Fuel tank issue

[Alecb]

So my legnum will start surging when I have under 1/4 Of a tank of gas to the point where I can't even drive iv removed the fual pump to find all the fuel Is in one side of the tank and isn't pumping to the Side with the fuel pump anyone had this problem before. Any advice would be much appreciated

[Nick Mann]

I've never heard of that before.
I've heard of surging when the fuel pump relay/resistor starts failing. The fuel pump runs at approximately 7 volts until you press the throttle enough to trigger a switch to 12 volts. The relay and resistor are mounted on the bulkhead.

[mitsiboyblue]

So my legnum will start surging when I have under 1/4 Of a tank of gas to the point where I can't even drive iv removed the fual pump to find all the fuel Is in one side of the tank and isn't pumping to the Side with the fuel pump anyone had this problem before. Any advice would be much appreciated

Hi there Alecb, i think..... i can explain your problem so read carefully why fuel is being left in the passenger / NS of the tank, there are a few possibilities.
I have described both vehicle condition based and Synario based for your vehicle as ive had experience of this problem years ago and studied the system.

Condition Based:
* Damaged or blocked pipework on the return side to the tank, this can be anywhere from the collapsed rubber hoses in the engine bay to crushed metal pipework along the floor panel under the car, so it's worth checking this first.
* Air leak to the siphon chamber at the pump unit, so while you have the pump out check for security of the fuel transfer hoses, clips and all the plastics of the assembly for cracking or separation of the moulded sections where air might enter when fuel levels are low.
* Worn out / tired fuel pump
* Partially blocked fuel filter, or a restriction on the delivery side,this can be over looked sometimes as a possible cause which will explain itself further in this post.

Synario Based:
* You have a worn out fuel pump and / or partiality block fuel filter with poor delivery but suppling just enough pressure to run the engine, but leaning out dramatically under acceleration enrichment or engine load, thus getting very little fuel return to the tank after the injection cycle.
* You have fitted a 'Rising Rate/ Boost Sensitive' fuel regulator and noticed you can't acheive the fuel pressure your aiming for and adjusted the regulator to maximum, literally closing off any return fuel to the tank.
Now i will explain!
I have attached a digital picture of the fuel pump module and edited some areas with coloured dots to identify fuel movements See key:

Green Dots: Fuel transfer pipe from passenger / NS of the fuel tank
Blue Dots: Fuel from engine return side of the injection rail
Red Dot: Siphon chamber

Part of your integral fuel pump module is a siphon chamber, this chamber is designed to pull the fuel from the passenger / NS of the tank over to the pump swirl pot side. It does this by using the returned fuel from the injection rail through the siphon chamber. If you have very low or no return on this line you will have no fuel transfer in the tank, This design of transfer is not the most efficient but is affective while the vehicle is running, this is most likely to your problem.

Hope this info helps in your diagnosis
Dave O






Sent from my SM-G930F using Tapatalk

[Alecb]

If there's more than 1/4 Of a tank the car runs beautifully and pulls hard I deffenty think it's not returning from passenger side of tank to drivers Side. I found that the p side is full and d side is almost empty I syphond the fuel from p side to d side and started it I took the line of the p side and it waz sucking gas into the p side instead of pushing it. I also noticed a small black tube coming off the bottem of the return line on pump (where the green and blue dots meet and come out into tank) but there isn't one it the pic of that one can anyone tell me if that's supposed to be there or not will get a pic up 2mw to compere

[mitsiboyblue]

If there's more than 1/4 Of a tank the car runs beautifully and pulls hard I deffenty think it's not returning from passenger side of tank to drivers Side. I found that the p side is full and d side is almost empty I syphond the fuel from p side to d side and started it I took the line of the p side and it waz sucking gas into the p side instead of pushing it. I also noticed a small black tube coming off the bottem of the return line on pump (where the green and blue dots meet and come out into tank) but there isn't one it the pic of that one can anyone tell me if that's supposed to be there or not will get a pic up 2mw to compere

Take the black tube or what ever it is off on bottom of the return im sure its not supposed to be there. if when you put the fuel pump assembly back into the tank and the end of that pipe is touching the bottom of the swirl pot it will be restricting the return flow which will also prevent siphoning from the passenger side of the tank.
There must be at least a 10mm clearance from the end of that pipe to the bottom of the pot to allow an unrestricted flow.
Please do take a picture and post it, im very interrested to see what this pipe is?
Dzve O

Sent from my SM-G930F using Tapatalk

[mitsiboyblue]

Take the black tube or what ever it is off on bottom of the return im sure its not supposed to be there. if when you put the fuel pump assembly back into the tank and the end of that pipe is touching the bottom of the swirl pot it will be restricting the return flow which will also prevent siphoning from the passenger side of the tank.
There must be at least a 10mm clearance from the end of that pipe to the bottom of the pot to allow an unrestricted flow.
Please do take a picture and post it, im very interrested to see what this pipe is?
Dzve O

Sent from my SM-G930F using Tapatalk

Please look again at my picture and see the rubber button on the end of pump securing bracket, when situated back in the tank and tight this rubber button will almost or will be touching the bottom of the swirl pot. so compere the high of this to the pipe you have on the end of the return. If it is longer then it must be a restriction so remove it if possible.
DaveO

Sent from my SM-G930F using Tapatalk

[Alecb]

IMG_20180917_111217.jpg

[Alecb]

IMG_20180917_111217.jpgIMG_20180917_111205.jpg

[mitsiboyblue]

IMG_20180917_111217.jpgIMG_20180917_111205.jpg

Yes! .... 100% take it off, it sould have never been put there, this is your problem. and the pipe has also collapsed.
Dave O

Sent from my SM-G930F using Tapatalk

[Nick Mann]

I completely agree with Dave. That black pipe should not be there.

[Alecb]

Pipe removed and problems gone thanks guys I still am puzzled as to how to hell it got there or what the person waz smoking haha

[mitsiboyblue]

Pipe removed and problems gone thanks guys I still am puzzled as to how to hell it got there or what the person waz smoking haha

HAPPY DAYS

Sent from my SM-G930F using Tapatalk

[EvilDmen]

Alecb, I've been getting exactly this issue for the last week! Is the pump easy to get out?

Thanks in advance.

Lee.

[elnevio]

Remove the rear seat base (two pull-tabs on the front edge) and the fuel pump assembly is under the passenger side. Undo the connector and the large plastic locking ring to remove it all.

[EvilDmen]

Is that it? Awesome. *Goes to have a look*

[EvilDmen]

What's the correct way to remove the ring please?

[elnevio]

What's the correct way to remove the ring please?

Usually to tap it relatively gently with a large flat head screwdriver and hammer, until it starts unscrewing.

[EvilDmen]

It was bending the fin I was tapping, so I wanted to know a none damaging way.

[mitsiboyblue]

It was bending the fin I was tapping, so I wanted to know a bone damaging way.

Couple of pointers,
* lube the plastic ring with some spray grease or WD40 before trying to loosen the ring
* Yes you can use the large flat blade screwdriver and hammer and tap gently to turn the ring counter clockwise. If the tabs are bending choosing another tab if accessible
WARNING
Please make sure that when the ring starts to turn hold the fuel pump assembly and pipework as tight as possible while loosing the ring SO IT DOES NOT TURN.
Paint mark the possition and use it as a reference point at all times.
Otherwise you will bend the fuel gauge float mechanism and damage the electronic sender as it sits in quite a tight rectangular section of the tank (swirl pot)
Dave O

Sent from my SM-G930F using Tapatalk