# Need to drop gas tank



## drifter79 (Oct 18, 2003)

I have a 89 GMC motorhome cannot get more than 20 gallons in the tank I did clean and check vent hose was clear. Plus was going to pull hose off of tank but tank is full so I figure must have a bad pickup tube or broken one was wondering how to get the top off the tank with out braking anything looks like I just tap the ring off right? There are three hoses coming off the top so figure one to fuel pump and one to generator is the third one a vent hose. Thanks for any help 20 gallons with a 454 dose not get you very far we call it gas station hopping....


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## kimber750 (Sep 19, 2011)

drifter79;1845077 said:


> I have a 89 GMC motorhome cannot get more than 20 gallons in the tank I did clean and check vent hose was clear. Plus was going to pull hose off of tank but tank is full so I figure must have a bad pickup tube or broken one was wondering how to get the top off the tank with out braking anything looks like I just tap the ring off right? There are three hoses coming off the top so figure one to fuel pump and one to generator is the third one a vent hose. Thanks for any help 20 gallons with a 454 dose not get you very far we call it gas station hopping....


Hammer and screwdriver to spin the lock ring.


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## kimber750 (Sep 19, 2011)

Normally you have supply line, return line and evap line.


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## drifter79 (Oct 18, 2003)

Thanks for reply going to have to try and trace lines and see where they go. I know generator take gas for the tank also..


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## BUFF (Dec 24, 2009)

drifter79;1845077 said:


> I have a 89 GMC motorhome cannot get more than 20 gallons in the tank I did clean and check vent hose was clear. Plus was going to pull hose off of tank but tank is full so I figure must have a bad pickup tube or broken one was wondering how to get the top off the tank with out braking anything looks like I just tap the ring off right? There are three hoses coming off the top so figure one to fuel pump and one to generator is the third one a vent hose.


Ok I'm a little lost...... How much did the tank use to hold?
Did the reduction in capacity take time to happen or happen quickly?
The Vent Hose and pick up tubes wouldn't have anything to do with mow much the tank holds. BTW pickup tubes don't break or go bad, they can get plugged though.

Say your tank use to hold 40gallons, being a thirsty 454 depending on the type of driving you're doing you can expect to see 5-10mpg and seeing a drop in the gauge is a common thing, some times quickly.

I think your sending unit is on it's way out and giving you a false reading. 
Tank volume/capacity doesn't change if the tank hasn't been caved in or crushed.

You can take a electric fuel pump and hook it up to the feed line and start filling jugs to drain the tank, plus if it is full you'll also find out how much can go in the tank.


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## drifter79 (Oct 18, 2003)

Buff, was not sure how to explain tank holds 45 gallons the sending unit did just go out so will fix that when I drop the tank. Runs out of gas and will only take 20 gallons and that is filling up to the gas cap so not sure why this is happening. Mileage around 7 miles per gallon.


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## BUFF (Dec 24, 2009)

drifter79;1845137 said:


> Buff, was not sure how to explain tank holds 45 gallons the sending unit did just go out so will fix that when I drop the tank. Runs out of gas and will only take 20 gallons and that is filling up to the gas cap so not sure why this is happening. Mileage around 7 miles per gallon.


Huh......... got me stumped.
As I mentioned before I don't believe the pick up tube is the problem but stranger things have happened...... I'd be interested to hear what you find when you drop the tank.


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## drifter79 (Oct 18, 2003)

Will update when I find the problem Thanks for the reply


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## drifter79 (Oct 18, 2003)

BUFF, here is what I found when I got in there. Motor would pop a little when first starting not any more.
The hose here in red was gone tested the pump ran good so just added the hose put 20 gallons in it and it ran where before if it had 20 gallons would be out of fuel.


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## BUFF (Dec 24, 2009)

drifter79;1848584 said:


> BUFF, here is what I found when I got in there. Motor would pop a little when first starting not any more.
> The hose here in red was gone tested the pump ran good so just added the hose put 20 gallons in it and it ran where before if it had 20 gallons would be out of fuel.


huh.......I've only seen hard lines on in tank pumps......

Well you go it fixed.


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## dieselss (Jan 3, 2008)

How did the missing hose still only allow you to put 20 gallons in a 40 tank


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## Banksy (Aug 31, 2005)

dieselss;1848624 said:


> How did the missing hose still only allow you to put 20 gallons in a 40 tank


This...X2. 

Maybe he meant he can't run on more than 20 gallons before it dies.


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## drifter79 (Oct 18, 2003)

Hey only telling what worked for me I did not set up the system only fixed what was there. With the hose gone pick up tube only goes half way down in the tank and the pump is pumping to no where just showing what worked for me before if I had 40 gallons in tank would only use top 20 gallons could not pump the lower 20 cause there was no hose connected to the pump.


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## kimber750 (Sep 19, 2011)

BUFF;1848622 said:


> huh.......I've only seen hard lines on in tank pumps......
> 
> Well you go it fixed.


I am very curious to how it ran at all if that hose was missing? And where did it go?

Glad you got it running again. Thumbs Up


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## BUFF (Dec 24, 2009)

kimber750;1848696 said:


> I am very curious to how it ran at all if that hose was missing? And where did it go?
> 
> Glad you got it running again. Thumbs Up


I'm lost too, but something's are better left unknown...........Thumbs Up


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## drifter79 (Oct 18, 2003)

was laying in bottom of the tank turned to gum had rubber clamps on the pump fell apart when I touched them.


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## Nozzleman (Feb 6, 2003)

The fuel line was probably not ethanol compatable and disintigrated.


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## Jeep_thing (Mar 3, 2014)

kimber750;1848696 said:


> I am very curious to how it ran at all if that hose was missing? And where did it go?
> 
> Glad you got it running again. Thumbs Up


When the tank was full it sucked fuel through the bottom of the pump, without the pickup screen. However when the fuel level dropped about 4" the pump opening would suck air.


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## dieselss (Jan 3, 2008)

Huh? .the pump is pushing fuel up through that line that wasn't there. If the tank had any fuel the pump was old faithful I'm there


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## mtnbktrek (Oct 25, 2013)

Is this plow site???


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## BUFF (Dec 24, 2009)

mtnbktrek;1850150 said:


> Is this plow site???


No it's PlowSite


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## kimber750 (Sep 19, 2011)

BUFF;1850160 said:


> No it's PlowSite


So close, it is

PlowSite.com Thumbs Up


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## mtnbktrek (Oct 25, 2013)

BUFF;1850160 said:


> No it's PlowSite


Lol don't know y I got confused


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## BUFF (Dec 24, 2009)

kimber750;1850162 said:


> So close, it is
> 
> PlowSite.com Thumbs Up


You're like "auto correct" ........


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## kimber750 (Sep 19, 2011)

BUFF;1850168 said:


> You're like "auto correct" ........


Nah, auto correct would of changed it to LawnSite.com or some other random crap that has nothing to do with what you are typing. :laughing:


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## xjoedirt55x (Dec 11, 2009)

Maybe the pump pushed hard enough to push fuel into the line above, even though pressure would have been lower, but a vacuum was created causing the fuel to suck into the line and keep the truck running for what would be close to 20 gallons worth of driving. Head scratcher for sure.


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## drifter79 (Oct 18, 2003)

It has a mechanical pump on the motor. The pump in the tank is a assist pump runs way better now with both pumps working, checked a few rv sites out seems to be a common problem with this type of setup on older models.


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## dieselss (Jan 3, 2008)

Ok, makes sense now drifter. Thanks for clearing that up


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