Fuel Injection System danger: Truth or Hoax?

**archielew** · May 6th, 2013 04:53 PM

Hi All,

Nabasa ko lang sa isang comment sa Yahoo! Nagcomment sya dun sa balita na Filipino Bride sa US na nasunog sa loob ng Limo. Gusto ko kasi sana iverify kung totoo yung comment nya, and I guess here is the right place, since marami ditong experts. Here is what the comment said,

"This is really very sad, I almost experience this situation in my car, Just want to share to everyone, I don't want to name the brand of my car since most of the new model cars are having the same system specially the cars with Fuel Injection system. Most of these fuel injection system cars that are having Fuel Pump motors submerged inside the fuel tank are dangerous.
How does it work:
1. The submersible pump is build with sealed type motor that works to pump the fuel from your tank then distribute to your injection system, it work simultaneously whenever you turn your key to ON position and start the ignition.
2. The sealded type submersible pump motor, are normally subjected to worn out and sometimes they are replace with alternative replacement or even sometime original parts.
3. This submersible motor pump sometimes if not properly check and maintain they cause fire due to the pump is powered by 12VDC,and when the submersible motor pump is malfunction, let say the brush inside this motor is worn out and the moror will not run or wont turn its armature, there will be heat generated from this malfuction motor and when the heat comes to extreme, this will cause explosion from your fuel tank, this is because it ignites the fuel inside your fuel tank.

This is an experience that I observed when my well conditioned car suddenly stopped, then I tried to re-start it wont start anymore, through my trouble shooting experience, I finally come to indentify the submersible motor pump that does not work but when I'm trying to remove it I felt extreme heat from this device, I then consulted a very experience electro/mechanic and he says, "Your lucky to find out the problem or else you will surely cook alive inside you car" Thanks God it din't happen... BE CAREFULL guys."

Totoo po kaya to?

**jick.cejoco** · May 6th, 2013 05:22 PM

Originally Posted by archielew

Hi All,

Nabasa ko lang sa isang comment sa Yahoo! Nagcomment sya dun sa balita na Filipino Bride sa US na nasunog sa loob ng Limo. Gusto ko kasi sana iverify kung totoo yung comment nya, and I guess here is the right place, since marami ditong experts. Here is what the comment said,

"This is really very sad, I almost experience this situation in my car, Just want to share to everyone, I don't want to name the brand of my car since most of the new model cars are having the same system specially the cars with Fuel Injection system. Most of these fuel injection system cars that are having Fuel Pump motors submerged inside the fuel tank are dangerous.
How does it work:
1. The submersible pump is build with sealed type motor that works to pump the fuel from your tank then distribute to your injection system, it work simultaneously whenever you turn your key to ON position and start the ignition.
2. The sealded type submersible pump motor, are normally subjected to worn out and sometimes they are replace with alternative replacement or even sometime original parts.
3. This submersible motor pump sometimes if not properly check and maintain they cause fire due to the pump is powered by 12VDC,and when the submersible motor pump is malfunction, let say the brush inside this motor is worn out and the moror will not run or wont turn its armature, there will be heat generated from this malfuction motor and when the heat comes to extreme, this will cause explosion from your fuel tank, this is because it ignites the fuel inside your fuel tank.

This is an experience that I observed when my well conditioned car suddenly stopped, then I tried to re-start it wont start anymore, through my trouble shooting experience, I finally come to indentify the submersible motor pump that does not work but when I'm trying to remove it I felt extreme heat from this device, I then consulted a very experience electro/mechanic and he says, "Your lucky to find out the problem or else you will surely cook alive inside you car" Thanks God it din't happen... BE CAREFULL guys."

Totoo po kaya to?

do it right and leave it to the professionals.
the fuel pump fuse should have cut off the circuit once the current was excessive. this could be caused by too thick of fuel ( stale fuel)or from worn out bearings or pump impeller. the fuel pump does not cause ignition inside the fuel tank since there is absence of air or oxygen (remember; liquid gasoline does not burn). even if the tank ran out of fuel, the fuel strainer sock would still be soaking in gasoline preventing air from getting into the pump motor. the possible cause of the ignition could be the wire lead inside the tank connected to the positive terminal of the fuel pump

**fourtheboys96** · May 6th, 2013 05:24 PM

OT. Sumakit ata ulo sa pag-intindi nung ng comment na iyon.

Well, first I am not an engineer.
It may seem logical that gasoline (fuel) together with an electrical-mechanical device (fuel pump) is a recipe for a fire accident.
But if I am right, it is improbable to create combustion when the fuel pump is submerged because you need oxygen for the combustion process to occur.

The probability is therefore very low for this to happen. Although I don't have the exact statistics, the fact that we don;t hear problems about this kind of fuel delivery system and it is still being used today means my thoughts are right.

**niky** · May 6th, 2013 05:59 PM

The chances of your car catching fire from a fuel pump are much, much lower than the chances of it catching fire from myriad other reasons. More cars catch fire from improperly fastened oil filters than from defective fuel pumps.

-

As jick says, there are fuses in the system to prevent heat build-up. There also needs to be the right proportion of oxygen and fuel vapors in the tank to cause a fire... it's actually not that easy to set gasoline on fire inside the tank.

And, in my experience, a modern fuel pump is not that finicky or hard to replace. You buy the whole thing as an assembly and it slots right in. It's not rocket science.

**EssB** · May 6th, 2013 07:28 PM

1. Electric fuel pumps do not immediately start whenever you put the key in ON position. Fuel pump circuit-opening relay coil would only be triggered when you turn the key to Start position -- and will continually run as long the ECU gives the trigger signal to relay coil (according to crank angle sensor signal). So when your engine stalls, the fuel pump also stops even if your key is still in ON position.
2.
3. Fuel pump generated heat is actually dispersed into the fuel. Even if the DC motor windings short circuit generate sparks, it would not start fire as there is very low oxygen concentration inside the fuel tank. The electric fuel pump power source also got a fuse protection.

**jick.cejoco** · May 6th, 2013 07:36 PM

Originally Posted by EssB

1. Electric fuel pumps do not immediately start whenever you put the key in ON position. Fuel pump circuit-opening relay coil would only be triggered when you turn the key to Start position -- and will continually run as long the ECU gives the trigger signal to relay coil (according to crank angle sensor signal). So when your engine stalls, the fuel pump also stops even if your key is still in ON position.
2.
3. Fuel pump generated heat is actually dispersed into the fuel. Even if the DC motor windings short circuit generate sparks, it would not start fire as there is very low oxygen concentration inside the fuel tank. The electric fuel pump power source also got a fuse protection.

Electric fuel pumps do not immediately start whenever you put the key in ON position

you got this all wrong sir. the fuel enable program of the pcm/ecm/ecu runs the fuel pump between two to three seconds to pressurize the fuel rail for easier start up. fuel control varies from model to model. some are pulse width modulated, some are returnless systems, some safety features like inertia switch (ford systems-cuts off fuel pump operation upon impact), some safety features prevent fuel pump operation when there is no oil pressure ( general motors systems) and some systems cut off fuel pump operation when vehicle rolls over. too many different systems but they all pre-pressurize the fuel rail before you even crank the engine

**lowslowbenz** · May 6th, 2013 07:45 PM

^
Yes, the pump activiates the instance the key is turned. Yes, some vehicle models are equipped with an inertia switch. There are some models where a sudden drop in pressure along the fuel lines, cuts off fuel pump operation.

On MB's .. once you hear the fuel pump going "bzzzzzt" before start-up, its a clear sign its going south na.

We had a dose too much of Hollywood movies .... sorry I just got to say that ..

**archielew** · May 6th, 2013 11:45 PM

Thanks sa inyo. Mabuti pala't naipost ko to dito, madami akong natututunan paunti unti.

**EssB** · May 7th, 2013 12:10 AM

Originally Posted by jick.cejoco

Electric fuel pumps do not immediately start whenever you put the key in ON position

you got this all wrong sir. the fuel enable program of the pcm/ecm/ecu runs the fuel pump between two to three seconds to pressurize the fuel rail for easier start up. fuel control varies from model to model. some are pulse width modulated, some are returnless systems, some safety features like inertia switch (ford systems-cuts off fuel pump operation upon impact), some safety features prevent fuel pump operation when there is no oil pressure ( general motors systems) and some systems cut off fuel pump operation when vehicle rolls over. too many different systems but they all pre-pressurize the fuel rail before you even crank the engine

Umm... on most car manufacturers today, the fuel system is one of those you mentioned. Though as an example, on older Toyotas fuel pump circuit opening relay is wired the way as I have stated above.

**jick.cejoco** · May 7th, 2013 08:34 AM

Originally Posted by EssB

Umm... on most car manufacturers today, the fuel system is one of those you mentioned. Though as an example, on older Toyotas fuel pump circuit opening relay is wired the way as I have stated above.

still wrong sir. on older toyota, they have "luft" type or "L" type fuel injection where it uses a vane or flap type airflow meter which has a mechanical switch in the airflow mete that closes if there is airflow that deflects the vane other than fully closed position. before there is sufficient airflow, the ecu, as what toyota called it before, "enables" the circuit open relay for two to three seconds to pre-pressurize the fuel rail. so, on the toyota you mentioned, the fuel pump is enabled two ways, KOEO (key on engine off) runs for 2-3 seconds and the closing of the FC (fuel pump control) terminal of the airflow meter against E1 (earth 1 or engine ground) thereby closing the circuit to the circuit open relay to close the +B to FP (fuel pump positive lead)