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Old 09-19-2022, 12:27 PM   #1
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Greyhawk fuel fill design error and how to fix it

We were going to leave for a few days in the mountains but I was unable to fill the gas tank. At first I blamed the gas station pump but when the next pump had he same problem it became my problem.

So drove home unhooked the toad to work on diagnosing it.
It acted like the fill line was blocked up. When trying to fill with a lawn-mower gas can it would take about 1/2 a gallon and fill to the top.
But when I snaked in a rubber hose it made its way 4 feet into the gas tank.
So I figured it was a blockage in the vent line that exits in the fuel entry fixture.
When I disconnected the air vent tube a bunch of gas ran out of it and sure enough, now the filling tube worked fine.

Problem is caused by overfilling the tank so gas gets in the top of the vent tube.

Design error is the falling height of gas coming in could not generate enough "head" to expel the gas in the vent line. Depending on how the fill line enters the tank, it may not be a problem on a nearly empty tank.

My fix was to extend the vent line by 18" with 1/2" fuel tubing so that you can loop it up and attach under the floor. Now if you overfill and get fuel in the vent line its only an ounce or two since it can't run higher than the entry.

I haven't actually tested it yet.
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Old 09-19-2022, 01:17 PM   #2
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There is a post on this issue. Might be worth spending sometime in the search engine or on the Class C forum. I suspect it is 3-4 years old. It pops up every now and then.

Edit, I think this is the post: https://www.jaycoowners.com/forums/f...27u-81577.html
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Old 09-19-2022, 02:46 PM   #3
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I discovered that the filler hose on mine kind of droops down and then slightly up into the fuel tank inlet. The filler hose at the tank inlet has a slight kink...not completely closed off.

My solution was to take 2.25" hose clamps and tighten on the slight kink to round the hose out more. Eventually, I will attempt to get a shorter filler neck so the hose would have a downward slope into the tank rather than having it run up like a P trap.

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Old 09-19-2022, 03:28 PM   #4
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I have noticed a slight vacuum whenever I open my fuel cap. With that in mind, I wonder if the issue is due to vacuum collapsing the fuel fill line where it forms a bend. I would be even more inclined to think this if the problem occurred after time and was not originally present. ~CA
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Old 09-19-2022, 03:37 PM   #5
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I have noticed a slight vacuum whenever I open my fuel cap. With that in mind, I wonder if the issue is due to vacuum collapsing the fuel fill line where it forms a bend. I would be even more inclined to think this if the problem occurred after time and was not originally present. ~CA
The inlet of the fuel tank angles upward so the filler hose has to go up, then downward. The kink is the upside down "V" shape where it changes direction. It is like this even with the fuel cap off.
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Old 09-19-2022, 04:03 PM   #6
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The inlet of the fuel tank angles upward so the filler hose has to go up, then downward. The kink is the upside down "V" shape where it changes direction. It is like this even with the fuel cap off.
Yes, I have looked at mine before as well which is the same design. However, mine isn't collapsed at the kink area and my suspicion is that with enough vacuum that kink area would be the first place to collapse and it certainly could stay collapsed even after the fuel cap is removed. Just a suspicion though, otherwise if the kink was always there then the issue would have been noticed even with the first fill-up.

I remember years back certain hoses subject to collapse (primarily radiator hoses) would have a spring inside. I am not sure if that can be done here or if it would help though.
~CA
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Old 09-20-2022, 04:07 AM   #7
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Quote:
Originally Posted by jyh818 View Post
I discovered that the filler hose on mine kind of droops down and then slightly up into the fuel tank inlet. The filler hose at the tank inlet has a slight kink...not completely closed off.

My solution was to take 2.25" hose clamps and tighten on the slight kink to round the hose out more. Eventually, I will attempt to get a shorter filler neck so the hose would have a downward slope into the tank rather than having it run up like a P trap.

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My 2007 Jayco class C had this exact same issue as described above. I could never get a full tank; only could get it filled to 3/4 at the gas pumps. When I installed a lockable gas door that's flush to the body of the camper, I used a Ford F-450 flatbed truck style angle to support/mount the filler neck, and a large 2" clamp to round out the kink in the filler hose from the previous setup in came from Jayco with. Plus, the Ford F-450 angle support lifted the fuel filler neck upward, so I no longer have the slope down then up scenario.

I think it was an issue with the camper body itself being assembled on a flatbed framed chassis. No one during planning/design bothered to look at the issue of how the filler neck was located/mounted when the camper was assembled to the frame.
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Old 09-20-2022, 11:57 AM   #8
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Well my fix with extending the vent tube up high to stop gas getting into it didn't work.

Symptoms:
2019 Greyhawk 30, gas tank 1/2 full.
1. I can pour in gas from a portable can as fast as it will go, no problem.
2. When filling at gas station it delivers about 1/2 gallon and clicks off with gas filling the entry. With gas nozzle all the way in or just at entry, same thing.
3. Completely disconnected the vent tube, same result.
4. Snaked a 1/2" rubber hose in the filling tube to test for blockage. After about 4 feet there was a resistance, presumably the 90 degree entry to the tank. After twisting and jiggling it got past the bend and went another 18" to the bottom of the tank.
4. Only thing left is the vent tube - - hit it with compressed air no problem, tank was building up pressure. (Not sure why the air would not come out the fuel entry path, perhaps there is a one-way valve?).
5. No visible kinks bends in the filler hose.

Well I can still use it but filling at a gas station with a 5 gallon can is going to take a long time .

Drove 20 miles to Camping World where we purchased it.
They said "We don't work on fuel systems, and gave some idiotic advise about making sure the vent line was above the fill line."

I see now why this 2019 had only 3000 miles on it. I ain't no dummy, just severely frustrated, I maintained and operated a 71 ft steel ketch liveaboard for 14 years.
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Old 09-21-2022, 08:47 AM   #9
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IF there is a kink in the hose at all, the gas station pump is probably filling the tube fast enough to make the anti spill pressure sensor click the pump off. This is likely why you can use the gas can without issue as it doesn't drain fast enough to fully fill the tube.

Is the main fill tube kinked? The modern fuel tanks should have an anti siphon/rollover ball in the tank or the tube to prevent anyone from putting the half inch hose in, but maybe the RV chassis don't have this?
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Old 09-21-2022, 09:40 AM   #10
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IF there is a kink in the hose at all, the gas station pump is probably filling the tube fast enough to make the anti spill pressure sensor click the pump off. This is likely why you can use the gas can without issue as it doesn't drain fast enough to fully fill the tube.

Is the main fill tube kinked? The modern fuel tanks should have an anti siphon/rollover ball in the tank or the tube to prevent anyone from putting the half inch hose in, but maybe the RV chassis don't have this?
You are correct on this. If I go to our local Sam's Club station, it fills just fine. When I use other stations that stops quickly, I would set the handle on the pump to the lower/slower flow and it would fill eventually. On instances where it stops, I would pull the nozzle out and see a pool of gas inside.
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Old 09-21-2022, 11:46 AM   #11
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UPDATE.

It is a design error. Jayco have a service bulletin out on it. A member here with exactly the same 2019 Greyhawk 30 saw my predicament and sent me the information in a PM.

The entry fixture is too low, there is not enough fall to the tank.
I've not yet seen the Jayco service bulletin but it involves 5 hours of extensive vehicle modification. Although out of warranty Jayco offered to fix his free.
However he didn't want the side messed up - - I suspect it involves a cutout in the slide-out to accommodate the new raised entry and the slide-out already looks flimsy when in motion.

His solution: Run the wheels up on a 4" ramp tilting the RV over to provide the downward slope on the existing entry. Way to go, KISS at work.

I asked him why not just extend the two levelling jacks on that side, a simple solution. He said it would be his luck that the leveler would chose that moment to die and block the gas station for 6 hours. His paranoia was convincing and I'm going to make a couple of wooden ramps.
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Old 09-22-2022, 03:54 AM   #12
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Your model is different than mine; my gas door is at least a couple of feet from the front slider, so raising the gas filler tube did not involve any cutting to the slide out. I would not like that fix at all.

I bought a piece of angle iron, cut it so it went from a frame box to frame box. Then installed a E-450 flatbed style fill tube with vent connection (about $12.00). Bolted that to the angle iron and raised it all up about 2". Then installed a flush locking fuel door to the camper body (after removing the black plastic bezel that held the old fuel fill tube.

No more kink in the fuel line, no more slope down, then up in the fuel hose that connects from the fuel filler to gas tank.

And I can get a full tank of gas now!
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Old 09-24-2022, 01:00 PM   #13
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This issue is a pain. I have to fill my greyhawk 2019 31f with gas valve tilted sideways to allow me to fill up. Sometimes upside down and it fills the tank without continuously stopping. If I try to fill gas normally it won’t go in and just stops every few seconds.
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Old 09-28-2022, 09:07 AM   #14
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21 Greyhawk 29MV check fuel filler code po457

Good morning group
Jayco solution replace filler cap
No solution
Ford dealer service unavailable in DFW
smoke test system next step @Rush truck center
Anybody had this done and did it locate evap system leak ? Need to get this code cleared and unit inspected or else yard art or possible bonfire
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Old 09-28-2022, 09:28 AM   #15
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Good morning group
Jayco solution replace filler cap
No solution
Ford dealer service unavailable in DFW
smoke test system next step @Rush truck center
Anybody had this done and did it locate evap system leak ? Need to get this code cleared and unit inspected or else yard art or possible bonfire
I would just clear the code and see if it comes back. Every code reader I have used has the option to clear the code(s). ~CA
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Old 09-28-2022, 03:49 PM   #16
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Long story short got the ck fuel filler warning click ok maybe 3-4 times then got chk engine light got the scanner cleared the code it comes back
Take it to ford they clear it it comes back they say it’s a jayco thing-I get a jayco warranty no take it to local jayco service replace cap tighten hose clamps clear code it comes back now it’s back to ford but no dealer has bay big enough for evap system leak smoke test so i am on a 90 day wait list to get this done and was wondering if anyone has had this done and did it identify the issue
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Old 09-28-2022, 03:57 PM   #17
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While I haven't done a smoke test on the RV, I've done it on my Toyota 4Runner. I bought a simple smoke machine from ebay a few years ago where it's made from a small paint can. Power wires with clamps came out to clip onto the car's battery to heat up a heating coil inside the can. It used mineral oil to burn to make the smoke. A pressure regulator is attached where you put into an air compressor that outputs 1 psi and you attach it to the EVAP test port under the hood.

You get a laser pointer and sweep across vacuum hoses and the smoke would be very easily seen. You could also smell it.
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