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

samstone@[EMAIL PROTECTED]
 wrote:
> On Thu, 13 Nov 2008 09:26:59 -0500, Usenet Newsreader
<usenet247reader@[EMAIL PROTECTED]
>
> wrote:
> 
>> samstone@[EMAIL PROTECTED]
 wrote:
>>> On Tue, 11 Nov 2008 19:47:44 -0500, Usenet Newsreader
<usenet247reader@[EMAIL PROTECTED]
>
>>> wrote:
>>>
>>>> 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 rear tank when the tank switch was set to "Rear", and the engine 
>>>> almost died when set to "Front" - I couldn't hear the front pump whir
at 
>>>> all when I turned the key when the switch was set at "front" but
could 
>>>> hear it whir when set to "rear".
>>>>
>>>> So I pulled the rear tank out, took out the fuel pump, tagged the
lines, 
>>>> and bagged the pump till I could put a new tank in.  That took a
while 
>>>> due to some family health issues, and when I put it back in, I added 
>>>> almost 5 gallons of fuel and the truck started right up.  It ran for
a 
>>>> bit last night, and then this morning it was hard if not impossible
to 
>>>> start.  It felt like it was out of gas.  So I added more from a gas
can, 
>>>> and it finally started up.  I went into the house to get my wallet
(to 
>>>> take the truck up to a gas station to fill it up) and when I got
outside 
>>>> it stalled again and won't catch.
>>>>
>>>> I wondered if there is a problem with the dual tank selector switch,
and 
>>>> I checked to see if there was a some sort of regulator or in line 
>>>> valving, but there is none.  It is possible that I got the fuel lines

>>>> reversed when hooking up the tank?  The truck ran good for a while,
but 
>>>> felt like it ran out of gas.  When I added a bit more, it ran OK but
ran 
>>>> for a much shorter time.  If I reversed the fuel lines at the fuel
pump 
>>>> on the rear tank, could this allow the truck to run until it pumped
fuel 
>>>>  through the fuel injector rail and then into the front tank?  Could 
>>>> the truck run without the front pump working at all?  There is no
three 
>>>> or six-way valving, so I assume that each tank has a Fuel Delivery 
>>>> Module in it.
>>>>
>>>> So do both fuel pumps need to work in order to run the vehicle, or
did 
>>>> something happen to just the rear pump which isn't running even
though 
>>>> it is whirring when I turn the key but don't start the vehicle?
>>>
>>>
>>> i THINK  , you have three fuel pumps - 
>>>  one in each tank ( low pressure )
>>> and one high pressure pump which pressurizes
>>> the injectors.   the front/back switch 
>>> changes only the power ( through a relay )
>>> to the pump in the tank selected.  
>>> the low pressure from the pump in the tank selected
>>> moves a valve ( where all four fuel lines are together )
>>> to have both the feed and return lines in use for that 
>>> selected tank.   there is no electrically move valve
>>>  has the fuel filter been replaced?
>>>
>>>
>> Read the rest of the thread.
>>
>> The fuel filter was replaced, and there is no valving in line between 
>> the tanks and the engine.  There is just the fuel pump relay, then the 
>> front/rear tank switch - there are supposed to be a check valve in the 
>> tank mounted pump itself.
>>
>> There si no other fuel pump on the engine.  There might have been for 
>> older trucks, but not for the 1990 model.
>>
> 
> 
> if you know all this why are you asking questions in here?
> 
I was asking people if they had similar problems with the specific model 
  and if it was caused by a valve in the fuel pump or something else - 
why would a front tank pump that wasn't working allow gas from the rear 
pump to full the front tank?  I find it hard to believe that one half 
the pump in the rear could work yet totally have a valve in the back 
(the other half of the pump) not work and pump gas into non-working tank 
- makes no sense to me at all.

So I was asking if anyone had similar problems with the same model and 
year truck - and all I got was "have you checked for this?" - most of 
which wasn't even applicable for my truck.  The most bizarre one was the 
fuel filter - which makes no sense whatsoever.  The engine was getting 
fuel because the pump was pumping gas from the rear tank to the fuel 
injection rail and through the fuel pump.  The fuel was not getting back 
to the rear tank - it was going into the front tank for some reason I 
can't figure out.  That is why I wanted to know if anyone had specific 
information about the 1990 pumps and check valves in them.