4.3l fuel starvation

S

Sean195

Member
Jun 29, 2019
59
Boat Info
1995 Sea Ray 195 Sport
Engines
4.3L
I purchased a 1995 195 sport last summer and have been chasing a fuel related issue. The issue starts once the engine is warm, and usually first arises when the engine is started after being stopped for a while. Once I start the boat after floating around for a bit, it starts and then stalls when throttle is applied and/or after a few seconds of idling. During this time, i do not hear the fuel pump running like it should when the engine is running

The only solution I have found is to hard wire the fuel pump directly to the battery. When this is done, the boat runs fine. This winter, I wired up a switch in the helm that allows the fuel pump to be turned on manually if the problem persisted this spring.

Here are the things I have replaced so far (in order):
Totally new carburetor, new oil pressure sender, new oil pressure switch (also replaced coil, plugs, fuel/water separator).

The problem continued after each one of the parts I replaced, leading me to believe that there is something else wrong.

I am not sure else could it possibly be. I traced the wiring coming from the fuel pump and I replaced everything (I think) that would cause the fuel pump not to run.

Took it out for the first time this year today, and the issue came back, so i was forced to run the fuel pump manually.

Any suggestions?
 
Sean195 said:
I purchased a 1995 195 sport last summer and have been chasing a fuel related issue. The issue starts once the engine is warm, and usually first arises when the engine is started after being stopped for a while. Once I start the boat after floating around for a bit, it starts and then stalls when throttle is applied and/or after a few seconds of idling. During this time, i do not hear the fuel pump running like it should when the engine is running

The only solution I have found is to hard wire the fuel pump directly to the battery. When this is done, the boat runs fine. This winter, I wired up a switch in the helm that allows the fuel pump to be turned on manually if the problem persisted this spring.

Here are the things I have replaced so far (in order):
Totally new carburetor, new oil pressure sender, new oil pressure switch (also replaced coil, plugs, fuel/water separator).

The problem continued after each one of the parts I replaced, leading me to believe that there is something else wrong.

I am not sure else could it possibly be. I traced the wiring coming from the fuel pump and I replaced everything (I think) that would cause the fuel pump not to run.

Took it out for the first time this year today, and the issue came back, so i was forced to run the fuel pump manually.

Any suggestions?
Click to expand...
When you were tracing the wiring, did you replace the fuel pump relay and take a close look at the contacts?

Is it possible this is actually a vapor lock issue and running the fuel pump manually is masking the issue?
 
The fuel pump relay/connector looked like it had been tinkered with before. I’m guessing the previous owner had a similar issue. I eliminated the connection all together and used marine grade plugs for the purple/yellow wire and the ground.
but yes, I checked all connections each time I dug into it and never saw any changes.

Is there a way I can diagnose the vapor lock issue ? If it truly was vapor lock, shouldn’t I hear the fuel pump running ? when I have the no start issue, the fuel pump isn’t audible/running, so that’s why I didn’t consider that as a potential problem
 
Last edited:
Sean195 said:
The fuel pump relay/connector looked like it had been tinkered with before. I’m guessing the previous owner had a similar issue. I eliminated the connection all together and used marine grade plugs for the purple/yellow wire and the ground.
but yes, I checked all connections each time I dug into it and never saw any changes.

Is there a way I can diagnose the vapor lock issue ? If it truly was vapor lock, shouldn’t I hear the fuel pump running ? when I have the no start issue, the fuel pump isn’t audible/running, so that’s why I didn’t consider that as a potential problem
Click to expand...
If you're sure that the pump isn't running then you are probably correct that vapor lock isn't the issue.

I'm not familiar with exactly how that unit is wired so I can't be a lot of help. If it were me I would make sure I was armed with a test light and a meter and be ready to troubleshoot when it happens next. Start at the relay to see if your issue is with the control side or the load side and go from there.
 
Got it thanks. There is no relay on my carbed engine. At least that’s my understanding
 
Doing some more brain storming and looking at some wiring diagrams- any chance the solenoid to the starter (powers the fuel pump) could need replacing ?
perhaps if the solenoid is bad and the fuel pump isn’t running during cranking, maybe it’s starving itself for fuel....?
The starter is a brand new Mercruiser starter (bought last year), so this seems unlikely.
 
hot wiring the fuel pump indicates you have a wiring issue. with the key on you should have 12v at the purple wire , that goes to the oil pressure switch and then to the pump.
click to enlarge
 
Bt Doctur said:
hot wiring the fuel pump indicates you have a wiring issue. with the key on you should have 12v at the purple wire , that goes to the oil pressure switch and then to the pump.
click to enlarge
Click to expand...
I will look over the wiring again, but each fix I have attempted involved me doing that and nothing stood out
 
If you have 12 volts at the electric choke or the coil, you can tap there to go to the pressure switch
 
No , you need the pressure switch , simply use a different feed . You said you hot wired the pump and it ran, if you hooked that hot wire to the pressure switch then the motor should also run.
 
Right. Got it. I’ll give that a shot. This problem really has me stumped though
 
Did you try replacing the oil pressure switch? It’s a common fail point. You can jumper around it to test.
 
I tried replacing the switch, yes. I am going to wire up a bypass for the pressure switch though, so I can determine if the new replacement switch is no good if the problem happens again the next time I’m out
 
Sean195 said:
I tried replacing the switch, yes. I am going to wire up a bypass for the pressure switch though, so I can determine if the new replacement switch is no good if the problem happens again the next time I’m out
Click to expand...
With engine running you could disconnect switch and check continuity across it with a volt meter. Carb should have enough fuel to run for a bit at idle before bowl runs dry.
If the switch is good I’d say you may have an issue with the harness either broken connection wire or corroded or loose terminal , which could be a PITA to trace out.
 
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