OMC LOOPER FUEL PRESSURE:output on fuel pump / vapor separator is not steady (< 3PSI)

[foca1]

2004 V6 carb Loopers

believe i am failing the 800rpm in FWD idle fuel pressure test as laid out in the OMC manual. it specifies that it should not go lower than 3PSI. could i be doing something wrong? or should i be seeing a SOLID 3PSI or more on these things??

I am running 50:1 premix, instead of the VRO pump, now.

the motors quit running on me while i am docking. very annoying.

on both motors the fuel pump pressure is doing some wierd stuff. it goes to 3PSI then, creeps down to like 2, then 1, then jumps back to 3PSI. both engines do the same thing. i took video of the gauge last night. does this mean i am getting air into the fuel pump, then the vapor separator relieves it or something? there is no air actually going to the carbs though, i verified this with some clear hose.

other info:
power and part throttle is good, they make power.
plugs are new and gapped at .030
carbs have been overhauled (though the bowls are warped on several)
idles at ~650, when it doesn't conk out
fuel suction-side is good to the OMC manual's spec

[Mark Poole ModVP]

First, I assume you are still using the VRO and have the oil side plugged to use premix. I believe the weird up and down reading you are seeing is the pump cycling. The VRO pump is driven off the crankcase and builds pressure in the "air motor" side of the pump. If you put your head close to the pump and listen carefully you can hear a VRO cycling with a clicking sound every few moments. Make SURE the entire fuel system is air/leak tight.

Also keep in mind that by going from VRO oiling to premix, this could change the idle charactaristics of the engine. You might need to reset the idle fuel adjustment screws or maybe even make small size changes to the idle air bleed jets. If your motors are "sneezing" just before they shut off that is a sign of possibly two things. The carb butterflies need to be synched or the idle mixture is too lean. All butterlies should be shut tight at idle position when there is no input (contact) from the throttle cam.

If all this does not solve anything then look to a fuel tank or fuel supply line problem since both motors are having the problem. Install all fresh filters.

[foca1]

i did post another thread, about the air box. when i had it off a couple nights ago, the motors did not conk-out even once when i was docking. it was nice.

they are definitely not lean-sneezing, they actually smell SUPER rich. makes your eyes water....


I understand where you are going with the air pump theory, but the VRO pump is capped, so unless the diaphragm is broken somewhere and it's getting crankcase air, there is no other way for there to be air in the system, right?

i have a video of the press test. only a 1meg file. i could email it to anyone that would like to see it.

thanks.

[Mark Poole ModVP]

From what you just said I would say they are rich, between the smell and idling better with the air boxes off. What about the gas in your built in tank...any chance that it could be oil rich?

[foca1]

yes, that is possible, as i didn't personally fill it. but, my buddy usually doesn't make those kinds of mistakes...

i am running the johnson oil at 50:1

gonna add more gas soon, let's see if that changes anything.

[nymack66]

Pointers
>Check all your re-circulating crankcase valves, plus hoses clean and flush per manual
>Remove and clean all check valves and test per manual
>Remove clean and inspect the crankcase flame arrester valve (to VRO)
Did this issue just started?