C5 HDi (110) Problem to Re-Start???

Grumpy · Post by **Grumpy** » 26 Aug 2011, 12:29

Hello all,

I recently found the forum and have found it very interesting and informative - but now I've got a little problem that has got me stumpt and I wondered if you kind folk could help???

I have a 2001 C5 HDi (110) Auto which I use as my 'sensible' car and which has always been very reliable - however, over the last month or so, it has started to become VERY reluctent to re-start ONCE IT HAS BEEN RUNNING...

When its cold (ie: first thing in the morning) or maybe within a minute of starting, or when it has had time to properly cool down after a run - it starts straight away with no problems (usually within 4 or 5 turns of the engine) however, if its been run for a bit longer and has got some heat into it, or its been on a proper run, it will refuse to fire up again once its been turned off - ie: after buying fuel etc...(it started being 'difficult' to re-start when warm at first, but has got far worse as time has gone on...)

I have found that if I spray some 'carb-cleaner' into the main air inlet pipe, she will start up again without a problem!

WHY?...Whats causing it?

I suspect that MAYBE it has an air leak on the fuel side somewhere? but I'm not convinced that this is the cause...

Could it be either a temperature sensor failing somewhere (the temp gauge has been playing up lately as well) or possibly a crank-sensor maybe? (if so, why does carb-cleaner help cure this though???)

Please help - its driving me mad!!!

SaabC5 · Post by **SaabC5** » 26 Aug 2011, 12:53

Dunno if this a common problem with Citroen's but several manufacturers have this problem with crankshaft sensors. They go "blind" when hot meaning the car won't restart, once cooled they start up fine again.

Post by **RichardW** » 26 Aug 2011, 15:05

Hi Grumpy - welcome to the forum

The fact that it will start on carb cleaner rules out the crank sensor I would think. I would do an injector leak off test - I suspect you will find one that is leaking badly. What is probably happening is that it is cracked internally, and opens up when hot causing a big leak off. When cranking, the ECU won't fire the injectors till it sees 120 bar on the rail, and with the leaky injector you can't get to 120 bar at cranking speed - with a bit of sniff in it, you get a couple of cylinders to fire which ups the speed enough to get to the magic 120 bar and away she goes. It might be the pressure reg, or LP pump, but you can diy a leak off test easily enough, so that is a good place to start. If that comes back negative, then you really need to get it onto a decent diag computer that can read live data to see what is going on with fuel pressures, crank signals etc.

hobblerian · Post by **hobblerian** » 26 Aug 2011, 21:50

Not sure if yours is the same as Dad' C5 2.2 mk1. His started doing the same. I discovered a broken ball and socket joint on the top righthand side of the engine as you look from the front of the car. This connects a rod to a vaccum pot or something and its to do with the injectors.

Once this was replaced it was back to normal. As a temp fix I wrapped a small elastic band around it.

Hope thats of some use.

Grumpy · Post by **Grumpy** » 28 Aug 2011, 09:35

Hello Gents - Thanks for both the replies and the welcome...their much appreciated!

RichardW - what you say makes perfect sense now - I presume therefore that the reason it starts ok when its cold or has cooled down, is that the fuel is 'thicker' (more dense) when cold, so it produces that bit of extra pressure thats needed???

I must confess, I have noticed a slight loss in MPG recently too and a certain degree of 'lumpiness' at idle - it all makes sense now!

Once again - many thanks to all!

Regards - Guy. (Grumpy

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