more updates later.

 

[Uncle Whitey]

Well, I put on the new mechanical pump. Tried to run the engine, wouldn’t stay running, still kept over fueling. Finally pulled the carburetor off and brought to a shop for them to look over. They called yesterday saying it’s done, $165 for repairs. I’ll pick it up today and get it put back on. Latest update