Carburetor Issues, Dripping Carbs...

[jimmbo]

What kind of float is in it?
Hollow, shake it to see if you can hear any liquid inside.
Solid, apply pressure on it to see if any fuel squeezes out. Or just get a new Float.
Also a new Needle and Seat, and Gasket for the Seat, and make sure it is tight.

 

[DangerMouse1]

What kind of float is in it?
Hollow, shake it to see if you can hear any liquid inside.
Solid, apply pressure on it to see if any fuel squeezes out. Or just get a new Float.
Also a new Needle and Seat, and Gasket for the Seat, and make sure it is tight.

Float is hollow. No fuel in it.

Going to test fuel pressure in the morning to see where it is. Then will go to carb if it isn’t the pump.

 

[dubs283]

Going to test fuel pressure in the morning to see where it is. Then will go to carb if it isn’t the pump.

Good plan

FYI that is a mercarb, most likely reman from sierra. Plenty of new, oem and aftermarket kits available for rebuild. Being new, from sierra there's a chance it's not properly tuned. As in, did you set idle speed/air mixture or just plug n play?

 

[Scott Danforth]

Remember Sierra is not OEM, however will-fit aftermarket. Normally sourced off-shore

 

[dubs283]

Normally sourced off-shore

Yummy

But, seriously. Sierra has many wonderful and solid, trustworthy parts. Some do suffer from outside vendors. Caveat emptor as such....

With any carburetor rebuild/replacement a set up, checking timing, and full load/rpm test is in order

 

[DangerMouse1]

Good plan

FYI that is a mercarb, most likely reman from sierra. Plenty of new, oem and aftermarket kits available for rebuild. Being new, from sierra there's a chance it's not properly tuned. As in, did you set idle speed/air mixture or just plug n play?

Yep it was working fine, and I had adjusted the mixture against manifold vacuum, and it was running really nicely. Maybe the float or needle changed, but the timing etc was fine when running, but maybe once running again I need to get into base timing.
Going to do some diagnostic now on pump and see what I’m getting.

 

[dubs283]

Naturally aspirated gassers look good at 17 hg/in for idle vacuum. With smooth drop at load increase. This indicates a sound engine, under the manifold

I owned one 351W that had 18" at idle. The Motorcraft 2bbl couldn't keep up with the throttle punch tho. Kinda disappointing but hearty as well

 

[Lou C]

Dripping issues can be a needle valve not seating or sealing properly. After replacing the valve & seat turn the carb upside down & try to blow thru the inlet. You should not be able to if the needle valve is sealing. Do you have grit or crud in the fuel?

 

[dubs283]

Every time I rebuild a Rochester I squirt a bit of power tune on the needle. After installing crank and run, set never had an issue with leaking. This is of course with idle air mix properly set.

Initial idle air mix is roughly 2-3 turns out, the bigger the engine themore turns out to prevent drips through venturis. 4, 6, and sbc 8 require little adjustment. BBC will mess your head at 4-8 turns out depending on long block condition

 

[tank1949]

I recently installed a new carb on a 5.7l mercruiser.

The carb and engine were running fine, and then I had difficulty starting after a few weeks. I looked down the carb and noticed it was dripping and flooding the engine.

I just took the carb apart, cleaned it as I thought maybe the float was sticking, but all looked good.

My only thoughts are that for some reason the float level has changed, or my fuel pump has gone. I have read that sometimes it is the fuel pump, but I don't seem to be having a problem getting gas, and would the needle/float not stop gas even if the pump had too much pressure?

Just wanting to get thoughts on what to do next.

Rochester Quad-Jet? When they work, they work fine. I had a few over decades that leaked. One leaker was on an Olds 442 Muscle car. A couple of others were on MC. I could never completely stop one off the MC leakers from leaking. I pitched and bought a rebuilt marine carb. End of problems. Usually, boat motors and their fuel systems set for months on end and are trash and moisture magnets. Eliminate trash and moisture before spending time a money on carbs. I learned the hard way.

 

[Lou C]

I seem to wind up rebuilding my Q-Jet about every 6 seasons or so. After a few times it's easy.

 

[DangerMouse1]

Ok solved…

I was found that the float had been installed and that there some side sway in it. This must have been causing intermittent sticking. I replaced it with a spare float, and problem solved. No longer flooding and dripping. Thanks for helping out.

 

[DangerMouse1]

Ok solved…

I was found that the float had been installed and that there some side sway in it. This must have been causing intermittent sticking. I replaced it with a spare float, and problem solved. No longer flooding and dripping. Thanks for helping out.

Just thought I would share a picture. I was seeing that the metal was able to wiggle a little in the float, and I am presuming that maybe this was getting dislodged. Pictures attached incase it helps anyone else.

 

[SternDriveEd]

If the float drags on the inside of the fuel bowl, it could easily cause flooding when the needle valve doesn’t close against the seat. Overflowing the bowl past the designed fuel level is likely the cause of the dripping fuel you see at idle in the Venturi area. At idle you should never see fuel dripping into the carburetor bores.

 

[todhunter]

Just thought I would share a picture. I was seeing that the metal was able to wiggle a little in the float, and I am presuming that maybe this was getting dislodged. Pictures attached incase it helps anyone else.

That's crappy. What brand / supplier did that float come from so we know to stay away?

 

[Scott06]

Just thought I would share a picture. I was seeing that the metal was able to wiggle a little in the float, and I am presuming that maybe this was getting dislodged. Pictures attached incase it helps anyone else.

This was in a new sierra Mercarb replacement right?

Mike's carbs sells brass replacements for mercarbs or at least used to last time I rebuilt a mercarb...

 

[jimmbo]

Float is hollow. No fuel in it.

Looking at the Picture you later posted, that is not a Hollow Float.

 

[alldodge]

Things get bounced around in shipping

 

[DangerMouse1]

Yep it is Sierra. Must have got bounced in shipping, but I think the float is a high density foam. I think. It doesn’t seem hollow, but that foam means that the metal can easily carve into it. I’m hoping that is what it was, seems most likely and fixed when I replaced it with the old tks carb. New new runs really well apart from that and I get a good low idle from it.

 

[jimmbo]

Foam Floats have been used for Decades in Cars/Trucks, and I have never seen one with a flexing fulcrum like the one you showed. I would raise hell with Sierra, as their supplier is apparently slapping parts together with no regard to Quality Control