Mercruiser 485 Starving for fuel?

[rtoomey641]

I have 485 Mercruiser was running fine then seawater pump imploded. Trying to start after rebuild and gas started dripping from carb figured stuck float or needle. Rebuilt carb with spring needle engine fires but will not start back fired a little moved timming slightly stopped backfire but still wont start seems like its running out of gas but I see wet fuel in carb and intake it is 2 barrel Mercarb. Any help much appreciated Thanks

 

[rtoomey641]

Possible bad anti-siphon valve?

 

[alldodge]

Sorry we missed you thread late yesterday evening but not good to start another one. Just post "bump" and it brings it back to the top

Going to need you engine serial number, I have not heard of the 485 but did find out most folks call it a 470. Being a 470 I try to stay away from them because I've been wrong a few times with my assumptions. Hope someone comes along which knows more shortly.

That said if the carb is dripping fuel, then the motor is flooded, and it will have a hard time starting.

 

[rtoomey641]

Ok Thanks serial number is 6001956 changed anti-siphon device but that is not it. It fires but won't keep running

 

[iand464]

Did it overheat when the water pump went?

 

[rtoomey641]

yes

 

[Bt Doctur]

pull the plugs to see whats there, suspecting you`ll find some AF

 

[rtoomey641]

Ok I put new plugs in when I did carb they look ok except a little black from carbon they are dry old ones were all black just did compression test cyl 1(135lb) cyl 2(140lb) cyl3(135lb) cyl4(132lb) getting fuel at carb don't know pressure but its getting here after I fixed seawater pump it ran for about a minute then carb started pouring gas into manifold that's when I rebuilt carb changed oil and plugs and try to start but it wont Thanks

 

[rtoomey641]

The gas cap o ring came off when I put gas in rightbefore we went out could that be it?

 

[NHGuy]

BT doc posted to check your used plugs for AF. I think he was expecting anti freeze. Is this a closed cooled engine with a heat exchanger? If so he may be on to something. Perhaps when it got hot the head warped and allowed coolant where it should not be. Although that is not indicated by your compression values.
Shoot some carb spray down the carb and see if it runs for a moment.
Is your fuel filter new? Is it blocked? You can disconnect the ignition, take off the line to the carb, and crank the engine with fuel into a bottle or plastic baggie to see how much it gives.
Did you taking out a float needle and rebuild with a spring needle? If so go back the way it was and see what happens.

 

[rtoomey641]

Yes no AF no fuel filter spring missing rebuilt with spring needle will try solid tomorrow it tries to start but wont keep running old plugs just carbon and gas from flooding

 

[s.hadley81]

Did you check the sight tube on your fuel pump? Maybe the diaphragm ruptured and is dumping fuel in the carb. Just a thought!

 

[NHGuy]

true that

 

[rtoomey641]

Ok cleaned filer bowl on pump had a lot of dirt switched back to no spring on needle runs for a few revolutions at WOT fuel coming out of line in spurts not a steady stream suspect bad pump?