So recently I've been having hard starting problems and occasionally at idle the engine will stall. However, today whilst I was driving, the engine cut out with the battery light on. Managed to get it over somewhere safe for now. A while back when I first started having these problems I checked the alternator voltage and it was producing an acceptable level and battery voltage was relatively okay. So my question is, do I need a new alternator or is it a battery issue? I tried starting it up again which worked, no battery light, but I fear that if I do drive, it'll die again and won't start anymore. Would love to know before spending on one. Also, does anyone know the procedure for replacing it? Cheers!

I'm reasonably sure that any time the engine cuts out, for whatever reason, the battery light comes on. So blaming the alternator or battery seems to be excessively hasty guesses as to what may be amiss.

Have you changed the crank sensor yet?

Yeah changed the sensor. It didn't change anything if I'm honest, the only thing I noted was better mpg. The only other concern is the plug that connects to the alternator (red and blue wires) seems to have undergone a repair by the looks of it. Maybe that is a factor?

2 hours ago, Frosty99 said:

The only other concern is the plug that connects to the alternator (red and blue wires) seems to have undergone a repair by the looks of it.

OK; when you switch the ignition on (not start the engine, just switch on), does the battery light come on?

Yes, I get the battery light on with ignition

2 hours ago, Frosty99 said:

Yes, I get the battery light on with ignition

OK, it's not what I was thinking then.

14 hours ago, Frosty99 said:

 A while back when I first started having these problems I checked the alternator voltage and it was producing an acceptable level and battery voltage was relatively okay.

 Do you want to put some factual numbers behind this statement and what you consider "acceptable" and "relatively". Another that may be relevant is battery voltage before turning ignition on, and one after ignition has been on and heater plugs have operated which will show voltage drop under high load without alternator trying to compensate. 

21 hours ago, Frosty99 said:

So recently I've been having hard starting problems and occasionally at idle the engine will stall. However, today whilst I was driving, the engine cut out with the battery light on. Managed to get it over somewhere safe for now. A while back when I first started having these problems I checked the alternator voltage and it was producing an acceptable level and battery voltage was relatively okay. So my question is, do I need a new alternator or is it a battery issue? I tried starting it up again which worked, no battery light, but I fear that if I do drive, it'll die again and won't start anymore. Would love to know before spending on one. Also, does anyone know the procedure for replacing it? Cheers!

 

Bad earth? Mine liked to throw a tantrum when the earth was dicky.

 

Mine cut out constantly but it was a lambda sensor issue. So make of that what you will.

Well I checked it over the other day after watching a few vids on alternator testing and it's fine, voltage is good and battery is also good. I replaced the fuel filter as I needed to do it anyway but still we have the same problem. The fuel pump is perfectly fine as it primes and starts the engine. My next guess is maybe a partially blocked injector? I'm not sure. I don't know what would cause the engine to randomly stall sometimes. The air filter is fine and had a new set of glowplugs not long ago. Quite stumped if I'm honest. It used to start first time on the turn of the key

 

You checked the output of the Tandem pump?

 

Have you hooked it up to VCDS to see if there are any codes, could be injector wiring harness or something like that

Edited 16 October, 20223 yr by SuperbTWM

3 hours ago, SuperbTWM said:

You checked the output of the Tandem pump?

 

Have you hooked it up to VCDS to see if there are any codes, could be injector wiring harness or something like that

 

I was going to say fuel related myself! Better mpg says fuel supply. Is there fuel in the filter bowl?

Conversely I reckon it's electrical, the injector loom is a good place to start on one of these.

7 hours ago, SuperbTWM said:

You checked the output of the Tandem pump?

 

Have you hooked it up to VCDS to see if there are any codes, could be injector wiring harness or something like that

I don't have a vcds cable or software. I think I may know someone that does have the cable, just would have to get the other part myself. If I was able to do so, what would I be looking for? I've not used vcds before. Also, how can I check the output of the tandem pump? I've heard about pulling off a line to the fuel filter and putting it in a container to check flow. However I've noticed now that some of the time, even from sitting overnight, the fuel pump doesn't make a priming noise like it used to do all the time, but afaik last time I tested it with a multimeter it was okay, I'll have to check again soon when I get a few minutes and report back.

 

Annoyingly I was driving yesterday at a steady speed of around 50-60 and the engine cut out and I had to restart it while rolling lol. That's what makes me lean towards the sender pump going bad

Lift pump fills the filter bowl, for the engine to stall the filter bowl would need to be empty and it would take a little while to refill and bleed the air from the injectors.

I see, sounds like the lift pump is acting up then. That would make sense if isn't priming as well

1 hour ago, Frosty99 said:

I see, sounds like the lift pump is acting up then. That would make sense if isn't priming as well

 

No, because you were able to restart it while still rolling so that rules out the lift pump!

1 hour ago, sepulchrave said:

 

No, because you were able to restart it while still rolling so that rules out the lift pump!

Oh right haha, my bad. I'm not familiar with how it functions. I'm not sure if it's worth mentioning but it still had to turn over a few times to start when rolling after it stalled. But if it's not the lift pump then my next suspicion would be to check the tandem pump? I might be wrong lol

You don't have to use VCDS, a half decent scanner will do the job to read engine codes, it might turn up nothing and leave you still guessing but it might also lead you right to the issue so its worth doing.

 

I wouldn't bother checking the tandem pump to be fair, if its running alright the rest of the time that will probably be fine.

There's no EML or fault codes coming up when scanning, so back to investigating. If it's not either pump, then the only other thing I can think of is the injector loom as suggested earlier

If you cycle the ignition can you hear the lift pump start reliably every time? out of say 10 cycles?

On 17/10/2022 at 10:47, SuperbTWM said:

If you cycle the ignition can you hear the lift pump start reliably every time? out of say 10 cycles?

By the lift pump start, I presume you mean the priming squirt noise? If so, out of 10 cycles, I've heard it once. I thought I would leave it a while between starts / cycles.