3.0 mercruiser ran for 5 min good. Then Just died?

[ilove2fixx]

Are you confident that you have idle mix set correctly? Set idle mix correctly first, then use idle speed screw to lower rpms to spec. If you cannot get rpms low enough you may need to adjust throttle linkage.

I suspect fuel issue like others have said. I would start diagnosing by testing fuel pressure (as was recommended earlier). Then you know if your issue is upstream or downstream of the carb. I would guess if you were to prime the engine several times before each crank, it'll probably start every time but die shortly after. I suspect either carb mix too lean, or pinhole leak in fuel line or vent issue or some other fuel starvation thing going on. Best way to find it is to be methodical.

i followed this but coudlnt get passed # 6 lowering the rpm to 700 using idle screw

 

[achris]

You've verified the timing? You've verified that the carb throttle butterfly valve is fully closing? If yes to both, then you may have a vacuum leak somewhere.

Chris......

 

[CaptnKingfisher]

i followed this but coudlnt get passed # 6 lowering the rpm to 700 using idle screw

View attachment 358759View attachment 358760

#2 "this should be sufficient for starting the engine"
Okay and it is sufficient, as you can start your engine. Now you need to adjust the idle mixture so it stays running using a tachometer. With engine running, slowly turn idle mix screw clockwise til rpms (on tach) begin to drop due to a too lean condition. Then turn idle mix screw counterclockwise til rpms begin to drop due to too rich condition. Now turn idle mix screw clockwise again making final adjustment for maximum engine rpm and smoothness.

Basically you go a little too far one direction, then a little too far the other to find your extremes and then settle in the middle where rpms are the highest. After that you adjust rpms using idle speed screw. And like I said, if you cant get rpms low enough then you need to adjust throttle cable

 

[j cat]

the carb plates can change a lock up position .. loosen the plates adjust the idle screw ...to unscrew .. then tighten up the carb plates..then turn the idle screw in the correct position then start up the engine and adjust the idle screw for 650-700 RPM...
your other post the engine idle was 1000 rpm did not drop the RPM..

 

[Grub54891]

the carb plates can change a lock up position .. loosen the plates adjust the idle screw ...to unscrew .. then tighten up the carb plates..then turn the idle screw in the correct position then start up the engine and adjust the idle screw for 650-700 RPM...
your other post the engine idle was 1000 rpm did not drop the RPM..

I've rebuilt/serviced many carbs over the years. The only time I had to loosen those plates is when someone did exactly what you just described. Experience lets me know that someone who didn't know what they were doing was messing where they shouldn't have been. If the plates are out of line it's possible the throttle shaft is loose in the bore, causing a vacuum leak. At that point the carb is junk, unless you have it re-bushed.

 

[ilove2fixx]

You've verified the timing? You've verified that the carb throttle butterfly valve is fully closing? If yes to both, then you may have a vacuum leak somewhere.

Chris......

ill check those thanks

 

[ilove2fixx]

ok i checked again and pump works good.. fuel has no water at all.. fuel is good / fresh very flammable even 1 drop and it goes.. I did notice for the 5th time AFTER it died, i go pump gas at the carb and no fuel at all squirts . Im 99% damn needle/float is sticking.

 

[nola mike]

I mean, sure sounds like the float based on your previous posts. Have you tried tapping the carb while it's running to see if that helps?

 

[achris]

Did you say earlier that you used an aftermarket kit and you had problems with it? That would be a good place to start...

 

[j cat]

ok i checked again and pump works good.. fuel has no water at all.. fuel is good / fresh very flammable even 1 drop and it goes.. I did notice for the 5th time AFTER it died, i go pump gas at the carb and no fuel at all squirts . Im 99% damn needle/float is sticking.

MY 1973 IMPALA bought in 1973 , then I had the engine running a few months new.. engine died , then I saw no gas in it ... then I took my shoe off and hit the carb ...then the engine works ..then I opened the carb and it was good setup .. I did a lot of carbs back in the 60-70's ..

 

[ilove2fixx]

Did you say earlier that you used an aftermarket kit and you had problems with it? That would be a good place to start...

yes i did, i will take it apart today and i do have an exrra needle / seat and float. ill rebuild it again. and hopefully third time does it

 

[j cat]

yes i did, i will take it apart today and i do have an exrra needle / seat and float. ill rebuild it again. and hopefully third time does it

I was repairing 1965-1975 outboard motors 2 years ago .. then the EBAY guy did a correct part on some of those carb's .. then the wrong carb part was not correct.. I fixed 5 motors ..sell them ..