Fuel Starvation 2003 280 Sundancer Twin 4.3 Merc

2003 Sundancer 280 Twin 4.3 Mercuiser engines.

I have searched the blogs best I could not sure if there info on this topic. But here is what we have tried so far.

Starts and idles fine both engines sound great. we go out to run and it gets up and goes then after about 1 minute at 3000 RPM port engine loses fuel pressure engine just shuts down for lack of fuel.

Has new lift pumps spring 2018.
We also bypassed the solenoid.
Switched around relays for the fuel pump
We haven't run on a portable tank yet.

I should also mention we removed the filter that separates water out and it was only half full of fuel only. This is located between the lift pump and the high pressure cool fuel pump. Is it possible the cool fuel pump could be bad, do they just die or can they be intermittent? If so is it possible it would allow air back in the line? The lift pump was new last spring.

With all that we get it up and going then the Starboard engine seemed to do it as well only when the other engine was running. The Kohler generator ran nonstop so Im not sure if I have a vapor lock or vacuum issue with the tank, but I will try with a portable tank. Sure is funny we would have this happen on both but mainly on the Port Engine.

So once it's down, to restart if we cycle the start button to engage the high pressure fuel pump a few times it will then start up and idle forever, it will also run at lower RPM's without issue but when we get going on higher RPM it will go for about a min and the fuel pressure gauge we installed on the rail drops right down to nothing. If I pull the throttles back when this does start to happen it will try to chug away on a rough idle burning up whatever fuel it has and then dies of fuel exhausting. I have only check the fuel/water separator filter one time and it was half full with air and fuel. Last year when I had this same issue on the same engine we replaced the lift pump and it solved it. Could the high pressure fuel pump be weak and causing the lift pump to have issues?

IAC have been replaced as well but seems they can go bad not sure if this is related.
The fuel is from July 2018 with stabilizer in it. We were down for a rusted through head. It's been a bad 6 months. Boat mechanics are in high demand.

I’d go for the portable tank next. Similar thread last year had an issue with fuel lines collapsing under pressure, another had problems with the main tank pickup clogging, and I believe there was a tank vent issue as well.

A separate tank plumbed straight into the main line should help narrrow down whether its on the supply side

Plugged fuel vent??

next time this happens open the fuel tank filler cap....if the problem clears up you have a blocked vent line from the fuel tank.....

if this does not help check the 'anti siphon valve' on the fuel tank....it has a spring loaded one way ball valve...sometimes this ball gets stuck in the closed (or nearly closed) position and will restrict fuel flow from the tank.....

cliff

Hey thank you all, I had my email incorrect so I just am seeing these responses. We replaced the fuel lines last year from the lift pumps. We also did remove the gas cap, while all this was going on the generator never quit. I do have two new cool fuel pumps to put on the boat. The current ones are original. Has anyone ever changed them on this boat, if so any tips or surprises I need to be prepared for in swapping out the pumps? Both engines have a similar issues however on the Port engine it won't hold fuel pressure while the Starboard stays running just fine. I was going to try and start and run it with a portable tank tomorrow. If the issue is the same I believe since the lift pump was new last year the cool fuel would be inoperable.

Spent 2 hours removing the pump and cooler GenII. It took me about 2 hours to put a new fuel cooler and pump in but it runs great, didn't even have to prime it. No issues so far. I have pics and I have shared them if it would be helpful for the forum. I just removed the power steering pump and the winterizing valve to get better access to the pump. Im going to change the Starboard engine when we do the risers, manifold and elbows this week.

Wow, thanks for the detailed pictures! how sore are you today? I know that working at those angles had to take a toll!

LOL not too bad but yesterday it felts like I boated all day. I was spent. I was able to get down in there and hug the engine really good and work underneath it and from the side. My hands are scratched up a bit but Ill recovered once I was able to run the boat up and down the intracoastal way. I had originally asked our mechanic to do this but the promise of "I will be there...." was like a broken record. So I did it.