Help with A8 non start issue

Singh · #1 27th July 2013, 08:13 AM

Guys, as you know, I have bought an A8 with a non-start issue. When I got to the sellers’ home, he tried the key – and it cranked up and ran for just under ten minutes, he had been trying to start it for a fortnight with no luck, I believe when he got in the car and applied some throttle it spluttered and died, the car has half a tank of fuel.

I’ve now got the car home; have replaced the ignition switch (which was knackered) and put in another 20 litres of fuel, every time I try to start the car, it blows the fuel pump fuse straight away.

The ex owner had just fitted a new fuel pump, the car also now has about ¾ of fuel in the tank, so what could it be?

Is it a badly fitted fuel pump, wiring? If so, could someone please get me Elsa instructions on how to take out and fit the pump in properly?

Thanks in advance guys.

ainarssems · #2 27th July 2013, 09:04 AM

First disconnect the pump, if fuse still blows then it's wiring, maybe relay, if not then it is the pump. Another possibility would be blocked fuel filter, lines or fuel pressure regulator making fuel pressure too high and causing pump to work extra hard which blows fuse.

What value fuse have you got, I think it's meant to be 30A, maybe somebody replaced it with lower value in the past.

awolfinsheepsclothes · #3 27th July 2013, 09:04 AM

Hi Amar it could be the fuel pump wiring shorting out somewhere a good auto electrician would find it easily if it is by checking at the fuel pump relay.
Good luck Dave

Singh · #4 27th July 2013, 09:22 AM

Thanks, guys. I'll try disconnecting the pump and see if it still blows, btw - there is a 15A in there at the moment and I have been replacing it with a 15A each time I re-try with more fuel/different time of day, I'm sure that's also what it said on the inside of the fuse box, unless I read it wrong? Should it be 30A? Hopefully, it is that simple...

ainarssems · #5 27th July 2013, 09:37 AM

It could well be that it is meant to be 15A, I just though from memory that it's supposed to be higher value. If it says 15A on the sticker then it's 15A.

Singh · #6 27th July 2013, 09:49 AM

Yes, 15A, the other A8 is 15A too. Will try the wiring disconnect trick and report back this evening. Anything else it could be or I could try whilst I'm down there?

Singh · #7 31st July 2013, 08:09 AM

An update – the ignition switch was knackered, the steering locked and it wouldn’t release, after putting a new switch in, it released straight away and the ignition now has that proper ‘springy’ feel.
Photo of the old switch here:

Car still not starting though, symptoms are as if it has a flat battery, but the battery is fine, so I took off the passenger wheel arch liners and found the fault, the wire going to the starter is bad, gave it a bit of a wiggle (disconnect the battery first), and the car is now trying to crank, not only that, but the fuel pump fuse is no longer blowing either! Some progress…
I
t won’t turn over though, it sounds as if it is being starved of fuel, so I whipped out the old fuel filter and replaced it with a new one – same thing!

Next job is to replace the fuel pump, the last owner replaced this, but with a second hand one, bugs me that does and total false economy, especially since a genuine new Simens VDO ones can be had for nearly half the second hand priced one! Keep your fingers crossed for me, I reckon I could have it working this week.

green A8 · #8 31st July 2013, 08:41 AM

Have you tried cleaning the earth lead at the front of the car (O/S chassis) Amar? I had all manner of problems similar to yours, lazy starter motor, self opening sunroof and windows ect. That was caused by one pesky corroded earth lead, since cleaning it at both ends all the electrical problems on the car have vanished. I cheated and added a second lead whilst I was in fixing mode

To complicate matters my car is dual fuel LPG/petrol. The installers had run the LPG supply pipes very close to the plastic petrol pipe in the engine bay and over tightened one clamp. Result? slightly crushed petrol pipe, and somewhat restricted petrol supply to engine.

Hope this helps.

Paul.

Singh · #9 31st July 2013, 08:56 AM

Paul, I believe we are talking about the same wire, although mine had no bearings on the other electrical items, they worked fine, it was just the starter motor not getting any power.

I don't believe it is a crushed fuel pipe as the car hasn’t been LPG'd, so reckon that's unlikely, it could be a badly fitted fuel pump, although the ex owner said he replaced the fuel pump, I don't know whether he had it running on this one or not. I'm about to order the new Simens VDO one regardless, I don't see the point in replacing an 18 year old fuel pump that has failed, with another 18 year old one that is likely to fail.

green A8 · #10 31st July 2013, 09:13 AM

I couldn't agree more with your above fuel pump comment Amar, the problem with some owners is that they are running the car on a shoestring and when a fault develops they opt for the cheapest fix that they can find. My motto is 'fix it once, fix it right' That usually means add new parts, not unknown second hand ones. it might cost more but saves on flustration and repeating repairs.

I'd tend to have a look at getting a new pump relay as well ae fitting a new fuel pump. That way you know that you've sorted the problem once and for all. I'm looking forward to reading that the car is up and running and congratulating you on a job well done

Paul.