NOS Locking Gas Cap

[74_Coach]

Does anyone know if an NOS GM #994529 locking gas cap would work properly on my ‘74 GMC? This cap appears to have a pressure relief in the cap.
--
Ed Clerkin | 1974 GMC Canyon Lands 26’

 

[Jim Hupy]

I'd like to see the guy that could siphon gasoline from a GMC gas tanks.
They would have to have a real set of lungs on them. A stock factory GMC
gas cap has both I would say they are semi-vented.
Jim Hupy
Salem, Oregon

On Thu, Jul 16, 2020, 6:28 PM Ed Clerkin via Gmclist <

> Does anyone know if an NOS GM #994529 locking gas cap would work properly
> on my ‘74 GMC? This cap appears to have a pressure relief in the cap.
> --
> Ed Clerkin | 1974 GMC Canyon Lands 26’
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[d c *mac* macdonald]

The reason for the locking gas cap is NOT to prevent syphoning but to keep a-holes from sabotaging your fuel and engine!

Mac Macdonald in OKC, OK

Sent from my iPad

>
> Does anyone know if an NOS GM #994529 locking gas cap would work properly on my ‘74 GMC? This cap appears to have a pressure relief in the cap.
> --
> Ed Clerkin | 1974 GMC Canyon Lands 26’
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[74_Coach]

> A stock factory GMC
> gas cap has both I would say they are semi-vented.
> Jim Hupy
> Salem, Oregon
>
> On Thu, Jul 16, 2020, 6:28 PM Ed Clerkin via Gmclist <

>
> > Does anyone know if an NOS GM #994529 locking gas cap would work properly
> > on my ‘74 GMC? This cap appears to have a pressure relief in the cap.
> > --
> > Ed Clerkin | 1974 GMC Canyon Lands 26’
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
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Jim: Confused - has both what? Thanks.

Ed
--
Ed Clerkin | 1974 GMC Canyon Lands 26’

 

[Jim Hupy]

They will prevent sloshing from the filler neck, and prevent a certain
(controlled) amount of evaporation into the atmosphere. But they allow air
to enter the system as fuel is consumed, and will vent higher pressure due
to heating and subsequent expansion of fuel in the tanks.
They are not just a gas cap that seals off the filler neck. If the
wrong cap is used on a GMC, they will exhibit fuel starvation issues. So,
if that is your problem, check for the correct cap first. Seen quite a few
coaches so equipped.
Radiator caps, same deal. They don't last a long time. There is more
information on these gas caps and the function of the liquid fuel/vapor
separator, charcoal canister, EFE systems in the emission sections of the
manuals.
Jim Hupy
Salem, Oregon

On Fri, Jul 17, 2020, 9:15 AM Ed Clerkin via Gmclist <

> > A stock factory GMC
> > gas cap has both I would say they are semi-vented.
> > Jim Hupy
> > Salem, Oregon
> >
> > On Thu, Jul 16, 2020, 6:28 PM Ed Clerkin via Gmclist <

> >
> > > Does anyone know if an NOS GM #994529 locking gas cap would work
> properly
> > > on my ‘74 GMC? This cap appears to have a pressure relief in the cap.
> > > --
> > > Ed Clerkin | 1974 GMC Canyon Lands 26’
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> Jim: Confused - has both what? Thanks.
>
> Ed
> --
> Ed Clerkin | 1974 GMC Canyon Lands 26’
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[74_Coach]

> They will prevent sloshing from the filler neck, and prevent a certain
> (controlled) amount of evaporation into the atmosphere. But they allow air
> to enter the system as fuel is consumed, and will vent higher pressure due
> to heating and subsequent expansion of fuel in the tanks.
> They are not just a gas cap that seals off the filler neck. If the
> wrong cap is used on a GMC, they will exhibit fuel starvation issues. So,
> if that is your problem, check for the correct cap first. Seen quite a few
> coaches so equipped.
> Radiator caps, same deal. They don't last a long time. There is more
> information on these gas caps and the function of the liquid fuel/vapor
> separator, charcoal canister, EFE systems in the emission sections of the
> manuals.
> Jim Hupy
> Salem, Oregon
>
> On Fri, Jul 17, 2020, 9:15 AM Ed Clerkin via Gmclist <

>

> >> A stock factory GMC
> >> gas cap has both I would say they are semi-vented.
> >> Jim Hupy
> >> Salem, Oregon
> >>

> >>
> >>> Does anyone know if an NOS GM #994529 locking gas cap would work
> > properly
> >>> on my ‘74 GMC? This cap appears to have a pressure relief in the cap.
> >>> --
> >>> Ed Clerkin | 1974 GMC Canyon Lands 26’
> >>>
> >>> _______________________________________________
> >>> GMCnet mailing list
> >>> Unsubscribe or Change List Options:
> >>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >>>
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> > Jim: Confused - has both what? Thanks.
> >
> > Ed
> > --
> > Ed Clerkin | 1974 GMC Canyon Lands 26’
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

The original cap is long gone and in its place is a locking gas cap. MH isn’t having fuel starvation problems but the cap just doesn’t feel like
it fits properly.

Ed

--
Ed Clerkin | 1974 GMC Canyon Lands 26’

 

[Jim Hupy]

Any signs of gasoline slopping out when the cap is in place and you are
under way? Jim K. has the correct cap in stock.
Jim Hupy
Salem, Oregon

On Fri, Jul 17, 2020, 5:01 PM Ed Clerkin via Gmclist <

> > They will prevent sloshing from the filler neck, and prevent a certain
> > (controlled) amount of evaporation into the atmosphere. But they allow
> air
> > to enter the system as fuel is consumed, and will vent higher pressure
> due
> > to heating and subsequent expansion of fuel in the tanks.
> > They are not just a gas cap that seals off the filler neck. If the
> > wrong cap is used on a GMC, they will exhibit fuel starvation issues. So,
> > if that is your problem, check for the correct cap first. Seen quite a
> few
> > coaches so equipped.
> > Radiator caps, same deal. They don't last a long time. There is more
> > information on these gas caps and the function of the liquid fuel/vapor
> > separator, charcoal canister, EFE systems in the emission sections of the
> > manuals.
> > Jim Hupy
> > Salem, Oregon
> >
> > On Fri, Jul 17, 2020, 9:15 AM Ed Clerkin via Gmclist <

> >

> > >> A stock factory GMC
> > >> gas cap has both I would say they are semi-vented.
> > >> Jim Hupy
> > >> Salem, Oregon
> > >>
> > >> On Thu, Jul 16, 2020, 6:28 PM Ed Clerkin via Gmclist >

> > >>
> > >>> Does anyone know if an NOS GM #994529 locking gas cap would work
> > > properly
> > >>> on my ‘74 GMC? This cap appears to have a pressure relief in the
> cap.
> > >>> --
> > >>> Ed Clerkin | 1974 GMC Canyon Lands 26’
> > >>>
> > >>> _______________________________________________
> > >>> GMCnet mailing list
> > >>> Unsubscribe or Change List Options:
> > >>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >>>
> > >> _______________________________________________
> > >> GMCnet mailing list
> > >> Unsubscribe or Change List Options:
> > >> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> > > Jim: Confused - has both what? Thanks.
> > >
> > > Ed
> > > --
> > > Ed Clerkin | 1974 GMC Canyon Lands 26’
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> The original cap is long gone and in its place is a locking gas cap. MH
> isn’t having fuel starvation problems but the cap just doesn’t feel like
> it fits properly.
>
> Ed
>
> --
> Ed Clerkin | 1974 GMC Canyon Lands 26’
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[74_Coach]

> Any signs of gasoline slopping out when the cap is in place and you are
> under way? Jim K. has the correct cap in stock.
> Jim Hupy
> Salem, Oregon

I haven’t had it on the road long enough to find that as a problem. I have it down at the shop now with the tanks removed cuz it threw up on me when
filling up and wouldn’t accept more than 12.0 gallons. Found out on Wednesday that the original owner son plugged the vent tubes on both tanks and
vented the tanks through some other method. I know this because I had the same shop replace all of the fuel lines to/from tank including carbon
canister. They should have used the shop manual to determine all of the correct fuel/vapor lines but apparently didn’t look at it - THEY WILL NOW.
Jim’ K’s shop up in Fremont CA is 242 miles north of me and the GMC shop down in Ontario CA is also 242 miles south of me. The MH is
uncontrollable above 45mph and I now have enough information to figure out what is causing the problem with steering this beast and that will be done
next. So, I am stuck in the middle of CA relying on local mechanics to solve well known GMC issues. If only I had a level driveway.

When I had my 57’ Ford Retractable, my retractable top was a tad dysfunctional and needed to be adjusted. So, I found an expert on these tops who
lived in Tennessee and flew him out to CA to adjust my top. I promoted the adjustment as a workshop and 3 retractable owners joined me to have their
tops adjusted. We all shared the cost and all 3 walked away happy. I am not sure that GMC folks have that kind of flexibility but it certainly helps
spread the tribal knowledge.

--
Ed Clerkin | 1974 GMC Canyon Lands 26’