4.3LX Question for Bondo

[Mark Bennett]

Bondo,<br /><br />I have a 1993 Mercruiser 4.3LX GenII with a Weber 4 Barrel AFB with 350 hours in a Thompson 210 Fisherman. I have had very good overall performance with this setup and have followed your posts for some time. The only problem that I seem to have with this carb is that it is a little difficult to start when warm and sitting for a short period 15-30 minutes. It usually has to crank a few times before firing up. I just replaced, plugs, wires, rotor and distributor cap without any change. The plugs have always been in great condition when I change them. Is there anything that I can check out. I do not have any other performance problems, idles very well for trolling and accelerates strongly to WOT at 4600 rpm. The only other condition that I have addressed is the addition of a manual primer to assist the electric fuel pump on initial start up. To my knowledge this carb has not been off of the engine and rebuilt. One last question is there a fuel filter built into the carb?<br /><br />Thanks<br /><br />Mark

 

[Trent]

Re: 4.3LX Question for Bondo

I think your problems are connected? Why would you "addition of a manual primer to assist the electric fuel pump on initial start up."??? Iv never heard someone adding a "primer"? You may have vapor lock going on. Run your blower a good bit more and let the engine idle a few min. before shut down and see if it helps in the "re-start"

 

[Mark Bennett]

Re: 4.3LX Question for Bondo

Trent,<br /><br />Thanks for the reply, however I do not feel the problems are related. The mercruiser electric fuel pump loses its prime after sitting for a week or so and is dry when the engine is first cranked over. I replaced both the anti-siphon and the fuel pump and still had the same results. The manual bulb-primer allows me to make sure the fuel pump is primed in these cases. If the boat only sits for a couple of hours or days there is no problem.<br /><br />Mark

 

[Bondo]

Re: 4.3LX Question for Bondo

Hi Mark,<br /><br />Issue A, You'll have to figure out whether it's Flooding, or going Lean, when it doesn't Start.....<br />It Should start right up, unless the carb's leaking raw gas.....<br />I Can't feature it's Starving.....<br />Vapor Lock, Maybe.....<br />Have you been to the Edlebrock site ???<br />I used Their Spec.s for mine.....<br />It's the Same Carb as the Merc./Weber.....<br />Using the Carter Strip Kit, I Leaned my Idle,+ Cleaned up the Plugs,+ Soot on the Transom.....<br />

One last question is there a fuel filter built into the carb?

Ya, But it's Inside(from the Bottom) the Top Cover........<br /><br />Issue 2, I Still haven't figured out, Where the Gas Goes ...............<br />More than a day or two,+ the carb is DRY.....<br />I Also tried the Primer Bulb Trick.......<br />Till the Night in the River.....<br />When the Check-valve in the Bulb Plugged the Fuel Line.......<br />After that, I did the No-No...........<br />I By-passed the Oil Pressure Saftey Switch.......<br />Now I Don't have to Burn-Out my Starter, Trying to build Oil Pressure......

 

[Mark Bennett]

Re: 4.3LX Question for Bondo

Bondo,<br /><br />I don't believe it is flooding, there is no gasoline smell at all. I don't believe I have an lean or rich issue, because the plugs are in great condition and are not fouled or burned up. I'm leaning towards a possible vapor lock, however I'm not very familiar with it. This boat is raw water cooled and runs at 140 degrees. The engine compartment is fairly spacious and is open to the outside air, it is not a totally enclosed system. I visited the Edlebrock site, but really didn't know where to start. If I am experiencing vapor lock is there a solution?<br /><br />Thanks<br /><br />Mark

 

[Mark Bennett]

Re: 4.3LX Question for Bondo

Bondo,<br /><br />If I am experiencing a heat-soak vapor lock would a phenolic spacer between the carb and the manifold help, along with some insulating wrap on the fuel lines?? I posed this questioin to the Edlebrock tech service as well.<br /><br />Mark

 

[Bondo]

Re: 4.3LX Question for Bondo

I don't believe I have an lean or rich issue,

It's Either 1 or the Other......<br />Unless you're Loosing Spark...........<br />You'll need to Inspect the Plugs, Right When the Problem is Happening........<br />If they're Wet(Rich), Then, the Carb is Leaking........(BTW, you won't Smell the gas in the Exhaust)<br />If they're Dry(Lean), it Might be a Vapor Lock issue.....(Doesn't really sound like it, with the temps,+ conditions)<br />Or,<br />There's No Spark At All...............<br />

If I am experiencing a heat-soak vapor lock would a phenolic spacer between the carb and the manifold help, along with some insulating wrap on the fuel lines??

IF that's the Problem.........<br />It sounds like a worthy plan of attack............

 

[dmorley]

Re: 4.3LX Question for Bondo

I've got the same set up and can let my boat sit all winter and the electric fuel pump does not lose its prime (or if it does, it primes itself when the key is turned to the first notch). Pretty clear the gas is leaking back into the tank due to something wrong with the carb rebuild or a malfunctioning check valve.

 

[achris]

Re: 4.3LX Question for Bondo

I have the same engine and EXACTLY the same problem as GMT, and a couple of friends with the same engine do too. I have isolated the problem to the carb 'dribbling' after shutdown. This is what causes the hard start after 10 minutes and the 'dry' carb after a couple of day, it syphons the bowl dry. I have also added an outboard primer to the fuel system. I once took the carb off the engine after I had run it and watched it dribble. I still haven't found a way of stopping it. I even replaced the carb with a new one from Mercury. Still got the same problem though....