Gas Tanks

W

william myers

New member
Sep 30, 1998
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Which tank is the main and which the aux? I get cough and sputter on
the main (lower fuel gage reading) and normal running on the aux
(higher reading). Haven't found in the literature which front/back is
which. Maybe a filter, tanks not empty.

Thanks,
Bill
'74

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Bill,
The rear tank is the main tank.

J.R. Wright

>
> Which tank is the main and which the aux? I get cough and sputter on
> the main (lower fuel gage reading) and normal running on the aux
> (higher reading). Haven't found in the literature which front/back is
> which. Maybe a filter, tanks not empty.
>
> Thanks,
> Bill
> '74
>
> _________________________________________________________
> Do You Yahoo!?
> Get your free @yahoo.com address at http://mail.yahoo.com
 
AFAIK the aux. tank is the one in the front. Your aux. reserve is the last
5 or 6 gallons in the front tank. Because the engine draws fuel off of
both tanks at the same time, ( no gate valve ) they will recede together.
Because of the normal sloshing and rolling of the fuel in the tanks the
front tank will naturally retain more fuel than the rear because of the
placement of the filler spouts on the two tanks. Darren

> Which tank is the main and which the aux? I get cough and sputter on
> the main (lower fuel gage reading) and normal running on the aux
> (higher reading). Haven't found in the literature which front/back is
> which. Maybe a filter, tanks not empty.
>
> Thanks,
> Bill
> '74
>
> _________________________________________________________
> Do You Yahoo!?
> Get your free @yahoo.com address at http://mail.yahoo.com
 
In my situation, on my motorhome, the only function of the fuel aux switch is
to turn off the low fuel light that comes on in the fuel main pos. when you
have approx. 10 gals. left in tanks..I can empty the tanks in either pos. I
have seen several postings that disagree with this so mine may be the only one
that works this way.
Bill 76 Edgemont

> AFAIK the aux. tank is the one in the front. Your aux. reserve is the last
> 5 or 6 gallons in the front tank. Because the engine draws fuel off of
> both tanks at the same time, ( no gate valve ) they will recede together.
> Because of the normal sloshing and rolling of the fuel in the tanks the
> front tank will naturally retain more fuel than the rear because of the
> placement of the filler spouts on the two tanks. Darren
>

>
> > Which tank is the main and which the aux? I get cough and sputter on
> > the main (lower fuel gage reading) and normal running on the aux
> > (higher reading). Haven't found in the literature which front/back is
> > which. Maybe a filter, tanks not empty.
> >
> > Thanks,
> > Bill
> > '74
> >
> > _________________________________________________________
> > Do You Yahoo!?
> > Get your free @yahoo.com address at http://mail.yahoo.com
 
Thanks, thats an idea I had not though of. My switch has no labels.

Seems like what I thought was a tank filter probem is either the inline
filter or the Holly fuel pump, no fuel pressure. Did you ever see a
Toyota 4-cylinder PU pull a GMC? Well, it was just a little way.

Thanks,
Bill

Awhile back I had a new switch put on and the mechanic switched the
wires inadvertently. I was drawing out of both tanks and didn't know
the reserve feature wasn't working. I ran out of gas with my gauge
still showing a fourth tank. You may want to check and see if yours is
wired correctly. I can't tell you how, but I bet someone can.
Justin
>>

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Hi Arch,
Good Luck!
Rob Teed 74 Painted Desert

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailto:owner-gmcmotorhome]On Behalf Of Gcbr
> Sent: Thursday, June 03, 1999 10:41 PM
> To: gmcmotorhome
> Subject: GMC: Gas tanks
>
>
> GMCers
>
> Well, tomorrow is a big day. I am going to roll the lady on the road.
> I am going to take her to the next town over which has a Chevy
> truck dealer who says he can drop the tanks. Yes, I chickened out on this
> phase of the project because all I have to work on is a gravel
> driveway. The
> beast has twice
> decided to shift on me while up on jack stands. I aint going to
> be under her
> when she decides to do that. What I have done is rig up a boat
> gas tank with
> a line that runs
> out the passenger slider window, Wire tied to the mirror. Then in
> the grill
> wire tied to the oil filler and down to the fuel pump. Gave a couple of
> squeezes
> on the bulb and the lady started right up. I have 6 gallons of
> fuel and only
> about
> 10 miles to go so I should be able to make it. My son will be in
> a chase truck
> with 5 gallons of fuel just in case. When I got the lady the
> gauge said there
> was
> fuel in the tanks-----------but it had been sitting for 4 or 5
> years. I added
> 10
> gallons and made it home. With the new fuel from the boat tank
> she runs much
> better than on the drive home from the junk yard. Thats what I am
> going to do.
>
> Take Care
> Arch
>

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Arch, the first thing I would look at for the not shifting to third problem
is vacuum to the modulator; this is common on the TH400/TH425 as they do not
have a throttle linkage and instead rely on the modulator to tell them when
to shift.

It could be a defective modulator, but 5 will get you 10 that you have a
vacuum leak.

Travis

- -----Original Message-----
From: Gcbr
To: gmcmotorhome
Date: Friday, June 04, 1999 9:01 AM
Subject: Re: GMC: Gas tanks

>Lanier
>
>Thanks! I made it. Got the ole gal there in one piece. Biggest problem
>was a wasp that came out of nowhere. One interesting thing the tranny
>worked just fine. Shifted good on the highway. Once I hit the city streets
>with a 30 MPH speed limit it never shifted into 3rd. Even backing off the
>gas it never shifted up to 3rd. I only dropped the passenger side off the
>road once and hit the curb once in a nasty little switch back S turn.
>Well, thats my big adventure for the day. When I get her back I will take
>some pics of the tanks and get them to whoever wants to put them up.
>
>Take Care
>Arch 76 GB IL
>
>In a message dated 6/4/99 4:38:43 AM Central Daylight Time, HLBF
>writes:
>
>>
>> Good Luck, Arch. Sounds like you're gettin' into the short rows.
>> Lanier
>>
>
 
>... chickened out on this
>phase of the project because all I have to work on is a gravel driveway.

When I had to service my fuel tanks I didn't have a good place to work
either. What I did was make a couple ramps out of 5 2x12's. I cut each one
about 8" shorter than the next, beveled one end and nailed them on top of
each other. I screwed a handle on the end so I could drag them around more
easily (they are quite heavy).

If you raise the rear you can drive both sets of rear wheels onto the
ramps. Then I block up the bogies (be sure to block up the bogies in case
you break an air line while working). Its nice and stable. Lots of room to
get under and do whatever needs to be done. Although dropping the fuel
tanks is no fun, even with good ramps...

Dave
73 Sequoia
 
Hi Dave, I have made similar ramps, but as a relative newbie, never
considered the risk of sudden loss of rear suspension air pressure. Thanks
for the post, it made me stop what I was doing and take notice. walter
bright, 76 GB.

- -----Original Message-----
From: Dave [mailto:DGMDGM

Then I block up the bogies (be sure to block up the bogies in case
you break an air line while working). Its nice and stable.
 
Arch:

My work number is 616-961-4809.

Unless I hear different, I'll meet you there. I'll be driving my silver
colored, Fiat Spyder car.

It's awful hot and uncomfortable here this week. High upper 80's - low
90's, with high humidity. Yuck!

Paul

P. S. If you're going to be in the area next Tuesday, a group of local
GMCers are going to get together for dinner that evening at Gun Lake? Emery
Stora from Santa Fe NM, is to be in the area then. We'd be honored to have
you join with us.

From: Gcbr [mailto:Gcbr]
Sent: Monday, June 07, 1999 3:24 PM
To: gmcmotorhome
Subject: Re: GMC: Gas Tanks

In a message dated 6/6/99 11:53:58 PM Central Daylight Time,

If you're interested, let me know date and time when you'll be there and
I'll meet you there.

Paul Bartz

Paul

I am going to be there Thursday at 10 AM if all goes well.

Could you give me a phone # to call just in case something goes wrong.

Take Care
Arch
 
Arch:

I'm told that many people are eliminating the fuel tank pick-up tube socks
in favor of an inline filter ahead of the fuel pump.

Paul Bartz

From: Gcbr [mailto:Gcbr]
Sent: Friday, June 04, 1999 9:25 PM
Subject: GMC: Gas Tanks

A report on the day. The tanks are off. They are in surprisingly good shape.
Very little rust. Most of the rust is on the brackets that hold them on. One
tank has some rust on one flange and that is it. I talked to Renuzit and
they said it would be ok to take them to the carwash and hose them down. I
have some consulting work in MI so I am going to take the tanks to them in
my Le Sharo. Go do the work and then pick them up on my way back. I talked
to Jim and he said that Golby has new senders and socks. Think I will do
that. Anybody have any different thoughts? Does anybody know if the senders
are the same as what we have? Somewhere I read they were different in some
way. Sure are a bunch of different vents on these tanks. Hope I can sort
them all out. Any thoughts on gas tanks, senders, lines,etc will be printed
out and used.
BTW it cost $91.80 to have the tanks removed.
If you are wondering the boat tank worked well. I had no problems.
Since several people ask me about the shift points on the tranny I did a
little extra driving around town to confirm what I thought I had seen. The
shift points are about 22 mph and 42 mph. I don't have a tach so I cant tell
you what RPM that is. I say the shift points are about that because with a
heavy foot they will go higher. The shifts were clean and crisp---no sliding
into gear. They also did not throw me back in my seat unless I was really
leaning on it. I also confirmed that as long as you are below the shift
point the tranny will not shift up even if you take your foot off the gas.
In rush hour traffic tonight I really liked it that way.
When it got down to a crawl first gear was there--------just moving with
traffic at say 35 and backing off the gas I still had second gear waiting
for me. I think this should help me stay out of the secondariness on the
carb. Oh well had fun today----hope you all can learn from it as much as I
did.
 
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