How should the tank pump sound? by Thack

Sorry to swamp the forum with all these questions!

I have one problem I'd like to discuss: the tank is 1/4 full, the car runs fine, except when I floor the throttle and accelerate to high(ish) speed - for example, on the entry ramp to a motorway. When I do that, it gets up to about 70mph and then cuts out (or radically loses power). If I ease the throttle it recovers almost immediately.

My searching suggests that this is typical of a failed in-tank pump. However, I can hear it running. I switch on the ignition but don't start the engine. The under-bonnet pump is very easy to hear if the bonnet is open. If I open the filler cap and listen carefully I can hear what I assume is the ITP. However, it doesn't make a nice, smooth buzz. Rather, it has something of a warbling quality to it.

Is this normal? Or does it suggest a fault? Can anything else cause these symptoms?

I should mention that I'm intending to take it back to the dealer to get them to look at it, but I want to be up to speed on it myself so I can be an "informed customer".



Posted 11 Jun 2012, 20:17 #1 

User avatar
Not an expert on this but the in tank pump is best listened for under the rear seat it should be heard for a short period when the ign is first turned on.
hopefully this bump will give a little better coverage of your query :)


Posted 12 Jun 2012, 21:14 #2 

User avatar
These are similar symptoms to those I was getting ... daily driving the ZT ran Ok most of the time ..

But if put under a bit of stress , I.E mine was foot to the floor up a hill on a very hot day .
It would cut out !

The fuel was low at the time too.

The pump I took off would still squirt a jet 5-6 feet . but since changing it all seems better ..

maybe the pumps can lose a bit over the years, mine was original and 112 k miles .

Well until I get to that hill again and give it a try :-D :-D

Got one for Me , Then one for her, and now a big one for me again, All BLOO! Well saves on the touch up paint

Posted 13 Jun 2012, 09:52 #3 

Thanks for those observations.

In fact the dealer has got it at the moment, as it's still under warranty. However, I promise to report back what he says the fix is, in case it's helpful to others.


Posted 13 Jun 2012, 20:45 #4 

bill melater
As a newbie,might I suggest that as you loose power going up hill, the fuel level will decrease around the In Tank pump pick up, so perhaps with a lowish level to begin with it might suffer a lower fuel pressure til you level off again.

The gurgling sound from the tank pump could possibly be from the returning fuel being aereated again being caused by the low fuel level.

I spent a frustrating week along the same lines(no pun inteded) until I found a pinhole in the main line under the Under Bonnett pump , short rubber piece, where it was rubbing on the chassis.

Local garage quoted lots of noughts, fearing the worst case, including injection pump and

Hope this helps, as Ive had lots of help from the boys on Forums.

Posted 01 Jul 2012, 20:39 #5 

Suffolk Man
the tank pump has a audible hum.which unless you no what it sounds like is a job to hear as its quite a low frequency.i have fine tuned hearing and after replacing x2 of them i should no.when mine went one it was a job to start and when it did after tapping the underbonnet pump it would not go over 30 mph.i think your problem is more than likely to be maf could try unplugging it to see if that makes any diffrence.also check to see if you have any oil down below you passenger side your intercooler oil seals might be gone had easy fix if they are.failing all this and instead of throwing money at it hoping it will fix it get on a t4 for a check up

Posted 02 Jul 2012, 12:45 #6 

Sorry to keep reviving these old posts...

I’m sure our tank pump is dead – it seems as quiet as a mouse, I can’t feel any sort of vibration, and as soon as the fuel gauge gets below a quarter of a tank – we run out of diesel - twice now so we only use the top 3/4 of the tank. Also as the fuel gets low it gets harder to start

The engine pump seems to be fine – although on a couple of occasions under heavy acceleration it as simply got to a certain speed and given up – which can be quite disconcerting.

From what I’ve read the engine pump doing all the work should have given up ages ago – so I can’t decide if the tank pump is dead or not.

Any opinions / obervations?

Posted 29 Nov 2012, 18:24 #7