How bad exactly is it if our cars run out of gas?
And does the pump require gasoline for lubrication?

If so, does it need to be fully submerged for proper lubrication... or is just partially okay?

Lastly, is the duke pump and v6 pump the same beast? Any difference in pumps over the years?

The gas is used to cool the pump. Running it dry will overheat and kill it eventually. The 4 and 6 cyl pumps are not the same.

How bad exactly is it if our cars run out of gas?

Well, it's pretty bad Blake-the car won't just run without gas. (Aren't ya glad Revin didn't answer this?)
It's not good to run out of gas, as the pump is now running dry during the 1st 2 seconds of 'key on' and during cranking.

And does the pump require gasoline for lubrication?
Yes well sort of, but even more important, it uses the gas for cooling the internals of the pump. Running low or out will significantly shorten the life of the pump. Even if you have enough gas to lubricate the inside of the pump, the upper part of the pump,, which houses the 'motor' windings is exposed to air, which does little in the way of cooling

If so, does it need to be fully submerged for proper lubrication... or is just partially okay?
I wouldn't routinely run less than 1/4 tank. Jane got in the habit of running down in the shaded area, and it wasn't long before the pump went out
Lastly, is the duke pump and v6 pump the same beast? Any difference in pumps over the years?
NO! The 4cyl/6cyl pumps are different. Look the same but the v6 pump is made to put up more pressure/flow. I don't know about the years being different.

[This message has been edited by maryjane (edited 04-23-2004).]

So how long would it take the pump to overheat with no load on it?

GL

Keeping the pump submerged is a bad myth.

For best pump life... You must keep enough fuel in the tank to have fuel flowing thru the pump at all times. Running a fuel pump, or many other pump types, dry for any legnth of time will ruin them. This means the intake sock must always be under fuel. Not the pump body.

In tank fuel pumps have wet motors. The entire pump/motor is inside a sealed shell and wet with fuel at all times unless the tank runs dry. Fuel serves as both lubricant and coolant.

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The only thing George Orwell got wrong was the year.

The Ogre's Fiero Cave (It's also at the top of every forum page...)

And the temp of the fuel in a 1/4 tank is just as cool as the temp of fuel in a 1/2 or fuller tank?

quote Originally posted by maryjane: How bad exactly is it if our cars run out of gas? Well, it's pretty bad Blake-the car won't just run without gas. (Aren't ya glad Revin didn't answer this?) It's not good to run out of gas, as the pump is now running dry during the 1st 2 seconds of 'key on' and during cranking. And does the pump require gasoline for lubrication? Yes well sort of, but even more important, it uses the gas for cooling the internals of the pump. Running low or out will significantly shorten the life of the pump. Even if you have enough gas to lubricate the inside of the pump, the upper part of the pump,, which houses the 'motor' windings is exposed to air, which does little in the way of cooling If so, does it need to be fully submerged for proper lubrication... or is just partially okay? I wouldn't routinely run less than 1/4 tank. Jane got in the habit of running down in the shaded area, and it wasn't long before the pump went out Lastly, is the duke pump and v6 pump the same beast? Any difference in pumps over the years? NO! The 4cyl/6cyl pumps are different. Look the same but the v6 pump is made to put up more pressure/flow. I don't know about the years being different.

You know all that, yet don't know how to get a broke key out?

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98 3800SC GTP motor,3.4 pulley, Getrag 5sp.
custom hood, trunk, side scoops, IRM front spoiler, 17" excel's , dk.Shadow Grey

quote Originally posted by revin: You know all that, yet don't know how to get a broke key out?

Well, we can't all be the end all-be all of the Fiero Community. I'll leave that up to you real
Fiero entheusiasts.

quote Originally posted by maryjane: And the temp of the fuel in a 1/4 tank is just as cool as the temp of fuel in a 1/2 or fuller tank?

As long as the pump has fuel to move.... Unless the fuel is well over 100 degress F it won't matter a bit. The fuel will evap long before there is a problem with pump temperature.

The key is that the pump must always have fuel to move. Any liquid fuel is more than cool enough to preserve the pump. The only thing that matters is the pump must never run dry. You can kill many types of pumps in minutes, even seconds, by running them dry.

quote Unless the fuel is well over 100 degress F it won't matter a bit.

With ambient air temps over 90F and eng compartment air temps pushing 130 or more, and eng coolant temps at 200F, it's hard to comprehend returned fuel in the tank being near 100F anytime after warmup, in a 1/4 filled tank. I can tell you-I've felt that tank, after a drive, & it's flat HOT! Hot enough you can't hold your hand on it.

Why thank you Don...

I did not realize that you, err... knew so much about pumps.
I ran the darn thing dry the other day (not the 1st time) so I am just guaging the potential for future trouble.

I appreciate the insight Ogre. I would think that the engineers would allow for a pump to be perfectly within spec on 1/8 of a tank or under. It just makes sense for most of America. We simply don't pull into the filling station until the tank is close to 'E'.

Now, OTOH, these are the same enigneers that made a water pump gasket that looks remarkably like the outline of the United States, and has 4!!!! different size Torx bolts. Go figure.

quote I would think that the engineers would allow for a pump to be perfectly within spec on 1/8 of a tank or under. It just makes sense for most of America. We simply don't pull into the filling station until the tank is close to 'E'.

Consider this. A company builds 1 PerfectPump for every car built. Do they make most of their $$ off those oem pumps that last forever under any & all circumstances, for that model year
OR,
Do they make most of their $$ on replacement parts over the years, by building an Imperfect Pump they know they will get paid to replace every time one goes bad??????????

I found this out through test... My car is carburated so my fuel pump used to work with the car in on position (not anymore) And my car had no gas what happens in that setup is there was not enough gas to push through the regulator and since I had a return line it always ran through the fuel pump but not enough fuel pressure to make it to the engine To simplify it it just recycles.

So your return line does alot in keeping that fuel pump cool.

It only recycles when you have more than enough pressure.

So how long would it take the pump to overheat with no load on it? (reduced load, anyway)

GL

IMHO, fuel pump life is directly related to how long you run it with a clogged fuel filter. A clogged filter increases the load on the pump, which greatly reduces its life. Most cars will run fine and you cannot even tell it is clogged until you take it off and try to blow thru it! Then you wonder how it even runs with a fuel filter clogged that bad.

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Tim
Red 88 Formula Auto 2.8 100K+ Miles - Hypertech - No Cat - No EGR

Logic is a systematic method of coming to the wrong conclusion with confidence!

quote Originally posted by theogre: The key is that the pump must always have fuel to move. Any liquid fuel is more than cool enough to preserve the pump. The only thing that matters is the pump must never run dry. You can kill many types of pumps in minutes, even seconds, by running them dry.

I agree that fuel flow is the key. No pump is 100% efficient. A portion of the power input to the pump is converted to heat even in a normally functioning pump. That heat is removed by the fuel flowing through the pump. It doesn't matter that much if the fuel 100 'F or 50 'F. What you're trying to protect against is running it dry where there is no heat removal and friction will eventually cause some very high temperatures.

Now as a practical matter I know I ran my '84 out of gas more than once over the years. I don't know for sure what the breaking point on the pump is but running dry for a few seconds never hurt it.

Just why would you want to run the fuel pump with no fuel to pump?? I would not run a fuel pump EVER without fuel PEROID.

Nearly all systems with electric pumps, whether the pump is in tank or elsewhere, are constant flow systems. They purposely build the pump to flow more fuel than the engine can use. This way the FP regulator is always returning fuel to the tank. Example: On a car that needs 9-13PSIG you'd run a pump that could make 15-20 and more than the needed volume.

Anything that blocks flow more than it shoud, bad filter, crushed line, bad carb conversion, etc, will make the pump not only work harder but prevent it from dumping heat. You're hitting the poor thing with a double whammy.

Many car makers, GM included, are moving the fuel regulator to the tank. This way the return fuel doesn't get heated in the engine bay. This is being done in part to reduce evaporative emmissions but any thing that keeps the fuel and pump cooler is good. You'll only see one fuel line to the rail/tbi on these engines.

Running the pump with a light load isn't an issue... It is when you run it with no/low fuel movment or worse dry that you can kill them rather quickly.

The car makers expect the thing to occasionally run out of gas and there is some tolerance for dry running. Doing it all the time will kill the pump.

As long as the fuel isn't boiling, the pump doesn't care. If the fuel is boiling you've got allot more serious things to worry about than the pump.

It's also bad to run out of fuel on the dragstrip

quote Originally posted by blakeinspace: Why thank you Don... I did not realize that you, err... knew so much about pumps. I ran the darn thing dry the other day (not the 1st time) so I am just guaging the potential for future trouble. I appreciate the insight Ogre. I would think that the engineers would allow for a pump to be perfectly within spec on 1/8 of a tank or under. It just makes sense for most of America. We simply don't pull into the filling station until the tank is close to 'E'. Now, OTOH, these are the same enigneers that made a water pump gasket that looks remarkably like the outline of the United States, and has 4!!!! different size Torx bolts. Go figure.

I pull up to the pump when my guage is close to 1/4, or 162 trip miles, that is "E" .

Around town, I keep around 1/2 or better in mine. My saying is 'it doesnt cost any more to keep it full than to keep it empty.' The girls are always running out of gas and needing to be rescued because they only have time between cell phone calls to put a few dollars at a time in If the Ferraro gets around a 1/4 tank, you can really hear it humming, gets quiet soon as I fill it up. I think mine is getting ready to go though, same pump that came from the factory so its got 150,000 on it. I think its not up to snuff because the turbo starves a little for fuel now at WOT.

I'm pretty sure it's a centrifugal pump, there shouldn't be much friction. Electric motors heat up under load. If it's not developing pressure, there's not much load on it. I don't think it's a big deal. Being under load with a lack of flow would be much worse.

GL

quote Originally posted by sqoach: It's also bad to run out of fuel on the dragstrip

HEY!!! That's not fair! I almost had that N* convertible... if only I hadn't run out of gas...

quote Originally posted by 86fieroEarl: I found this out through test... My car is carburated so my fuel pump used to work with the car in on position (not anymore) And my car had no gas what happens in that setup is there was not enough gas to push through the regulator and since I had a return line it always ran through the fuel pump but not enough fuel pressure to make it to the engine To simplify it it just recycles. So your return line does alot in keeping that fuel pump cool.

When I carbureted my 2.8 I had a choice on fuel pump. I stayed with the V6 fuel pump and a return line for a couple of reasons.

1. having the return line means the pump does not work as hard when you use a bypass regulator

2. my pump was replaced the year before

3. the 45 psi cycling thru the primary line means that my 6.5 psi I am using for the carb will always have max amount of fuel available.

4. I didn't even consider cooling the pump, just keeping its load light

Arn

quote Originally posted by Tugboat: I'm pretty sure it's a centrifugal pump, there shouldn't be much friction. Electric motors heat up under load. If it's not developing pressure, there's not much load on it. I don't think it's a big deal. Being under load with a lack of flow would be much worse.

Actually I beileve it's a little gear pump. While fuel does provide cooling, it needs "something" to move, otherwise it grinds itself to death.

Ben

Definately not a gear pump, you can blow right through it.

GL

yes the fuel pump WILL FAIL after it is run dry
how long is variable, but it will fail

and remember the gas guage in the fiero is a bad joke
if when you fill the car full with gas the pointer is past the "F" line
it will run dry BEFORE it gets down to "E"

index the gas guage by filling the car and index the pointer RIGHT DEAD ON THE "F" line
you index the pointer by pulling it off the pivot and pressing it back on BY THE HUB not the needle

some people want to mess with the sender in the tank
BUT it sure is eazyer just to move the pointer on the guage
and that saves droping the tank and burning up the pump by running out of gas

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Question wonder and be wierd
are you kind?