Fuel pressure issue

[PSDOWN]

So I tried to replace the stock pump with a walbro GSS342 unit. 1st time I tried i tried to put the little plastic cap from the stock pump onto the walbro, didn't work too well as the car was hesitating (the cap came off). I've also noticed that when I switch the car off, the car is more difficult to start next day, seems like there are no fuel pressure in the line. So I took the little cap off, and the hesitating was gone, but I'm still losing fuel pressure when the car is switched off. I then replaced the stock pump and put it back everything the way it was, but the problem still persist? I'm a bit puzzled as to what could've gone wrong? Before I did the whole exercise, the car would starts in just a second, and now it needs about 3 seconds to crank after leaving it for just a few hours. Once it starts, it drives fine without any issues.

Is the fuel pump suppose to prime when I put the key to acc? I don't hear it prime at all. Please help.

PS. Car is a 97 Legnum vr4, pretty much all stock.

[Nick Mann]

The seal is not sealing on the pump, where the feed pipe from the pump goes in to the pump housing assembly. There should be an O ring on there, if the O ring is not sealing then the fuel can drain back and it takes 3-4 seconds of cranking to get the fuel back through all the lines.

[PSDOWN]

I did put the oring back and there is also a little plastic seating underneath that. It seems to be ok, but I will get a new one just in case.
Can I possibly put 2 in just for good measure?

Oh and do I need to buy fuel resistant o ring or any o ring will do? Thanks

[Davezj]

i believe Viton is oil and fuel resistant and is a comon material to have oring made from.

below is only for TRE GSS342 fuel pumps not walbro type.

i am not saying this is anything to do with you fueling issue but you will need to do it as you may shorten the life of your new fuel pump if you do't do it.

what you do have to remeber is the the TRE GSS342 fuel pump needs a 12V power supply all the time, it does not like to run on 7V. the stock factory setup on the car only feeds 7V to the fuel pump when the car is at idle, and as soon as you start driving off the voltage is switched to 12V.
This is designed to reduce the noise of the fuel pump when sitting in the car at idle, e.g. when sat in traffic.

you need to bypass the voltage dropping resisitor on the bulkhead in the engine bay. there is a relay sat next to it and at idle the relay switches and put the resistor in line with the power feed to the fuel pump and drops the 12V to about 7V, so if you cut the wires going to the resistor from the relay and join the wires together coming from the relay, the relay will still switch on and off at idle but the voltage to the fuel pump will stay at 12v always.

As you have fitted a walbro GSS342 255pL fuel pump you do not need to do this as it is happy to run on less voltage at idle, but if you had fitted the TRE GSS342 it would not be.

[TAR]

Davezj - the Walbro GSS342 pump is a 255lph pump (maybe you mean the TRE pump?)

:happy:

[Davezj]

sorry yes when i saw the reference to GSS342 i assumed it was TRE.

i will edit the above post to make this apparent.
thanks Tim well spotted.

[rajvr497]

the same thing happened to me the first time i installed my walbro,i'm sure it's the O ring seal,what i did was i took out the plastic seating and instead i placed a 5/16'' piece of gas hose the same height of the plastic seating and then i placed the O ring on top the hose and fitted it up into the the housing and till now it works great....

[Kenneth]

My TRE fuel pump has worked fine for years with no modifications to the standard wiring. Nice and quiet too.


i believe Viton is oil and fuel resistant and is a comon material to have oring made from.

below is only for TRE GSS342 fuel pumps not walbro type.

i am not saying this is anything to do with you fueling issue but you will need to do it as you may shorten the life of your new fuel pump if you do't do it.

what you do have to remeber is the the TRE GSS342 fuel pump needs a 12V power supply all the time, it does not like to run on 7V. the stock factory setup on the car only feeds 7V to the fuel pump when the car is at idle, and as soon as you start driving off the voltage is switched to 12V.
This is designed to reduce the noise of the fuel pump when sitting in the car at idle, e.g. when sat in traffic.

you need to bypass the voltage dropping resisitor on the bulkhead in the engine bay. there is a relay sat next to it and at idle the relay switches and put the resistor in line with the power feed to the fuel pump and drops the 12V to about 7V, so if you cut the wires going to the resistor from the relay and join the wires together coming from the relay, the relay will still switch on and off at idle but the voltage to the fuel pump will stay at 12v always.

As you have fitted a walbro GSS342 255pL fuel pump you do not need to do this as it is happy to run on less voltage at idle, but if you had fitted the TRE GSS342 it would not be.

[PSDOWN]

Thanks guys. :) i'm going to try to source some new oring and try. I also ordered a DW 200 pump as i heard they are quieter. The evo kit comes with 2 oring

[Davezj]

My TRE fuel pump has worked fine for years with no modifications to the standard wiring. Nice and quiet too.

I can only go by what the instruction say with the pump, and it says don't run it at less then 12V.
i am happy that your pump is still running well, but i was not going take the chance after reading the instruction.
maybe we can get away with it.

[Davezj]

Thanks guys. :) i'm going to try to source some new oring and try. I also ordered a DW 200 pump as i heard they are quieter. The evo kit comes with 2 oring

aren't the evo fitment pumps different to the VR4 requirements, the pipe come out on the opposite side.
isn't this the issue we had with the original gooup buy we got TRE GSS341 which were evo fitment pumps and they did not fit the VR4.
I could be mistaken but i thought htis was the case.

[TAR]

After re-reading your initial post, I think that the sealing ring between the tank and the fuel pump assembly is not seated or worn.

These seals are notorious for expanding when removed and require cooling in the freezer to get them to shrink again. I have personally had this issue on 2 cars. The first required a new seal, the second was OK after freezing it for an hour.

:happy:

[swinks]

aren't the evo fitment pumps different to the VR4 requirements, the pipe come out on the opposite side.
isn't this the issue we had with the original gooup buy we got TRE GSS341 which were evo fitment pumps and they did not fit the VR4.
I could be mistaken but i thought htis was the case.
You are :)
It's GTO aka 3000GT pump other way round i.e. GSS 341. Evo pumps are the same, although asssembly is bit different.

[swinks]

After re-reading your initial post, I think that the sealing ring between the tank and the fuel pump assembly is not seated or worn.

These seals are notorious for expanding when removed and require cooling in the freezer to get them to shrink again. I have personally had this issue on 2 cars. The first required a new seal, the second was OK after freezing it for an hour.

:happy:
Big o-ring rubber seal has rather no effect on pump performance. Of course you'll get cabin full of fumes and smell.

[Davezj]

You are :)
It's GTO aka 3000GT pump other way round i.e. GSS 341. Evo pumps are the same, although asssembly is bit different.

so will the evo style fuel pump fit the VR4 you say there is an assembly difference. i am only asking to save this guy some money if will not fit, he can cancel his order.

[swinks]

Yes, pumps are the same.
Evo assembly: http://forums.evolutionm.net/sale-engine-drivetrain-power/494720-fs-evo-8-fuel-pump-housing.html

[Davezj]

I see, the assembly the pump fits into is different in an evo compared to the VR4.

not, the pump assembly is different.

[PSDOWN]

The sealing ring between the pump assembly and the tank seems to be fine. It takes a bit of fiddling to get them to fit properly as they expand, but once its in, its good.

I'm going to replace the pump with a DW unit with new o-ring and see if it solves the problem :-)

[Davezj]

The sealing ring between the pump assembly and the tank seems to be fine. It takes a bit of fiddling to get them to fit properly as they expand, but once its in, its good.

I'm going to replace the pump with a DW unit with new o-ring and see if it solves the problem :-)

take note of the alignment of the pump with the tank, if you get the pump twisted in the tank from where it should be the float assembly will snag on the inside of the tank and your fuel gauge will not work, it will get stuck.