Dual gas input issues

Pfu

GreatGrady Captain
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Age
64
Location
Burlington Vermont
Model
Gulfstream
I have dual 92 gal tanks on my Gulfstream 232 and can’t for the life of me figure out why I can’t get fuel in either. Both tanks allow for a small amount of fuel to be filled and then overflows at the nozzle. Assume the fuel tube is having an air lock but no idea how to check or clear the air line back. Las year had no issues with either and now can’t put gas in to finally get in the water.

To say the least very frustrated as boat remains on trailer. Never been this late getting into the water as normally in mid April.

As always very appreciated of all thoughts and comments!

Randy
 
Hello Randy,
do you have a external fuel tank vent, or inside the fuel filler?
If outside of the hull vent, then check if some insect/s built a nest inside what clogs the air vent stream.

Have you tried to fill sloooowly, some gas station pistols are very fast and can lead to airlock and spitting fuel out.
You may try to use a jerry can and a thiner hose to let air escape if you have the vent integrated in the filler cap just to check if slower filling will solve problem.

Chris

BTW: Dumb question, are you sure the as tanks are low on fuel or you forgot that you filled them totally for winter?
 
Hello Randy,
do you have a external fuel tank vent, or inside the fuel filler?
If outside of the hull vent, then check if some insect/s built a nest inside what clogs the air vent stream.

Have you tried to fill sloooowly, some gas station pistols are very fast and can lead to airlock and spitting fuel out.
You may try to use a jerry can and a thiner hose to let air escape if you have the vent integrated in the filler cap just to check if slower filling will solve problem.

Chris

BTW: Dumb question, are you sure the as tanks are low on fuel or you forgot that you filled them totally for winter?
No external vents. Assumed was vented through a second line in the fuel line but don’t see one. Will remove flooring to get to tank vents. Is there a “trick” on cleaning vent?

Should have stated also tried using five gallon tank to slowly add fuel and did same as filling station. Gas does get into tank but extremely slow.

No dumb questions. Both tanks show 25% full on gauge.
 
My money would be on tank vent, take line off of tank and blow into it, should flow pretty easily, if clogged you can run a single conductor wire (like house wire) up into it. Sometimes wasps make a nest inside vent.
 
Assumed was vented through a second line in the fuel line but don’t see one. Will remove flooring to get to tank vents. Is there a “trick” on cleaning vent?
Then you have the vent hose attached to the filler assembly and that makes insect related clogging implausible.
Do you have a removable access plate near the filler you could remove to check inside if there are a big and a thinner hose, the thinner one is the vent hose.
If you can reach the thin hose and unscrew it you could check if she is free or clogged without pulling fuel tank cover.
I expect you have two fillers, one for each tank, right

No dumb questions. Both tanks show 25% full on gauge.
Tank gauges can get stuck or malfunction and show low, but tank has more than showing
So your boat was the winter on a trailer and no work was done? That should exclude that a hose should got bent or collapsed or for whatever reason clogged.

If you have compressor or a high flow pump than you could pump air in the filler and check if air is flowing out the vent, but you have the vent - as me - inside the filler assembly what makes it hard to verify with blowing in. In case, don't use high pressure to not damage something if clogged.

Chris
 
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As mentioend already, the MOST common reason for this is a clogged vent system. This can be a clog in the hull vent or even the vent line. And you ABSOLUTELY have a vent line. If your deckfill plate is basically flush with the cap, then you DO have a hull vent. If your cap is vented, then it is raised up.

But, you just need to look at your cap in your hand to tell if it's a vented cap.

Blow through the vent line and/or inspect it for being old/collapsed internally or a low spot (belly) that has collected fuel/moisture, thereby creating a clog.
 
Did you add a treatment for the winter layup? If so did you happen to use a separate bottle for each tank:) Sometimes captains unknowingly leave the cap seal on the fuel treatment bottle and if flows down the fill line and clogs the flow. I highly doubt you would do that to both tanks. It is possible that someone sabotaged your boat. I have seen that but it is very rare.
Do you run each engine ( you have two, yes) on a separate tank. I am surprised that both tanks read the same level. Did you make a note as to the level of each tank when winterized?
What year is the boat?
You most likely have a combo fuel fill/vent fitting. If the vent is clogged, the boat will usually stall when at speed under load. If it does, open the gas cap and try again. If it doesn't bog down, the vent is blocked.
Later model yeas will probably have a vapor canister to trap fuel vapors. That system is trickier to troubleshoot.
 
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I'm having deja vu
You posted same problem last year in July.
https://www.greatgrady.com/threads/gas-filling-tube-clogged.38177/post-270974

Both tanks same problem...very odd
You are sure it has two 92 gal tanks?

Possiblities;
Blocked /bent vent hoses
Blocked/bent fill hoses

Full tanks (possibly filled with water...)and your gauge is incorrect.

Are you sure the gas you added is not in the bilge now?

Do motors run?
 
If your deckfill plate is basically flush with the cap, then you DO have a hull vent. If your cap is vented, then it is raised up.
My Canyon. has two horizontal slightly raised flush deck fills on top of the gunnel and no hull vent and when i fill the air escapes thru the filler hole. I never verified if there is a vent line going to the filler assembly, however there must be one as i can use high speed pistols.

Similar to this type, with the wide, knurled cap, but not 100% sure about the vent as i would have to remove the pie plate to peek inside.
But as a lot of air escapes there i guess it is this type.

Chris
Bildschirmfoto 2025-06-25 um 09.56.21.jpg
 
Thanks for posting that picture, Chris - yes, that is a vented cap. The style I was referring to was where the cap essentially fits inside the plate, not over top like yours.

Yes, the ones you wite of are the ones i dislike as water drops can get trapped in the void between the cap and the filler and every time cap is unscrewed some drops can get in the tank.
Thats why i prefer the over the plate caps and not the screw in the plate caps, but probably i am picky ...

I am in Zurich now for my birthday and will fly back to Sardinia Saturday, next time i am on the boat i will pop off the pie plate and peek inside to see how the vent is made.

However, many good hints from all, something on OP's problem does not makes sense, a clogged filler hose would be most logic and the fell in seal from additive bottle is common, but could be anything else what restricts fuel flow. If tank is really empty....

On all the fuel tanks i had my hands on i never saw one where fuel or vent hose got bent by itself, those pos are so stiff that it's difficult to bend them. If OP did not touched them then previous owner may used a wrong (garden) hose or dropped something in.
First i would do is:
pull the fuel senders to verify if tank is really at 25%, if so then use a blower to blow low pressure but high volume (small leaf blower?) in the fill hose to see if and where the air escapes.
Worst case and risky scenario would be to stick a bore camera in the filler hose to check for restriction.

Chris
 
Yes I have two 92 gallon tanks. I also have the screw top in the picture above. When I get home today will check out. Question if I blow air down or use wire. Not sure how anything could get in. Also very careful when adding additives as always remove foil before adding to tank. Baffled as boat is 2000 and have had no issues prior.

When I winterized the boat I always fill both tanks to same level. Boat sits in my yard and doubt anyone could have done anything (protected neighborhood and boat was covered immediately).
 
I'm having deja vu
You posted same problem last year in July.
https://www.greatgrady.com/threads/gas-filling-tube-clogged.38177/post-270974

Both tanks same problem...very odd
You are sure it has two 92 gal tanks?

Possiblities;
Blocked /bent vent hoses
Blocked/bent fill hoses

Full tanks (possibly filled with water...)and your gauge is incorrect.

Are you sure the gas you added is not in the bilge now?

Do motors run?
No fuel in bilge or anything else as was cleaned at year end. No fuel smell either.

Tanks have always read well on gauges and aligns with fuel added. Fuel separator never shows much water and changed during cleaning process to get ready for summer. Motors both start.
 
I'm having deja vu
You posted same problem last year in July.
https://www.greatgrady.com/threads/gas-filling-tube-clogged.38177/post-270974

Both tanks same problem...very odd
You are sure it has two 92 gal tanks?

Possiblities;
Blocked /bent vent hoses
Blocked/bent fill hoses

Full tanks (possibly filled with water...)and your gauge is incorrect.

Are you sure the gas you added is not in the bilge now?

Do motors run?
Totally forgot about that posting. Dad passed and put the boat away without out thinking on fixing. Wish I had so I can use boat.

Will post my findings by the weekend.
 
I had a 2004 Gulfstream and it had a 92 and a 56 gallon tank for a total of 148. Duel engines had a 90 and a 56 gallon tankor 146 total You may want to check with GW on the tank size for your 2000 model. Not sure it would have anything do with the fill issue though. I had an issue on a 19 foot mako that was about 20 years old and the fuel hose leading to the tank had deteriorated to a point that is was restricting fuel flow. Eventually it it started to leak into the bilge when attempting to fuel. Good luck finding your issue
 
Yes, the ones you wite of are the ones i dislike as water drops can get trapped in the void between the cap and the filler and every time cap is unscrewed some drops can get in the tank.
Thats why i prefer the over the plate caps and not the screw in the plate caps, but probably i am picky ...

I am in Zurich now for my birthday and will fly back to Sardinia Saturday, next time i am on the boat i will pop off the pie plate and peek inside to see how the vent is made.

However, many good hints from all, something on OP's problem does not makes sense, a clogged filler hose would be most logic and the fell in seal from additive bottle is common, but could be anything else what restricts fuel flow. If tank is really empty....

On all the fuel tanks i had my hands on i never saw one where fuel or vent hose got bent by itself, those pos are so stiff that it's difficult to bend them. If OP did not touched them then previous owner may used a wrong (garden) hose or dropped something in.
First i would do is:
pull the fuel senders to verify if tank is really at 25%, if so then use a blower to blow low pressure but high volume (small leaf blower?) in the fill hose to see if and where the air escapes.
Worst case and risky scenario would be to stick a bore camera in the filler hose to check for restriction.

Chris
Happy Birthday!
 
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