Fuel Pump Overheating: Fact or Fiction?

Recently, I saw an auto care video in which the guru claimed that one should not consistently run your car with less than 1/4 tank of gas. Doing so could overheat the fuel pump and cause it to fail or work poorly.

I believe that, if it does happen, it would only happen on some cars in some situations, depending on their designs.

So, Fact or Fiction?
Fact, the gas flows constantly out of the tank to the fuel rails and returns to the tank. The gas cools the pump, but when you get low, crud that settles out in the bottom of the tank, is picked up and can plug the filter which in turn causes more damage to the pump.
 
Fact, the gas flows constantly out of the tank to the fuel rails and returns to the tank. The gas cools the pump, but when you get low, crud that settles out in the bottom of the tank, is picked up and can plug the filter which in turn causes more damage to the pump.

Only on older return-type systems.

Interesting about the crud, I used to think that as well but when I opened up the fuel tank on my 25 year-old BMW the tank was essentially pristine and there was very little crud on the pump sock, same as my almost as old Accord last summer. Maybe the gasoline you're getting in your area or at your station is particularly bad?

And why wouldn't the crud always be at the bottom of the well regardless of how much fuel is in the tank?
 
The lower the fuel level, the hotter the fuel gets. As said above this could also result in an intermittent supply which isn't good for any pump.

Consider modern fuel injection systems operate at 20,000+ psi.

I would have to agree with this. Fuel pumps do in fact get cooled by submersion, less fuel in the tank less fuel to circulate. Some Diesels like the GM 6.6L have a fuel cooler on the return line mounted right by the fuel tank.
 
Only on older return-type systems.

Interesting about the crud, I used to think that as well but when I opened up the fuel tank on my 25 year-old BMW the tank was essentially pristine and there was very little crud on the pump sock, same as my almost as old Accord last summer. Maybe the gasoline you're getting in your area or at your station is particularly bad?

And why wouldn't the crud always be at the bottom of the well regardless of how much fuel is in the tank?

Ford 7.3L Diesels from the factory have "Dead Head" injector systems, but some people, myself included re route the rear on both sides by removing a fuel plug in the heads and make what is call a regulated return system. Only the return side is regulated and the benefit is that any air if any ever gets into the fuel system it can be returned to the fuel tank and not out the injector which is a major down fall of a Dead Head injector system. Air is very bad for Diesel injectors. Air also makes cylinders knock or cackle more than they do already. "Air Bad"
 
Ford 7.3L Diesels from the factory have "Dead Head" injector systems, but some people, myself included re route the rear on both sides by removing a fuel plug in the heads and make what is call a regulated return system. Only the return side is regulated and the benefit is that any air if any ever gets into the fuel system it can be returned to the fuel tank and not out the injector which is a major down fall of a Dead Head injector system. Air is very bad for Diesel injectors. Air also makes cylinders knock or cackle more than they do already. "Air Bad"
I'm guessing you mean the Powerstroke 7.3 HEUI system? The 7.3 IDI in my sig has a regular fuel return system from the injection pump & daisy chained to all 8 injectors, just like the GM 6.2/6.5.
 
I'm guessing you mean the Powerstroke 7.3 HEUI system? The 7.3 IDI in my sig has a regular fuel return system from the injection pump & daisy chained to all 8 injectors, just like the GM 6.2/6.5.

So, your 7.3L I.D.I. does not have the fuel galleries along with oil galleries in the heads with a High pressure oil pump "HPOP" to provide the high pressure to the injectors to push fuel at very high pressures above the 20K range activated electronically by the E.C.M./ I.C.M.

The Caterpillar designed injector system on the 1993/2003 7.3L Powerstroke has a total of 4 Orings, 1 circlip, And 1 copper crush ring. I assume your I.D.I does not have all that mess, your injector system must be somewhat that the same as a 12 valve Cummins.

For the record, the 7.3L Powerstrokes have an external high pressure fuel pump, Or what is considered to be a High pressure fuel pump until the Bosch common rail system came out in 2001 on the GM Duramax. The 7.3L Powerstroke fuel pump is in the range of 60/80 psi If I recall.

https://www.hotshotsecret.com/history-of-the-heui/
 
Last edited:
If you are getting condensation in the tank, you have bigger issues. It is a sealed system.

Does the fuel tank vent valve control the flow of air getting into and out of the charcoal canister not allow air into the fuel tank on a controlled basis? The fuel tank would siphon lock if it did not allow atmospheric air into the tank to displace the fuel consumed. Is the atmospheric air dehumidified at 100% somehow? The fuel used must be displaced by air due to the emissions systems and the positive fuel tank pressure that modern vehicles require for emissions requirements. So, there is the ability for humidity to accumulate in any fuel system. Granted more manufacturers have gone to plastic fuel cell's and that does in fact help somewhat with the accumulation of moisture, but it does still exist.


Not in diesels-many of the issues we had with diesels were caused by running them low & freezing fuel lines or growing fungus in the tank. Fuel gets hot from return fuel or ambient temps, cools overnight-how does the tank not collapse? Most fuel systems have a one-way valve somewhere, to allow air IN.

Mostly I would agree with you, but Fuel gets hot from, or any fluid gets warmed up by P.S.I., its a compression thing. No way around it. Return coolers if needed are the remedy, but alot of older motors don't really need it unless they are tuned and tweaked. Freezing lines on small "Brake Line" sized fuel lines directly to each individual injectors are always going to be a problem. Even the 7.3L Powerstroke with the oil and fuel galleries in the heads cause issues in the cold below 10/15F. The Powerstrokes you can plug in for 45 minutes and they will fire up due to the fuel and oil galleries in the heads and not externally exposed like the I.D.I. you describe.

Fungus in the tank on a diesel needs to be addressed well in advance, it is caused by moister, there are many. Easiest is Power Service Clear-Diesel Fuel & Tank Cleaner available at walmart. One of the better is, Power Service Bio Kleen Diesel Fuel Biocide, Nissan also makes a top notch allege biocide treatment available at class 8 truck truck parts house stores.
 
Does the fuel tank vent valve control the flow of air getting into and out of the charcoal canister not allow air into the fuel tank on a controlled basis? The fuel tank would siphon lock if it did not allow atmospheric air into the tank to displace the fuel consumed. Is the atmospheric air dehumidified at 100% somehow? The fuel used must be displaced by air due to the emissions systems and the positive fuel tank pressure that modern vehicles require for emissions requirements. So, there is the ability for humidity to accumulate in any fuel system. Granted more manufacturers have gone to plastic fuel cell's and that does in fact help somewhat with the accumulation of moisture, but it does still exist.




Mostly I would agree with you, but Fuel gets hot from, or any fluid gets warmed up by P.S.I., its a compression thing. No way around it. Return coolers if needed are the remedy, but alot of older motors don't really need it unless they are tuned and tweaked. Freezing lines on small "Brake Line" sized fuel lines directly to each individual injectors are always going to be a problem. Even the 7.3L Powerstroke with the oil and fuel galleries in the heads cause issues in the cold below 10/15F. The Powerstrokes you can plug in for 45 minutes and they will fire up due to the fuel and oil galleries in the heads and not externally exposed like the I.D.I. you describe.

Fungus in the tank on a diesel needs to be addressed well in advance, it is caused by moister, there are many. Easiest is Power Service Clear-Diesel Fuel & Tank Cleaner available at walmart. One of the better is, Power Service Bio Kleen Diesel Fuel Biocide, Nissan also makes a top notch allege biocide treatment available at class 8 truck truck parts house stores.
No. The charcoal canister allows air to enter the canister, absorb fuel vapours and the go on to to intake manifold to be burned. When it is doing that, it is separated from the fuel tank.

The fuel tank contains fuel and vapours from the fuel. When filling up, those vapours are pushed into the charcoal canister.

Any air in the tank would create a possible explosive environment with all the electrical components in the tank.
 
No. The charcoal canister allows air to enter the canister, absorb fuel vapours and the go on to to intake manifold to be burned. When it is doing that, it is separated from the fuel tank.

The fuel tank contains fuel and vapours from the fuel. When filling up, those vapours are pushed into the charcoal canister.

Any air in the tank would create a possible explosive environment with all the electrical components in the tank.

How does the fuel that is consumed from the tank get displaced by air? Does the Fuel tank collapse as the fuel is depleted.

Are you saying there is "NO" air present in a fuel tank?

Remember, you worked as an Acura or a Honda Tech right? They have metal tanks, no?
 
How does the fuel that is consumed from the tank get displaced by air? Does the Fuel tank collapse as the fuel is depleted.

Are you saying there is "NO" air present in a fuel tank?

Remember, you worked as an Acura or a Honda Tech right? They have metal tanks, no?
How does the fuel that is consumed from the tank get displaced by air? Does the Fuel tank collapse as the fuel is depleted.

Are you saying there is "NO" air present in a fuel tank?

Remember, you worked as an Acura or a Honda Tech right? They have metal tanks, no?
It doesn’t get displaced by air. The vehicle runs the tank at a vacuum. Any vapour pressure comes from the fuel. Any air entering the system would trigger a check engine light due to an evap leak.
 
It doesn’t get displaced by air. The vehicle runs the tank at a vacuum. Any vapour pressure comes from the fuel. Any air entering the system would trigger a check engine light due to an evap leak.

So, by explanation, what happens when you only fill your tank half way? I understand the evap and the vacuum of the evap system. I've had a number of vehicles diagnosed by a trouble shooting tech with a smoke machine that pressurized the fuel system.

How fast can the negative pressure of the evap system turn the remaining half tank of air once I opened the fuel cap into vapor?
 
^^I'd suppose half the vapor in the tank gets pushed out by the incoming fuel, partly through the vehicle's evap system and partly around the pump nozzle to the outside (or recovery system attached to the nozzle in places where that's required).
 
^^I'd suppose half the vapor in the tank gets pushed out by the incoming fuel, partly through the vehicle's evap system and partly around the pump nozzle to the outside (or recovery system attached to the nozzle in places where that's required).
You would be 100% correct in the assumption that the vapor recovery fuel nozzles do in fact have a vacuum system that recovers most all of the vapors coming out of the tank as the gasoline is displacing the fuel vapors.

We don't seem to have them here. They seem to be in more populated area's. I suppose they are really more of an EPA emissions thing and they don't seem to care enough yet about the less populated area's.
 
Question, how many vehicles have blown up due to the most common C.E.L. that is the loose gas cap that brakes the vacuum in the fuel system? It has to be way over the 100k's of vehicles that have been back to the dealer even though it's a "Soft" code which would have reset it's self if the owner would have just clicked the fuel cap a couple of times. Soft codes go away after 3 short engine running cycles with the problem no longer present. hard codes do not. A fuel vacuum leak is a soft code.
 
Back
Top