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problem with one of the 2 internal tanks on my boat causing fuel starving at idle.

9/8/21 @ 4:56 PM
ORIGINAL POST
Bruceb
USER SINCE 11/6/07

I have a 2000 200 HP merc efi and my boat has 2 internal tanks. I call them the front and rear tanks. I have developed an issue with the front tank. When running on the rear tank all is well. It will continue to run at any RPM for as long as there is gas.
On the front tank it will starve of fuel after 5 minutes at idle but will run fine at 4000 RPM's.
It has once stalled on me at 3200 RPM but rarely. The symptoms are as follows
Running fine(5 minutes)
Starts to slow down(2-3 seconds)
Dies and will not restart until I pump up the fuel bulb until tight.
Then it will happily idle for 5 minutes then die again.
Switching back to the rear tank after pumping up the fuel again I have left it idle for 15 minutes without it starving. Switching to the front tank and it will die again after 5 minutes after I have pumped the fuel bulb tight.
The tanks are run through a 2 tank rotary fuel switch that feels like it is new even though it is
as old as the boat(21 years). It is a wood/epoxy center console that my wife and I built.
I am looking for suggestions as to what may cause it to run on the front tank at high RPMs but starve of fuel at low RPMs.
Thanks

DISPLAYING 1 TO 10 OF 11 POSTS
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9/14/21 @ 5:34 PM
Bruceb
USER SINCE 11/6/07

Well, I bypassed the two tank valve and it idled for 20 minutes.  So I think that is the problem.  I am going to replace the valve and all my fuel lines just to be safe.
I will report back after all that.

9/13/21 @ 9:58 AM
Bruceb
USER SINCE 11/6/07

Is it possible that the anti-siphon valve is not opening at low RPMs and that is causing the fuel starvation at idle??

9/10/21 @ 9:36 AM
Bruceb
USER SINCE 11/6/07

I understand your fuel filter idea but it runs with no issues on the rear tank and both tanks go through the same 2 filters.  One in the engine and a separate water separator near the engine.  I drained the water separator and there was no water in it and the fuel looked good.  



9/9/21 @ 6:21 PM
prop-buster
prop-buster
USER SINCE 6/14/05

but.....did you change the fuel filter? didn't affect mine at high speed but sure messed up idle and slow.....EFI might even have two filters...do what you want....filters are cheap



9/9/21 @ 4:58 PM
Bruceb
USER SINCE 11/6/07

I tightened all the hose clamps(2 per fitting) and tried again.  Same issue.  After it stalls out(on the trailer ) I can pump it back up and it will idle again for 5 minutes then dies again.  Rinse and repeat.

9/9/21 @ 3:25 PM
Fish Hound
USER SINCE 1/29/02

Also check the tank vent, the front vent could be partially plugged, idling doesn't draw hard and builds a vacuum. Running hard could cause more draw and able to pull through the partial plugged vent.

9/9/21 @ 3:04 PM
Wjbk95
USER SINCE 4/12/21

If you have a EFI motor do you need a primer ball?? Thought the was just for carb motors

9/9/21 @ 1:04 PM
mattw
mattw
MEMBER SINCE 5/6/16

Sounds like to me you have a pickup issue , when you are at speed and the bow is up slightly , the fuel runs to the rear of the tank , but when you are slow the fuel doesn't fit the pickup tube .  But would double check the fuel line as well for any restriction because that's the easiest to check.  I would definitely look at your sending unit in the tank to make sure it's where its supposed to be , and the fuel runs to where it can be picked up . 

9/9/21 @ 10:25 AM
Bruceb
USER SINCE 11/6/07

there is only one in line fuel filter and both tanks go through it.  If that was the issue, wouldn't it starve out at high RPM's as well??


9/9/21 @ 7:26 AM
prop-buster
prop-buster
USER SINCE 6/14/05

have you tried changing the fuel filter (s) ?

DISPLAYING 1 TO 10 OF 11 POSTS
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