Vs Fuel Pump and LPG

[demenace]

Hi all, ive a '96 Vs Berlina, recently the fuel pump as become noisy, suspect its time to have it changed, however, being xmas time, not many places are open.
On a Vp comm I had, the fuel pump didnt run when i was running on LPG, can I do the same to the Vs?? Ive removed the fuel pump fuse while running on LPG and the car stopped, I then removed the fuel pump relay when running on LPG and the car stopped. Is there something I can do to turn off the fuel pump so the car wont stop when on LPG?
thanks heaps...

 

[dufus]

Hi all, ive a '96 Vs Berlina, recently the fuel pump as become noisy, suspect its time to have it changed, however, being xmas time, not many places are open.
On a Vp comm I had, the fuel pump didnt run when i was running on LPG, can I do the same to the Vs?? Ive removed the fuel pump fuse while running on LPG and the car stopped, I then removed the fuel pump relay when running on LPG and the car stopped. Is there something I can do to turn off the fuel pump so the car wont stop when on LPG?
thanks heaps...

The ability to drive with the fuel pump not going might depend on what gas system you are using. I know when my cars fuel pump died I could still drive around on gas and did for 3 days until my mechanic got a fuel pump to replace the dead one, thats an almost 10 year old Impco system so yours might be different.

 

[Not_An_Abba_Fan]

It depends on how the system is wired. Maybe the gas pump gets it's power from the pump side of the relay. The pump shouldn't run when it is switched to gas. Who ever wired it could have just wired the switch to disable the injectors, rather than the whole EFI system.

 

[commsirac]

Not to sure on what is meant to happen here, and what follows is just me thinking out loud.

One recommendation of the system is to not let the petrol fall below 1/4 full......one theory for this is that if the tank is run empty and the car still operated on gas then the petrol pump continues to run and can be damaged by not having any fuel going through it.
Why isnt there a simple switching off of the petrol pump while on gas? Not sure, though think its probably connected to full throttle acceleration on the fact mixer systems where petrol is also used......for instant response the fuel line needs to be pressurised and hence the petrol pump operating continuously.
Also in the fact mixer system, petrol is needed for startup on lpg.....so pump is primed.

I dont know about the system demance has, even if it is not a fact system it possibly operates in the same way and switching out the fuel pump may make the car impossible to start on lpg.

The car has fail safe features to cut power to the fuel pump if the engine stops......possibly the lpg solenoid electricity supply has just been piggy backed onto the petrol pump output relay which is controlled by the ecu and has an in series switch for petrol only use.
possibly if you go to the petrol tank there is connections for the fuel pump at that end, try removing those and see how you go it may leave the lpg connections intact at the other end.

 

[JBDrifter]

Most systems actually have the car start on petrol, kicking over to LPG automatically once your engine hits 1000rpm or something. I would say this is most likely your problem... without a working fuel pump your car is unable to start.

Could be wrong though, your system may be different. But I'd suggest just put up with the noisy pump until you can get it fixed.

 

[demenace]

thanks everyone for your help, I got under the car and unplugged the fuel pump and the motor still ran, so, looking at the fuel pump relay, i can see the gas man spiced his wire to the wire that goes from the fuel pump relay to the fuel pump, which explains things, so...even if the fuel pump dies, the lpg will still function. I think the injectors only are disabled when switched to gas. the system used is a gastech.
Regards

 

[commsirac]

Excellent ^, thought that would work........have you done a cold start with it like that yet?

 

[94 Stato V8]

thanks everyone for your help, I got under the car and unplugged the fuel pump and the motor still ran, so, looking at the fuel pump relay, i can see the gas man spiced his wire to the wire that goes from the fuel pump relay to the fuel pump, which explains things, so...even if the fuel pump dies, the lpg will still function. I think the injectors only are disabled when switched to gas. the system used is a gastech.
Regards

I had a bit of a wire melting problem behind the dash (trailer lights earthed out) and did some funny things to all sorts of accesories. 1 thing it did was make the fuel pump stay on even when on gas (which it never used to). I tried pulling fuse too and it killed the gas, I then pulled the relay, that killed the fuel pump, but not the gas. I then wired in a relay after the fuel pump relay on the fuel pump feed wire that switches off the pump when it gets power from the gas solenoid. Problem solved!!!
I always start my cars when cold on petrol and turn to gas after a couple of minutes, they start heaps quicker and dont freeze up the gas convertor in winter too.

 

[Cheap6]

This highlights that with LPG systems where the installer makes the decision as to how to do things a variety of solutions amy be used. One reason the installer may choose to power the LPG system off the fuel pump relay is to ensure that the LPG system is not able to work with the engine stopped, which is a legal requirement to meet AS 1427.

 

[commsirac]

One reason the installer may choose to power the LPG system off the fuel pump relay is to ensure that the LPG system is not able to work with the engine stopped, which is a legal requirement to meet AS 1427.

Id of thought they'd use the ecu output to the petrol pump in some way every time.......no hardware needed. Is it done in another way with the fact systems?