Choke Plate Closing & Carb Dumping Fuel (leaky carb float)

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **DUMPING FUEL AT SHUTDOWN**

Re: Choke Plate Closing After 1 Hour **DUMPING FUEL AT SHUTDOWN**

The gas line from the fuel pump to the carb used to be all metal. Part of it has been replaced with black Gates fuel line. Per the manual, looks like I have the Carter fuel pump. The pump top portion is the filter cover (metal cup) held down by a retainer with a screw on top. The cup holds a spring and the filter, which sits on the black rubber gasket. I change the gasket every time I change the filter. The diaphragm is underneath the valve body, per the manual. Anyway, I don't think there's any glass.

Question--is the idea that a ruptured diaphragm in the fuel pump would allow fuel to flow from the fuel tank through the pump and then into the carb (by gravity, because the carb is lower than the tank)? The fuel dumping at shutdown stops after about a minute or so. Why wouldn't it just keep dumping?

 

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **DUMPING FUEL AT SHUTDOWN**

Re: Choke Plate Closing After 1 Hour **DUMPING FUEL AT SHUTDOWN**

I removed and looked at both fuel filters. Still look brand new and very clean.

I ran a strong fuel system cleaner/gas solution through for about an hour, then ran regular fuel for 15 minutes. Lots of tapping on the carb during this. NO CHANGE. On shutdown, the carb dumps fuel. The rear barrel is getting the fast drips (almost a stream), the front barrel much, much slower drips.

I looked in there while it was idling and also at 1200 rpm. It is dripping fuel even at those settings.

After shutting down the dripping stops after about a minute.

The fuel pump seems to operate great at any rpm setting, at least in terms of volume and pressure (no hesitation or stalling).


QUESTIONS

1) How do I tell if this is the carb or the fuel pump diaphragm (could it still be the diaphragm given the symptoms above)?

2) If it's the carb, what exactly would cause the sticking float or needle? If it's just some dirt/gummy gunk, is that something I can fix quickly by pulling the top of the carb off? I have Mercruiser Service Manual 2 open to pages 4B-2 through 4B-8. It doesn't look that bad to get to the float. I guess I'm not seeing all the springs and little steel balls or whatever supposedly makes rebuilding a carb so horrifying with my giant fingers. I might even have the gaskets here in a carb kit--gotta look.


So those who have been inside these 2GC carbs, should I try it or just pull it and pay an expert?

Thanks.

.

 

[jtybt]

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Not sure where the drip is coming from. Is it coming from between the cover and body?

Actually sounds like float is stuck open. If tapping doesn't do it, may have something holding it open. Take it apart and clean it. The rebuild kit has all the settings and directions. Not any harder than the choke.

 

[ziggy]

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

hum, man, yer getting the blues for sure.
sounds to me like you have the same carb and fuel pump i do. i think their the same for the 140 and my 165.
yer fuel pump.
assumingit's the oem one. old, you may not have the return line from the fuel pump to the top of the carb. i've had 2 old boats w/165's in them. both have had, i hate to say it, but auto fuel pumps. no 3rd yellow fuel line up to the carb. when the diaphragm ruptures the fuel comes out a hole in the bottom of your fuel pump. must be under pressure too as that hole is a fitting on a marine carb w/the yellow fuel line going up to the carb. it must pump it against gravity as the system works. look in the service manual. your fuel pump should put out i believe 3-6psi. maybe less, go look at the spec. test it. put a fuel pressure gauge tee'd between the fuel pump and the carb to test it i believe. the fuel system test in the adults only sticky will lead ya righter than i can for other fuel system test.

as for your carb. yer not accomplishing anything. take it apart, soak it in carb cleaner, wash it with soap and water, used compressed air and blow every little hole out and dry it. if it's still dirty, do the cleaning again. i did on mine. then use your book and set ea. of the 5 or 6 specs to what their supposed to be. then give it a try.

one thing i don't think i've seen mentioned yet and a test i did on my carb when i rebuilt it was to see if the float leaked. i think the old metal ones can. if the float leaks and absorbs fuel it'll be to heavy and more fuel must pump into the carb to fill the bowl, but the float takes to long or never closes the needle to the seat cause it's to heavy. best test i could think of was to sink the float by itself in some water, weight it down. sunk. leave it there for a while and check it out. see if it feels heavier, shake it to see if any water got in. i suppose it'd be better to sink it in fuel as i suppose water and fuel could penetrate a small leak different, but testing in fuel sounded to dangerous to me, so i chose the water...

imho...
oh, and if anyone wants to bust my chops, feel freely, i don't mind, i'd rather the op have the best info possible....

 

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Not sure where the drip is coming from. Is it coming from between the cover and body?

Actually sounds like float is stuck open. If tapping doesn't do it, may have something holding it open. Take it apart and clean it. The rebuild kit has all the settings and directions. Not any harder than the choke.

 

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Thanks for all the info, ziggy. I'm going to reread the manual and decide what to do. I would prefer to open up the carb, clean up the problem and close it back up. The wakeboarding season is just about over here for my kids, so I'd like to get it fixed for the next few weeks. Then if I'm still having trouble, I'll either try the rebuild or take it to the carb shop. Ditto on the fuel pump. (I don't have that extra clear line and the pump has never leaked.) I will check the float for a leak, that sounds like it might be the ticket.

Some thoughts...

The leak is probably because the float and needle valve are letting the bowl overfill, and then it just pours through openings--rather than because of a failed gasket--is that the right idea?

Why doesn't it keep leaking? I assume it's leaking off the pressure in the fuel line from the pump to the carb. That line goes uphill, so it just bleeds off the pressure and then stops. If the fuel pump were allowing fuel through, it would leak until the gas tank was empty, right?

 

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Re: Choke Plate Closing After 1 Hour **STILL DUMPING FUEL**

Pulled the air horn assembly and took off the float. The float is about 1/4 full of gas. Everything else looks brand new from the recent rebuild. New float should be here in a few days. Think that'll solve the fuel dumping?

 

[ziggy]

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Ditto on the fuel pump. (I don't have that extra clear line and the pump has never leaked.)

be very aware of what you have there. it can leak. mine did. the '75 in my sig. the diaphragm degraded around where the screws are. and it leaked. fuel into the bilge. that's a bomb looking for a spark. i look at my fuel pump every time prior to going out. if the diaphragm ruptures, the fuel leaks out a little hole into the bilge. same bomb waiting to happen. i really think that's the way our old boats came. i don't think the uscg rules were applicable for fuel pumps w/the dump to the carb at that time. i back that statement up with the fact that the return line don't show up for the carter fuel pump untill service manual #3. about 1978. just be carefull and understand the ramifications...

Think that'll solve the fuel dumping?

got to be a step in the right direction i'd think...

 

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

I didn't know that about this fuel pump. I always run the blower for a few minutes (blower motor is in a different compartment). I'm pretty anal about fumes--the blower vent is out the side behind the captain's seat--I take a whiff before starting. Love that oil/engine smell, without gas fumes... seriously, I really love that smell (so it's gotta cause cancer or something...).

 

[jtybt]

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Yup, that would prevent the float from rising high enuff to close the valve.


Over time, you could fill the crankcase with gas and cause excessive wear of some of the cylinders due to oil wash out.

 

[Silvertip]

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Lets look at this logically. On a cold engine we have a choke plate that is wide open. On a hot engine it is fully closed. What's wrong with this picture? Directly opposite of what should be happening. Someone, at some time, or due to an act of nature, the choke mechanism is pushing rather than pulling the choke plate. There IS a connection between the parts or the choke would not be working at all. Remove the disk, check the internals, and then make sure the spring on the back side of the choke cover is installed the right way around and the loop at the end captures the tang on the choke linkage. There are rich-lean notations on the cover. Rotating the cover to rich should close the choke. If it doesn't the spring is installed backward. There are very nice pictures in virtually any service manual.

 

[smartwork]

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

On a cold engine we have a choke plate that is wide open.

If I understood his original post correctly, his plate wasn't open when cold. I believe his choke begins closed when cold, opens correctly when warming, and then returns to closed.

On my own choke ('97 Mercrusier 2B), the coil does not catch the choke linkage. As it heats, it simply backs away from the choke linkage to allow the choke lever/flap to fall open under it's own weight through gravity. When the coil cools, it then returns to its original shape which then pushes the choke lever/flap closed because there is no other mechanism to return the choke to closed. This one may be different though.

 

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

sw> If I understood his original post correctly, his plate wasn't open when cold. I believe his choke begins closed when cold, opens correctly when warming, and then returns to closed.

That is correct. The choke works correctly until the engine is fully warmed by about an hour of towing skiers. Never did figure this out. I fully disassembled the choke and cleaned it really good. We'll see.


sw> On my own choke ('97 Mercrusier 2B), the coil does not catch the choke linkage. As it heats, it simply backs away from the choke linkage to allow the choke lever/flap to fall open under it's own weight through gravity. When the coil cools, it then returns to its original shape which then pushes the choke lever/flap closed because there is no other mechanism to return the choke to closed.

Yes, that's how my 1974 Merc 140 choke works, too. It's a Rochester 2GC with the thermal choke (not the other carb with the electric choke).

Once I get the new float and hopefully solve the fuel dumping problem, I hope to have good weather to give this another go yet this season.


Thanks for all the input.

 

[myoldboat2]

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

Re: Choke Plate Closing After 1 Hour **BAD FLOAT**

YAHOOO! One problem fixed! Replaced the leaky carb float and the fuel dumping at shutdown is gone. I have my instant starting engine back! When the engine is warm, don't touch the throttle at all... run the blower for a bit then turn the key for about 1/4 second... starts idling immediately like it was never shut off. Not bad for a 35 year old engine! Cold starting is still easy, three pumps and crack the throttle, starts immediately. Love it.

Still don't know what was causing the choke plate to close tightly when warm-soaked. I fully disassembled the choke and cleaned it thoroughly, so we'll see if it happens again. If it does, I'll probably just take the throttle plate off. I suppose it would make sense in that case to replace the fast idle cam screw with one without a shoulder, to lock the cam in the "warm" rotated position? Because I'm always setting my own warm up RPM anyway.

Thanks for the help! This was a very tough one for me to find... I wasn't familiar with fuel dumping and didn't think to look for it. It seems so obvious now... I guess that's the way it always is.

Still have the big fingers problem. I of course dropped the carburetor fast idle cam screw. Strange sound, didn't sound like it hit the bottom of the bilge. It took almost 3 hours for my kids and me to find it! It had wedged behind the solenoid bracket on the hydraulic trim pump. Finally found it with a droplight and a mirror.

One thought on the choke plate... here are photos of the linkages as they were before I pulled the air horn. I reassembled them the same way. Does it all look correct?

 

[myoldboat2]

Re: Choke Plate Closing & Carb Dumping Fuel (leaky carb float)

Out over the weekend--no more fuel dumping, but the choke pate still closes tightly after towing wakeboarder. Cannot understand why. So I will take the choke plate off.

QUESTION: What is the best way to handle the fast idle cam? With the choke misbehaving, the cam goes with it. I plan to remove the choke rod (vertical linkage), but then the cam wants to fall down so far that the idle screw misses it. So maybe put a serrated lock washer under the cam screw? Might have to replace the shouldered screw with a normal screw, too. Or is there an easier way, like removing the cam and using a longer idle screw that bottoms on the cam screw, or....?

Your input will be appreciated.

 

[Glastron_V210]

Re: Choke Plate Closing & Carb Dumping Fuel (leaky carb float)

Instead of doing away with the choke, I would go buy a pull cable and convert the choke to manual...work very well (KISS Baby!). I had this on my pre fuel injection vehicles...can't beat the controllability of it.


Chay

 

[myoldboat2]

Re: Choke Plate Closing & Carb Dumping Fuel (leaky carb float)

A manual choke is something we discussed somewhere in this thread. Charlie said that the 140 doesn't really need the choke. I ran through my cold starting routine (three pumps, crack throttle, crank and it starts) with the flame arrestor off and watched the choke plate closely. It opens fully almost immediately while I have my warm-up rpm set manually at about 1500 rpm. So I'll try it without the choke. Just the plate and vertical rod are coming off, and I'll obviously keep them if I decide to go to a choke cable or figure out the problem.

I'm looking for advice on what to do with the fast idle cam.