Running a diesel out / dual tanks

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M Warren - 10 Dec 2006 03:58 GMT

I have never had a diesel with dual tanks before so am not sure how to
approach it. With gas engine I have simply run one tank out and then
switched to the other. How hard is it to start the 7.3once it has run out?
I know some diesels are buggers, while my VW would fire right back up after
a few seconds of cranking. So I guess my question is this: can I run a tank
dry and be okay, or do I avoid that at all costs. Thanks

Matt
'96 F-SD 7.3

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My Name Is Nobody - 10 Dec 2006 04:18 GMT

>I have never had a diesel with dual tanks before so am not sure how to
>approach it. With gas engine I have simply run one tank out and then
[quoted text clipped - 5 lines]
> Matt
> '96 F-SD 7.3

I know you were asking about the dynamics of the engine running out of fuel,
but another problem, is running your in tank fuel pumps with too little/no
fuel, it is not good for them.

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Steve Barker LT - 10 Dec 2006 19:44 GMT

The bit about running low on fuel being hard on pumps is a wives tale.
There's no scientific evidence that it makes a difference.

Signature

Steve Barker

>>I have never had a diesel with dual tanks before so am not sure how to
>>approach it. With gas engine I have simply run one tank out and then
[quoted text clipped - 9 lines]
> fuel, but another problem, is running your in tank fuel pumps with too
> little/no fuel, it is not good for them.

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Spdloader - 10 Dec 2006 20:05 GMT

> The bit about running low on fuel being hard on pumps is a wives tale.
> There's no scientific evidence that it makes a difference.

I disagree. It is better not to run a tank low. The frequency of pumps going
out prematurely does increase in vehicles where the owner consistently runs
the vehicle tank too low on fuel.

Just my .02, and lots of years of experience with it-----especially on GM
and Jeep.

Spdloader

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Steve Barker LT - 11 Dec 2006 02:51 GMT

oh, well. Thanks for the clarification. GM i would expect that. It makes
no difference on fords.

Signature

Steve Barker

>> The bit about running low on fuel being hard on pumps is a wives tale.
>> There's no scientific evidence that it makes a difference.
[quoted text clipped - 7 lines]
>
> Spdloader

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My Name Is Nobody - 10 Dec 2006 23:43 GMT

> The bit about running low on fuel being hard on pumps is a wives tale.
> There's no scientific evidence that it makes a difference.
[quoted text clipped - 12 lines]
>> fuel, but another problem, is running your in tank fuel pumps with too
>> little/no fuel, it is not good for them.

Ya Steve, you are probably right.
It a good bet all these other bozos have just been sucked in by an old wives
tale...
OK Then...

TEC TIP #1620
Federal-Mogul Document #1620, Technical Education Center
Keeping Your New Fuel Pump and Fuel System Healthy
Don't make a habit of driving with a nearly empty gas tank. Running out of
gas is not only inconvenient, it can burn up your fuel pump since the pump
relies on the gas flowing through it to cool it.
http://www.napacoppercountry.com/tips.php

Allowing a pump to run with little or no fuel will cause the pump to
overheat, leading to build-up and formation of gum within the pump housing
and higher than normal amperage draw, resulting in a meltdown of the brush
housing.
http://members.aol.com/agspeed/efi-pump.htm

Most modern vehicles place the pump in the tank where it can be kept cool
with a constant bath of fuel, but this location isn't so ideal when it comes
time to replace that troublesome component.

One thing that I did learn from dealer was that the only time the parts guy
saw pumps dead this early was on short haul delivery trucks and taxis that
were driven with mostly empty tanks of gas. (Being submerged is a coolant.)
Turns out my van had been previously a hotel shuttle. So the when gas hits
$4 a gallon and most people drive around with 1/4 tank and put in $12 every
3 days - it's gonna be a good time to be in the fuel pump business.

The pump needs a steady supply of fuel around it to maintain a reasonable
operating temperature, and running the tank too low deprives it of this. It
also makes the pump work somewhat harder, which means that running most
vehicles down below the 1/4-tank mark (or thereabouts) is a good way to
shorten the life of the pump.
http://www.autoblog.com/2006/08/03/autoblog-maintenance-101-in-tank-fuel-pump-randr/

Electric Fuel pump
Placing the pump in the tank puts the component least likely to handle
gasoline vapor well (the pump itself) farthest from the engine, submersed in
cool liquid.
http://en.wikipedia.org/wiki/Fuel_pump

The pumps are designed to run submerged in gasoline.
http://www.volvoclub.org.uk/faq/FuelSystem.html

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Steve Barker LT - 11 Dec 2006 02:54 GMT

I agree the fuel cools the pump. BUT, if you run out, then the pump stops
running. Then you switch tanks and the other pump runs. The most the pump
could run with no gas is the amount of time it takes the oil pressure to
drop off to nothing. I manage a fleet of 34 trucks, 18 of them fords and
have not seen an excessive amount of fuel pump replacements. And we always
run them till they drop before switching.

Signature

Steve Barker

>> The bit about running low on fuel being hard on pumps is a wives tale.
>> There's no scientific evidence that it makes a difference.
[quoted text clipped - 59 lines]
> The pumps are designed to run submerged in gasoline.
> http://www.volvoclub.org.uk/faq/FuelSystem.html

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websurfer - 10 Dec 2006 08:52 GMT

>I have never had a diesel with dual tanks before so am not sure how to
>approach it. With gas engine I have simply run one tank out and then
[quoted text clipped - 5 lines]
> Matt
> '96 F-SD 7.3

Matt,

I wouldn't do it just as a matter of principle, however another good
reason to NOT do that is because in the 7.3 the injectors use the fuel as a
lubricant, and in case you haven't priced them, they're VERY expensive to
replace. Secondly you run the risk of picking up "stuff" from the bottom of
the tank, this could lead to all kinds of problems. I would highly
reccommend you go to "thedieselstop.com" and just read through some of the
information provided there. Ask questions, those folks are very
knowledgeable. I think you'll like the site, I always learn something
there.

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Steve Barker LT - 10 Dec 2006 19:45 GMT

the fuel is drawn off the bottom of the tank all the time. I never did
understand this line of thinking.

Signature

Steve Barker

>>I have never had a diesel with dual tanks before so am not sure how to
>>approach it. With gas engine I have simply run one tank out and then
[quoted text clipped - 16 lines]
> knowledgeable. I think you'll like the site, I always learn something
> there.

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Dave and Trudy - 10 Dec 2006 12:32 GMT

>I have never had a diesel with dual tanks before so am not sure how to
>approach it. With gas engine I have simply run one tank out and then
[quoted text clipped - 5 lines]
> Matt
> '96 F-SD 7.3

Matt,
I have two diesel Ford pickups, a Peterbuilt w/a Cat diesel, and my other
vehicles are Prevost and MCI motorcoaches with Series 60 Detroiters in them.
I have learned that it is best to run the tank down to 1/4 then fuel or in
your case switch tanks. Given a diesel's abhorence for dirt or any sort of
crud in the fuel, air, or oil, this is just a further safeguard for your
motor. I don't believe that the 7.3 has a self-priming system on it. I know
my 94 7.3L IDI does not, so if you run out of fuel a lot of cranking will be
required to get the air out of the system. Of course, you can crack an
injector to help bleed the air but still about three or four batteries will
be required to restart it, unless you are very, very lucky. Just my
observations.
DaveD

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Steve Barker LT - 10 Dec 2006 19:43 GMT

It was my experience on mine, that if you're going 65+ mph when it goes
down, you'll be fine. Just flip the switch, floor the pedal and wait. BUT
if you're going to be puttering around with a low tank, then you'd better go
ahead and switch it and wait 'till you're on the highway to run it out. At
best, they're a real pain to start when they've been run out. At worst,
you'll be bleeding the filter housing and cranking the battery dead.

Signature

Steve Barker

>I have never had a diesel with dual tanks before so am not sure how to
>approach it. With gas engine I have simply run one tank out and then
[quoted text clipped - 5 lines]
> Matt
> '96 F-SD 7.3

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