G60 fuel pump relay battery drain

[northG60 0]

Hello all

 

hope someone can steer me in the right direction

 

so i took my car in to a car electics place because of a battery being drained all the time

 

i was told that because supercharged VW's run hot and with hot start issues the fuel pump relay will run for a while to drain the lines of vapour and fuel

 

so basicly my fuel pump is staying on constantly (and draining 5 amps at all times according to the garage)

 

should i just look to replace the existing relay or could there be another issue?

 

cheers guys

[dannyboy 0]

The fuel overrun is a feature.Unplug the brown connector at the right hand side end of the fuel rail(where the U rubber pipe connects to) This will stop the fuel pump overrun from working but on hot days you may end up with vapour lock causing hard restarting.

 

is the fan overruning to? if so the small thermistor behind the ISV is earthing out(common fault causing flat batteries on G60s)

[northG60 0]

right i'll give that a go today... but my fuel pump is stuck on all the time atm so should i try buying a new relay? i had noticed this overrun before but it has previously stopped after about 10 mins

 

yes the fan will overrun too so i'll give the isv thermistor a check over too...

 

my G60 does run pretty damn hot with an average water temp of 100 and oil will be around the 100- 110 so this hot start issue will almost deffinatly be a problem for me even in colder weather

[northG60 0]

Update

 

I went down to my local VW Vindis and ordered a new fuel pump relay (marked 90 and fits into the no 16 relay house)

PT no: 357906363

£37.28 inc vat

 

it will arrive tomorrow morning so i'll feep my fingers crossed that this will solve the issue, i think the existing relay was the orginal unit so 20 years is pretty good

[Yandards 0]

The fuel pump run on relay (old one marked 90) contains the timer mechanism for the fuel pump run on engagement - this should not occur until after 2 minutes have elapsed post engine off.

 

There is a time limit for the entire process (rad fan and fuel pump) of 10 minutes, this time is controlled by the fan run on unit which should be marked up as 31 in position 14 on the fuse box (position is probably different).

 

If your system is running on (fan & pump) when not hot then it is likely your thermo switch is degraded, this sits near the fuel rail and is a simple switch that starts the entire run on process.

[northG60 0]

cheers yandards

 

According to the above my fan is about right say around the 10 min mark on overrun when hot, but my fuel pump would stay on for a lot longer so if the new relay doesnt solve the issue then i'll look at the thermo switch as the problem, i may just replace it for peice of mind as i have no idea how long its been on the car.....

 

is fuel pump relay failure a fairly well documented ? or pretty uncommon ?

[Yandards 0]

The power to run the fuel pump comes from the fan relay thanks to the wiring sequence so it is more than likely an issue with the fan run on relay not powering down properly.

 

As for failure, 20 year old car with a 20 year old timer relay - just fair wear and tear but there is no 'common' failure.

 

Problem most G60 folks have it that they don't know what should be happening, your fuel pump and fan should run when the engine bay is hot for a maximum of ten minutes but there is the fuel pressure switch that prevents the fuel pump running if the fuel pressure drops below 1.2b to stop fuel being pumped all over the hot engine bay.

[northG60 0]

right..... so i picked the unit up today and fitted it, i then ran the engine for a few minuets and before it got the first reading of 50c oil temp i switched the car off ... the fuel pump then ran without the fan coming on?. i heard the pump running from the fuel tank area and also from under the bonnet there was a strange noise coming from around the fuel rail which is hard to explain (it didnt sound like an electrical buzz if that helps).

 

i really am pants with electrics so you'll have to cut me some slack lol....

 

note on the side for G60 owners, i asked how many of the relay in question are left and there are only 11 in stock

Edited November 24, 2011 by northG60

[dannyboy 0]

buzz may be from the fuel rail as fuel passes through or you maybe hearing the isv buzz.

 

Try this

 

turn the engine off and remove the key.Behind the ISV take the single spade connector off the thermo switch(brown wire)

Earth the wire to the engine block by touch it to metal.The fan and the pump should run together(youve find the pump is difficult to hear over the noise of the fan so feel the fuel hose)

At the end of the fuel rail disconnect the brown,two pin connector for the fuel pressure switch.touch the single connector on engine metal again.only the fan should run.to listen if the pump is running disconnect the fan.The pump should not run.If it does you have a short somewhere