Hard starting after engine warms up. Carburetor ID

[Skidude17]

4.3mpi

Electronic ignition...Duh. I'm awake now.

 

[Bondo]

Electronic ignition...Duh. I'm awake now.

Ayuh,..... Multiport Injection,....

 

[achris]

How do you tell if they're marine rated? Is there a specific vehicle you look under, or do you just go to anything with a 5.7L engine?

Marine rated electrical equipment must carry a 'SAE-J1171' label. That is how you determine if it's 'marine'.

https://forums.iboats.com/forum/engi...omotive-engine

Chris...

And oh, this....

Electronic ignition...Duh. I'm awake now.

No, not yet. I stopped the dribbling carb by changing the complete engine, for a carbed with electronic ignition (4.3LX) to an injected (4.3MPI). All Mercruiser V6 and V8 engines have had electronic ignition since 1982. The inline 4s were phased in around the mid 80s. They experimented with distributorless ignitions, and EST. But now, even the humble '140'/3 litre engine is injected.

 

[Skidude17]

Marine rated electrical equipment must carry a 'SAE-J1171' label. That is how you determine if it's 'marine'.

https://forums.iboats.com/forum/engi...omotive-engine

Chris...

And oh, this....


No, not yet. I stopped the dribbling carb by changing the complete engine, for a carbed with electronic ignition (4.3LX) to an injected (4.3MPI). All Mercruiser V6 and V8 engines have had electronic ignition since 1982. The inline 4s were phased in around the mid 80s. They experimented with distributorless ignitions, and EST. But now, even the humble '140'/3 litre engine is injected.

Yes, fuel injected. I'll get it right eventually. As for me, I'm still struggling with my dribbler:lol:

 

[Skidude17]

Rebuilding the Weber does not fix the dribble. I once had a Weber on the bench with the top off. I filled both sides with fuel. No dribble. I then blew air down one primary throttle barrel (with the throttle full open). I saw the fuel level in that side float chamber start dropping, and fuel being sprayed out of the bottom of the carb. I stopped blowing the air and refilled the float chamber to the same level as the other side. The venturi in that barrel continued to drip, and 2 hours later, that float chamber was empty.

The only conclusion I could reach on the reason was that the passages in the carb between the chambers and their venturis are so small as to allow fuel to be drawn up and to continue to make its way through the carb by 'capillary action'... When I suggested this to carburetor 'specialists', I get told that can not happen. When I tell them I saw it with my own eyes! they go very quiet!

Webers dribble, causing hard starting, and nothing can be done to fix them, short of putting a different carb on. End of story.

I did eventually fix my engine's dribble problem... See my signature.

Chris........

I'm putting the carb back together using a new rebuild kit. I have a few questions. The rebuild kit came with a weight for the check ball in the "fuel squirter" (I don't know the technical name), but it originally had a spring for the check ball.
1. Should I put the original spring back in?

The directions in the rebuild kit say I should have a 15/16 in. drop for the floats. Both are at 1.25 in.
2. Is the drop different for the marine application. There is only one drop listed in the directions, and it doesn't show different amounts for different engines.

There were screen filters on the original needle seats, but the new seats didn't have them.
3. Will it hurt anything if I put the screens on the replacement seats?

Thanks everybody!

 

[achris]

1. Yes.
2. Float drop should be 51mm (2") (Do you have the MERC factory manual?)
3. No. (make absolutely sure you have the right needles and seats)

Chris........

 

[Skidude17]

1. Yes.
2. Float drop should be 51mm (2") (Do you have the MERC factory manual?)

Chris........

I have a manual now

The carb rebuild kit I got has a felpro kind of gasket for between the carb and the intake manifold. Before removing the carb, there is only a rubber gasket that goes into a purpose made groove. Do I reuse the rubber gasket, get a new rubber gasket, use the rubber and felpro gasket, or other? The rebuild kit says it is a marine kit.

 

[Searay205]

vapor lock probably, if you have enough room you can buy a phenolic spacer in place of the paper thin carburetor gasket. probably 1/2" thick it isolates the carb from the hot manifold, not boil the fuel. In the future learn the boat, push throttle wide open crank engine when it catches pull back. You never sovle it completely. I had a 3.0 liter do it forever gave up just pushed throttle wide open.. in fact if was going to anchor i would push throttle wide open as soon as I shut engine off so when i was ready to go it would fire instantly. again carburetor suck but easy, fuel injection fire instantly but complex. i did it for 30 years with a boat. i admit i miss the smell of ether. also your starter should be cranking about 200 rpms. mine was only doing about 100 rpm's (under water a couple times lol) that really helps. if you have a compromised starter not turning engine over fast enough then your fighting a rising tide. truth be told once i got good starter didn't use ether to start engine anymore.....

 

[achris]

vapor lock probably, if you have enough room you can buy a phenolic spacer in place of the paper thin carburetor gasket. probably 1/2" thick it isolates the carb from the hot manifold, not boil the fuel. In the future learn the boat, push throttle wide open crank engine when it catches pull back. You never sovle it completely. I had a 3.0 liter do it forever gave up just pushed throttle wide open.. in fact if was going to anchor i would push throttle wide open as soon as I shut engine off so when i was ready to go it would fire instantly. again carburetor suck but easy, fuel injection fire instantly but complex. i did it for 30 years with a boat. i admit i miss the smell of ether. also your starter should be cranking about 200 rpms. mine was only doing about 100 rpm's (under water a couple times lol) that really helps. if you have a compromised starter not turning engine over fast enough then your fighting a rising tide. truth be told once i got good starter didn't use ether to start engine anymore.....

Do you (or most people who use the term) know what 'vapour lock' is?

Throttle full open actually reduces manifold 'suction', not increase it.

And your insulating gasket, has been tried. It's not vapour lock, it's not heat soak. It's the design of the carb. They dribble after engine shut off. End of story.

Chris........

 

[Searay205]

wow glad you solved it. oh make sure you patent your carburetor it a perpetual machine, frictionless. It the only pump on planet that disperses gasoline with no external engergy input. Oh wait its sitting on the manifold and the heat from the engine is putting energy into the carburetor expanding the gasoline. gasket didn't work because it wasn't thick enough. once the engine is running its a venturi effect that pulls gas out of float boat. when starting its the accelerator pump that puts gas in to the carburetor. when sitting there unless you have a leaf blower going across the top you have no venturey effect and you have no accelerator pump you have heat from engine

 

[achris]

wow glad you solved it. oh make sure you patent your carburetor it a perpetual machine, frictionless. It the only pump on planet that disperses gasoline with no external engergy input. Oh wait its sitting on the manifold and the heat from the engine is putting energy into the carburetor expanding the gasoline. gasket didn't work because it wasn't thick enough. once the engine is running its a venturi effect that pulls gas out of float boat. when starting its the accelerator pump that puts gas in to the carburetor. when sitting there unless you have a leaf blower going across the top you have no venturey effect and you have no accelerator pump you have heat from engine

Nope, not a perpetual machine, it's called 'capillary action'. If you'd read post #16 of this thread, you'd understand the how and why of the problem. You'd also understand what I did to prove that to be the problem. Nothing to do with perpetual machines, nothing to do with heat soak or manifold temperature. Read that post, then I expect to see you post an apology.

Chris......

 

[Searay205]

Sorry no apology. I find it hard if not impossible for there to be enough surface tension / capillary action to cause the dribbling. I don't know the details of the carburetor passages in your carburetor but for capillary action to be the culprit they would have to be thousands of an inch.

 

[achris]

... I find it hard if not impossible for there to be enough surface tension / capillary action to cause the dribbling.....

How about, "I saw it happen", and yes, the passages up to the venturis are very very small. Initial I was also skeptical of what I'd found, but there is no other explanation. And, as trees manage to 'pump' water up from their roots to the leaves at the very top, sometimes many many metres, a few millimetres doesn't seem all that improbable.

Chris..