Long cranking time for 406 Hdi ?

[arnie]

Hi all, I,m having a problem with a 406 Hdi 90 , it is cranking over a lot longer than it used to , used to be like in other posts about 2-3 secs even when cold. The cranking time isn't so bad when first starting in the morning ( although the temps are still fairly warm at this time of year) , I can turn it off and it can then take a good 5 - 6 secs straight away. The symptoms are the same wether the vehicle is hot or cold. A new fuel cut off solenoid has been fitted to the rear of the HP pump. Does anyone have any sensible ideas I could try to rectify the problem before I go ahaed and assume the HP pump is at fault... many thanks Arnie...

[Doggy]

Is it spinning over fast enough? - apparently HDi's won't inject any fuel unless the ecu registers a cranking speed of 60 RPM, (this possibly explains the normal 2-3 second delay).

Worth checking the crank sensors not loose / connections etc?

If you get someone else to turn the key, you should be able to tell if the injectors are 'firing' audibly - maybe put a screwdriver on the top of one, rest your ear on it.

If it's trying to inject, I'd try to verify you have fuel reaching the HP pump. (Don't crank it too much without fuel BTW, this can wreck the pump).

[arnie]

Thanks for the reply, as I had a HP pump anyway, I have fitted it and the problem is still the same, very strange as when driving it ,it drives fine ?. It 'hunts' quite a bit after cranking for a long time. Has anyone had any problems with the filter housing head as the hunting seems to be worse when moving the filter housing about ?, also can a low pressure drop cause this problem ?, I believe it has to be 2.5 bar on the LP side and 0.7 bar on the return. cheers arnie.

[DiscoPol]

Has anyone had any problems with the filter housing head as the hunting seems to be worse when moving the filter housing about ?

air leak from the filter housing somewhere? its not uncommon when people do a service to have issues with starting afterwards if they havent got an airtight seal on the housing, maybe you have a cracked pipe on there letting a bit of air into the fuel system when the engine is off, the fuel will drain back to the tank if there is any air getting in, in turn this will make starting harder as the system needs to prime again everytime

[arnie]

Thanks Discopol I do not disagree that this would be priming itself again as the fuel had run back, the problem is you would need a slight period of time for the fuel to run back, where as when the car is running it runs perceftly well yet as soon as I switch off , even if I crank immediately again after it has stop which is probably less than a second or two, the cranking problem is there straight away . I don't think the fuel would have enough time to run back, I could be wrong of course ?, another thing is there a possibility that a cam or crank sensor could have this effect or would this not allow i to start at all ?, I am a commercial engineer working at a bus company and have dealt with god knows how many problems conserning common rail fuel injection systems and have all the diag kit to do so too, but cars are a different product altogether and I like most of the people on here do not really want to spend anymore fixing a problem than necessary. I appreciate the help people are giving on here and will endeavour to help individuals myself if I can... Thanks Arnie...

[arnie]

Problem solved !

[Doggy]

Good!

- what was it?

[arnie]

Pressure regulator on the back of the HP pump, I had changed this , but it turned out that the one I fitted was faulty too.... Lesson learned I guess, never buy of Ebay, but how many of you would of stumped up £250 for a recon pump and pressure reg on a hunch .... ? :-/

[Doggy]

That's not the first dodgy pressure regulator that's been posted on here, (but only the 2nd or 3rd in several years, I think).

You're right - I wouldn't have gone for a new or recon pump, given a choice. Probably have tried one from a breaker, on the assumption that two identically faulty ones would be pretty unlikely.

- just checked ServicePox.

Reference Description Quantity Price - VAT Price + VAT Total + VAT Selection
0000193338 REGULATOR 278.29 GBP 333.95 GBP 333.95 GBP