Fuel Pump

[NRX]

I was driving during the Wesak heavy traffic with 4 heavy passengers on-board for about 15Kms. After arriving home and switching off the ignition and key taken out I could hear a humming sound (similar to what you get when operating power mirrors) from the back seat area for about 10 seconds. At the same time I felt a strong petrol smell from the outside of the car, the smell went away when the humming sound stopped. I checked under the car for any petrol spots but there was nothing.

My car is a FB13 with an electronic Carb engine and my tank was half full. The next day i drove the car for about 25 Kms with the same load but I couldn't reproduce the issue.

As per my research most Carb engines use a mechanical petrol pump located near the engine, if so what was the sound ?

Here are few things that I think would be useful to isolate the problem

* I usually drive the car only on weekends, the car idles during weekdays

* I pumped petrol about 1 month ago. (Still the tank is half full)

* When I opened up the fuel tank lid right after the above incident happened, instead of usual 'whoosh' suction sound, it gave me a kind of a pressure releasing sound.

Could anyone elaborate on this ?

Edited May 8, 2012 by NRX

[pug306xsi]

why fix anything if there is nothing wrong and you cant specially "reproduce" the sound?

Edited May 8, 2012 by pug306xsi

[NRX]

why fix anything if there is nothing wrong and you cant specially "reproduce" the sound?

It's always good to learn a new thing and, most importantly a petrol smell is not something you can just forget :)

[CARBON B4]

I had a very similar experience myself, this was on a Grand Vitara, the hum was very faint and gradually went away after sometime. It was quite annoying as I simply couldn't pin point from where it was coming from. The sound faded away on its own and I never experienced it again...

[NRX]

I had a very similar experience myself, this was on a Grand Vitara, the hum was very faint and gradually went away after sometime. It was quite annoying as I simply couldn't pin point from where it was coming from. The sound faded away on its own and I never experienced it again...

Was there a petrol smell too ?

[vishkid]

Well, I've noticed this a couple of random times in my Axela too after shutting down the engine at home - no patrol smell, nothing amiss so didn't think much about it.

Would like to know the reason as NRX mentioned though ...

[harshansenadhir]

Are you sure that this model equipped with a mechanical fuel pump? there can be instances where this model equipped with an electrical pump. Assuming if it's an electrical pump, this sounds like a stuck relay since it was driven in relatively hot engine temp (Vesak traffic means very less movement and engine room temp goes up with that kind of routine).

Do some rearch to find out whether this has mechanical or electric pump, if found electric, check the relays and wiring loom coz petrol pump is not suppose to be running after shutting down the engine under any circumstances.

Other assumption is that there is a pump to route petrol vapour inside the tank through the intake and it worked excessively due to some reason. However, i'm still inclined to think it's more relevant to the first assumption, that is petrol pump related.

[CARBON B4]

Was there a petrol smell too ?

No petrol smell..

[NRX]

Are you sure that this model equipped with a mechanical fuel pump? there can be instances where this model equipped with an electrical pump. Assuming if it's an electrical pump, this sounds like a stuck relay since it was driven in relatively hot engine temp (Vesak traffic means very less movement and engine room temp goes up with that kind of routine).

Do some rearch to find out whether this has mechanical or electric pump, if found electric, check the relays and wiring loom coz petrol pump is not suppose to be running after shutting down the engine under any circumstances.

Other assumption is that there is a pump to route petrol vapour inside the tank through the intake and it worked excessively due to some reason. However, i'm still inclined to think it's more relevant to the first assumption, that is petrol pump related.

Harshan, I'm not quite sure about it, the manual doesn't help either. But I see there is a mechanical petrol pump kinda thing under the hood. Check the pic (Highlighted in red)

Is there a possibility to have both electrical and mechanical pumps at both ends, the tank and the engine ? mind you this is an electronic carb

Edited May 10, 2012 by NRX

[VVTi]

Harshan, actually some cars have their puumps running before and after engine start and shut down. Our Punto, when you open the driver side door, the pump starts. It's a very audible and very clear. But that has a safetly mechanism where the pump sucks out all the fuel from teh lines back in to the car and shuts off all valves. When you opne the door, it pumps fuels in to the fuel rails to prepare for engine start.

My BIL's fomer Swift had the pump running for about 2 mins after shut down of the engine. Had it checked and A*W and they said it was normal for that model. it was the rare AWD model.

[harshansenadhir]

This surely is a fuel pump. Yes, there can be a feed pump in the tank although the mechanical pump exists to avoid starting delays. Why don't you give a peep by removing the rear seat cusion? or just forget it until that happens next time. Also give a look into the relay diagram to find out whether there are any relays meant to power a fuel feed pump.

[harshansenadhir]

Harshan, actually some cars have their puumps running before and after engine start and shut down. Our Punto, when you open the driver side door, the pump starts. It's a very audible and very clear. But that has a safetly mechanism where the pump sucks out all the fuel from teh lines back in to the car and shuts off all valves. When you opne the door, it pumps fuels in to the fuel rails to prepare for engine start.

My BIL's fomer Swift had the pump running for about 2 mins after shut down of the engine. Had it checked and A*W and they said it was normal for that model. it was the rare AWD model.

Thanks mate. Yes running the pump to load the lines before start is understood. But running a pump (assuming it's a feed pump) for this long after engine shuts off i have never encountered, may be as you said if it drains the lines, but I doubt that kind of a mechanism exists in FB13, specially it's being a carb model.

I may be wrong, but my assumption was a stuck relay or foul electric supply causing the feed pump to work extra longer than expected, what do you say?

[NRX]

This surely is a fuel pump. Yes, there can be a feed pump in the tank although the mechanical pump exists to avoid starting delays. Why don't you give a peep by removing the rear seat cusion? or just forget it until that happens next time. Also give a look into the relay diagram to find out whether there are any relays meant to power a fuel feed pump.

Harshan, what's weird is I have never heard this pump sound when the car is running/idle( may be because of the engine sound ), or after switching on the key.

The manual is a headache, all I could found was the US model manual (Sentra, which is EFI ) this car is a non JDM one imported brandnew so the car is a bit different. and it's from the last batch of B13 (1994 Jan).

I'm looking in to a B13 pulsar manual, let's see if that helps

Edited May 10, 2012 by NRX

[NRX]

Double post!

Edited May 10, 2012 by NRX

[VVTi]

Hearing the pump running when the engine running is normal. But now I am starting to think that it might be a stuck relay as Harshan mentioned. Why dont you check the fuse box and pull out the fuel pump relay, if there is one, and give it a tap and see if the problem rectifies.

[vishkid]

I found in Mazda 3 forums that this - confirmed fuel pump related - noise is quite common. There apparently are a couple of relays running after engine shutdown and takes care of returning fuel to tank and such stuff. Doesn't give a very clear explanation but no one had a 'issue' or a bust pump because of this. Must look at the repair manual.

[Malaka2]

Long time ago I had seen this same thing in my brother's N16. After battery change of removal it occurred every time. Agents said it about the ECU or central computer( I don't know what it means) resetting it self for new parameters. They also said it goes 15-20 KMs to all set.

Edited May 10, 2012 by Malaka2

[jdnet]

edit: dont want to anger peri.

Edited May 10, 2012 by jdnet

[shanX]

I think I notice the same thing in my car, I thought this might be the petrol that returns to the tank from return lines..

[T-Bag]

No straight answer until I hear the sound some day in my car.

[sira]

I was driving during the Wesak heavy traffic with 4 heavy passengers on-board for about 15Kms. After arriving home and switching off the ignition and key taken out I could hear a humming sound (similar to what you get when operating power mirrors) from the back seat area for about 10 seconds. At the same time I felt a strong petrol smell from the outside of the car, the smell went away when the humming sound stopped. I checked under the car for any petrol spots but there was nothing.

My car is a FB13 with an electronic Carb engine and my tank was half full. The next day i drove the car for about 25 Kms with the same load but I couldn't reproduce the issue.

As per my research most Carb engines use a mechanical petrol pump located near the engine, if so what was the sound ?

Here are few things that I think would be useful to isolate the problem

* I usually drive the car only on weekends, the car idles during weekdays

* I pumped petrol about 1 month ago. (Still the tank is half full)

* When I opened up the fuel tank lid right after the above incident happened, instead of usual 'whoosh' suction sound, it gave me a kind of a pressure releasing sound.

Could anyone elaborate on this ?

This is the fuel tank gas pressure and when ever the tank get shaked (slow run stop and pickup) , there will be a high pressure gas will be generated in the tank. best thing open the fuel tank cup and you will hear gas discharge sond. it is normal for some cars. even my Honda had same issue when the tank is some where 25% fuel

[sira]

If this car Brand new imported, then Oxigon sensor will not be there