Fuel Pump Electric Supply

[215m3]

Hi all

Finally got the car back together after fitting a new radiator, silicone hoses and associated gaskets etc. Gave the engine a steam clean as it had years of grime on it. Plus it makes it nicer to work on!

When I turn on the ignition, should there be a clicking from the fuel pump as it primes, is this correct? If it is supposed to, mine does not. How can I test the wiring to see if it is live? Also is there a fuse for the pump too?

Tested for spark, which it has. Then checked the fuel feed pipe on the passenger side and was dry.

I have the pump out of the car, and the hoses were dry too and wondered if there was a way of testing it? (I did put 20ltr in the tank before trying to start her, so fuel is there)

Any help, as usual, is gratefully appreciated.

[madjack4]

Hi the fuel pump feed wire is not fused it amazed me when i had mine out so dangerous turn ignition on check for a 12v feed to pump if it has got one check earth with a test lamp from feed to earth if it has feed and earth power up pump with a seperate power and earth to check pump works could be stuck with sitting by the way i put a inline fuse before pump to be safe

Regards Rob

[Paul Buckley]

Give it a sharp tap!

[MarekH]

Dear Toby,

The s3 has two fuel pumps mounted back to back with each other. The black earth return is common and comes through the chassis of the pump. The white, unfused, 12v feed comes via a Lucar connector mounted on either end of each pump.

As you have the pumps out of the car, you can test the individual pumps dry just by connecting 12v across those contacts for each pump and you should see the points chatter and it make a machine gun like sound for each pump.

Assuming all is good, to test fuel flow safely, you have to have a safe proximity between fuel, fuel vapour and any electrical connection which may cause sparks as wires come undone or are connected up.

Connect up a temporary fuel feed and a way to collect the pumped fuel safely. Do it somewhere outdoors. Next, connect up the black and white wires securely at the pump using long (e.g. 6-8 ft) extension wires. This is so when you finally connect the circuit, your fuel is a long way away from any potential sparks at the battery where you complete the circuit. Test each pump separately, they should both pump fuel. Before you do that, test your remote pumping setup dry without fuel, so you can anticipate movement or spillage. The best solution is to have two people, one holds the pump and the other is a distance away with the electricity.

For the in-car wiring, a better solution is to have a fused supply via a relay to bypass the ignition switch (but whose relay winding is fed by the ignition switch) for the fuel pump. The wiring loom thick white wire can be intercepted under the right hand of the dashboard just before it disappears into the right hand scuttle on ts way to the back of the car and a relay fitted there.

Alternately, feel free to follow Rob's James Joyce-like stream of consciousness advice if you can understand it.

kind regards
Marek

[215m3]

Thanks for your replies. I was unsure if I could just put the positive and negative on either end to see if the pump worked. I will give that a try soon. If nothing I will try the hammer treatment too.

Will see how this goes to start with.

[215m3]

No joy with adding power as well as taping it with a hammer.

It may be the original, so might as well get a new pump.

[Ole-xke1974]

Toby,
the hammer treatment is more like a road side emergency solution. The mechanical shock will cause the contacts to make contact and the pump will potentially keep going for hours after. However, the pumped stopped because one of the contacts are burned and couldn't make contact and it will fail on you again.
The proper solution is to replace both sets of contacts plus various rubber parts inside the pumps.

Cheers ...... Ole