Re: fuel delivery problems with 1990 F-250, 5.8 L engine, dual tanks& Fuel Delivery module

"Usenet Newsreader" <usenet247reader@[EMAIL PROTECTED]
> wrote in message 
news:491C0F0A.70702@[EMAIL PROTECTED]
> david wrote:
>> On Wed, 12 Nov 2008 17:25:55 -0500, Usenet Newsreader rearranged some
>> electrons to say:
>>
>>> Usenet Newsreader wrote:
>>>> Ulysses wrote:
>>>>> Usenet Newsreader <usenet247reader@[EMAIL PROTECTED]
> wrote in message
>>>>> news:491B21E0.1020700@[EMAIL PROTECTED]
>>>>>> Mike K wrote:
>>>>>>> "Usenet Newsreader" <usenet247reader@[EMAIL PROTECTED]
> wrote in
message
>>>>>>> news:5pSdnSsqs80DuofUnZ2dnUVZ_tXinZ2d@[EMAIL PROTECTED]
>>>>>>>> Had a problem with my F-250.  The rear tank rusted out.  I tried
to
>>>>> siphon
>>>>>>>> the fuel out of the rear tank and run off the front tank, but the
>>>>>>>> front
>>>>>>>> tank fuel pump didn't seem to work.  But the truck ran fine off
the
>>
>> There should be a shuttle valve (looks like a big can) that switches 
>> between the tanks depending on which in-tank  pump is energized.  Those

>> can get clogged up and not switch back and forth.  Search the 
>> alt.trucks.ford newsgroup, there was a discussion on this topic a
couple 
>> of weeks ago.
>
> For 1990 trucks there is no such shuttle valve on the frame of the truck
- 
> this is all done inside the fuel pump.  That is why I am asking if any
of 
> you know how the fuel pumps control the valving of the gasoline
returning 
> to the tank.
>
> There are at least three separate systems for switching dual tanks. One
is 
> for carbed vehicles that have a fuel pump mounted on the engine - they 
> obviously don't need gas to return into the tank.
>
> The earlier fuel injected engines did need such valving going both ways 
> into and out of the tank - and that valving was outside of the tanks. 
> Later EFI dual-tank set-ups didn't have that separate valving outside of

> the tanks - they only switched power from one pump to the other, and the

> valving was inside the fuel pump itself.  That is the system I have and 
> that is what I am asking about.  So please do not confuse the systems -
I 
> am asking specifically about the later EFI dual tank system with a check

> valve inside the pump itself.

I found a repair manual,  the pump in the tank is not a simple pump but a 
fuel control module.
When the fuel pump is shut off, it is suppose to close the fuel return
line 
to the tank.

I would figure the shut off valve in the front tank is not closing or the 
valve in the rear tank is not opening.

The reason to check fuel pressure is to make sure the pressure regulator
is 
allowing fuel to the return line or if the pressure is too high which
might 
force the fuel through the front pump into the tank.