No gas to carb

g3nu1n31

Recruit
Joined
Dec 16, 2020
Messages
4
Hello everyone,
I have a 1984 mercrusier 470 that just isn't getting any gas. I have bought and installed a new fuel pump and have it pulling gas from an external gas can. I had this issue before and I thought the pump was bad so I bought a new one and installed it. But I'm still getting the same challenge. It's getting fuel into the line to the carb but for sone reason the carb is just completely dry. I know theirs fuel in it because when i disconnect the fuel line from the carb, it bubbles and a bit of gas comes out. I even pulled the fuel filter out of the carb and still no go. I checked the carb and it's clean but I wouldn't think that would be the issue. To test, I had the carb top off turned it upside down and poured gas into the changer and it flowed into the next chamber with no issue. I don't know much about carbs and engines, just the basics so I'm at a complete loss. Does anyone have any ideas what might be happenig? Thank you for your help.
 

airshot

Commander
Joined
Jul 22, 2008
Messages
2,386
What about the fuel line itself, they do go bad. Shouldnt be that hard to trace fuel flow to a carb.....
 

Scott Danforth

Grumpy old guy who plays with boats
Joined
Jul 23, 2011
Messages
41,983
Welcome aboard. Suggest you PM a mod and have moved to the Mercruiser forum

Check your needle and seat

Check your anti-siphon valve
 

g3nu1n31

Recruit
Joined
Dec 16, 2020
Messages
4
Oh, sorry, i thought i was in the correct one when posting, please forgive me. Yes, I replaced the metal fuel line from the pump to carb and the old one stripped when connecting to the pump. The fuel line from external tank to pump is brand new.

Anti-siphon valve? Can you please explain? Like I said, I don't know much about these.
 

Scott Danforth

Grumpy old guy who plays with boats
Joined
Jul 23, 2011
Messages
41,983
Anti-siphon valve is the barbed fitting at the top of the fuel pump pickup. It's basically a check valve.

Also, check the pickup filter. Suggest removing
 
Joined
Mar 27, 2010
Messages
3,008
Disconnect the fuel line from the carb inlet. Have someone hold it in a pail and crank over the engine about 10 seconds, see if an gas comes out; if yes, then you have a carb issue, if no gas, the problem is upstream. Like Scott mentioned, could be a problem with the anti-siphon valve which is screwed on the top of the gas tank and where the line connects to... or the pick up tube in the tank, there is sometimes an inline filter screen that could be blocked.
 

g3nu1n31

Recruit
Joined
Dec 16, 2020
Messages
4
Thank you for all the suggestions. I will do some more testing and checking and will let yall know what I find.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
69,455
Thank you for all the suggestions. I will do some more testing and checking and will let yall know what I find.
Ayuh,..... Welcome Aboard,..... A quick, 'n easy way to test the boat-side of the fuel system is hook up a gas can, 'n 3/8" hose to the fuel pump/ fuel filter, to eliminate the tank as the problem,....
 

g3nu1n31

Recruit
Joined
Dec 16, 2020
Messages
4
Yes, that is what I am doing. I am running a new hose to the pump with the hose in an external gas can.
 

ROY WILLIAMS

Petty Officer 2nd Class
Joined
Aug 8, 2022
Messages
126
Yes, that is what I am doing. I am running a new hose to the pump with the hose in an external gas can.
you should put the fuel pump in a cup of gas.. remove the fuel filter pump can, put a small cup of gas , then install the fuel filter pump filter cover , see if the engine runs .
then cranks 5-10 sec .. another crank later 2-4 min ..5-10 sec cranks it ..
then no engine runs .. then use a gas suction hose then the gas flows or not. From the gas boat tank...
 
Top