Weber carb on 4.3 LX

[achris]

Hi Guys,<br /><br />I have a Weber 4BBL on a Mercruiser 4.3LX(1994) and it dribbles after shutdown. Thus flooding the engine for the next start. I have tried a variety of fixes but, so far, to no avail. I have stripped the carb many times and even bought a new one complete. Mercury Marine don't have any answers, so I am wondering if anybody else has the same problem or if someone has fixed it. All suggestions welcome.

 

[akriverrat]

Re: Weber carb on 4.3 LX

what have you tried and is the rest of the system stock? i read a post somewhere that person with same problem had mistakenly installed efi fuel pump. much higher pressure than carb pump.

 

[Chris1956]

Re: Weber carb on 4.3 LX

AChris - You may have a fuel expansion problem. The gasoline pickup may have a anti-siphon valve which keeps fuel from returning to the gas tank. When you shut off the motor, the residual heat from the motor may cause the gasoline in the fuel pump and lines to expand. Since it cannot return to the tank, it it forced past the carb inlet needle and floods the bowl.

 

[achris]

Re: Weber carb on 4.3 LX

Ok. Here's what I've tried, and yes the rest of the system is as delivered from Mercury.<br /><br />1) Choke plates. Open.<br />2) Fuel pump pressure. 4 psi.<br />3) float levels and float drop. actually set at 0.080 less than spec.<br />4) Jet sizes in carb. This problem on both a 9600 and a 9666 carb.<br />5) replaced solid needle valves with spring loaded ones<br />6) Idle speed, in gear at 650rpm<br />7) engine temperature/thermostat<br />8) fuel tank vent line is clear (not building pressure in the tank)<br />9) only running the factory fuel filter and no anti-syphon valve.<br /><br />What I can tell you is that I have had the other carb on the bench for the last couple of days and the fuel is leaking out from the discharge nozzle in the primary venturi(s). I think it's running up there by capillary action. The problem is that I don't know how to stop it.

 

[Mark Bennett]

Re: Weber carb on 4.3 LX

achris60,<br /><br />I am planning on doing a rebuild on my Weber 4bbl in the next week or so and will let you know if anything changes. How much cranking does yours take to start after you've shut down for awhile. I'm still debating if I really have a problem or not. Mine takes 15-20 secs of cranking before it fires up. Maybe I'm expecting to much for it to fire right up at the turn of the key, I do not have any other performance problems with the engine or carb??? The reason that I am doing the rebuild is that the boat is a 93 with 350 hrs, I've owned it since 98, and have not had any significant reasons to pull and clean it yet.

 

[Northern Eclipse]

Re: Weber carb on 4.3 LX

Do you have any fuel in the clear plastic sight tube that runs from the fuel pump to the carb, if so then the fuel pump has a leaking diaphram.

 

[achris]

Re: Weber carb on 4.3 LX

GMT. Yeah, takes about 15-20 seconds but always catches. It's just a PITA. The other annoyance is the dry carb and the need to open the engine cover every morning. <br /><br />Northern Eclipse. No clear hose from fuel pump to carb. These run electric pumps.

 

[achris]

Re: Weber carb on 4.3 LX

GMT,<br /><br />Have you done the rebuild on your carb yet? Just wondering how it went.<br /><br />Chris..........

 

[Mark Bennett]

Re: Weber carb on 4.3 LX

Chris, <br /><br />No I haven't, I've been playing with the power steering system, ended up having to switch out the power steering pump. I am going to rebuild the carb some time this summer, I'm not in a big hurry since I really don't have any significant performance problems, and the walleye fishing is starting to heat up on Lake Erie right now. I'll post back when I rebuild it.<br /><br />Mark

 

[achris]

Re: Weber carb on 4.3 LX

Thanks Mark.....

 

[achris]

Re: Weber carb on 4.3 LX

Bump

 

[Mark Bennett]

Re: Weber carb on 4.3 LX

Chris,<br /><br />How is your Carb working, did you rebuild it yet? Mine has been working beautifully this year and I'm probably going to delay pulling off until this winter. I eased up on how much I've been pumping the throttle and it seemed to make a big difference. I cut back from 4-5 pumps cold to 1-2 and it starts right up, I also went from 1-2 warm to none and it seemed to like that as well.<br /><br />Mark<br /><br />Mark

 

[achris]

Re: Weber carb on 4.3 LX

Hi Mark,<br /><br />I did strip and clean the carb. Hasn't changed the flooding/dribbling problem but I did get some benefit. The carb was clean inside and all the adjustments were spot on. Float level, float drop, accel pump stroke all good. I refitted the carb and on the next run noticed that the engine vacuum was a lot higher for the same revs and speed as before. 3000rpm, 20 knots WAS 6" vac, now 9". The engine feels a whole lot smoother and no hesitation (was very slight) on accel. (That one was usually only after I hadn't use it for a couple of weeks.) The confusing thing is that I changed NOTHING! Just cleaned what looked like a pretty clean carb. Go figure?!?! <br /><br />Chris.........

 

[achris]

Re: Weber carb on 4.3 LX

Mark,<br /><br />Have some new info on this problem. Through another thread I have discovered that the Weber is a 'squarebore' carb and the manifold that it bolts onto is a 'spreadbore'. From that thread I also learned that there are 'gas pooling' issues if there is not a 'ported adaptor' on the manifold to take the squarebore carb. <br /><br />What I would like to know is whether your engine has an adaptor between the carb and the manifold.<br /><br />Chris..............

 

[Mark Bennett]

Re: Weber carb on 4.3 LX

Chris,<br /><br />I'll check tonight, however my setup is as delivered from Merc. I wonder if someone swapped your carb before you bought the boat? Here is a link to Edelbrock. http://www.edelbrock.com/automotive/index.html <br /><br />I believe that I am bolted directly to the manifold, but I'll double check tonight.<br /><br />Mark

 

[Mark Bennett]

Re: Weber carb on 4.3 LX

Chris,<br /><br />Take a look at this item on Ebay it is exactly what I have. Item number: 2484512451<br /><br />Mark

 

[achris]

Re: Weber carb on 4.3 LX

Mark,<br /><br />The engine is as supplied by Mercury. I un-boxed it myself. I have had a look at the eBay item you mention and that exactly how mine is too. No spreadbore to squarebore adaptor. And that manifold is quite clearly a spreadbore.<br /><br />I will be able to get an adaptor on Friday. It's only $50 so it's cheaper than the injection upgrade. The only potential problem is that the adaptor adds 0.8" to the carb height and we have hard fuel lines. Might be time to pull the bender out of the box again.<br /><br />Will let you know how I go.<br /><br />Chris..............

 

[Mark Bennett]

Re: Weber carb on 4.3 LX

Chris,<br /><br />What adapter did you buy, who is it from??<br /><br />Mark

 

[achris]

Re: Weber carb on 4.3 LX

Mark,<br /><br />Haven't bought the adaptor yet. Will get it on Friday. And it'll be from the local Holley dealer.<br /><br />This is a picture of it.<br /><br /> http://www.martelbrothers.com/customer/product.php?productid=EDE2696&cat=&page=1 <br /><br />Chris..........

 

[Mark Bennett]

Re: Weber carb on 4.3 LX

Chris,<br /><br />I've been on vacation for the last week, and was wondering how your carb adapter worked out??<br /><br />Mark