Fuel starvation issue...

[kai1414]

Alright I'm sure this has been beat to death but here's my situation.

Twin 140 OMC outboards 1990-1992 Era, both fed from the same 210 gallon fuel tank, both thru the same water separating fuel filter, through transom fitting, fuel primer bulb in each line outside the transom, line in smaller fuel fliter under the cowl, line in to the fuel pump.

I just installed the water separating fuel filter and chnged fuel hoses. After filling the filter element tried to pump up the bulbs to prime the system. It never felt like they adequately primed and pumped up like they should have. At one point I found and air leak upstream (tank side) of the primer bulbs. When I would squeeze either bulb I could hear air being sucked in at the one fitting. Tightened it and I think its solved. ( I didn't replace the primer bulbs, just the hoses, the primers are merc quicksilver bulbs that were on the boat when I bought it.)

Took the boat out for a shake down cruise, the port engine developed a fuel starvation issue while the starboard engine was fine, keep in mind they are both fed from the same source and the same water sep. filter and tank. Idled the boat down for a few minutes, throttled it back up and they both ran just fine at WOT for about 5 minutes. My brother then had the boat out a few min later and appparently it was having idle issues and he had difficulty keeping them running. Any ideas?

 

[kai1414]

Re: Fuel starvation issue...

Just to add something quickly, should I get rid of the two small filters under the cowl? I'd heard that the VRO pump doesn't do well with too many restrictions.....

 

[Silvertip]

Re: Fuel starvation issue...

I'm taking a stab at this and my feeling is that since you have essentially "T'eed" the two fuel lines, one engine sucking fuel is reducing the fuel flow rate in the other line hence starving that engine. Ideally you should have separate fuel pickups in the tank and separate filters. In other words the fuel feeds to each engine should be totally separate from tank to engine.

 

[kai1414]

Re: Fuel starvation issue...

There are two fuel pickups in the tank, one line running to each engine. The only place they are "teed" is at the water separating filter. I'd been told that since they are designed with two inlets and two outlets and act as a resevoir of sorts that this shouldn't be an issue. The other thing is that both engines were having a problem at the end.

 

[kai1414]

Re: Fuel starvation issue...

anybody?

 

[tashasdaddy]

Re: Fuel starvation issue...

i would run them totally independently.

 

[Silvertip]

Re: Fuel starvation issue...

Since the problem apparently surfaced when you added the filter, disconnect one engine from the filter and plumb it directly. If the problem goes away, you identified the root cause. Because their are multiple ports on the filter doesn't necessarily mean you can run multiple engines from it. I still feel you need two filters and a totally separate fuel source to each engine. A "Tee" is a "Tee" no matter where you place it.

 

[kai1414]

Re: Fuel starvation issue...

i would run them totally independently.

What's your reasoning behind this suggestion?

 

[kai1414]

Re: Fuel starvation issue...

Since the problem apparently surfaced when you added the filter, disconnect one engine from the filter and plumb it directly. If the problem goes away, you identified the root cause. Because their are multiple ports on the filter doesn't necessarily mean you can run multiple engines from it. I still feel you need two filters and a totally separate fuel source to each engine. A "Tee" is a "Tee" no matter where you place it.

Well here's the fun part, I don't have a baseline to how they ran before the filter as I didn't own it then. Adding multiple filters is not a viable option at this point as I don't physically have another place to mount one. Having a "totally separate" fuel source for each is not an option either if you are reffering to separate tanks. If separate lines then yes if I physically had room to mount another filter I would. Right now the transom is so packed with battery switches, livewell pumps, battery's, fuel lines, cables, electronics, trim tab resevoirs, twin remote oil tanks etc that I don't physically have room.


With all of this said, I went back through and double clamped my lines where I think I may have had an air leak previously and reprimed the system. I also dumped the contents of the filter and the fuel looked good that came out, a few small particles but no water. Additionally I didn't realize that primer bulbs don't work very well unless they are vertical (brand new dual check valve bulbs from the store included), so I changed thier orientation in the system which allowed me to prime the system much better. I've run them at idle with no load (no back pressure either for that matter) and both now stay running, and seem to not exhibit the problems that i had previously experienced.

I greatly appreciate the responses and the help, I'll be sure to post when I sea trial again to let you know how it went and if that cleared it up.

 

[kai1414]

Re: Fuel starvation issue...

Quick update, the repositioned primers (to make them work to prime the system) combined with double clamping a few suspect fittings worked to perfection. Took the boat out this afternoon and it ran great.