Starting issues

[dug]

Hi,

My 2012 1.6 TDI Caddy has had some issues starting for a few years now. Although recently it's left me stranded, asking strangers for a jump start.

It turns over just fine, but will sometimes crank over until the battery is flat without starting. It's worst when I've only driven a short distance and try to start again after popping into a shop. Strangely, it seems to start better if it's cold!

It's been regularly serviced and has had the fuel filter replaced multiple times; the filter never looks dirty and doesn't seem to make a difference. It has had the injectors replaced by a reputable garage, and I replaced the glow plugs recently. No fault codes are shown, so I'm at a loss.

Any ideas? Is it fuel pump related?

Thanks
Doug

[STP]

Seems more likely a crank or cam sensor, have you scanned it for fault codes? This is the only way to know. Cam/crank synchronization needs to be OK for the engine to start and sensors often fail when hot or warm, but work when cold.

For any fault, codes are required, otherwise people are just guessing mate.

[dug]

Thanks, it's not showing any fault codes unfortunately. I'm using a Launch CRP123X Elite scan tool, not the fanciest, but not the most basic. I'll take a closer look at the crank sensor and its wiring, I'll probably replace it for peace of mind too.

[STP]

If it does live data then look at cam/crank sync and fuel pressure, needs to be about 300 bar while cranking. VW stopped the crank sensor throwing a fault as it did it when not running on the MK3 golfs - obv it shouldn't be logged as a fault with the ignition on and not actually running or cranking so I reckon it now gets ignored, could be a chance it's that (no code). They are hall-effect sensors so are prone to hot failure when they go bad.

I like Launch stuff, it's not bad. Should have a good bit of live data to look at. Unfortunately you'll have to check these things when they are good, and when bad to see the comparison. it does disconnect a lot of things when it's turning over but hopefully the OBD socket stays on during cranking.