Niels Jørgensen

Hi Guys - need your help again...

Came out this morning, and suddenly the car won't start. Ran fine yesterday.

It cranks, but doesn't start. I'm no expert, but my guesses are:

Worst case: TB (shudder!) (This is 2 years 3 months old, 50KKm)
Second: LH (Original AFAIK)

Others: Fuel Pump, Spark (plugs, dist. ...) (Plugs are 6 months, dist. caps+rotor 1 year+)

Any relays I need to check first?

Anything to rule out or add? And any ideas on how to check each of these and in what order? As always, any input is much appreciated, TIA.

drnick

neils,

you should hear the fuel pump whirring when the key is turned and before the starter motor is engaged.
if not this could be the problem and it is easily solved. you can substitute another non critical relay in its place ie windscreen wiper or something. also check fuses.

Niels Jørgensen

Thx. Nick...

I guess if it is indedd the TB, I have already done whatever damage I'm going to do, so it won't get much worse if I crank it again? (I'm not going to repair the engine if it's foobar'ed anyway, I'll get a cheap donor car from Germany instead)

I couldn't hear the fuel pump, but maybe I'm deaf... I'll try switching relays, if that's not it, I'll probably have to have the car towed to a shop as I don't have a spare pump lying around.

Niels Jørgensen

Hm.. No luck switching relays... (Jeez, they're hard to get out)

The only whirring I can hear is coming from around the glove-box area (AC and fan is turned off).

Anyway, I'm draining the battery, so I'll probably need to recharge before doing much more.

UKKid35

To check if your belt has slipped/failed turn the crank carefully (stop if it feels wrong) by hand using a 27mm deep socket while peering through the inspection hole on either of the cam belt covers. Just pull the air duct off to see, you may need a torch, if the belt moves that's a start, and if the TDC marks line up then you're in the clear. Check one of the online Cam Belt procedures for pics of the alignment marks, or the WSM. Takes five minutes to check.

If the belt has failed I can tell you what to expect if you decide to repair rather than find a replacement.

Niels Jørgensen

Thanks Paul...

A few questions (and yes you guessed it, I'm no mechanic ) :

If I disconnect one of the fuel rails and turn on ignition (without cranking) should I see gasoline squirt out from the pressure build up by the fuel pump? (Or, in other words, is this a way to test if the fuel pump works?) I know it'll be a mess, but I figure I could point the pipe into some kind of container.

I'm aware what TDC means, but what exactly does it mean that the TDC marks line up? Anyone have a picture or know where I can find one?

John Speake

Hi Niels,
It's unlikely to be the cambelt if the engine was running well before you parked the car.

You can check fuel delivery when engine cranking by disconnecting the fuel return pipe at the tank (under the RHS of the floor in the boot) and run it into a suitable container.

You will find it very difficult to hear the fuel pump while the engine is cranking.

The other possibility is the LH ECU or the MAF. Check the fuel delivery first. If you don't like the idea of playing with fuel, get someone to measure the voltage at the fuel pump while you crank the engine.

Let us know how you get on, and we will help you to diagnose the next part.

Niels Jørgensen

John, your words of comfort are much appreciated, though I thought cranking was one of the more stressfull times for a TB? No wait, don't confirm that...

Just to clear out what is probalby a misunderstanding on my part: I thought the fuel pump was engaged on ignition (I.e. without cranking) - do I have to actually crank the engine to get power to the pump?

IIRC you got a fix for dead LHs, right? If all else turns out OK, can I send you my LH for testing? Maybe the MAF also (though I find it hard to believe it failing completely overnight?)

Garth S

Neils,
Back to some basics, do you smell raw fuel at the exhaust outlet after cranking? Yea or nay here can direct your efforts somewhat.
There are 3 relays and corresponding fuses to check before making life any more complicated - and if you're handy with a multimeter and a jumper wire, pretty easy to check out. (ECU,fuel pump, EZK) . IIRC, someone nicely detailed their numbers in a post within the past 2 weeks on a 'no start' thread.

John Speake

Hi Niels,

If your TB was only changed a couple of years ago, it's unlikely to fail.

The engine has to be turning for the fuel pump to run. (anti-fire precaution).

On a very few contollers, the fuel pump gets a short burst of power when the ignition is first switched on, but this is rare.

Yes, I can check out your LH controller, but try some of the other checks first. Having said that the early S4 ECUs are very prone to failure.

Good luck !

Niels Jørgensen

Thanks all,

I accidentally swapped fuelpump for LH relay (clever, eh?)... So I tried relays again, this time getting three relays from functions I know work (VIII defrost, X interior fan, XII Horn) and inserting them in XXV (LH) XX (Fuel Pump) and XVI (Elec. ignition sys).

No change.

Oddly, XXV, XX and XVI are the only three relays that look non-standard. XX and XXV looked like the original but in a plastic casing (VW, AUDI stamps on them) but XVI is larger (wider, taller) and has a little green led on top of it and the word "TEST" in white letters...

I can't smell fuel at the exhaust, so I guess fuel pump is still a candidate. Garth, you say relays and corresponding fuses (as in more than one). Only fuse I can find that seems to relate to this is the fuel pump fuse? Am I missing something?

To check TB, which way do I turn the crank? (Seem to recall reading that turning "the wrong" way is bad - if so, when facing the engine do I turn clockwise or counter-clockwise?)

Garth S

Neils,
You're correct - fuse #42 is it. WallyP posted on 03-12-2004 a thorough rendition of most of the relay checks: you may wish to look at it.
Clockwise - is the rotation of choice when facing the engine.

edit BTW, when swapping relays - do one at a time with the same 'confirmed to be good' relay. Minimizes the variables !

John Speake

Niels
You always turn the crank clockwise when facing the engine.

You are correct that only the fuel pump is fuse protected. The LH and EZK do not have fuses in their supplies.

No fuel pump can be :
1) Faulty crankshaft position sensor
2) EZK (which passes an "engine turning" signal to the LH.
3) The LH which uses the pulses form the EZK to energise the fuel pump.

try making a jumper lead to bridge the fuel pump relay. Pins 30 to 87.

The fuel pump should then run. Try and start ............

Niels Jørgensen

Fuel pump works. I jumped the relay and could clearly hear the pump running. Still no start though.

I'm worried that I've cranked the engine enough to drain the battery, possibly introducing an additional problem. Also, when fighting the relays, I've managed to undo the socket for the fuel relay meaning I can't really get the relay back in again. Sigh!

I still need to verify fuel at the rails, and spark...

I do not have a socket deep enough to turn the crank, so can't check TB right now without removing covers.

Anyway, thanks so far guys. I'll continue once I get the battery re-charged...

UKKid35

There is a test point on the right hand fuel rail, many people have a fuel pressure meter permanently fitted there, you simply need to remove the plastic rail cover to gain access (it slides forward).

You don't really need a deep socket to turn the crank, a chrome one with a short extension will do.

Once your battery is charged pull a plug and test for a spark, this will confirm that the EZK and LH ECU are and their relays are working.

If you have both fuel and spark, then you may not have compression - which is what I found - hopefully you'll be luckier than me.