Car not cranking.

[Dadscab]

Hi all. 

 

Got a problem with my 13 plate 1.6 greenline.

 

Ignition comes on but it won't crank first time, but if I try it a couple of times, then leave it for 10 minutes or so, it starts but I have to keep the key turned in the ignition for 5/10 seconds before it cranks, feels a bit like it's thinking about whether it wants to start or not.

 

Once started the problem disappears, but then returns again when the cars not used for a day or two. Fitted a new Bosch S5A08 - 70A/H - 760A - Agm 12 months ago and it's fully charged and working fine. Any help or advice would be much appreciated. Thanks. 

 

 

[superbdreams]

ignition switch contacts perhaps?

[Dadscab]

2 hours ago, superbdreams said:

ignition switch contacts perhaps?

That's a good call, one of my friends suggested the same, so I'll start there. Car's done 160k so I might need to start a check list. 

[xman]

If your car doesn't have start/stop (micro hybrid setup) then its alternator output voltage is not suitable for AGM, its too low so the battery never gets fully charged and may now be damaged/dead.

 

Get the battery checked with a tester, free service at most garages/places that sell batteries to eliminate the obvious

[xman]

If it does have stop/start, did you recode the vehicle to tell it when you fitted the new AGM battery? Needed to change the charging profile/voltage.

[Dadscab]

Hi xman. My friend checked the battery and it's fully charged, the car has stop start but the first thing I did when this problem started was switch it off. 

[xman]

11 minutes ago, Dadscab said:

Hi xman. My friend checked the battery and it's fully charged, the car has stop start but the first thing I did when this problem started was switch it off. 

 

Did your friend use a proper battery tester that measures its performance under load, internal resistance etc? Just putting a simple voltmeter on tells you very little, a fully charged duff battery is still a duff battery.

 

Was the previous battery on the car also an AGM battery or was it an EFB or even a standard battery? Did you recode?

 

Forgot to ask, do the dash lights go dim or out when trying to crank (unsuccessfully)?

 

 

Edited 19 January, 2022 by xman

[Dadscab]

I haven't got a clue about recoding the vehicle, wasn't aware this type of thing was even required when changing a battery. But then the last time I properly worked on a car myself, was our old 1980 Mini Clubman Estate. Where would I start or is it something that needs to be done by a technician? 

 

Previous battery was also AGM. The dash lights and headlights don't dim when I try to start the car. 

[xman]

1 minute ago, Dadscab said:

Previous battery was also AGM. The dash lights and headlights don't dim when I try to start the car. 

 

Perhaps I should have asked this first. So its reasonable that the battery is ok. And you need to look at that ignition switch or your immobiliser. Have you tried the spare key?

[nige8021]

Manual or auto transmission ? if it's auto it could be starter inhibit relay 

[Dadscab]

Good shout. Car's a manual. 

[Dadscab]

Just tried the spare key, but it didn't work, good shout still. 

I've just spent the last 5 minutes trying to get it started and one thing I noticed was that I couldn't hear the usual fuel pump noise when turning the key, then after 20 or so attempts I heard the fuel and it started. 

[xman]

Suggests its either the ignition switch or perhaps some issue with the immobiliser. IIRC the immobiliser has a pickup coil in the ignition barrel area that interrogates the passive chip in the key.

 

 

From the above video you can see there is the coil connector in the outer ring, maybe try pushing that outer ring back while turning the key?

 

Another thing to check is all the fuses are properly seated in the fusebox, I once had an issue with rear wiper that was due to a fuse not fully pushed in.

 

Not sure if a faulty fuel pump/no fuel pressure would prevent your car from cranking, I wouldn't have thought so.

[xman]

Further thought, if the dash lights always comes on even with no fuel pump noise, its unlikely the ignition switch itself. Fuel pump will only operate if the pressure is too low in the lines, not sure on your diesel but on most cars it operates only briefly to top up the pressure when turning the key on and won't operate until the pressure drops below a certain level.

 

Which leaves the immobiliser, a diagnostic scan with a capable tool, e.g. VCDS would confirm if the immobiliser is blocking

 

Edit: forgot that the starter is a seperate switch to the main ignition so ignore above

Edited 19 January, 2022 by xman

[nige8021]

The immobiliser won't stop it from cranking, if it was an immobiliser fault it would start and run for about 3 seconds then stop as it kills the injectors 

[Dadscab]

Is there any way to reset the immobiliser that won't cost me a fortune as I'm broke at the moment

[Dadscab]

So that leaves the ignition switch, so that should be the first port of call do you think? 

[xman]

1 minute ago, nige8021 said:

The immobiliser won't stop it from cranking, if it was an immobiliser fault it would start and run for about 3 seconds then stop as it kills the injectors 

 

 

Need to look at the electrical schematic, does the ignition starter switch operate a relay which in turn operates the starter motor? Could be a faulty relay (dry joint?) or even a faulty starter motor.

 

[Dadscab]

My friend suggested the starter motor. I'll go now and have a quick look at the fuses. Cheers 

[Breezy_Pete]

9 minutes ago, xman said:

does the ignition starter switch operate a relay

2 relays, in series, positions 2 and 3 in wherever the relays are on a Superb 2, E-box under bonnet? 

Might be worth giving either/both a tap when the car's next misbehaving.

 

[Breezy_Pete]

In cabin I think. Starter relay 1 is in position 2.2 on relay holder underneath Onboard Supply Control Unit

Starter relay 2 in position 2.1 on relay holder above Onboard Supply Control Unit

 

Different positions in cars built from May 2013, working on it.

Same pos for relay 1, this for relay 2:

Starter relay 2 in position 3.1 on relay holder above Onboard Supply Control Unit

 

 

Edited 19 January, 2022 by Wino

[Dadscab]

13 minutes ago, Wino said:

In cabin I think. Starter relay 1 is in position 2.2 on relay holder underneath Onboard Supply Control Unit

Starter relay 2 in position 2.1 on relay holder above Onboard Supply Control Unit

 

Different positions in cars built from May 2013, working on it.

Same pos for relay 1, this for relay 2:

Starter relay 2 in position 3.1 on relay holder above Onboard Supply Control Unit

 

 

I ain't technically capable of all this, but I can wiggle a fuse. I'll get my friend to have another look and show him this thread. Thanks for the help.