406 HDi not terribly interested in starting - any ideas?!

[quatfro]

Hi there,

Apologies if this is deemed to be in the wrong topic area but it's a bit of a broad problem.

I've not long become the owner of a Pug 406 HDi - Economic and less holes than the Alfa 75 it replaces...that'll do, or so I thought!

Having only ever started straight on the key when I bought it, cranking it for 30 secs+ seemed the norm for the 1/2 dozen journeys I've done in it...a problem ignored is a problem solved, especially with a big battery...

Anyhow, on my way home from Banbury to Swansea it began conking out on the exits of roundabouts, though not always, turning left rejoining carriageways, and after being left for a while it would eventually show signs of life after prolonged cranking periods until I reached Hirwaun.

The fault codes which initially appeared were, using a Mac tools reader,

P0230 - fuel pump relay circuit malfunction.
P0220 - throttle position sensor malfunction (Switch B)
P0120 - throttle position sensor malfunction (Switch A)
P00CCpd - Not in database.
P00C8 - Not in database.

The latter two wont clear. The rest don't re-appear, though this may be because it's not started again.

I was baptised with petrol as opposed to holy water and embarrassingly Diesel systems are a bit of a mystery - Fuel pump makes a noise and sounds like it's pressuring, plenty in the filter bowl, no obvious corroded electrical connections.
The only strange thing is that I can only measure a fixed resistance at the throttle pot which would indicate that it is f*cked, but a local specialist (Which I'm trying to avoid paying) says that it should start despite this apparent fault so...

Any ideas?!

[mjb]

The throttle pot codes could just be random glitches from 5 years ago, so ignore them unless they come back (in which case you'll probably notice as you should go into limp-home mode). You're probably measuring resistance across the 2 tracks instead of one, which will stay the same.

A duff fuel pump relay could indeed cause death in the way you describe though. I'd slap your multimeter on it and check it out. Unfortunately I haven't got a clue where you'd find it...

[steve_earwig]

I think that depends on year, early HDis it's along side the ecu in the box, later cars I have a feeing it's part of it...

[quatfro]

X 592 YDY is what's written on the plate...

[steve_earwig]

That would make it a 1983. No, hold on, 2000? Something like that It's early anyway, so lift the lid of the ecu box and there should be a relay pack there.

[quatfro]

Not long told to try starting it with easy start by a mates dad who's and RAC bloke, so in this case I used brake cleaner and you know what, it fired up nearly straight away!

So I'm pleased, but also slightly bemused as to what it could be...and then tried the switch off and then re-start test to see if it's any better having just been run seconds before and...nothing. So it works and runs, but it wont start itself...

[poddack]

Nothing as simple as the in-tank pump then?

[quatfro]

Kept fiddling for a further morning but I've generally given up - infact I've booked it into a specialist, so I'll let you all know what this intriguing problem is or was, as soon as it's back!

[steve_earwig]

Oooh, scarey, good luck!

Nothing as simple as the in-tank pump then?

I think they're more "not start at all" than anything. Still, can you hear it running when you switch on?

[quatfro]

Oh yeah, with the seat and cover off you can hear it working fine. Ignition on and it runs, audibly builds up pressure and stops.

Once it's fired up using brake cleaner sprayed up the inlet it stays running and works fine, though I've yet to take it for a run yet.

[Doggy]

Sorry if you've already mentioned this, but have you changed the fuel filter?

I think the in-tank pump is supposed to run:
a) for a few seconds whe you tuen on the key,
b) while the starter's turning,
c) when the engine's started & you have oil pressure.

could you be missing b) ?

[Welly]

Duff crank angle sensor?

[quatfro]

Right, turns out it was the pressure regulating valve on the end of the pump.

£82 worse off for the diagnosis but for peace of mind having found something definitely wrong, worth every penny...

£89+vat for the new one...hopefully that'll be then end of my woes for a very long time!

[Doggy]

That's good news. As you say , worth it if that's the end of your problem.

£82 worse off for the diagnosis

Beginning to seriously think about setting up, 'Doggy's Dognostics'......