'96 VX-250 theory of operation

[fultsie]

Nice site!<br /><br />Does anyone know if the electric fuel enrichment is for cold starts only, or does it also add fuel at WOT? She runs out of fuel after about 10-15 seconds at WOT and I'm trying to determine if it is the electric pump or the 3 pulse pumps. Thanks much! Steve

 

[rodbolt]

Re: '96 VX-250 theory of operation

can ya post the model number, VX250 does not show up as anything in 1996.<br /> the VX indicates 3.1L EFI but was not produced in the US markets 96 model run, first of the EFI motors was 97 and the first VX250 I can find is is in the 02 model run

 

[fultsie]

Re: '96 VX-250 theory of operation

The engine cover says VX 250 76 degree and the model is an S250TURU. I just purchased the boat, could someone have changed the cover? Anyway, it has carbs and electric fuel enrichment fed from the #6 carb bowl. I would imagine the electric enrichment is for cold start only, but I read a post stating the electric enrichment is used under high load too. Seems it would run the #6 dry if used for any lenght of time. This motor will run 5,500 for about 10-15 seconds and then starve for fuel. Fuel to the engine is unrestricted and flows freely.

 

[rodbolt]

Re: '96 VX-250 theory of operation

its an s250 with a VX cover.<br /> the electric pump operates anytime the key is on. enrichment is used at any sudden throttle openings as well as when knocking is detected, it can vary fuel delivery.<br /> have you replaced the 3 lift pumps? if any are bad it will fuel starve at WOT. it will also run #6 bowl dry if the t-stats are stuck open or removed as the engine will think its cold and all six enrichment solinoids will open and #6 goes dry.<br /> you can identify which carb is going dry with a squirt can full of premix and the airbox removed.<br /> what is the fuel system vacum at the lower lift pump intake at or near 5500 ?<br />fuel pump pressure at the top pump outlet should never be lower than about 3PSI. that motor has to be able to move 25 gallons per hour at or near WOT and at 70*s and 4"Hg fuel boils easily. anything over 6"Hg is not acceptable. on that motor fuel system vacum should be 1.5 to 6"Hg. anything less indicates an air leak and anything more means there is a restriction someplace or the fuel line is to small.<br />that motor loves gas at WOT.

 

[fultsie]

Re: '96 VX-250 theory of operation

Wow, just what I wanted to know and even more. I,ve already ordered the lift pumps. I will report back with results. Thank you very much, I really appreciate your sharing knowledge....Steve

 

[fultsie]

Re: '96 VX-250 theory of operation

Well, I finally got around to installing the 3 fuel pumps. Same symptoms, no change. Broke down and decided to clean/rebuild the carbs. They all looked very clean, no varnish etc. anywhere visable and thoughout the passages. I was surprised that the problem is now resolved after reinstalling them. I did notice that one of carbs seemed to have a partial obstruction between the main fuel inlet and the underside of the float needle seat. That inlet is about 5/16" and the needle seat oriface is much much smaller. If any debris at all enters the inlet, the fuel is restricted from entering the bowl freely. While not absolutely positive, I would say this was the cause. Thanks for all the help, sharing knowledge is really good thing!