fuel pump wiring dilema???

[GQ Bear]

Nissan Patrol TB42e dual fuel.

OK, got bogged in snow on weekend and ran out of petrol whilst winching. Because of the lean of the vehicle i couldnt pour petrol in so continued to run on gas.
As this dual fuel setup starts on petrol then switches to gas we thought we needed to keep pump powered in order to start car so we kept putting fuses in whenever they blew, untill we ran out of 15amp fuses and started putting 25A's in.
Fuel pump is absolutely toasted. I've replaced it with a new one but it's not working. Here's my dilema.

In order to drop tank out i had to cut wires and i'm 99% sure i've wired it together correctly. 15A fuel pump fuse is ok, fuel pump relay appears to be ok. Cars starts and runs perfectly on gas.

On fuel tank it has 5 wires labelled

EARTH Brown
+ White/purple
?can't read Yellow
- Blue/red
S Yellow/Blue


Gas converter has extended loom with these corresponding wires

E Brown -> brown
+ white/purple -> white
? yellow -> yellow
- blue/red -> red
S yellow/blue -> green

Now using a multimeter, these are voltage figures with key turned on and with engine running

E 0V 0V
+ 0V 13.98V
? 4.5V 5.14V
- 0V 13.96V
S 12.16V 14.15V


Does this make any sense? I don't want to just go swapping wires. It seems strange that NEG is reading 13.96V (shouldn't it read 0V?). The ? terminal seems strange also to have such a low voltage.

The pump does work. I've joined a power source to it directly and it spun.

Thanks for your help
Bear



If i can't fault find this tonight i'll be dropping car to auto elec tommorrow or tuesday = $$that could be spent on another 4wd trip

[-Scott-]

Does anybody have a wiring diagram which can tell us what the 5 wires are supposed to do?

I'm guessing the low voltage line is fuel gauge sender, the + / - lines are the fuel pump motor, and it's negative switching. It would be nice to know what they really do.

[GQ Bear]

The gregory's manual's a waste of time. It only shows one wire going to pump and a earth out. Colours don't correspond either.

[chimpboy]

When you say the fuel pump relay appears to be okay... how sure are you?

Does the pump fire up if you hotwire the relay, either by sending power straight down its output wire or by triggering the relay coil?

Like Scott I was guessing that the ~5V wire might be the gauge sender. And, I have a sneaking feeling that the gauge has three wires going in, so that only two are for the pump.

What would be good would be the multimeter readings with the key turned to off as well.

[GQ Bear]

Problem fixed.

When the gas installer extended the loom he put in a plug from where tank used to be. The earth wire had burnt out at this plug.

At least i didn't fudge the wiring. But if i'd had removed the access cover in the floor where the pump used to be i may have seen the melted plug and realised the problem, maybe??

Thanks guys for your help in trying to solve this problem.

[date]

Cannot answer your question fully, but may be able to help. My Pajero (dual fuel) petrol pump has the float for the fuel gauge mounted along with the pump. Also there is the low fuel warning light. The 4.5 V signals would be the fuel gauge, one of the 12 V lines would be the low fuel warning light and the other 12V would be the fuel pump.

You may be interested in my modification. I have rewired my car so that when it is on gas, the petrol pump doesn't operate. This allows me to run on petrol when I am outback, and to run the petrol tank to empty, whilst keeping a full bottle of gas until I get within refilling range again. That way, the petrol pump doesn't run on a dry system, thus cooking the pump.

I used a relay which opens the petrol circuit whenever gas is selected. You just have to get a relay which has normally open (NO) and normally closed (NC) contacts. The biggest disadvantage of this sis that the petrol system doesn't get pressurised that often, but in nearly 200000 km, I have had no problems.

[GQ Bear]

Cannot answer your question fully, but may be able to help. My Pajero (dual fuel) petrol pump has the float for the fuel gauge mounted along with the pump. Also there is the low fuel warning light. The 4.5 V signals would be the fuel gauge, one of the 12 V lines would be the low fuel warning light and the other 12V would be the fuel pump.

You may be interested in my modification. I have rewired my car so that when it is on gas, the petrol pump doesn't operate. This allows me to run on petrol when I am outback, and to run the petrol tank to empty, whilst keeping a full bottle of gas until I get within refilling range again. That way, the petrol pump doesn't run on a dry system, thus cooking the pump.

I used a relay which opens the petrol circuit whenever gas is selected. You just have to get a relay which has normally open (NO) and normally closed (NC) contacts. The biggest disadvantage of this sis that the petrol system doesn't get pressurised that often, but in nearly 200000 km, I have had no problems.

I was thinking of wiring in a switch that cuts power to the pump in case of emergency. But i wired in a plug as the wiring was so short when they did the LPG conversion i had to cut it anyway. Incase of emergency it's not too difficult to just undo the plug to stop the pump. That way the injectors and fuel lines are still being lubricated the rest of the time.