no voltage at fuel pump

[python_hunter1]

hi ppl. i am having trouble with the gas system on my vr. the car starts and runs fine on lpg, but when i switch to petrol the car just dies. ive checked for voltage at the pump( white round plug) and there is no voltage there when the switch is set to petrol. ive also checked the switch and it is fine. ive only just got the car and have never had it running on petrol. also tried new relays and checked all fuses with no difference. i need to get this fixed asap so i can get the rwc. like i said it will start and run fine on lpg? any help greatly apprecieated

[ephect]

u only get power there for 2-5secs on ignition when the pump primes.. the only way to check it is to be under the car at the plug, and have someone to switch the key to ignition n see if u have voltage

other than that, check ur error codes n see if theres anything else that could relate to petrol side of things

what happens when u try start it on petrol? does it crank? does it try to start but stalls?

[python_hunter1]

yeah there is def no voltage at the pump. i can see my multi meter when turning ign on. the car cranks over really strong but just will not fire.

[ephect]

is it a 6 or 8? did someone turn the key for you? or did u turn the key then get under the car n check voltage?? cause power is only there for a couple secs n wont work like that.
can u hear the pump prime when turning the ignition on?

u can test the pump by placing 12v at the pins from a battery pack to see if the pump works at all.

any codes logged?

[python_hunter1]

the leads on my multi are long enough so as i can see the meter as i turn the ign. no codes have been logged. there is no sound coming from the pump. unfortunatly i dont have a spare batt to test the pump. ive got 10.8 volts at the sender unit though. how likely is it to be the pump even though there is no voltage there?

[python_hunter1]

sorry forgot to mention its a v6

[ephect]

apart from tracing back the wire to the ecu, swapping relays and fuses just to make sure ones not screwy.

u could pull the pump out, apply 12v to see if she still works, if so place it back in the tank, bit of a prick of a job, but doesnt cost you anything. u could pull off the fuel reg on the fuel rail to see if fuel is flowing.

im starting to run out of ideas sorry mate

[tt460]

no need to pull it just run some wire direct from the battery to the fuel pump, only need to be for a bit to make sure it works

[python_hunter1]

so i checked codes and i have code 31.. thieft deterent signal missing. it has an aftermarket alarm and it all works ok.. would this code stop the fuel pump from getting power? thanks ash

[ephect]

yes if the keyhead isnt making contact with the metal surrounds on the ignition barrel properly it cant turn off the factory imobiliser, and wont let the car start.

try bending the metal contacts out a smige to get it to make a better connection.

[python_hunter1]

just tried that and still no good. the thieft light on the centre console also works as it should. any other ideas? this is really getting frustrating

[Helicopter]

hi ppl. i am having trouble with the gas system on my vr. the car starts and runs fine on lpg, but when i switch to petrol the car just dies. ive checked for voltage at the pump( white round plug) and there is no voltage there when the switch is set to petrol. ive also checked the switch and it is fine. ive only just got the car and have never had it running on petrol. also tried new relays and checked all fuses with no difference. i need to get this fixed asap so i can get the rwc. like i said it will start and run fine on lpg? any help greatly apprecieated

The fuel pump gets its 12v from the fuel pump relay via F23 fuse. The fuel pump relay is activated by the EFI computer. As already mentioned, on start up the computer activates this relay for around 3-5 seconds, and if in that time the engine does not start it simply de-activates the fuel pump relay.

Go to:
http://www.memcals.com/pdf/VRV6%20Ma...%20Diagram.pdf

Download the circuit diagram for the V6 and you can clearly see the fuel pump relay.

Unplug the fuel pump relay and check for +12v on point 'O', otherwise F23 is blown.

Alternativelly turn ignition to ON [just to make sure other modules etc that should be on are on] and simply short out the two connections 'O' to 'V' using a bare wire and hear if the fuel pump starts, but only for a few seconds. Thats exactly what I did to verify if the pump was working or not, which in my case it had shit itself.

Last thing, while very unlikely, the +12v wire to the fuel pump could be open.....Not!

good luck.

[python_hunter1]

so i have 12 v power at the o terminal on the relay. bridged out the o and v terminal and it will start and run and gas but there is still no priming of the pump? any other ides folks. the fuses and relays have all been swaped with known good ones. i have 12v power at the f/pump fuse under the bonnet aswell. im starting to think there is a broken 12v wire running to the actual fuel pump. thanks for all your ideas guys

[VrWagz1]

if you got 12v on the line side of the relay then you gotta work out why its not closing and putting power onto the load side. Again try bridging it line-load and see if theres 12v at the purple pump wire at the rear. If not then maybe there is an issue with the wire goin to the back, but would be highly unusual and almost never happens. Its always a burned plug/connector somwhere in that case.

[Cheap6]

If with the o and v terminals jumpered, there is still no power to the pump, it has to be that broken (purple) wire to the fuel pump. One way to check would be to run a test wire all the way from the back of the relay terminal block to the connector at the pump, bypassing the wire in the car. Another is to use the ohmeter function on the multimeter between the same two points.

If it is "broken", the modifications made when the LPG was fitted would be a great place to start - you might find another relay fitted into the fuel pump wire that is (meant to be) switched by the fuel changeover switch (but is not).

[VrWagz1]

If for some reason they cheaped out and broke into the purple wire goin to the fuel pump instead of the coil for the fuel pump on the gas/petrol controller, then there is a good chance some dodgy wiring might have come undone there

[python_hunter1]

thank f#$@ i finally got it sorted. it turned out to have a dry solder joint where the gas fitter sliced into the 12v fuel pump wire. resoldered the wire properly and away it went. took ages to find where the join was though. went through the whole lpg wiring system to find it.......on the up side i changed the rocker cover gaskets and upon taking the covers of i found a nice set of yella terra roller rockers bolted in place the previous owner said the engine had just been rebuilt with lots of performance parts before he got it (i didnt believe that too much as he had no reciepts) and has now only done 15,000 k's. makes me wonder what else was done to it, as it goes extremly harder than any other v6 ive ever been in and that was just on lpg. now its running on petrol its an absolute rocket ship. guess i lucked out on the engine thanks for all your help too guys.