1.4 tdi - engine starts but dies immediately

[Creliseth]

Hi everyone,

I've recently bought myself a 2001 Lupo with 1.4 tdi amf engine.

What I've noticed lately, following somewhat colder weather (around 10°c), is that it takes me long time to get my engine actually running.

This happens only when the engine is cold, I try to crank it, it fires up for a second and then it immediately dies. It takes me 5-10 minutes to get it to actually start working like this.

Does anyone have an idea what could cause this? Only thing that falls on my mind is perhaps bad glow plugs, which I'm planning on replacing since I have no clue when they were changed last time.

Thanks for any help in advance!

[tchouki85]

hi the first thing to check would be to know when the last timing belt was, then I doubt that the problem is the glow plugs because it only works if the temperatures are below 4 degrees, check your battery cable instead and  the masses, look if these are not oxidized

[mk2]

Yeah, glow plugs are for starting, but vdub also keep them powered after starting to help the cold engine idle smoothly. So could be the battery terminal like @tchouki85 says.

Other things to check are stuck EGR valve or fuel supply from lift pump (power or pump issues). In a nutshell, if the engine gets no fuel it dies. But since the injectors and fuel circuit are run by system electrical power, if the 12V supply fails the injectors or lift pump could stop- killing the engine.

Worth monitoring the battery voltage which should jump to over 13.5V straight after starting. 

There are a few classic loom faults on AMFs... The alternator sense wire snaps, so the little battery symbol in the dash stops working. Check that when you switch on (without starting), you get a solid battery light (not charging), which goes out the second the engine starts. 👍🏻

Let us know what you find

 

[Creliseth]

Thanks for replies guys!

2 hours ago, tchouki85 said:

first thing to check would be to know when the last timing belt was

It's been around 40k km since timing belt change, could loose timing belt make the engine behave like this?

2 hours ago, tchouki85 said:

check your battery cable instead and  the masses, look if these are not oxidized

I will give it a look today when I come back home.

1 hour ago, mk2 said:

Other things to check are stuck EGR valve or fuel supply from lift pump (power or pump issues). In a nutshell, if the engine gets no fuel it dies. But since the injectors and fuel circuit are run by system electrical power, if the 12V supply fails the injectors or lift pump could stop- killing the engine.

Worth monitoring the battery voltage which should jump to over 13.5V straight after starting. 

There are a few classic loom faults on AMFs... The alternator sense wire snaps, so the little battery symbol in the dash stops working. Check that when you switch on (without starting), you get a solid battery light (not charging), which goes out the second the engine starts. 👍🏻

Let us know what you find

EGR seems to be okay, I cleaned it first thing after I got Lupo back home. As for lift pump, po told me that he got it rebuild recently, if it's to believe his words. I will also check both battery voltage and alternator wiring (though I'm 99% sure battery light goes out like it should, can't hurt to double check).

I will report back what I find out today.

[Creliseth]

Seems like my positive battery cable has a little bit of greenish corrosion.

I will give it some proper cleaning tomorrow morning and see if that does anything.

Other than that, masses seem to be corrosion free, alternator wiring is okay, only thing that I found was bad vacuum hose that goes into EGR valve, but that didn't fix anything sadly.

[RAB]

On 11/4/2022 at 7:51 AM, mk2 said:

Other things to check are stuck EGR valve or fuel supply from lift pump (power or pump issues). In a nutshell, if the engine gets no fuel it dies. But since the injectors and fuel circuit are run by system electrical power, if the 12V supply fails the injectors or lift pump could stop- killing the engine.

 

 

Come on, come on! The tandem pump is mechanical, mounted on the end of the camshaft. Early TDis also had an electrical lift pump as well as a tandem pump.

RAB

 

[mk2]

@RAB, can the high pressure pump (the one on the end of the camshaft) suck all the way from the tank, through the filter, if the lift pump isn't running? All 1.4 tdi lupos have the electrical lift pump. Don't the 1.2 always have both?

And there's that fuel return circuit with the cooling fins under the driver's seat, that emits steam if you drive through a tiny puddle!

[Creliseth]

I still can't figure out what is going on with my engine.

I decided to start with new glow plugs, but there seems to be 3 different sizes of glow plugs available, not sure which one suits my engine.

N 103 021 02 (71mm), N 101 401 05 (91,7mm) and N 105 792 01 (97mm).

 

[mk2]

I'm 99.9% sure that it's not the glowplugs if it starts, runs for a moment then dies.

Sounds most likely to be fuel starvation. But could be something obscure like a loose crank sensor or some wiring disconnect. Diagnostics will help you a "bit", so maybe worth a try. VCDS software works best with 20 YO vdubs. You just need a lead and an old XP laptop (charity shop?).

Ah, hang on. Just had a thought. It might be the security system cutting in- no comms between the key and the ECU? Tried another key? Symptoms are- it starts completely normally, runs for about two seconds then stops. Often there's a little amber warning light that lights up in the cluster- key shaped. But not sure if your model has that. 🤷🏻‍♀️

[Creliseth]

7 hours ago, mk2 said:

Ah, hang on. Just had a thought. It might be the security system cutting in- no comms between the key and the ECU? Tried another key? Symptoms are- it starts completely normally, runs for about two seconds then stops. Often there's a little amber warning light that lights up in the cluster- key shaped. But not sure if your model has that. 🤷🏻‍♀️

Sadly, car came only with one key, and remote controls don't even work, if that's what you mean by no comms between the key and the ECU. Even the alarm behaves weirdly, PO removed alarm fuse because whenever it rains, the alarm would go on without any reason.

As for warning light, that's a negative.

[mk2]

Hmm. In that case, I have a hunch it might be something to do with the locking/convenience module. Or at least a signal that's not getting through. I once fixed a 2002 polo tdi with very similar symptoms and it ended up being a loose contact in one of the cluster connector circuit boards- just where you plug it into the car. The soldered connector pin became loose and gave exactly the symptoms you described. Alarm. Remotes not working. Sometimes cutting out... Took two seconds to re-solder it and everything worked perfectly again! Known common issue with polos.

The key has a tiny rice grain sized passive transponder chip in, just like a contactless bank card. Around the lock barrel is a sensor ring that picks up the signal and verifies the serial number inside the rice grain, which then allows the engine to start. Sometimes the radio signal doesn't get through from the key. Sometimes there might be a break in the circuit between the sensor ring and the control unit. The alarm going off tells me that I think it has something to do with security lock out. Usually the alarm is controlled by the remote, and when locked, if someone opens a door unexpectedly, it goes off. So lock switches are another suspect- but not the cause. 

You could try removing the transponder chip from the key and holding it against the pickup ring. But be very careful. If you damage/break the chip it's game over and you'll need a de-immobilised ECU or a new key from vdub (and the cost of pairing the car to the chip).

[Creliseth]

I suppose this is the immobilizer chip that you were talking about.

While disassembling the key, I heard something tiny shaking inside of it.

This little piece somehow got torn from pcb. I hope that's why remote locking isn't working.

As I don't feel comfortable soldering something so tiny like this, I will take it to some mobile service shop and have them do it for me.

Also, could a vacuum leak somewhere cause the engine to die like this?

I remember on my old E36, I had badly damaged crankcase ventilation hose that gave me almost the same problem I'm experiencing right now with the Lupo.

[mk2]

Bingo! That's the chip- actually a late one. Early ones were made of glass and were round. Yes, try holding it right up against the sensor ring with bluetac or something when you crank it.

That little component is an adjuster (like a volume control) for the the circuit. Be sure that it doesn't get accidentally turned a bit. Or maybe that's how it got broken off- the remote wasn't working so someone thought that perhaps by adjusting it, might sort it out... There might still be a fault on a module circuit board connection somewhere.

Where in the UK are you?

[Creliseth]

On 11/8/2022 at 8:01 PM, mk2 said:

Bingo! That's the chip- actually a late one. Early ones were made of glass and were round. Yes, try holding it right up against the sensor ring with bluetac or something when you crank it.

That little component is an adjuster (like a volume control) for the the circuit. Be sure that it doesn't get accidentally turned a bit. Or maybe that's how it got broken off- the remote wasn't working so someone thought that perhaps by adjusting it, might sort it out... There might still be a fault on a module circuit board connection somewhere.

Where in the UK are you?

Same thing happens whether I hold immobilizer next to the sensor or it's in the key.

I had adjuster soldered back to the pcb and what do you know, I have remote central locking again! Trying to fix one thing, I ended up fixing something else. 😁

Sadly, I'm not from UK, I'm all the way from Serbia.

We had some sunny weather here today and little Lupo fired up on first crank without any hesitation. I really don't understand why cold weather troubles him so much 😞

 

[mk2]

Yay! Ok, so back to the original problem. Key most likely eliminated then. Possibly.

Do you have VCDS diagnostics?

[RAB]

On 11/5/2022 at 6:16 PM, mk2 said:

@RAB, can the high pressure pump (the one on the end of the camshaft) suck all the way from the tank, through the filter, if the lift pump isn't running? All 1.4 tdi lupos have the electrical lift pump. Don't the 1.2 always have both?

And there's that fuel return circuit with the cooling fins under the driver's seat, that emits steam if you drive through a tiny puddle!

Electric lift pumps were only fitted to early Audi A2 TDis, according to 7zap. Our 1999 Lupo 3L doesn't have one for sure. So the tandem pump is the lift pump, not the high pressure pump. The high pressure pump is the injector itself.

RAB

Edited November 11, 2022 by RAB

[Creliseth]

Sorry for not being active for a while, I've had some stuff going on in a meantime.

I don't have VCDS diagnostics, though I've purchased VAGCOM cable (OBD to USB thingy), I'm just searching right now for free software and a laptop.

I've also bought timing set kit (which I will probably do over a weekend) and new glow plugs.

What I noticed while replacing glow plugs is that one of them was wet with diesel/oil mixture (black color). I'm talking about cyl. num. 3. Could that be the culprit?

Here's also a picture of old glow plugs, one far most left was cyl. num. 3 (why the tip of it doesn't look the same like other two?)

[mk2]

Someone replaced the glowplugs... with a wrong 'un. They're not critical, but certainly make for smoother idling. Only really needed when it drops below about -5c overnight. 

Judging by the tip colour, the engine's running in good condition. When it decides to run.

Search for VCDS or VAGCOM (renamed a few years ago), written by Uwe Ross. He's the guy who cracked the vdub codes about 20 years ago and wrote a nice interface for all the VAG lineup. Now runs a decent sized business from what I hear. Well done him! 👍🏻😀 His professional (paid for) tool suite is apparently better than the genuine VAS (official volkwagen) diagnostic system.