4.3 LX electric fuel pump

[egldvrbags]

1995 4.3 LX SN 0F436164 4BL Carb

Sometimes it's a couple of weeks between times I use the boat. It takes about 30 secs of cranking to get the engine to fire when it's this long between uses. The choke is closing, using the carb cranking procedure, etc.

At first, there isn't any fuel squirting in the carb when I move the throttle.

When does the electric fuel pump begin running? Is it when the starter soleniod is engaged?

I'm assuming the fuel is evaporating from the bowl after 2 weeks and it takes about 30 secs of cranking to get the fuel to the carb??

Any thoughts??

Thanks,
Dave

 

[Maclin]

Re: 4.3 LX electric fuel pump

The fuel pump will (should) always run during cranking, but when the key is in the ON position it will only run when there is oil pressure. This is controlled by an oil pressure safety switch that only turns on when there is oil pressure, the main feed to the fuel pump goes thru this switch. The fuel pump receives power during cranking via a bypass circuit.

 

[achris]

Re: 4.3 LX electric fuel pump

Welcome to the club!!!

This is a problem with the Weber 4bbl... I had a 1994 4.3LX (4bbl Weber) for 12 years, same thing... I talked to Merc about it... "There is no problem" was the continued answer... I also had about a dozen customers (when I had the shop) with the same thing happening... "There is no problem". They even replaced my carb, complete! Same thing...

Ok, what happens is the carb continues to dribble fuel after you shutdown the engine... I proved it with the body of a carb on the bench. Blew air though one venturi and got it to draw fuel... Left it with both bowls full and the next morning one bowl was empty and the other was still full. "There is no problem".

The cause, as I see it, is that the drillings in the idle circuit are very small, and the fuel continues to run though them by 'capillary action'. It would require the air bleed orifices at the top of the primary venturi clusters to be opened out to stop the capillary action, and that would need the idle jets and the emulsifier tubes to be recalibrated. Equipment I don't have... but, "There is no problem"...

The 'quick fix' is to put an outboard primer bulb in the fuel line and give it a couple of squeezes while someone else cranks the engine.. (can't squeeze fuel though an electric pump that's not running, like you can a mechanical one)

Chris............

 

[Maclin]

Re: 4.3 LX electric fuel pump

That does sound like classic carb bowl evap/drain down. If mine (Holley 4bbl carbed 5.7 with mech fuel pump) sits 30 days or less it will start right away usually. The 30-45 day and on duration seems to be where mine drains/evaporates down enough to need to crank for a couple of 10 second bursts to fill the carb up again. I never worry about it as it runs and starts just fine for days after that first cranking after a longer layup.

 

[Maclin]

Re: 4.3 LX electric fuel pump

Looks like achris and I were preparing these carb related posts at the same time. He has more experience with your exact setup, my experience is more general and Carter and Holley based at that.

 

[egldvrbags]

Re: 4.3 LX electric fuel pump

Welcome to the club!!!

This is a problem with the Weber 4bbl... I had a 1994 4.3LX (4bbl Weber) for 12 years, same thing... I talked to Merc about it... "There is no problem" was the continued answer... I also had about a dozen customers (when I had the shop) with the same thing happening... "There is no problem". They even replaced my carb, complete! Same thing...

Ok, what happens is the carb continues to dribble fuel after you shutdown the engine... I proved it with the body of a carb on the bench. Blew air though one venturi and got it to draw fuel... Left it with both bowls full and the next morning one bowl was empty and the other was still full. "There is no problem".

The cause, as I see it, is that the drillings in the idle circuit are very small, and the fuel continues to run though them by 'capillary action'. It would require the air bleed orifices at the top of the primary venturi clusters to be opened out to stop the capillary action, and that would need the idle jets and the emulsifier tubes to be recalibrated. Equipment I don't have... but, "There is no problem"...

The 'quick fix' is to put an outboard primer bulb in the fuel line and give it a couple of squeezes while someone else cranks the engine.. (can't squeeze fuel though an electric pump that's not running, like you can a mechanical one)

Chris............

Thanks Chris,
Glad? to hear this is "normal." Thanks for the info.

I wonder if changing the starting procedure may help? ie, Crank it for about 10 secs so the fuel pump will pump fuel to the bowl. Then, do the carb/throttle starting procedure. I'll give it a try.

Just got to make sure I keep a good battery............

Dave

 

[Maclin]

Re: 4.3 LX electric fuel pump

If mine has been sitting a long time I will crank it for 10-15 seconds first with no throttle action, wait a bit then pump it twice then try to start. If it does not start or starts then dies I wait just a bit then just crank it for 10 seconds again with no throttle action, then wait a bit and pump it and try again. Doing the cranking with no throttle gives the carb a chance to fill, and the two pumps of the throttle gives the accelerator pump circuits a chance to prime once the fuel is in sufficient quantity and level in the bowl and I think this makes a difference. Leaving the cranking to 10 second bursts and waiting a bit in between is easier on the starter. With mine, after that first start after sitting a while, the thing will start every time hot or cold with no throttle and idle right away, and behave that way for 2 or 3 days in warm weather.

 

[Don S]

Re: 4.3 LX electric fuel pump

Have run into the same issue. One customer had me install a push button in the engine compartment so he could run only the electric fuel pump to "Prime" the carb without using the starter.
Primer bulbs should not be used in an engine compartment of an IO. They can leak, will NOT pass a fire test of any kind.

 

[wca_tim]

Re: 4.3 LX electric fuel pump

That's great solution. Do you see any downside to that at all? I had the same kind of an issue at one point...

Have run into the same issue. One customer had me install a push button in the engine compartment so he could run only the electric fuel pump to "Prime" the carb without using the starter.
Primer bulbs should not be used in an engine compartment of an IO. They can leak, will NOT pass a fire test of any kind.

 

[egldvrbags]

Re: 4.3 LX electric fuel pump

Have run into the same issue. One customer had me install a push button in the engine compartment so he could run only the electric fuel pump to "Prime" the carb without using the starter.
Primer bulbs should not be used in an engine compartment of an IO. They can leak, will NOT pass a fire test of any kind.

Thanks all through Don.

If it's been sitting a while, I guess I could also just place a jumper across the oil pressure switch, turn the key to ON (no cranking), let the pump run to fill the bowl. Then, take the jumper off and start normally??

I do like the push button switch idea which is way more foolproof.

Dave

 

[egldvrbags]

Re: 4.3 LX electric fuel pump

With mine, after that first start after sitting a while, the thing will start every time hot or cold with no throttle and idle right away, and behave that way for 2 or 3 days in warm weather.

Yep, mine's the same. I'll give your technique a try!

Thanks,
Dave

 

[Maclin]

Re: 4.3 LX electric fuel pump

I just could not recommend the jumper thing, too risky except to troubleshoot a bad oil pressure switch. I would have probably wired in something more permanent if it was my boat and had that chronic problem but I felt kind of odd recommending it for others even though I have probably done worse things on my own stuff! I really like the idea of the momentary on push button or spring loaded toggle, that way it only runs when the operator wants it to. But if the cranking for 10 seconds first thing works then, well, that is easy enough to do and the price is right!