Testing carbs, does air filter/flame arrester have to be on?

[elmorekevin]

I've been rebuilding carbs, fuel pumps, replacing filters and the gray fuel lines trying to track down my power loss issue. Each time I don't think I have replaced the airbox so I could tweak the carbs and fuel lines. Does it have to be on to create the correct vacuum or the like?

My symptoms are that the ski will start and idle fine, and when you punch the throttle you get great response for ~2 sec, then she sputters and dies. I have found that I can get up to a higher speed by "throttling" the choke along with the gas. This seems to me an indication of fuel starvation.

Also, I jump started the ski at the beginning of the summer, and now the low voltage battery light is always illuminated. After going through the fuel system so many times, i'm wondering if I damaged the MPEM somehow...

BTW I have a '96 GTI

Thanks for any help.

 

[seadooya]

as long as the "host' battery, wasnt powered up....ie, car truck, tractor..etc, then you'll be fine.

Yup, need to install everything, to get an accurate reading response. With air assy off, your manifold pressure is low.

If you rebuilt/gone thru the carbs, and didnt replace/install a different set of n/s springs, then you should be good. Set lsa/hsa to fact. settings, bolt everything back, and should be good. Make sure the fuel selector switch is on or res. set.

 

[elmorekevin]

What are n/s springs? If you're talking about the needle valve springs, I didn't change them nor did I change jets/screws or anything. I have the selector switch bypassed at the moment.

Unfortunately the boat engine was running when I jump started. Neither of the fuses have blown, just that voltage light stays on...makes me think somethings weird with it. Have checked battery voltage 12.5 off, 13.6 or so from idle up to mid throttle.

I've got some new plugs to try too, if I get it all back together and still have the same issue.

 

[seadooya]

cool. If you didnt replace the n/s springs..(needle/seat), then you be good. CLose it all up, replace the grey fuel line, and hit start button. The low voltage light will go away after a minute or so.

If you did everything right, then the carbs should be fine....cleaned them out, cleared out the excel pump, if applicable, new fuel lines.....etc

 

[elmorekevin]

ITS ALIVE. finally....And I would add a couple things to the list of things to check. I think my check valve for the fuel tank vent was in backwards, so no air was being let into the tank. Second, I guess you have to do your testing with the air box/flame arrester on (thought it's impossible to adjust anything with them on). I guess this limits the vacuum that is created causing the carb to reduce the amt of fuel pulled through.

Thanks for the help,
I feel like a pro on this fuel system now!