help,mk3 vr6 keeps popping fuel pump fuses!!!

[AudiA8Quattro]

Yeah I know, I just thought that 'do your homework' was a bit below the belt 

Yeah I can see now we were saying the same thing, I think I should wind my neck in

by 'default map' I mean the ecu has a standard map whish does not need the lambda sensor.  Not that there is a default value for the lambda, just that without one, it doesn't matter.  i.e. the lambda output isn't an essential part of the fuel/air calaculation the ECU uses.  If it was, removing it would ruin the air/fuel ratio and prevent the engine from running.

As we can see from various sources the output from the lambda is ignored and no substitute sensor readings are used, the lambda output is only used to adjust the engine map.  Which when you think about it is all it can do, since the reading from the lambda is basically telling the ecu what happened the last time it calculated the air/fuel ratio, since it is sensing the output from the last combustion cycle.

<bang> nope sorry to rich! <bang> thats a wee bit lean... <bang> yeah thats it! <bang> spot on woo you rock <bang> etc..

All you had to say was 'I wouldn't leave it disconnected too long, it may damage the CAT' 

Yeah sorry mate, no offence intended  :embarassed:
We got so obsessed with the argument, that we were basically the same thing anyway.
It wasn't until i read it all again i realised  

[AudiA8Quattro]

cool,now u got that out the way,anymore advice please people! 

As i already said, trace the wiring, looking for obvious damage. The most likely place is where the loom runs under the floor by the doors.
If all is ok, replace the fuel pump.

[rubjonny]

Yeah sorry mate, no offence intended  :embarassed:
We got so obsessed with the argument, that we were basically the same thing anyway.
It wasn't until i read it all again i realised  

Hurt my feelings you know, I cried myself to sleep that night
Yeah complete waste of time really, at least the thread got lots of free bumps

The fact its so random leads me to belive its a wiring fault somewhere as well, gotta be rubbing on the chassis somewhere, check all the rubber grommets where the wires pop thru the bodywork, and the metal flap under the boot carpet where the wires run down to the pump/level sender.  Worth taking out the driver side dash under tray out and dropping the fusebox down as well.

[AudiA8Quattro]

I still think its the pump itself.
A while back my brother had a Rover which kept blowing the wiper blade motor circuit fuse, you would think again wiring fault, but it was the motor the whole time.
If you can't find any problems with the wiring as Jon suggests, try a new pump.

[rubjonny]

Good point, MK3s are 'at that age' when bits like this can start to fail.  I still think of the MK3 as quite a 'young' car, but it isn't really!

[B.I.G DUB]

cheerz people you've been a great help.gonna get a new fuel filter,checked and re-checked all wires and lamda sensor,which also made me fit a de-cat.a few people have suggested a blockage in the fuel filter so i will try that while working my way back to the pump if neccessary.trying all easy options before i attemp the pump!   

hopefully my v-rarrrrr will be back to normal by the weekend! i hope 

any hints or tips on the above would be greatfully recieved! cheerz 

[rubjonny]

ah so you've got rid of the cat?  If so you can safely unplug the lambda sensor for a bit to see if its a wiring problem to the lambda heater

[B.I.G DUB]

ok,so what will happen if i do that? im gonna try the fuel filter,how much difference will it make to my car now ive de-catted it? thanks again for all the advice! 

[rubjonny]

all it will do is confirm if the fuse blowing is anything to do with the lambda or not, since you say its protected by the same fuse?  The car wont run as well with the lambda unplugged and there is a possibility of CAT damage, but since you don't have one we don't care