4.3 fuel problem?

[13crazyhorse]

I have a 2002 4.3 I/O carb model. Go to the marina start it up runs perfect at idle through full throttle. Shut it off on the lake for 2 or 3 hours. Start it up it idles for roughly 5 seconds then stalls. Won't restart. Pour a little gas in the carb it starts and runs for a couple of seconds. After doing this 3 or 4 times it will stay running and run perfect again. If I run the boat and shut it off it will always restart. Only when it sits for a couple of hours will it not start. If I let it sit all night it always starts right away in the morning. I'm thinking fuel pump maybe? My SS checks aren't that big so I'm looking for a little input before I go for the 4 bills for a new pump. Thanks ahead of time for the thoughts.

 

[Scott Danforth]

Have you checked fuel pressure or made sure the pump is priming?

Open your fuel cap when it wont start. If you hear hissing your fuel vent is plugged

 

[CaptnKingfisher]

Could be your anti-siphon valve is failing. Normally gas would stay in your fuel line with the engine off but a failed valve would allow gas to run back into the tank. After sitting with the engine off there is no fuel in the fuel lines so it takes a lot of cranking in order to re-prime the lines.

 

[13crazyhorse]

I have checked the fuel vent it is clear. If the anti siphon valve is failing why would it start right up in the morning?

 

[CaptnKingfisher]

Ah good point. It's strange cuz it cold-starts fine when you get to the marina, but you run the boat, sit for 2-3 hours and now you're cold-starting again and suddenly have this issue. What is your starting procedure?

 

[Scott Danforth]

Check the oil pressure switch and that the pump is actually running

 

[Rick Stephens]

Might be slowly emptying the carburetor and flooding the motor. Have you tried opening the throttle all the way when restarting? Treat it as flooded. Was a common Weber carburetor problem.

 

[13crazyhorse]

Check the oil pressure switch and that the pump is actually running

Scott,
How do I check the OPS and should I be able to hear the pump run like on an automobile? thanks for the help.

 

[nola mike]

Scott,
How do I check the OPS and should I be able to hear the pump run like on an automobile? thanks for the help.

What carb do you have? Your ops has 3 terminals. 1 gets 12v when cranking, 2nd is always hot when ignition is on. 3rd has 12v out to fuel pump, which is present when cranking (from 1st terminal) and when op is high enough to close the switch and send the 12v from the ignition. The pump doesn't operate just when the ignition is on/engine off. If it doesn't start you can jump terminals 2 and 3, that will bypass the switch

 

[13crazyhorse]

What carb do you have? Your ops has 3 terminals. 1 gets 12v when cranking, 2nd is always hot when ignition is on. 3rd has 12v out to fuel pump, which is present when cranking (from 1st terminal) and when op is high enough to close the switch and send the 12v from the ignition. The pump doesn't operate just when the ignition is on/engine off. If it doesn't start you can jump terminals 2 and 3, that will bypass the switch

Awsome thanks for the input I'll check that out.

 

[13crazyhorse]

The pressure switch actually has two wires. If I get in this no start condition again I'm assuming that if I jump these two wires together it will bypass the switch?

 

[Rick Stephens]

Best test that oil pressure switch. Make sure everything works the way it is supposed to. That is an important safety feature.

 

[13crazyhorse]

Best test that oil pressure switch. Make sure everything works the way it is supposed to. That is an important safety featur

Best test that oil pressure switch. Make sure everything works the way it is supposed to. That is an important safety feature.

Rick,
Thanks for the quick reply. I totally understand the importance of any safety feature on a boat I would never bypass anything as important as that for more than a minute. I was just looking for a quick diagnosis for my problem. Thanks again for your input it is appreciated.

 

[Bondo]

The pressure switch actually has two wires. If I get in this no start condition again I'm assuming that if I jump these two wires together it will bypass the switch?

Ayuh,..... Ignition power in, 'n out to the fuel pump,.....
Jumpin' it, by-passes it, Yes,.....

Which carb do you have,..??
As Rick says in post #7, the Weber is known to leak internally, causin' the symptoms yer sayin' yer seein',......

 

[13crazyhorse]

Ayuh,..... Ignition power in, 'n out to the fuel pump,.....
Jumpin' it, by-passes it, Yes,.....

Which carb do you have,..??
As Rick says in post #7, the Weber is known to leak internally, causin' the symptoms yer sayin' yer seein',......

Thanks Bondo. Carb is a Rochester.

 

[Lou C]

If it’s a Rochester style carb it’s gotta be the Mercarb which is a slight modification of the old Rochester 2GV 2 bbl. I think testing for fuel pressure when it fails to start is the way to narrow this problem down. This is one reason why I’m reluctant to give up my old pre vortec 4.3. Simple & cheap to replace mechanical fuel pump.

 

[13crazyhorse]

If it’s a Rochester style carb it’s gotta be the Mercarb which is a slight modification of the old Rochester 2GV 2 bbl. I think testing for fuel pressure when it fails to start is the way to narrow this problem down. This is one reason why I’m reluctant to give up my old pre vortec 4.3. Simple & cheap to replace mechanical fuel pump.

Well I tried jumping the oil pressure switch today when it did its daily possession, but that didn't work I was sure that would work. I also checked power to the pump and I have that also heard it running when it was jumped. Back to the drawing board I guess.

 

[13crazyhorse]

Well I tried jumping the oil pressure switch today when it did its daily possession, but that didn't work I was sure that would work. I also checked power to the pump and I have that also heard it running when it was jumped. Back to the drawing board I guess.

I'll have to look I think I have a fuel pressure gauge don't know how I'll attach it to this engine though all steel lines. Maybe somebody makes a unit you can attach easily and leave on the engine?