406 'Rocking'

[AdamJ]

Hi Folks,

My 406 [N reg, 1.9 dt lx, which has done about 195,000 miles] has some problems starting up in the morning. When I turn the ignition, it vibrates and knocks back and forth, but does not start up unless I keep the ignition turned with the accelerator pedal kept pressed.

The 'rocking' goes on for about 15-20 seconds before it finally kicks into life and revs up. This process gives off a lot of thick white smoke from the exhaust, and I am also concerned that it disturbs the neighbours.

It starts normally during the daytime thereafter. Then it recurs the next morning. The car was starting up fine up to a week ago or so.

Any ideas/suggestions/solutions?

Many thanks.

[spider]

Air ingress is likely as you said white smoke.

It could be glowplugs but they tend to cause darker smoke (at least from what I've seen)

Apart from the one behind the pump, the other three are easy to replace. Its likely that one was not changed last time (if they were done before)

[AdamJ]

Thanks for the reply, Spider.

If it is due to air ingress, what is/are the solution/s?

Though perhaps I have exaggerated the thickness of the smoke, not being an expert on cars [far from it!].

Many thanks.

[myglaren]

Before starting, squeeze the primer pump about ten times or until it becomes very firm, then start the car. If it starts straight away as normal then there is a leak in the fuel delivery pipes to the HP pump.

Fitting a length of clear hose between the primer and the HP pump will let you see if there are bubbles in the fuel, indicating an air leak somewhere.

There could be a pinhole or tear in the pipes, a leak in the diesel filter or more commonly hardened and cracked leakoff pipes on the injectors - look there first.

[addo]

I'd suspect the head gasket. Has it been running hot or losing coolant lately?

[CitroJim]

Another potential cause of this is tight valve clearances.

It is a quirk of the XUD that the valve clearances are tightest when the engine is stone-cold and if they're tight the valves can be held just off their seats until a tad of heat expands the head sufficiently to increase the clearance.

This is a very common problem on the 1.7 NA XUD and is not so often seen on the 1.9TD but worth a check anyway.

They're easy to check but a bit of a game to reset as you need to calculate new shim thicknesses and the cam need to be removed to swap shims.

The Haynes manual is pretty good on this subject, especially the Peugeot Diesel Engine book, even though it claims to cover only to N plate vehicles.

[HDI Dave]

My 406 [N reg, 1.9 dt has some problems starting up in the morning. When I turn the ignition, it vibrates and knocks back and forth, but does not start up unless I keep the ignition turned with the accelerator pedal kept pressed.

The 'rocking' goes on for about 15-20 seconds before it finally kicks into life and revs up. This process gives off a lot of thick white smoke from the exhaust, and I am also concerned that it disturbs the neighbours.

It starts normally during the daytime thereafter. Then it recurs the next morning.

I had the exact same thing with my pug 306 xud,embarrassing!

I only bolded the last bit of your post as -

it doesn't happen all the time, just when flat cold.

Glow plugs cured my problem, and I only changed 3, one was hard to get at,so I left it! Started on the button thereafter

When were the glow plugs last changed? Surely the cheapest and easiest option first?

[AdamJ]

Hi Folks.

Sorry for this belated response guys. I was busy with work and away from home during the week. Here is my response to your helpful posts:


[i] Myglaren, I squeezed the primer pump/bulb about 20 times and it still did not become firm! It started after rocking about tthree times, but that is most probably because I was driving till about 11.30 pm last night, and then tried to restart it after 9 hours. I normally tend to park the car in weekdays around 6pm and then start it in the morning after around 13-14 hours.


[ii] Addo, not being a mechanic or a diy man myself, how would I know whether the head gasket has been running hot or losing coolant?


[iii] CitroJim, mine is an N reg. But the process for checking valve clearances seems a bit involved to a novice like myself.


[iv] Hdi Dave, ofcourse mine is not an hdi, but a standard 1.9 lx td, but it seems to me changing the glow plugs might be a good place to start. However, the smoke is white, whereas Spider suggested above that it is likely to be dark smoke if it is due to glowplugs.


Where do I go from here? An interesting thing is that I noticed about 2 weeks ago that the under-shield was missing. It was there the last time I looked about a month ago or so. This would suggest to a novice like me that the problem might be caused by cold during the night. What do you think?


Many Thanks Again Guys.

[pug_owner2002]

I think the fact that the primer bulb did not get firm could be pointing to the issue.
On my old 306 I would have struggled to pump it 20 times as it got very firm.
I think the primer bulb has a valve in it, maybe this could be at fault. Can one of the experts here confirm if this is correct?

[myglaren]

I think the fact that the primer bulb did not get firm could be pointing to the issue.
On my old 306 I would have struggled to pump it 20 times as it got very firm.
I think the primer bulb has a valve in it, maybe this could be at fault. Can one of the experts here confirm if this is correct?

Not an expert by any means but the pump would have to have a non-return valve in it for it to work and it looks like either that is defective or something upstream is allowing the fuel to go 'somewhere', possibly through the return line to the tank. If this is so then fuel would drain back to the tank overnight creating the difficulty in starting.
I'd set about solving that in the first instance and see what transpires when it is cured.

[spider]

Not an expert by any means but the pump would have to have a non-return valve in it for it to work and it looks like either that is defective or something upstream is allowing the fuel to go 'somewhere', possibly through the return line to the tank. If this is so then fuel would drain back to the tank overnight creating the difficulty in starting.
I'd set about solving that in the first instance and see what transpires when it is cured.

I've had to add a few months ago two one-way valves (proper ones meant for this purpose) into my fuel line, although only one may of been needed.

I have one just (about an inch!) before the fuel inlet into the pump, and the other just after the fuel filter (as my fuel filter location is quite a way away from where it normally is, mines right near the N/S suspension turret. This one (was) needed due to the problem of fuel running back down the line across the bulkhead due to crap pipe work (since fixed) but left the valves in place anyway and I had at least two air leaks (apart from the pipes) so a 'belt and braces' approach was needed.

All's good now , but bear in mind mine had the 'back of block I love to take in air' fuel heater and the 'not very good when new' stand alone filter assembly behind the battery.

As above though, these fuel draining issues only happen overnight, constant use and they will not happen as the fuel never gets chance to run away.

[RichardW]

white smoke = vaporised, but unburnt diesel. Odds on it needs a set a glow plugs, especially as the symptoms appeared to start suddenly. The one behind the pump is not that bad with a decent 12mm cranked ring spanner.

[AdamJ]

Thanks guys. Ok, I think I've moved one step forward.

I was advised to switch ignition on on and wait until the amber coil light goes off. Then switch it on again and repeat twice. After the third time, switch ignition full on, and if the car no longer rocks/judders, then the fault lies with the glowplugs.

So I tried it this morning, and the car started up with slight juddering once or twice. It normally judders about 7-10 times or so before it starts up.

So does this point to the glowplugs, or something else in addition to it? Should I replace the glowplugs before I try out the other suggestions?

Many thanks Guys.

[spider]

If two / three glowplug sessions before starting reduce it then change the glowplugs, the 'glow twice' trick is a reasonable test. As its better with a couple of glows, you need to replace them, one if not two will be faulty. I would actually guess you have one completely dead and one partly working (possibly glowing in the middle) from your description.

Bear in mind, if you have more than two faulty, that trick will not work (just pointing out for future reference)

If you do this trick too much, it will burn the others out as they do not like being left on for too long. Typically two 'glows' is a sensible limit.

I would say replace the glowplugs, you 'must' replace the one behind the pump (sorry) as I bet when they were changed before this was not done.

They can part fail so you cannot rely on reading their resistance etc, its possible for them to (electrically) appear to work but when you bench test them, they glow in the middle etc and not the tip.

Grab yourself a set of (decent) glowplugs and replace them or get them replaced and then see how it goes. It may cure it it should certainly reduce it a lot.

[RichardW]

Grab yourself a set of (decent) glowplugs and replace them

Indeed - fit only Beru plugs to these unless you want to do the job again in a few months - they are available from GSF for <£10 each. The job is not too bad - the one behind the pump is a bit if a git, but there are tricks to make it easier (see Xantia glow plug info). If it's got a Lucas pump you're laughing!