Gas Starvation Issue

Tom Lins

Tom Lins

New member
Dec 30, 2005
939
0
1
Elkton, FL
I dropped both gas tanks and replaced all the fuel lins.
Driving the coach after this was done using the main tank and everything was fine.
After using about 1/8 tank I switched to the aux tank to use that one for a while.
After a short time (1-2 minutes) the engine started acting like it was starving for fuel.
I switched back to the main tank and the problem went away,

so since the tanks are linked and I always refuel when I use about half the fuel I figured I would just stay on the main tank.

To my surprise as I was approaching my exit on the interstate the low fuel light came on.

I looked at the gauge and the main tank was almost empty. I switched to the aux tank again and it showed almost full.
and I again started having the fuel starvation issue. I switched back to the main tank and got off at the exit and pulled into the gas station.

I filled the tank and it took 20 gallons.

My question is What could cause the fuel in the Aux tank to not drain into the main tank as you drive down the road?

Keep in mind I live in Florida and it is fairly flat.

--
Tom Lins
St Augustine, FL
77 GM Rear Twin, Dry Bath, 455, FI-Tech EFI
Manuals on DVD
http://www.bdub.net/tomlins/
 
Possibly the vent on the second tank is obstructed preventing the fuel
from leaving that tank into the other as well as preventing the fuel from
that tank from leaving via the fuel line to the carb

Sully
Bellevue wa.

On Wed, Feb 20, 2019 at 5:28 PM Tom Lins via Gmclist <

> I dropped both gas tanks and replaced all the fuel lins.
> Driving the coach after this was done using the main tank and everything
> was fine.
> After using about 1/8 tank I switched to the aux tank to use that one for
> a while.
> After a short time (1-2 minutes) the engine started acting like it was
> starving for fuel.
> I switched back to the main tank and the problem went away,
>
> so since the tanks are linked and I always refuel when I use about half
> the fuel I figured I would just stay on the main tank.
>
> To my surprise as I was approaching my exit on the interstate the low fuel
> light came on.
>
> I looked at the gauge and the main tank was almost empty. I switched to
> the aux tank again and it showed almost full.
> and I again started having the fuel starvation issue. I switched back to
> the main tank and got off at the exit and pulled into the gas station.
>
> I filled the tank and it took 20 gallons.
>
>
> My question is What could cause the fuel in the Aux tank to not drain into
> the main tank as you drive down the road?
>
> Keep in mind I live in Florida and it is fairly flat.
>
>
>
> --
> Tom Lins
> St Augustine, FL
> 77 GM Rear Twin, Dry Bath, 455, FI-Tech EFI
> Manuals on DVD
> http://www.bdub.net/tomlins/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> I dropped both gas tanks and replaced all the fuel lins.
> Driving the coach after this was done using the main tank and everything was fine.
> After using about 1/8 tank I switched to the aux tank to use that one for a while.
> After a short time (1-2 minutes) the engine started acting like it was starving for fuel.
> I switched back to the main tank and the problem went away,
>
> so since the tanks are linked and I always refuel when I use about half the fuel I figured I would just stay on the main tank.
>
> To my surprise as I was approaching my exit on the interstate the low fuel light came on.
>
> I looked at the gauge and the main tank was almost empty. I switched to the aux tank again and it showed almost full.
> and I again started having the fuel starvation issue. I switched back to the main tank and got off at the exit and pulled into the gas station.
>
> I filled the tank and it took 20 gallons.
>
>
> My question is What could cause the fuel in the Aux tank to not drain into the main tank as you drive down the road?
>
> Keep in mind I live in Florida and it is fairly flat.

Hmmm. Not sure how that could happen, but it sounds like your tank switching valve is bad. Either that or you mixed up the supply and the vent lines
on the aux tank.

--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
> I dropped both gas tanks and replaced all the fuel lins.
> Driving the coach after this was done using the main tank and everything was fine.
> After using about 1/8 tank I switched to the aux tank to use that one for a while.
> After a short time (1-2 minutes) the engine started acting like it was starving for fuel.
> I switched back to the main tank and the problem went away,
>
> so since the tanks are linked and I always refuel when I use about half the fuel I figured I would just stay on the main tank.
>
> To my surprise as I was approaching my exit on the interstate the low fuel light came on.
>
> I looked at the gauge and the main tank was almost empty. I switched to the aux tank again and it showed almost full.
> and I again started having the fuel starvation issue. I switched back to the main tank and got off at the exit and pulled into the gas station.
>
> I filled the tank and it took 20 gallons.
>
>
> My question is What could cause the fuel in the Aux tank to not drain into the main tank as you drive down the road?
>
> Keep in mind I live in Florida and it is fairly flat.

**********

The tank issue is what I am finding also.

My fuel hoses were changed out when the tanks were dropped. There were put back and I had problems ever since. We have found, by process of
elimination, that the problem is from the gas tank area.

If your reserve tank is not draining back to the main tank, you need to think back, what did you do with that 3 inch line that ties the main tank to
the reserve tank? Did you plug the line with a rag, maybe forgot to pull it when you reassembled it???

The fuel SHOULD freely flow through that fill line to either tank. If you only were able to add 20 gallons to the main tank, you have a kink or a
plug in the big hose.

If you large hose was not plugged or kinked, and you stayed on the main tank, I think you would get to use all the fuel EXCEPT for about 7 gallons
which would be reserve.

EVen if the reserve vent were plugged, that fuel should still be able to transfer to the main tank.

From what you have said, it sounds like the large fill line is plugged or kinked.

--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
How do you fill one tank?
I wouldn't trust those low fuel warning lights as far as I could
throw them. I go by miles traveled, and use 8 mpg as an approximation for
fuel consumption. I do like you do, I drive on the top half of the tanks,
and fill up every 250 miles or less traveled. I would add an electric fuel
pump, energized by the auxiliary fuel tank switch. I use a Carter 4070
pump, and plumb it in downstream from the tank selector valve. Oh yes, by
the way, you have replaced your selector valve, haven't you? The OEM valves
really, really do not like fuel with alcohol in it.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Wed, Feb 20, 2019, 6:16 PM Tom Lins via Gmclist I dropped both gas tanks and replaced all the fuel lins.
> Driving the coach after this was done using the main tank and everything
> was fine.
> After using about 1/8 tank I switched to the aux tank to use that one for
> a while.
> After a short time (1-2 minutes) the engine started acting like it was
> starving for fuel.
> I switched back to the main tank and the problem went away,
>
> so since the tanks are linked and I always refuel when I use about half
> the fuel I figured I would just stay on the main tank.
>
> To my surprise as I was approaching my exit on the interstate the low fuel
> light came on.
>
> I looked at the gauge and the main tank was almost empty. I switched to
> the aux tank again and it showed almost full.
> and I again started having the fuel starvation issue. I switched back to
> the main tank and got off at the exit and pulled into the gas station.
>
> I filled the tank and it took 20 gallons.
>
>
> My question is What could cause the fuel in the Aux tank to not drain into
> the main tank as you drive down the road?
>
> Keep in mind I live in Florida and it is fairly flat.
>
>
>
> --
> Tom Lins
> St Augustine, FL
> 77 GM Rear Twin, Dry Bath, 455, FI-Tech EFI
> Manuals on DVD
> http://www.bdub.net/tomlins/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I am sitting here at the airport after midnight trying to figure out why a newly installed 150 meg business internet service only runs at .6 to 18 meg
at the edge of my network. The service tests out at 179 meg at the point of delivery from Comcast. The router is rated at 250 meg on each of it's 2
upstream wan links. Testing here in the middle of the night so as not to interfere with airport business and also to eliminate / reduce any possible
co-channel interference by other non-airport users.

So you come here and fix my problem and I'll gladly work on / fix yours. I'm just joking.

First on yours, I am guessing at possibly 4 issues.
1. Your gauges are incorrect. Possibly senders or good ground connections at or near the tanks.
2. A small leak in the hose / pipe between the tank selector solenoid and the pickup port on the Aux tank. So the system is sucking air only when
aux is selected.
3. Aux pick up hose and vent hoses are reversed.
4. Crack in plastic tank selector. I had one once and ended towing the coach home with my Blazer. It was not fun towing without the engine running
and no power brakes.

Those are just guesses. More than one thing could be wrong at the same time.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> After using about 1/8 tank I switched to the aux tank to use that one for a while.

I’d be thinking about the fuel supply line on top of the aux tank being crushed between the tank and the floor of the coach as there isn’t much clearance there. Or perhaps the supply and vent lines managed to cross one another when the tank was reinstalled and they are both crushed.

This should be relatively easy to prove by disconnecting the supply line from that tank at the selector valve and drawing from it either with an electric pump or by initiating a siphon.


Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
Maybe you reversed hoses or senders in the process. My guess is hoses at the input to the selector valve. Easy enough to do a blow through test with
no 12v. That's main nipple. Apply 12V and that's the Aux
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
It's the tank valve. Pain in the butt to change. Best solution IMO is use the dash switch to operate a relay. This relay can then run either of the two pumps. One for each tank. I then put the relay, pumps, filters, and steel gas line on the outside of the frame. You then have simple access to all components, and everything is in a cooler air stream. Very simple to do. Carb, or EFI. Bob Dunahugh 78 Royale
 
> I dropped both gas tanks and replaced all the fuel lins.
> Driving the coach after this was done using the main tank and everything was fine.
> After using about 1/8 tank I switched to the aux tank to use that one for a while.
> After a short time (1-2 minutes) the engine started acting like it was starving for fuel.
> I switched back to the main tank and the problem went away,
>
> so since the tanks are linked and I always refuel when I use about half the fuel I figured I would just stay on the main tank.
>
> To my surprise as I was approaching my exit on the interstate the low fuel light came on.
>
> I looked at the gauge and the main tank was almost empty. I switched to the aux tank again and it showed almost full.
> and I again started having the fuel starvation issue. I switched back to the main tank and got off at the exit and pulled into the gas station.
>
> I filled the tank and it took 20 gallons.
>
> My question is What could cause the fuel in the Aux tank to not drain into the main tank as you drive down the road?
>
> Keep in mind I live in Florida and it is fairly flat.

Tom,

Remember that there is nothing that says that you can only have one failure at a time.

I have had a lot of experience with the coach fuel system and have learned a lot at my own expense.

The scenario as you relate is simply not possible with an intact original fuel system. But, let me ramble on and I will get to your issues.

I have seen all four possible failures of the selector valve. They are:
No Select - Mail only
No Select - Auxiliary only
Select Both
Select Neither

The senders report full when the connection or sender is open.

It is easy to confuse the sender leads under the coach by the selector valve.

It is not likely, but the fill line that communicates between the auxiliary (front) and the main (rear) tank must be plugged. This can happen when
one of the rubber parts comes apart. Otherwise the tanks - even on level ground - fuel will seek an even level at just below the half tank mark. As
said, at fill at in this condition would be more than 20 gallons.

If you are traveling and running on the front (auxiliary) tank, and that sender is connected to look like it is the main (rear) tank and your fuel
goes low, so you switch and get nothing. The level reports as full because that sender or the lead to it is bad. There is either no fuel in that
tank, or it is not accessible because both the selector valve has failed and the communication between the tanks at the fill line is blocked. So, the
condition of the main (rear) tank must not be known.

This all happened with just four possible concurrent failures: (This would not be a record.)
The selector valve has failed .(A real good bet an a place to start.)
The fill line between the two tanks (that long easy to remove run) is blocked by something.
The leads to the level senders have been swapped. (This is easy to do down by the selector valve.)
The level sender currently reading the main (rear) tank is open or the connection to it is.

I have had the selector valve fail when I had no working senders, but I was still able to fuel the coach at about 40 gallons.

My plan would be:
First, run or drain the fuel down as low as you dare.
Change out the selector valve if you have not. The only replacements are upside down and backwards so it takes some creativity to get it in there.
While it is loose, blow into both lines. You might hear bubbles in one (full) tank and not the other. This should also help to confirm which fuel
line is which.
When you have that, and if there is fuel in one tank, you can use that to confirm that the sender is reporting the correct tank.
There are drain plugs in the tanks, if you can still use them - great! Because you are going to have to pull that long fill line off to find out what
its problem is. As I said, I had a piece of the rubber on mine fail and while mine did not, I can imagine it plugging that line. My bet would be on
the rear, because the front is just a short stub and so has less opportunity to snag something. The part of my fuel fill system that failed was the
rubber elbow. That would cause me to look there first.
If the accessible connections to the senders are all good, then you may have to attack a sender directly. You know about that.

Good Luck

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Tom,

I had the same problem after I had removed both tanks for cleaning and painting and putting new fuel lines on. When I put the tanks back in place, I
had let one of the fuel lines get pinched between the coach and the tank. The line had slipped out of the groove on the tank top when I was lifting
it back into place. If I couldn't draw fuel from it, then it couldn't take any more fuel in. Slightly dropping that tank and repositioning the line
fixed it.

Jerry
--
Jerry Sitzlar..... 77 Eleganza II, Twin bed, dry bath......
Lenoir City, TN (near Knoxville)
 
A helpful trick. Duct tape is your best buddy here. Put the hoses on the
tank, or metal lines, if that is what you prefer, lay them in the
depression intended for this purpose, and duct tape them to the top of the
tank. Works every time.
I absolutely hate pinched fuel hoses, because it is always MY FAULT
when it happens.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Thu, Feb 21, 2019, 2:28 PM Jerry Sitzlar via Gmclist <

> Tom,
>
> I had the same problem after I had removed both tanks for cleaning and
> painting and putting new fuel lines on. When I put the tanks back in
> place, I
> had let one of the fuel lines get pinched between the coach and the tank.
> The line had slipped out of the groove on the tank top when I was lifting
> it back into place. If I couldn't draw fuel from it, then it couldn't
> take any more fuel in. Slightly dropping that tank and repositioning the
> line
> fixed it.
>
> Jerry
> --
> Jerry Sitzlar.....
> 77 Eleganza II, Twin bed, dry bath......
> Lenoir City, TN (near Knoxville)
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Goes without saying. GATES BARRICADE FUEL INJECTION HOSE. (ALCOHOL
RESISTANT).
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> A helpful trick. Duct tape is your best buddy here. Put the hoses on the
> tank, or metal lines, if that is what you prefer, lay them in the
> depression intended for this purpose, and duct tape them to the top of the
> tank. Works every time.
> I absolutely hate pinched fuel hoses, because it is always MY FAULT
> when it happens.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>
> On Thu, Feb 21, 2019, 2:28 PM Jerry Sitzlar via Gmclist <

>
>> Tom,
>>
>> I had the same problem after I had removed both tanks for cleaning and
>> painting and putting new fuel lines on. When I put the tanks back in
>> place, I
>> had let one of the fuel lines get pinched between the coach and the
>> tank. The line had slipped out of the groove on the tank top when I was
>> lifting
>> it back into place. If I couldn't draw fuel from it, then it couldn't
>> take any more fuel in. Slightly dropping that tank and repositioning the
>> line
>> fixed it.
>>
>> Jerry
>> --
>> Jerry Sitzlar.....
>> 77 Eleganza II, Twin bed, dry bath......
>> Lenoir City, TN (near Knoxville)
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
 
I go along with John, in that it is easy to mix the two lines that come
from the sender.

On Fri, Feb 22, 2019 at 1:15 AM James Hupy via Gmclist <

> Goes without saying. GATES BARRICADE FUEL INJECTION HOSE. (ALCOHOL
> RESISTANT).
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>

>
> > A helpful trick. Duct tape is your best buddy here. Put the hoses on the
> > tank, or metal lines, if that is what you prefer, lay them in the
> > depression intended for this purpose, and duct tape them to the top of
> the
> > tank. Works every time.
> > I absolutely hate pinched fuel hoses, because it is always MY FAULT
> > when it happens.
> > Jim Hupy
> > Salem, Or
> > 78 GMC ROYALE 403
> >
> > On Thu, Feb 21, 2019, 2:28 PM Jerry Sitzlar via Gmclist <

> >
> >> Tom,
> >>
> >> I had the same problem after I had removed both tanks for cleaning and
> >> painting and putting new fuel lines on. When I put the tanks back in
> >> place, I
> >> had let one of the fuel lines get pinched between the coach and the
> >> tank. The line had slipped out of the groove on the tank top when I was
> >> lifting
> >> it back into place. If I couldn't draw fuel from it, then it couldn't
> >> take any more fuel in. Slightly dropping that tank and repositioning
> the
> >> line
> >> fixed it.
> >>
> >> Jerry
> >> --
> >> Jerry Sitzlar.....
> >> 77 Eleganza II, Twin bed, dry bath......
> >> Lenoir City, TN (near Knoxville)
> >>
> >>
> >> _______________________________________________
> >> 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
http://www.appliedgmc.com
1-800-752-7502
 
You must log in or register to reply here.
Applied GMC
Get your shine on at www.cruzingear.co

Share this page

Share this page
Top Bottom
Back