Can someone help me figure out why my engine is flooding?

[findinghomer]

I have a 1997 5.7 350 MerCruiser, the carburetor is dumping gas and it floods immediately, even from startup on the trailer to the dock it floods. I I rebuilt the carburetor last year and it was better, but it got super bad this year so I just replace the entire carburetor assembly. Still the same problem, can anyone give me some ideas where I need to start? I don't think it's anything within the carburetor because I just replaced the entire assembly... Any help would be appreciated thanks guys

 

[harringtondav]

Engine experts on this forum will certainly address your issue. But I believe you have a mechanical fuel pump that could be your problem. If so, the pros will tell you where exactly where to look

 

[findinghomer]

Okay thanks, I'm going to do some digging on that in the meantime. I know when I take my flame arrestor off and watch it as I fired up , as soon as I turn the key it just pours gas into the nobody. What I would think is excessive.

 

[Scott Danforth]

if you have a mechanical fuel pump and the yellow/amber line to the carb full of fuel? if so, its your fuel pump diaphragm has ruptured. time to replace the fuel pump

if you have an electric fuel pump, your float/needle/seat could have failed, then pull the carb apart

what is your fuel pressure? should be between 5-7psi

post your motor's serial number

 

[alldodge]

Agree, check your fuel pressure
Since this appears to have been an issue since you owned the boat, then was the fuel pump replaced by previous owner?

 

[Bondo]

Ayuh,...... Welcome Aboard,..... Bein' a '97, it should have an electric fuel pump,.....

What carb is on it,..??
I'd pop it's top, 'n check the float level, regardless whether it's brand new, or not,.....

 

[findinghomer]

Thanks guys, so Bondo, if it's an electric fuel pump does that mean it's non serviceable? That it's operating properly?. Or is it possible that It could still be delivering too much fuel? It's a 2 Barrel mercarb with an electric choke. I just find it to be too big of a coincidence that both carburetors are doing the exact same thing. Even the new one

 

[Bondo]

Ayuh,..... The stock fuel pump delivers the required 4 to 6 psi,......

I donno what you've got, You've gotta look, 'n do the diagnosis,.....

 

[Scott Danforth]

Thanks guys, so Bondo, if it's an electric fuel pump does that mean it's non serviceable? That it's operating properly?. Or is it possible that It could still be delivering too much fuel? It's a 2 Barrel mercarb with an electric choke. I just find it to be too big of a coincidence that both carburetors are doing the exact same thing. Even the new one

no, not a coincidence, its a giant red flag with 130 decibel horns....saying find out whats wrong before swaping parts

the purpose of the needle and seat in the carb is to shut off fuel flow. so doesnt matter how much the pump pushes, as long as the fuel pressure is 7psi or less, the needle and seat (if properly set) would shut off fuel.

what is the fuel pressure? (plenty of links on testing fuel pressure)

 

[findinghomer]

if you have a mechanical fuel pump and the yellow/amber line to the carb full of fuel? if so, its your fuel pump diaphragm has ruptured. time to replace the fuel pump

if you have an electric fuel pump, your float/needle/seat could have failed, then pull the carb apart

what is your fuel pressure? should be between 5-7psi

post your motor's serial number

Engine serial number is 0k165513. I'll have to find the links to figure out how to test fuel pressure

 

[findinghomer]

no, not a coincidence, its a giant red flag with 130 decibel horns....saying find out whats wrong before swaping parts

the purpose of the needle and seat in the carb is to shut off fuel flow. so doesnt matter how much the pump pushes, as long as the fuel pressure is 7psi or less, the needle and seat (if properly set) would shut off fuel.

what is the fuel pressure? (plenty of links on testing fuel pressure)

Okay I'll have to figure out how to test for fuel pressure. Is it possible for the fuel pump to be faulty and deliver too much fuel pressure? Also is it normal for the Jets to drop fuel when the key is turned. I know it needs fuel to ignite, but I've never actually watched one in operation as the key is turned , until now. Seems like an excessive amount that it drops. Also I would imagine it would be more of a spray? mine just drops like a dripping faucet. lm assuming that's not normal

 

[Bt Doctur]

A good carb with a good needle and seat with a properly adjusted float will not leak fuel wih the key on or off.
Remove the fuel line from the carb, plug a gauge into it with fittings, connector block, hose and clamps, etc
Turn the key to on and report the fuel pressure

 

[Rick Stephens]

Big alarm goes off for me that:

I know when I take my flame arrestor off and watch it as I fired up , as soon as I turn the key it just pours gas into the nobody.

Is it possible somebody bypassed the oil pressure switch power source for the fuel pump, or it is shorted out and powering directly off the ignition switch? Very dangerous if so. Or when he says turns key, it is during cranking that it pours gas?

Rick

 

[findinghomer]

Big alarm goes off for me that:



Is it possible somebody bypassed the oil pressure switch power source for the fuel pump, or it is shorted out and powering directly off the ignition switch? Very dangerous if so. Or when he says turns key, it is during cranking that it pours gas?

Rick

It is during cranking that it drips gas Into the throttle body. And I'm not entirely sure what you mean by the oil pressure switch power source, I havent tampered with it, and when I first got it, the boat ran fine.

 

[Scott Danforth]

throttle body or carb.

post your serial number and a picture of what you have

 

[harringtondav]

Your electric fuel pump has a oil pressure cut out switch in the circuit. It normally shares a T with the oil pressure gage sender. I've seen pics from this forum's pros that show it's location on a 350. It's designed to open and shut down your elec. fuel pump in key-off or engine stall. It had male spade connectors, the harness two female spades. Owners may jump the harness connectors to get fuel pump delivery at key-on to help prime the carb. (I was guilty and got a first class talking to about the hazards). If your fuel flows into the carb at key-on, I bet this has been by-passed per Rick Stephens . Locate this switch, and reconnect it if it has been bypassed.

 

[findinghomer]

Serial number 0k165513

 

[harringtondav]

Need input from someone with more mechanical fuel pump knowledge than me. But that yellow hose looks like the one Scott Danforth mentioned. Review his remarks. Could be your problem.

 

[Bt Doctur]

and that yellow hose is not used with a electric fuel pump

 

[findinghomer]

Need input from someone with more mechanical fuel pump knowledge than me. But that yellow hose looks like the one Scott Danforth mentioned. Review his remarks. Could be your problem.

Yeah I did see that comment, it sounds like it would mean I have a mechanical fuel pump? It doesn't appear that there's gas inside that yellow tube though, which he said would indicate a faulty diaphragm.

Here's a link to how much fuel my carburetor drips. I just went out and tried to start it. It would not even try to start until I opened up the choke , even then it wanted to start , but soon as I stopped turning the key it dies. And as you can see it just continues to drip gas when I'm done.



https://youtu.be/nM-SRaOJ-w4