5.7 Hard starting after sitting!

[Johnc3211]

I have a 93 250 EC with a 5.7 Mercruiser Alpha 1 gen 2. Over last winter I rebuilt the Weber 4 barrel carb. Last year it was sucking down the gas and finicky to start cold or hot. This summer it got noticably better fuel economy and gained some WOT rpm. We keep it in a marina on Lake Erie which is 2+ hours from home. This season we were on the boat a little less than last year, the boat would sit for more than 3 weeks a few times. When it would sit for more than a couple weeks it would be very hard to start the first time. It would crank and crank, maybe 30 seconds total until it would start. After that first time after sitting it would usually start right up with a couple pumps on throttle. Also started fine warm. It seemed like the carb bowl was dry and needed to be cranked long enough to fill up. Is this common? Could my mechanical fuel pump be going bad? Would an electric fuel pump help? Thanks guys.

 

[ttmott]

Ebay or Amazon carb rebuild kit?

 

[Johnc3211]

Ebay or Amazon carb rebuild kit?

"Mike's Carburetor Parts" kit. Seemed like a high quality kit, excellent gaskets and detailed instructions. Have not rebuilt a carb in a long time but the Weber (Carter AFB) is fairly simple compared to Q-jet or Holley. Last year I think it tended to flood out some. I had to give it a lot of throttle to finally start and would smell gas behind boat and see black residue floating. This year there is no smell or residue. No odor out of blower vent either. Searching on this forum, my problem is not too uncommon. Seems the choke is the most advised fix, some claim Mercruiser went to electric fuel pump to fix problem. My choke is bimetal coil in intake with linkage to carb. Adjusted to instructions and seems to work perfectly.

 

[ttmott]

"Mike's Carburetor Parts" kit. Seemed like a high quality kit, excellent gaskets and detailed instructions. Have not rebuilt a carb in a long time but the Weber (Carter AFB) is fairly simple compared to Q-jet or Holley. Last year I think it tended to flood out some. I had to give it a lot of throttle to finally start and would smell gas behind boat and see black residue floating. This year there is no smell or residue. No odor out of blower vent either. Searching on this forum, my problem is not too uncommon. Seems the choke is the most advised fix, some claim Mercruiser went to electric fuel pump to fix problem. My choke is bimetal coil in intake with linkage to carb. Adjusted to instructions and seems to work perfectly.

The needle float valves in the Chino kits fail right a way. The rubber tip swells up and will block the fuel passage to the bowl.

 

[Johnc3211]

The needle float valves in the Chino kits fail right a way. The rubber tip swells up and will block the fuel passage to the bowl.

The kit I used claimed made in USA. Wouldn't I have problems with WOT if that was my problem?

 

[ttmott]

The kit I used claimed made in USA. Wouldn't I have problems with WOT if that was my problem?

I would say so. The parts could just as easily stick the needle valve and cause high fuel levels in the bowls and cause hard starting due to a rich condition. Just a thought from experience I had on a 5.0 in a 205 SR.

 

[scoflaw]

This is how my carbed cars act after a few weeks, sound normal. Bowl is vented and gas does evaporate.

 

[Johnc3211]

I read guys talking about electric fuel pumps on other posts. They also talked about wiring it so it runs when the engine has oil pressure. Would that fill the float bowl faster than cranking and cranking?

 

[Scott215]

If you lose oil pressure the engine will die and hopefully save it

 

[Johnc3211]

I never smelled like it was flooded nor did it help to have the throttle wide open.

 

[Scott06]

I have a 93 250 EC with a 5.7 Mercruiser Alpha 1 gen 2. Over last winter I rebuilt the Weber 4 barrel carb. Last year it was sucking down the gas and finicky to start cold or hot. This summer it got noticably better fuel economy and gained some WOT rpm. We keep it in a marina on Lake Erie which is 2+ hours from home. This season we were on the boat a little less than last year, the boat would sit for more than 3 weeks a few times. When it would sit for more than a couple weeks it would be very hard to start the first time. It would crank and crank, maybe 30 seconds total until it would start. After that first time after sitting it would usually start right up with a couple pumps on throttle. Also started fine warm. It seemed like the carb bowl was dry and needed to be cranked long enough to fill up. Is this common? Could my mechanical fuel pump be going bad? Would an electric fuel pump help? Thanks guys.

I see this exact thing with my edlebrock 1409 which is basically the same as your webber 4 bbl. Carb gets dry there is no fuel in it. The cranking is just to get fuel in it. The fuel pump runs off the starter until ignition is on then it goes through and oil pressure switch.
folks have wired momentary 12 v supply to the fuel pump to prime it. Also if you spray starting fluid in flame arrestor it will run until fuel bowl is full. Or you just learn to deal with it knowing nothing is really wrong with the carb

I get my carb parts from Mikes too never had an issue with their parts

 

[hughespat57]

They sell a 3 terminal oil switch kit.
One wire is pump
One is ignition
Third goes to starter
This way it primes as you crank it up.

 

[Johnc3211]

Will an electric fuel pump fill the carb faster than the mechanical pump when cranking?

 

[Scott215]

Yeah but they get hot

 

[Johnc3211]

If I went with the electric pump, I saw a video where they wired in a relay with the pressure switch. I looked at relays and saw some with fuses. In the video they took 12 volts from the circuit breaker on the motor and did not talk about a fuse. I could run a wire to the ignition switch which has a circuit breaker instead of the relay.

 

[hughespat57]

The new fuse and relay are because most ignition circuits cannot handle the additional load.

 

[Scott215]

And you want your engine to shut off if you lose oil pressure so you want that pump to turn off if you ever lose pressure