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

[rubjonny]

yup thats what I'd try next, but GTI filters usually don't get blocked unless you've filled up with some dodgy fuel.

I'm putting my money on a damaged wire somewhere!

[AudiA8Quattro]

well how does the 9a 2.0 16v manage without a lambda then

Is that a 9A using k-jet or a 9A using ke-motronic?

[AudiA8Quattro]

As for the fuse popping problem, trace all the wiring as Jonny says, if it is fine, change the fuel pump.

[rubjonny]

It doesn't matter
It works like this:
You have a complex fuel injection map equation, which involves feeds from the MAF, inlet air temp sensor, RPM, Hall sensor, coolant temp sensor, etc to get your final figure for how much the injectors should open at any given time, and exactly when the spark should occur.  Then AFTER this is worked out, the feed from the lambda is used to adjust the final result.  If the lamda is not present, no adjustment occurs, as it says in that guide.

Remember, the lambda isn't even used right after a cold start!

[AudiA8Quattro]

Thats right, the lambda is only there to fine tune the mixture, basically to protect the catalyser, hence why an engine can run without it.
Cheers you've just proven my point really.
BTW if you use a 9A with k-jet then that won't even use an ECU, so it does matter what system is used.
KE-motronic uses an ECU, however it is a completely different fuel injection system to the motronic system used on the AAA engine.
Do your homework 

[rubjonny]

There is no default backup setting if the oxygen sensor is unplugged, so not sure that is a good idea. If you do unplug it, then only leave it unplugged for short periods, otherwise the catalyer could be damaged.
My money is on the fuel pump itself being faulty.

eh? YOU are the one that said it had no default map?

I said it doesn't matter what 2.0 16v I was talking about because I was trying to make you see that no lambda isn't the end of the world for a cat, its fine without one.  As you say it catches any other problems with the injection system, but it will still run fine without and wont damage the cat unless something else is wrong.  I know the K & KE Jet are completly different to the VR6 system, please don't try to make me sound like an idiot

The default fuel map will NOT damage the lambda on its own.  I have no idea what point you were trying to make really! 

[B.I.G DUB]

how do all im back! like hardcore said we tried everything,the sparky disconnected a wire from the lambda to see if that would cure the problem and for a couple of journeys it seemed to work,then started popping them again! i have stuck a fair bit of injection cleaner thru it to try and clean the fuel lines but the last time i used my vr it was still doing it,cats been changed along with lambda. i reckon u might be right with the loose wire.is it possible that there could be an earth thats causing the problem,just a thought coz if u wire an amp up and dont earth it properly,the fuses pop!? thanks for all the advice and help and i will check all the wires from the pump back as far as i can. please keep helping as i have had to drive my mums corsa for the last week!!!!!  :embarassed:

[AudiA8Quattro]

There is no default backup setting if the oxygen sensor is unplugged, so not sure that is a good idea. If you do unplug it, then only leave it unplugged for short periods, otherwise the catalyer could be damaged.
My money is on the fuel pump itself being faulty.

eh? YOU are the one that said it had no default map?

I said it doesn't matter what 2.0 16v I was talking about because I was trying to make you see that no lambda isn't the end of the world for a cat, its fine without one.  As you say it catches any other problems with the injection system, but it will still run fine without and wont damage the cat unless something else is wrong.  I know the K & KE Jet are completly different to the VR6 system, please don't try to make me sound like an idiot

The default fuel map will NOT damage the lambda on its own.  I have no idea what point you were trying to make really! 

Right lets start from the beginning again.
If the lambda has no signal then you said that the ECU runs off a default map.
For the ECU to run off a default map, you need either a back up sensor/s for the ecu to make the calculation, or a default setting for the sensor.
In this case the lambda has no back up sensor/s, neither does it have a default reading.
So as i said in the first place, which is exactly what that guide says, no signal means no regulation, basically meaning the ECU will ignore the sensor.
I'm not saying that if you unplug the lambda that you will deffo ruin the catalyser. It just something i wouldn't risk myself in the long term because that sensor is basically there to protect it.
I'm not trying to make you out as an idiot, just pointing out what i think mate, don't take it so personally 
If you read through the whole lot again i think we are basically saying the same thing anyway 
We both agree that the engine can run without the lambda sensor, we both agree that the map will be slightly different, as there is no lambda input.
What we are effectively disagreeing about is whether the lambda has a default setting, or whether it is just completely ignored.
The map could be the same or just a modified one with the lambda sensor ignored, i think it is probably the same standard map with the lambda ignored, what i don't agree with you about is that the lambda has a default setting, as it doesn't.

[rubjonny]

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' 

[B.I.G DUB]

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