89 F150 dual tank issue.

<letterman DeleteThis @invalid.com> wrote in message
news:3qnof419j6359f15dltsfvgm6tg53kma84@4ax.com...
> On Sun, 19 Oct 2008 10:03:09 -0400, "Ted" <Ted DeleteThis @NoSpam.com> wrote:
>
>>
>><letterman DeleteThis @invalid.com> wrote in message
>>news:le2gf4tniiqavscinrith51lfutn7jn8k8@4ax.com...
>>> On Thu, 16 Oct 2008 17:21:58 -0400, "Ted" <Ted DeleteThis @NoSpam.com> wrote:
>>>
>>>>If the pump in the rear tank is bad, why when the switch is in the rear
>>>>position would the front pump
>>>> still work? Wouldn't the truck die from lack of fuel?
>>>>
>>>>Ted
>>>
>>> If I switch to the rear tank with the engine running, the truck quits
>>> running from lack of fuel. Now you know !!!!
>>>
>>
>>That's my point. On my truck, if I switch from the front to the rear tank,
>>it
>>continues to run, pulling gas from the front tank. It always pulls gas
>>from the front tank.
>
> That's really odd. I dont know how that is possible unless the switch
> is defective. The switch switches fuel pumps, or is supposed to
> anyhow. The only other possibility is that the pumps are both
> connected to a fuel line directly, which I'd suspect would pump gas
> backwards to the other tank. I'd sure like to learn how that is
> occurring. If you find out, please tell all of us. VERY STRANGE!


Does it transfer the fuel out of the rear into the front while it's running?
Some of the new GM trucks are set up that way. Rear tank feeds into front
tank which feeds engine.

--
Old Crow
'82 FLTC 'Pearl'
'87 FLTC 'Fugly'
'61 F-100
BS#133, SENS, TOMKAT, SLOB#13, MAMBM

On Oct 20, 9:37 pm, letter....TakeThisOut@invalid.com wrote:
> On Sun, 19 Oct 2008 10:03:09 -0400, "Ted" <T....TakeThisOut@NoSpam.com> wrote:
>
> ><letter....TakeThisOut@invalid.com> wrote in messagenews:le2gf4tniiqavscinrith51lfutn7jn8k8@4ax.com...
> >> On Thu, 16 Oct 2008 17:21:58 -0400, "Ted" <T....TakeThisOut@NoSpam.com> wrote:
>
> >>>If the pump in the rear tank is bad, why when the switch is in the rear position would the front pump
> >>> still work? Wouldn't the truck die from lack of fuel?
>
> >>>Ted
>
> >> If I switch to the rear tank with the engine running, the truck quits
> >> running from lack of fuel.  Now you know !!!!
>
> >That's my point. On my truck, if I switch from the front to the rear tank, it
> >continues to run, pulling gas from the front tank. It always pulls gas from the front tank.
>
> That's really odd.  I dont know how that is possible unless the switch
> is defective.  The switch switches fuel pumps, or is supposed to
> anyhow.  The only other possibility is that the pumps are both
> connected to a fuel line directly, which I'd suspect would pump gas
> backwards to the other tank.  I'd sure like to learn how that is
> occurring.  If you find out, please tell all of us. VERY STRANGE!

A glance through this thread suggests that the following may be
helpful. If the 6 is like my V8, the key is a thing called the dual
purpose reservoir. As stated above, selecting the tank activates the
low pressure pump in that tank which feeds the reservoir. The latter
contains some sort of flip flop diaphragm which does the actual
switching. The high-pressure pump draws fuel from there and directs it
to the fuel rail.

Something else: if one tank has had it anyway it does not matter. But
anyone should realise that, if a steel tank is left empty for long
periods both the tank and the sender corrode. So aim to keep both
tanks full. Obviously it does not matter as long as the tanks are both
full frequently. But if, as tends to happen, you favour one tank, then
keep the other one full (and every six months, at the most, use the
fuel in the spare tank and replace it - petrol left in the tank for a
year is barely recognisable as petrol).

I learnt this the hard way and replacement of tank, pump and sender
was not cheap.