Fuel Tank issues

[MistyTazzvon]

Hello all, I seem to have a fuel tank issue. Let me explain my setup and what i have tried.

1989 Sunbird Corsica 185 with OMC 3.0 Cobra Sterndrive.

Fuel system is setup in the following configuration:
Fuel tank --> Fuel/Water separator --> Fuel Pump w/filter

Every time i use the onboard fuel tank it and get underway it lasts for about a minute or two then bogs down and dies. It will not start back up from the onboard fuel tank. if i switch to the following configuration:
5 gal gas can --> Fuel/Water separator --> Fuel Pump w/filter

This runs fine all day long any speed.

I have made this switch while on the water so i know the fuel.water separator is not full of water as i do not dump it between switch.
I have taken the air intake line off the onboard tank so i know it is not creating a vacuum
I have completely suctioned the fuel out and replaced it (as best i can with an oil removal canister to suck the fuel out through the hole from the gage sensor)

The only thing i have not done is remove the fuel pickup from the tank as i cannot get it to break lose from the big nut no matter how much power i use.

I don't know what else the issue could be and i hate running off gas cans as they are dangerous and take up precious deck space. Any ideas?

Please note i am pretty sure it is the tank as it seems to run fine by only changing the line from the tank to a gas can.

 

[ThomW]

When the motor dies and you switch to the remote tank, have you tried switching back to the other tank after a few minutes or an hour? Does it then run again for a minute or two and die? Did this happen once or multiple times? If it happens more than once, or you can switch back to the onboard tank and run for another minute or two, I'd agree its a tank issue and not bad gas. It really sounds like the tank is vapor locking, somehow. I'm not really sure if the pickup tube would cause that, or how. You are sure the vent to the tank is clear and working fine?

 

[MistyTazzvon]

ThomW, I have switched back and forth it it does die every time i go back to the onboard tank. I completely disconnected the hose to the tank vent so it was venting right from the tank and it still did the same thing. I was just curious if there could possibly be larger sediment in the tank that would clog the pickup tube when i get on it. I am not sure how to figure this out as i really cant see the pickup from the float hole. I have successfully let it idle for long periods running from the onboard tank but not when i get under way. If it is trash in the tank how would i go about getting it out with no visual?

 

[ajgraz]

Have you tried running with your gas cap off? Maybe the vent is plugged at the tank nipple, have you probed inside that? Maybe your fuel line from onboard tank to separator is kinked or partly blocked up, can you run a (temporary) replacement fuel line there?

 

[MistyTazzvon]

Have not tried without gas cap but it has a seperate air intake line which i disconnected so fill line would not matter if its blocked i wouldnt think..
I did run a diffetent line from tank to seperator but when i swap from tank to gas can it is the same line only difference in running it tank or gas can.

 

[Bondo]

The only thing i have not done is remove the fuel pickup from the tank as i cannot get it to break lose from the big nut no matter how much power i use.

Ayuh,.... The hose barb at the tank's outlet should be an anti-siphon valve,....

Pull it, 'n make sure it's clear,...
At that point, you can blow through the dip-tube to make sure it's clear,...