Rare Engine Starting problem

[aneesh84]

Its been 3 months since I have owned a Citroen C5 2005 2.0 HDI 136.

During this period I have twice faced engine starting problem on two different long trips. On both the occasions the car was hot (but within range) after a long country drive. The engine starter motor was cranking but engine not starting. On both the occasions after leaving the car for about 2 hours, the engine started fine. During regular city drives, I never faced this issue, hence it is hard to replicate.

Checking with lexia, I couldnt find any errors. Could it be the crank sensor or cam sensors (i guess should have 2 cam sensors)? Any suggestions how i can check them? any other possibilities?

[Peter.N.]

I had an earlier C5 with the 2.0. 8 valve engine that suffered a similar problem and it was the presure regulator valve on the back of the HP pump but I don't know if yours uses the same system.

Peter

[aneesh84]

I had an earlier C5 with the 2.0. 8 valve engine that suffered a similar problem and it was the presure regulator valve on the back of the HP pump but I don't know if yours uses the same system.

Peter

Hi Peter. Is there any way I can check if that is the problem. I have a lexia, if that can help?

I never had the car stop while in operation, only while starting.

[Peter.N.]

I didn't have a lexia at the time, I found it by trial and error so I don't really know. What mine used to do was start OK from cold but the hotter the engine got the more difficult it became to start until it became impossible and you had to leave it to cool down.

I just had a look on ebay but the regulator looks different to mine which was on the back of the HP pump. There are a few here, don't know what year your car is.:
http://www.ebay.co.uk/itm/CITROEN-C4-C5 ... SwFEFXJnPj


Peter

[aneesh84]

It is a 2005. The symptoms seem very similar to mine. So basically it is a sensor that measures the pressure and sends it to the ECU? In that case, when hot, a faulty unit sends a higher fuel pressure reading, and hence the pump stops pumping, and the car doesnt start. Does that seem like a probable explanation?

I am carrying around my lexia now, and I could try to measure the fuel pressure reading, but if it is using the same sensor, then the lexia would also show a faulty reading. Is there an alternate way to verify real fuel pressure?

I didn't have a lexia at the time, I found it by trial and error so I don't really know. What mine used to do was start OK from cold but the hotter the engine got the more difficult it became to start until it became impossible and you had to leave it to cool down.

I just had a look on ebay but the regulator looks different to mine which was on the back of the HP pump. There are a few here, don't know what year your car is.:
http://www.ebay.co.uk/itm/CITROEN-C4-C5 ... SwFEFXJnPj


Peter

[Peter.N.]

The usual problem with my type of sensor is that the internal filter gets blocked and is very difficult to unblock as its a hard stainless steel tube with very tiny holes in it, I believe yours uses a different type and so may not be the problem. I will do a little research and see what I can find.

Peter

[Peter.N.]

There don't seem to be any regulators for yours on ebay which would seem to suggest they don't give trouble, I have looked at your engine in the manual but that doesn't help in the least I'm afraid.

Peter

[aneesh84]

You can check the result of the Lexia session here:

[Peter.N.]

I can't see to much wrong with that, but of course it wasn't taken when the fault was present. If you can connect the Lexia when it wont start, turn it over and check the fuel pressure compared with when its running.

Peter

[aneesh84]

Could it also be a problem with a faulty cam shaft sensor or a crankshaft sensor. The error log under injection menu on the lexia though does not show any recorded error.

[chris222333]

Does it start when the engine cools? The heat can expand the crank sensor and expose hairline cracks thus causing the magnetic field to collapse. I had exactly the same on a saab once it never logged a fault code.

[aneesh84]

Does it start when the engine cools? The heat can expand the crank sensor and expose hairline cracks thus causing the magnetic field to collapse. I had exactly the same on a saab once it never logged a fault code.

Yes it starts after cooling down in like 2 hours. You feel the crank sensor is more likely than the cam sensor? I will try reaching it and cleaning it to see if it helps.

[Peter.N.]

The only other thought that struck me is a leaky injector, they can become much worse when hot causing the fuel rail pressure to drop. You can do a leak off test or compare the the injector correction values hot and cold, I think No 4 was the most at variance.

Peter

[aneesh84]

Can anyone please describe or point to a picture/map to help locate the crankshaft sensor on the C5?