12 replies to this topic

[Lou_m]

Leading on from my car wont start topic the other week, I've managed to get the fuel pump plug disconnected and I am trying to see what voltage is there. There are 2 black cables and one brown and one green. I have checked my battery voltage and it is obviously dying as it was only 10V. Should I see 10V at the plug? Which wire is earth? The black wires are lettered as C and D. Green is A and brown is B. When I had the car battery connected to my other car last week I didn't get the starter motor priming so I don't think the low battery voltage was the cause, although it will need replaced now.

[slindborg]

Should see battery voltage. If not then something is wrong,

[rik]

http://www.speedster...m/Fuel pump.pdf
according to this, they are 1mm, C=black=gnd, B=brown/grey=pos but sometimes those colours in the tis are wrong

If you are using a multimeter it will tell you if the voltage is negative or positive depending on which way around you connect the black/red probes
You will only see voltage there briefly when you turn ignition on (2-3 secs), or when engine is cranking/running

The other 2 wires are for the fuel level sensor which are apparently D=black and A=green/black and 0.75mm http://www.speedster...m/Instument.pdf

edit: it does say the connector

Edited by rik, 12 April 2013 - 11:00 PM.

[Lou_m]

Thanks. Seems that I am only getting 5v at the plug even though the battery still has 10v. Does the voltage get reduced somewhere?

[Nev]

No way, those pumps need full 12 volts (or about 14v when alternator is turning) and lots of current. Check your relay and/or test/trace the voltage back from the plug.

Edited by Nev, 13 April 2013 - 07:09 AM.

[Lou_m]

Thanks, will do. I was just reading this thread and the last post suggested that it should be 5v.

http://www.vx220.org...-the-fuel-pump/

[slindborg]

12v or nothing. 1mm wires should too thin IMHO.

[turbobob]

With 10v at the battery, that is a very weak battery. I wouldn't be surprised at some V losses between the battery and pump. Get the battery charged and then check it.

[Lou_m]

After further investigation I think I have a bad earth.



When I put my metre across 30 and 85 i get 4v, across 86 and 85 I get 4v. However if I put the metre across either 30 or 86 and an external earth I get the same voltage as the battery is holding.

So should I just try and run another earth to no 85 on the relay?

[Claws]

Exactly that, seems that earth on 85 is faulty, which means the relay won't pull in. Temporary earth to 85 to prove it, then trace your 85 black wire to see what is wrong with it

[ciderbooze]

Yes, but if your bat voltage is 10v there is something wrong .

[Lou_m]

Am I right in thinking that the fuel pump relay is the 2nd from the left?

I seem to have lost all voltage at the relay conections. Tried to see if I could get a voltage reading from the crash switch but there doesn't seem to be any there (my skills with a multimeter leave a lot to be desired).

Still seeing between 4-5 volts at the pump(battery is now charged)....

Now i need to either try and get the car to an auto electrician or find a decent mobile guy.

[H1 HWK]

With 10v at the battery, that is a very weak battery. I wouldn't be surprised at some V losses between the battery and pump. Get the battery charged and then check it.

Hi Lou,

Save yourself some time chasing your tail........low battery voltage on the VX seems to throw up loads of anomolies when you're trying to isolate a fault and nothing seems logical. Charge/replace the battery then stert fault finding if neccessary.

Good luck.