Holley carb

[Lawnpro979]

Can't find previously post....but I think I've asked before

I did a carb rebuild on my VP 4.3 2700 carb
The build went well, replaced pump power valve 2.5 main jet seat.....checked the float level...

When taking the boat out it runs great...can go all over the lake...run wide open for ever. Stop somewhere let it sit for 5 or 10 minutes then when taking off it will die. Like it's running out of fuel...cranks back up fairly quickly....then can run again all over the lake with no issues.......
Stop somewhere let it sit and it keeps running.....
There seems to be no rhyme or reason. And it does act like float is sticking but only sometimes....
This is not why I did the rebuild. This is new. And I can't figure it out....

Thanks

 

[Scott Danforth]

did you replace the needle and seat when you did your carb?

 

[Lawnpro979]

Yes that too. Forgot to say that in post.......

 

[Maclin]

Sounds sorta like a mild vaporlock. How much effort is it to restart? When was fuel/water separator filter last changed? Is there a raw fuel smell when this happens? Can it idle for long periods of time with no problems?

 

[Lawnpro979]

Starts very quickly, this was the main reason to do the carb kit....she idles great and yes for a long time.....
I thought I smelled fuel none of the other passengers said they smelled any. I got back there and look but didn't see any......
I've had it out 2 times since the carb kit. And it did it on both occasions.......
I was thinking if the floats were sticking it would do it more often....." maybe I'm wrong" during the card rebuild there was nothing that jumped out at me....no sludge no excessive wear.....

This ones got me stumped....was seeking advise before I tear the carb apart again. And I'm not really sure what to look for......

 

[Lawnpro979]

Ahhhh... REstart.....it does take some effort....it's almost like it's out of fuel....but after about 10 to 15 secoands she fires right up. And runs all over the lake....wot
The only way I can reproduce the issue is to let her sit for 5 to 10 minutes......
1st arrive at lake there is no issue......

 

[loco]

Could you have exhaust fumes building up in the engine bay somehow when it's sat idling? Then when you try to pull off, it's starved of air?
Do you have a bilge vent fan fitted?

Contaminants in the fuel tank? I once had a kit car where a previous owner had let some rubber sealant fall into the fuel tank. Occasionally, the fuel pickup would be clogged by the bit of sealant floating about in the fuel tank, and kill the engine for a while. When you turned it off, the fuel pump would stop holding the sealant against the pickup, and it would float off again, allowing the car to run as normal.
Only fix was to clear out the tank.

 

[Lawnpro979]

Yea I'm not letting it sit idle.....I'll go to the marina and purchase a few items in there prob 5 minutes.... taking off in a no wake zone. It's done it two times oncewhile in the no wake zone. And once getting out of it...at a higher rpm......
The boat ran fine except hard starting before the kit.....so not so sure about something clogging it up...

I think my best bet is to pulll the carb again but I'm not sure what to look for.....when doing the rebuild I checked the floats at 3 different levels to make sure they were right.....meaning I flipped them over a few times rechecking.......just to make sure......also I can let the boat idle on the hose in the back yard forever......or at least until it's up to operating temp......

 

[Lawnpro979]

Also wondering if anyone has experience with the NITROPHYL FLOATS? If they give trouble or anything I should know....I don't know anything about them..

 

[Maclin]

Floats hanging would be very noticeable, very strong raw fuel smell and fuel pouring out of the j tubes into the bores, and would be very hard to start as it would be flooded, would have to open throttle all the way while cranking to clear the flooded condition. Spark plugs would eventually foul, and you would see general driveability and starting problems all the time.

Does sound more like a mild case of vaporlock. The fuel is "boiling" into vapor state in the lines from the separator to the carb. Maybe. So your carb bowl still has fuel and engine can run out a ways, then the bubble-laden stuff shows up and carb is not filling well until the more dense fuel comes along. So when was last time the water separator was changed and rubber hoses and metal line connections between the tank and carb inspected, that kind of thing. Might also check the anti-siphon valve at the fuel tank, if it has restriction then the fuel pump has a slightly harder time drawing fuel in to keep the fuel pressure up during a start right after sitting. And a hose leak there (before the fuel pump on vacuum side) could cause same similar symptoms.

Usually a system has been designed with keeping vaporlock situation abated. Like avoiding a steel line with a long run next to hot engine or other hot components, things like that. Some manufacturers have put out kits when they did not get it right at the factory. Your vintage of VP should be Ok in that regard, but "your mileage may vary". ​Is your fuel delivery plumbing all original or has it been modified, maybe you disturbed something during the carb r&r, some things to consider.

I think your engine uses electric fuel pump. If these conditions persist with no obvious problems with plumbing or other components then you might consider putting in a momentary switch that would put power to the fuel pump without engine running, Wired to where the ignition has to be on, but with engine not started yet, then hit that momentary for a few seconds, that would compress the expanded fuel/bubbly emulsion back to a more normal state. Kind of radical, and I would do this only after checking everything else. Or just living with it! Your condition is very mild, in some cases the engine will not be able to be started until after a long cool down period.

Good luck

 

[Lawnpro979]

No Title

I pulled the carb back off, wanted to recheck the floats and discovered that the Metering Body Vent Baffle was not in proper place. i suppose when i installed i put it behind gasket becasue it fell out when i opened it up.....