Home » Public Forums » GMCnet » [GMCnet] Why we own, and fix these GMCs (author Bob Dunahugh)
[GMCnet] Why we own, and fix these GMCs [message #336005] |
Fri, 10 August 2018 19:09 |
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pjburt
Messages: 436 Registered: February 2016 Location: Fresno, California
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This post on the mailing list by Bob Dunahugh deserves to be transferred to the forum. Well said Bob
Aug 7
Other recipients: gmc...@list.gmcnet.org
We will do it if for no other reason than to uncover fields of unprofitable endeavors. We love to take them on trips to make list of things that we can fix when we get home. We can't die till all our projects are complete. Thus that's why the average age of owners is near death. May we all enjoy our ADVANCED age. As to the real young owners. You know. The owners under 55. As to those youngsters. May the GMC extend your life with joy. Bob Dunahugh
Jerry Burt Fresno, CA.
73 Gmc 26' Canyon Lands
Members: FMCA - GMCMI - GMCWS
A truly happy person is one who can enjoy the scenery on a detour.
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Re: [GMCnet] Muffler ? [message #336007 is a reply to message #336006] |
Fri, 10 August 2018 20:57 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
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Art,
Have you replaced ALL the rubber fuel and vapor hoses?
How did you apply the aux. pump.
Call me so I can help you do it right and solve the problem.
On Fri, Aug 10, 2018 at 5:57 PM, amansfield1104@charter.net <
amansfield1104@charter.net> wrote:
> I have had trouble with vapor lock and the generator quits if I have been
> driving for a while. I have one muffler sitting across the bottom and a
> little lower than the two mufflers that came out. Vapor lock has been a
> problem if I’m driving with the out side temperature above 85F. Living in
> Alabama that makes for problems. I been trying different things to fix the
> vapor lock. I installed a electric pump in series with the mechanical fuel
> pump. The electrical is where it will not get hot and still vapor locks.
> I turn on the electrical pump when it is needed. I do not like to run both
> pumps and fuel pressure goes up to 9 PSI. I worry about the float not
> holding 9 PSI. I heard of to many fires on these old RV’s. I checked mine
> an it seems to work fine at 9 PSI but I am not comfortable at that pressure
> although I have run some at that pressure when having vapor lock problems.
>
> Art
> _______________________________________________
> GMCnet mailing list
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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Re: [GMCnet] Muffler ? [message #336009 is a reply to message #336006] |
Fri, 10 August 2018 21:21 |
Ken Henderson
Messages: 8726 Registered: March 2004 Location: Americus, GA
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Art,
Where are you in Alabama (I was born in Troy)? You need to join the GMC
Dixielanders -- we had a rally at Noccalula Falls two weeks ago; we could
have met there! :-)
Re: Vapor lock. I can honestly say that in 20 years of GMC ownership, all
of it while living in GA, but travelling everywhere from Key West to
Fairbanks, I've never had vapor lock. I thought I did a couple of times,
but subsequent troubleshooting found true problems. I tell you all that so
perhaps you'll consider some of my mods to be worth considering. Remember
that these occurred progressively since 30 Apr 1998. Also, ALL of it
depends upon clean fuel tanks, good filters, and new fuel lines.
My first upgrade to the fuel system was made in preparation for the trip
for which I originally bought the coach: A trip to Alaska. Anticipating
the vapor lock I'd experienced in the western mountains with other
vehicles, I installed an electric pump, immediately downstream of the
selector valve. Its output was plumbed directly to a tee at the input to
the carburetor. I would NEVER run an electric pump in series with a
mechanical pump. Two reasons for that: 1. The possibly excessive
pressure you're seeing. 2. Even more importantly, the possibility of a
failed diaphragm in the mechanical pump allowing the electric pump to fill
the crankcase with gasoline.
As it turned out, that was not a good arrangement -- I counted on the
output valve in the mechanical pump to act as a check valve for the
electric pump when it was in use. In Yellowstone NP, the top gasket on the
mechanical pump failed, allowing either pump's output to dump straight out
on the ground. Luckily I caught it early and had parts to correct it.
My most important upgrade to the GMC's fuel system was elimination of the
tank selector valve and replacement of the mechanical pump with an electric
pump for each tank, mounted immediately forward of the Aux tank and tee'd
together with check valves into the rear-to-front fuel line. That
improvement alone eliminates the ethanol-sensitive valve and provides the
needed pressurization of most of the fuel line. It should prevent most
vapor lock.
Perhaps an under-rated reason for my vapor-lock free life is the "surge
tank" I installed. That's a 12" section of 10" diameter, 1/4"+ thick
aluminum tubing with caps/mounting feet welded on each end. That tank is
equipped with a fuel inlet (fed by the selected electric pump), a fuel
outlet for a return line to the drain fitting on the Aux tank, and a fuel
outlet to the carburetor (now to the EFI's high pressure pump). It also
has a port into which the return line from the EFI's throttle body is
plumbed. That tank is mounted beneath the step riser under the driver's
seat, a free space that's protected from high temperature air by the wheel
well liner.
The surge tank provides the engine with a source of fuel which is always
purged of vapor; generally, any vapor lock in the rear-to-front line will
be evacuated before that wrote:
> I have had trouble with vapor lock and the generator quits if I have been
> driving for a while. I have one muffler sitting across the bottom and a
> little lower than the two mufflers that came out. Vapor lock has been a
> problem if I’m driving with the out side temperature above 85F. Living in
> Alabama that makes for problems. I been trying different things to fix the
> vapor lock. I installed a electric pump in series with the mechanical fuel
> pump. The electrical is where it will not get hot and still vapor locks.
> I turn on the electrical pump when it is needed. I do not like to run both
> pumps and fuel pressure goes up to 9 PSI. I worry about the float not
> holding 9 PSI. I heard of to many fires on these old RV’s. I checked mine
> an it seems to work fine at 9 PSI but I am not comfortable at that pressure
> although I have run some at that pressure when having vapor lock problems.
>
> Art
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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Re: [GMCnet] Why we own, and fix these GMCs [message #336022 is a reply to message #336019] |
Sat, 11 August 2018 10:25 |
James Hupy
Messages: 6806 Registered: May 2010
Karma: -62
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9 psi is courting fire and disaster. Try to maintain 5 psi max in the fuel
lines ahead of the Carburetor inlet. That is about all the inlet needle and
seat float valve can safely and reliably handle.
Keep a cool fuel and it will be less likely to form bubbles, although
with today's formulations, that is like a lifetime of rolling boulders
uphill nonstop. Stay away from off season gasoline, particularly in
California.
The main reason fuel injection has less trouble with vapor lock type
issues is that the fuel system operates under higher pressures than carbs
do (fewer bubbles in the fuel), and today's gasolines are formulated to be
sprayed through an injector instead of atomized through a venturi and
needle jet. If it is available in your area of the country, no alcohol
gasoline is the fuel to use.
High octane is of little value in our motorhomes due to the low
compression ratios of our engines, so, use the lowest octane listed on the
pump. If your engine pings on the stuff, retard the base timing a couple of
degrees.
As always, check your rubber fuel system parts often, alcohol laced fuel is
hard on them. If in doubt, throw it out. Always use barricade hoses.
There are many different configurations of fuel pumps and lines and
filters, some have advantages, some have disadvantages.
It is kinda like 5 blind guys looking at an elephant. Each holding
onto a different part, and trying to imagine the whole beast. Not exactly a
clear picture.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Sat, Aug 11, 2018, 7:52 AM Johnny Bridges via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Dump the mechanical pump and go to two new (lower pressure) pumps:
>
>
> http://www.gmcmhphotos.com/photos/g6198-cane-9-creek-rv-park-heflin-2c-al.html
>
> They're Mr. Gasket pumps for carburetors. Toss the filters that come with
> the pumps and replace with Wix replacements. Run the relay through a
> shutoff (Oil pressure or overturn) and the dash selector switch.
>
> --johnny
> --
> 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> "I forgive them all, save those who hurt the dogs. They must answer to me
> in hell" - ol Andy, paraphrased
>
>
> _______________________________________________
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Re: [GMCnet] Muffler ? [message #341944 is a reply to message #341943] |
Sat, 23 March 2019 20:40 |
Jim Miller
Messages: 501 Registered: March 2008
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On Mar 23, 2019, at 8:16 PM, amansfield1104--- via Gmclist wrote:
> I have never been able to keep the Generator running when driving. After about an hour on the road it quits. When I park the generator will not run for a while. Once everything cools off the generator runs fine.
The next step in troubleshooting this problem is to drop the bowl off the Onan’s carburetor AFTER it has quit while you are on the road. If the bowl is dry then you have a fuel starvation problem and can proceed down that route - OTOH if there is a full inventory of fuel in the bowl then you may have a heat-related ignition problem.
You don’t have an email signature that tells us what kind of coach you have so it is difficult to diagnose further. GM outfitted coaches have a separate dip tube in the main tank to feed the Onan, other non-GM outfitted coaches such as the Royale have a tee in the engine fuel line that serves the genset. Onan cautions against this latter configuration in their literature and they state that it can cause fuel starvation.
—Jim
Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
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1977 Eleganza II
1977 Royale
Hamilton, OH
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Re: [GMCnet] Muffler ? [message #341946 is a reply to message #341944] |
Sun, 24 March 2019 01:37 |
Ken Burton
Messages: 10030 Registered: January 2004 Location: Hebron, Indiana
Karma: 10
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The only time that I had Onan vapor lock was when the outside temperature exceeded 100 degrees. I made the mistake of filling up with 42 gallons at a "Top Tier" (10% craponol) gas. I spent the day driving 30 to 50 miles and then hiding out in the shade for a while. Same thing happened 2 days later when the temp exceeded 100. It was a bad week for on the few days that we traveled. I finally got a 5 gallon gas can strapped it to the back bumper and ran a hose to the Onan fuel pump. I got around 5 hours per fill up but only used it during the heat of the day.
My more permanent solution, after I got home, was to cover the fuel line inside the Onan cabinet and the fuel pump with fire sleeve and aluminum reflective tape. I assumed those were the hottest areas when the Onan was running and most likely places to boil the gasoline. I have never had an Onan vapor lock problem since then.
Where you buy and what fuel (not brand) you buy does make difference. Summer mix fuel kicks in on May 1 and June 1. Here is the EPA listings by county of the RVP required to be sold at retail for on road use. A lower number is better in the listings. Keep in mind if you buy 10% crapnol diluted fuel, add 1.0 to the number read in the table.
If you read the table closely you will find some strange anomalies. Things like only Elpaso, Texas but nothing in the rest of the state, or parts of Missouri and all of Michigan.
https://www.epa.gov/gasoline-standards/gasoline-reid-vapor-pressure#B
Reformulated Gas requirements in EPA non-attainment areas:
https://www.epa.gov/gasoline-standards/reformulated-gasoline
We have one guy at my airport buying and using 100 octane AV gas at $4.00+ per gallon for his generator in an SOB during the summer. I offered to help him "heat proof" his generator. He refused and said he had money to burn so he will burn it in his generator. He already installed an aux tank for the generator to use in the summer. AV gas has a RVP of 7.0 year round.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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Re: [GMCnet] Muffler ? [message #341951 is a reply to message #336006] |
Sun, 24 March 2019 19:07 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
Karma: 9
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You might want to replace the oil pressure sender with a lower one as the
oil gets hit , pressure drops and shots the unit off.
On Sun, Mar 24, 2019 at 8:00 PM amansfield1104--- via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I have a 76 26’ Eleganza. Yes! It could ignition. I changed the
> condenser and the coil and it does the same thing. What makes me thing it
> is a gas temperature problem is how warm the back of the RV was when it was
> 35 outside. It was actually warmed in the back than up front with the
> heater on. I had the exhausted checked for leaks last summer as none were
> found. How can the back be that warm? My assumption is the cross muffler
> that has both exhausted going into the muffler is heating the back end. SO
> they will be change in the next few weeks. I looking for a good exhaust
> shop that can do an RV as mine has closed and the building is no longer
> there.
>
> Art
>> On Mar 23, 2019, at 8:40 PM, Jim Miller via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> On Mar 23, 2019, at 8:16 PM, amansfield1104--- via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>>> I have never been able to keep the Generator running when driving.
> After about an hour on the road it quits. When I park the generator will
> not run for a while. Once everything cools off the generator runs fine.
>>
>> The next step in troubleshooting this problem is to drop the bowl off
> the Onan’s carburetor AFTER it has quit while you are on the road. If the
> bowl is dry then you have a fuel starvation problem and can proceed down
> that route - OTOH if there is a full inventory of fuel in the bowl then you
> may have a heat-related ignition problem.
>>
>> You don’t have an email signature that tells us what kind of coach you
> have so it is difficult to diagnose further. GM outfitted coaches have a
> separate dip tube in the main tank to feed the Onan, other non-GM outfitted
> coaches such as the Royale have a tee in the engine fuel line that serves
> the genset. Onan cautions against this latter configuration in their
> literature and they state that it can cause fuel starvation.
>>
>> —Jim
>>
>> Jim Miller
>> 1977 Eleganza
>> 1977 Royale
>> Hamilton, OH
>>
>>
>>
>>
>> _______________________________________________
>> 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 Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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Re: [GMCnet] Muffler ? [message #341954 is a reply to message #341946] |
Sun, 24 March 2019 19:29 |
amansfield1104
Messages: 80 Registered: August 2009
Karma: 0
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Thanks good read. I will add the insulation to the fuel line when I place it under the generator. I will add the tape never thought of that. Will rap the headers and mufflers before they are installed. My concern is that will add a lot more heat to the 3” pipe.
These RV can be a problem figuring out what is what. I use to have over heating problem with the 455. I changed radiator which helped but did not fix the problem. I changed the carb set up and richened the mixture and no more over heating problems even when 95F and pulling hills. I guess not having a stock cam was the problem. To my surprise the gas milage was a little better and not worst. I have no idea that my EV has the problem carb on it. Boy did it pull better. Now if I can figure out the generator life will be much better.
Art
76 26' Eleganza
> On Mar 24, 2019, at 1:37 AM, Ken Burton via Gmclist wrote:
>
> The only time that I had Onan vapor lock was when the outside temperature exceeded 100 degrees. I made the mistake of filling up with 42 gallons at a
> "Top Tier" (10% craponol) gas. I spent the day driving 30 to 50 miles and then hiding out in the shade for a while. Same thing happened 2 days later
> when the temp exceeded 100. It was a bad week for on the few days that we traveled. I finally got a 5 gallon gas can strapped it to the back bumper
> and ran a hose to the Onan fuel pump. I got around 5 hours per fill up but only used it during the heat of the day.
>
> My more permanent solution, after I got home, was to cover the fuel line inside the Onan cabinet and the fuel pump with fire sleeve and aluminum
> reflective tape. I assumed those were the hottest areas when the Onan was running and most likely places to boil the gasoline. I have never had an
> Onan vapor lock problem since then.
>
> Where you buy and what fuel (not brand) you buy does make difference. Summer mix fuel kicks in on May 1 and June 1. Here is the EPA listings by
> county of the RVP required to be sold at retail for on road use. A lower number is better in the listings. Keep in mind if you buy 10% crapnol
> diluted fuel, add 1.0 to the number read in the table.
>
> If you read the table closely you will find some strange anomalies. Things like only Elpaso, Texas but nothing in the rest of the state, or parts of
> Missouri and all of Michigan.
>
> https://www.epa.gov/gasoline-standards/gasoline-reid-vapor-pressure#B
>
> Reformulated Gas requirements in EPA non-attainment areas:
> https://www.epa.gov/gasoline-standards/reformulated-gasoline
>
> We have one guy at my airport buying and using 100 octane AV gas at $4.00+ per gallon for his generator in an SOB during the summer. I offered to
> help him "heat proof" his generator. He refused and said he had money to burn so he will burn it in his generator. He already installed an aux tank
> for the generator to use in the summer. AV gas has a RVP of 7.0 year round.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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Re: [GMCnet] Muffler ? [message #341958 is a reply to message #341951] |
Sun, 24 March 2019 19:44 |
amansfield1104
Messages: 80 Registered: August 2009
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Thanks Jim I wonder about that.
Art
> On Mar 24, 2019, at 7:07 PM, Jim Kanomata via Gmclist wrote:
>
> You might want to replace the oil pressure sender with a lower one as the
> oil gets hit , pressure drops and shots the unit off.
>
>
> On Sun, Mar 24, 2019 at 8:00 PM amansfield1104--- via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> I have a 76 26’ Eleganza. Yes! It could ignition. I changed the
>> condenser and the coil and it does the same thing. What makes me thing it
>> is a gas temperature problem is how warm the back of the RV was when it was
>> 35 outside. It was actually warmed in the back than up front with the
>> heater on. I had the exhausted checked for leaks last summer as none were
>> found. How can the back be that warm? My assumption is the cross muffler
>> that has both exhausted going into the muffler is heating the back end. SO
>> they will be change in the next few weeks. I looking for a good exhaust
>> shop that can do an RV as mine has closed and the building is no longer
>> there.
>>
>> Art
>>> On Mar 23, 2019, at 8:40 PM, Jim Miller via Gmclist > gmclist@list.gmcnet.org> wrote:
>>>
>>> On Mar 23, 2019, at 8:16 PM, amansfield1104--- via Gmclist > gmclist@list.gmcnet.org> wrote:
>>>
>>>> I have never been able to keep the Generator running when driving.
>> After about an hour on the road it quits. When I park the generator will
>> not run for a while. Once everything cools off the generator runs fine.
>>>
>>> The next step in troubleshooting this problem is to drop the bowl off
>> the Onan’s carburetor AFTER it has quit while you are on the road. If the
>> bowl is dry then you have a fuel starvation problem and can proceed down
>> that route - OTOH if there is a full inventory of fuel in the bowl then you
>> may have a heat-related ignition problem.
>>>
>>> You don’t have an email signature that tells us what kind of coach you
>> have so it is difficult to diagnose further. GM outfitted coaches have a
>> separate dip tube in the main tank to feed the Onan, other non-GM outfitted
>> coaches such as the Royale have a tee in the engine fuel line that serves
>> the genset. Onan cautions against this latter configuration in their
>> literature and they state that it can cause fuel starvation.
>>>
>>> —Jim
>>>
>>> Jim Miller
>>> 1977 Eleganza
>>> 1977 Royale
>>> Hamilton, OH
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> 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 Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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Re: [GMCnet] ADD AC under the bench seat [message #341961 is a reply to message #341956] |
Sun, 24 March 2019 20:47 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
Karma: 9
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Senior Member |
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There is a Vintage Air unit that can be joined into your present unit.
I am on the road, presently in Tallihassie ,FL then heading to
Chulavista,CA Wed.
The unit is around $350 and around $ 100-140 hoses, connections.
Call me : 408-639-0737 should you have interest.
On Sun, Mar 24, 2019 at 5:32 PM amansfield1104--- via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Has anyone added AC from the engine under the bench seat in the front. My
> wife likes to ride there and not up front with me. Life would be much
> better if I could get that to work.
>
> Art
> _______________________________________________
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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