PLEASE HELP. Fuel pump fuse keeps blowing! A3 1.8t 1998/ VAGCOM NEEDED

[eltonking]

So basically as I was driving along (approx. 70kph) the car just died. It had had a funny idle all week (would be at rest, then rev up to ~1200rpm then go back down) was awaiting a vag com cable to scan the car but the day before it came the car died. Have not been able to scan the car so no codes, vagcom cable came but is being difficult greatly appreciate anyone around the south-east burbs (brighton) to give me a hand to scan this bad boy and at least clear the codes!

ive managed to narrow it down to the fuel pump fuse constantly blowing (#2 before that, the car would just crank, and crank, an crank...)
I am getting a spark, and when a new fuse is put in it starts, idles etc.

i put in a 20a fuse (meant to be 15a) and it lasted a fair while longer...
... But blew.


Please help! I've ordered a new fuel pump relay and will be picking it up tomorrow, fingers crossed that works. Any other ideas?
Thanks!

[buzuki]

chances are your fuel pump is stuffed . . .

Vagcom isnt going to help you if your sure its the fuel pump fuse.

[jamesdavid]

EltonKing if the fuse keeps blowing you have clearly got a short, whether it be internally in the pump or wiring from the fuse carrier to the pump etc you've got a short. Fuses are designed to regulate current in a circuit, once that current is exceeded they blow, thus preventing overload of the circuit.

Buzuki is correct, vagcom wont help and i can assure you neither will the manufacturers equipment as i've had it before. If you have a little know how and a multimeter use voltage drop testing to isolate the fault as far as possible. Check your earth at the fuel pump connector, check your voltage drop from the fuse carrier to the fuel pump connector whilst under load, and from the battery to the fuse carrier again under load, this should rule out wiring from the battery to the fuse carrier and from the fuse carrier to the fuel pump connector.

If this all seems ok then you need to make a judgement call and be ready to purchase a fuel pump/sender unit.

[Lito]

sounds like it could be the fuel pump relay, apparently this is a somewhat common problem with the mk4/a3s. if it is actually your pump then i recommend you set aside at least 3 hours to swap it. i guarantee you'll end up with bloody knuckles and a full swear jar by the end of it, that rubber nut thing is an absolute pita to get off

[jamesdavid]

You could always just bridge the relay if that is the case, then you ll know for sure . hahah the sealing ring on the outside of the tank Lito??

[eltonking]

Yeah I've got a step by step DIY on replacing the fuel pump, so worst comes to worst ill be needing to replace that. Picking up a new relay today so will see how that goes. Managed to get the car home so this weekend will be spent testing everything with a multi meter thanks a lot guys! Will keep you updated as to how everything works out

[eltonking]

unfortunately the relay didn't help... will be having a crack on sunday to see what i get from running around with a multimeter

[jamesdavid]

No harm in having tried it mate, best case scenario it was a fuel pump relay and you would have saved yourself the cost and labour of a fuel pump/sender unit. Keep us updated and ask if you need help,

James

[eltonking]

some fault codes if it helps..

VCDS-Lite Version: Release 1.1
Friday, 12 October 2012, 16:09:32.


Chassis Type: 8L - Audi A3/S3
Scan: 01,02,03,08,15,16,17,22,35,37,45,55,56,57,75,76

-------------------------------------------------------------------------------
Address 01: Engine Labels: Redir Fail!
Controller: 06A 906 018 AQ
Component: 1.8L R4/5VT MOTR HS D03
Coding: 04000
Shop #: WSC 06313
VCID: 719556C728A7
11 Faults Found:
00561 - Mixture Adaptation
14-00 - Adaptation Limit (Add) Exceeded
16500 - Shareware Version. To Decode all DTCs
P0116 - 35-10 - Please Register/Activate - Intermittent
17978 - Shareware Version. To Decode all DTCs
P1570 - 35-10 - Please Register/Activate - Intermittent
00543 - Maximum Engine Speed Exceeded -- Engine Warranty VOID!
35-10 - - - Intermittent
18259 - Shareware Version. To Decode all DTCs
P1851 - 35-10 - Please Register/Activate - Intermittent
16514 - Shareware Version. To Decode all DTCs
P0130 - 35-10 - Please Register/Activate - Intermittent
01247 - Activated Charcoal Filter (EVAP) System Solenoid Valve 1 (N80)
29-10 - Short to Ground - Intermittent
01249 - Shareware Version. To Decode all DTCs
29-10 - Please Register/Activate - Intermittent
01250 - Shareware Version. To Decode all DTCs
29-10 - Please Register/Activate - Intermittent
01251 - Fuel Injector for Cylinder 3 (N32)
29-10 - Short to Ground - Intermittent
01252 - Shareware Version. To Decode all DTCs
29-10 - Please Register/Activate - Intermittent
Readiness: N/A

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 1J0-907-37x-ABS.LBL
Controller: 1J0 907 379 E
Component: ABS/EDS 20 IE CAN 0001
Coding: 13504
Shop #: WSC 06435
VCID: 33199CCF123B
2 Faults Found:
00668 - Supply Voltage Terminal 30
16-10 - Signal Outside Specifications - Intermittent
01312 - Shareware Version. To Decode all DTCs
37-10 - Please Register/Activate - Intermittent

[Speed]

The short to ground can't be good.
I've not seen the shareware stuff before either.

What happened when you cleared the codes? Did they come back?

I have had intermittent readings but when I cleared them on my gti, they never came back.

[eltonking]

The short to ground can't be good.
I've not seen the shareware stuff before either.

What happened when you cleared the codes? Did they come back?

I have had intermittent readings but when I cleared them on my gti, they never came back.

yeah they went away but then came back later when the car started up again using a 20a fuse for approx 1-2 minutes, had shorting in 3 of the 4 cylinders 'shorting'



and i think the shareware stuff is due to me having vcds lite - it wouldnt let me complete a full 'autoscan' after scanning 'engine' and 'abs' it would then cut out and say 'unable to complete, need to register for full version on ross-tech' (or something along those lines..)

[jamesdavid]

EltonKing,

First speed is right, to give you a better idea you need to identify those missing fault codes.

None of those codes that i see will cause the car to not run. The n80 is simply a switching solenoid for the charcoal canister, very common to see that code. The fuel injector for cylinder 3 that i haven't seen alot of but regardless the car will still run, will just have a misfire depending on what it is/isn't doing, i think they are a ground switched solenoid injectors so it may be intermittently not activating.

The fuel pump fuse is the main issue here, no point trying to diagnose anything else until you can get the car to run all the time, even if it has a miss in it. Check for power at the fuel pump connector and the appropriate fuse, use a voltage drop test, the circuit must be under load and make a note of battery voltage, it shouldn't deviate much from it at either point. Check your earth from the fuel pump connector just create a bridge with the positive on your multi to the positive on the fuel pump connector and the negative on the fuel pump connection with your negative on your multi if that makes sense, again, whilst under load. Voltage drop must be tested on a loaded circuit as high resistance values will be identified also.

Use your multi on the fuel pump its self, you can use resistance here, identify your power on the fuel pump and your earth, attach your multi, you should have a complete circuit, if not you have a short in your fuel pump and it will require replacement.

Keep us posted,

James

[eltonking]

EltonKing,

First speed is right, to give you a better idea you need to identify those missing fault codes.

None of those codes that i see will cause the car to not run. The n80 is simply a switching solenoid for the charcoal canister, very common to see that code. The fuel injector for cylinder 3 that i haven't seen alot of but regardless the car will still run, will just have a misfire depending on what it is/isn't doing, i think they are a ground switched solenoid injectors so it may be intermittently not activating.

The fuel pump fuse is the main issue here, no point trying to diagnose anything else until you can get the car to run all the time, even if it has a miss in it. Check for power at the fuel pump connector and the appropriate fuse, use a voltage drop test, the circuit must be under load and make a note of battery voltage, it shouldn't deviate much from it at either point. Check your earth from the fuel pump connector just create a bridge with the positive on your multi to the positive on the fuel pump connector and the negative on the fuel pump connection with your negative on your multi if that makes sense, again, whilst under load. Voltage drop must be tested on a loaded circuit as high resistance values will be identified also.

Use your multi on the fuel pump its self, you can use resistance here, identify your power on the fuel pump and your earth, attach your multi, you should have a complete circuit, if not you have a short in your fuel pump and it will require replacement.

Keep us posted,

James

thanks a lot to everyone for all their help, received a set of coilpacks today so chucked them in - didn't change a thing. ah well, will be doing a proper run around with the multi on sunday (working tomorrow) but pretty sure its the fuel pump now. should be having some fun replacing that bad boy sometime next week loving uni exams!

[eltonking]

All sorted! Changed the fuel pump and its never been better. Also replaced a split breather hose and have new fuel filter, oil filter, plugs (just changed the coilpacks) cabin filter and oil on the way !! Woo!!

[Stan]

cool, good to be going again!