Yesterday I had a great fully running Cayenne. Today (like a fool) decided to do the spark plugs - long overdue and it was sunny

I changed 1 spark plug at the front on the V6 using BOSCH Ref: 0 242 135 510 / YR 7 LPP 332 W - and then as I always do, I started the engine to check that Spark Plug went OK (I usually do this after I changed each Spark Plug)

Car started and then after 30 seconds struggled and then died

Tried multiple times same issue car loses power and dies

I cant believe changing just one spark plug could cause this so I thought maybe its the Fuel Pumps. Took out fuses 13 and tried same issue. Took out fuse 14 and tried same issue so it cant be the fuel pumps

Plugged in VCDS and iCarsoft POR V2 and no errors come up at all what-so-ever

So just in case it was a bad Spark Plug I tried another new one. Same issue

Then thought id put back the original old NGK spark plug. Same Issue

Could it really be the Coil Pack??? Seriously? All I did was remove it and swap the spark plug

Any ideas anyone?

 

The VR6 won't automatically switch to the aux fuel pump when you pull fuse 13. This does sound like a fuel pump issue.
The second pump kicks in at start, which is why you get about 30 seconds then dies. Possibly just a horrible coincidence with the spark plug change.
No codes usually means fuel delivery. It does in mine at least.

Good luck,
Thad

 

I’m a newbie with all this - can you elaborate please

so with fuse 13 pulled what pump is actually running then?

and with fuse 14 pulled what pump?

the reason I ask is that whichever fuse I pulled I get the same issue - so I took that as it NOT being fuel pumps

You seem to be saying that secondary pump kicks in at start? If that’s the case when does primary kick in?

 

Fuse 13 controls the main pump which is the left (driver's side in the U.S.). The trick of pulling one fuse and having the other pump take over seems to only work on V8 models. At least that's the case on my 2006 VR6.
Normally the main/left pump (protected by fuse 13) runs all the time and the secondary pump only comes on momentarily at start and (maybe) above 4000 RPM. I just had fuse 13 blow on mine and had the exact same symptoms.
Now I'm wondering if the fuse just got tired, or do I have a bad fuel pump or short somewhere. So far it's been running for 2 weeks on a new fuse

 

OK so forget fuses. I decided to track down the relays

Where fuses 13/14 live so do the Relays.

Relay marked with BLUE Circle which I presume is RIGHT Fuel Pump was removed. Car acted the same and switched off almost immediately

replaced that relay....

Relay marked with RED circle removed which I presume is LEFT Fuel Pump and car stayed on running. Kind of a misfire every now and then but stayed running didn't switch off

This would point to the fact that the LEFT Fuel Pump is faulty

So a few questions:

1 how easy is it to replace these fuel pumps?

2 How much would I expect to pay for these pumps?

3 Is it worth replacing BOTH Left and Right and be done with?

4 Would the slight mis-firing also show that at least the Coil Pack i replaced a spark plug on also needs replacing?

 

So today decided to tackle the replacement of the two fuel pumps. Have to say what a horrible job - absolutely hated it lol

anyway both pumps replaced albeit with some cheaper OEM pumps (not VDO) and put everything together switched on ignition and hurray we have a running Cayenne

took it for a drive and all seems good HOWEVER - I can hear a humming buzzing noise very noticeable in the cabin coming from under the seats - it’s the brand new fuel pumps!

ive taken relays out to see if it was just one of them but no it’s both - constant humming noise

is this normal and to be expected ? Is it a sign I’ve done something wrong (although I can’t see how I could have)

Cayenne is running great but I’ve never noticed that humming with the original pumps in but now with these two new ones it’s very noticeable

fuel level is just under half a tank although the LEFT was drained to a very low level and RIGHT tank area was almost at top

should I be worried? Or is it normal?

 

If You put all the insulators and covers in place and everything else is working fine, it's just an annoyance but otherwise fine. The cheap pumps just produce more operating noise.

 

yep everything all back in place inc covers and insulators - just very noticeable louder running noise on both - kinda worrying lol

im also wondering if having low fuel level
on one side could be an issue making the pump work harder

fingers crossed it’s all good