Tech query one: Diesel running/cold starting issues

[Kitch]

Right, I've had two motoring cock-up's in two days! The only car I have left which runs fine is the TVR, and it has no tax. The Xsara's....I don't even know where the Xsara is! But that works too.


Problem one....106 1.5D. Once warm, runs happy as Larry and does stupid to the gallon every time. Great!
However.....try and start it first thing in the morning and it's a different story. If it's not icey, it'll start in a slightly lumpy fashion but first time. It'll then sit there and hunt around with the revs after a couple of minutes. If you drive it, it tries to speed up and slow down even with a steady throttle. It's like a choke that's stuck open.

If it is icey, I get the same scenario, only worse. And the extra bit of fun is that it's a nightmare to start. It turns over for ages and ages and eventually gets going in a cloud of smoke. Sometime it starts runnning, hunts and dies. Then it turns over until it flattens the battery (like this morning )

I think the glow plugs are ok though. Light goes on and off and if I try to start it later in the day it's straight into action.
The wax stat thingy cable on the pump seems tight in the morning, but the lever itself has play and it doesn't do a fat lot if I wiggle it around, although don't read into that too much as I have zero clue about what I'm doing on diesel engines!

help!??

[DavidRutherford]

To check the glowplugs you need to remove the connecting rail between them all, and then check each one, resistance between connector and block. Should be about an ohm.

Sounds to me like the rest of the problem is air in the fuel line, which then clears once it's been running for a bit. This would suggest the leak is in the return line (or the leak-offs) rather than the supply line, although there's no guarantee. Start looking for perished hoses, or (IIRC) a porus fuel pre-heater.

If you're having real problems locating the issue, smearing grease over the connecting points can sometimes isolate the problem (as it either seals the problem, or is rinsed away by the leaking fuel.)

[Kitch]

The leak off's appear to be bone dry, are there any other return lines to check? I'm guessing it's return lines between injectors and pump only?

I had a mate once who had to buy a new Purflux filter housing cos the seal in the top on the primer had perished letting air in. This one has the primer bulb, but I'm guessing thats on a low pressure feed before the pump?

I know nowt about diesels, but I have a feeling I'm going to have to learn

[DavidRutherford]

The leak off's appear to be bone dry, are there any other return lines to check? I'm guessing it's return lines between injectors and pump only?

No. Theoretically the leak could be anywhere in the lines from the tank to the injection pump. You'll find that any leak probably won't show up as wet with diesel, as it's allowing air back in. Bear in mind that the lift pump to draw diesel from the tank is part of the injection pump, so the line from the tank to the pump is under "suction", so the slightest leak will allow air in.

In theory, any leak on the return side would be wet with diesel, but as the injection pump is higher than the tank, they often don't, and also just let air in. This isn't a problem when the engine is running, but when you stop it, that air gets back into the pump, and it effectively loses its prime, hence the need to crank it loads.

Try priming the pump with the primer bulb before starting. If there is an improvement, then you have the fault (just not the location!)

[CitroXim]

Hi Kitch,

Have you mislaid the Xsara somewhere?

I don't know if this applies in the TUD but on the XUD there is a quirk whereby the valve clearances are tightest when the engine is stone-cold. If it so happens that they are a bit marginally tight when at reasonable tenmperatures, in the real cold they can be so tight as to lift the valves off the seats and thus loose compression. A bit of heat and all fine again. It might be worth checking valve clearances.

Glowplugs are worth a check. Ensure you are getting at least 10V across them when they are on and ensure they are on for all the time the orange lamp is on. Have them out, put them across a battery (carefully) and check they glow nicely at the tip. If in doubt, replace them.

Change your fuel filter. If it's not been done recently and you have a bit of water in your tank (most have after a few years) you could have ice crystals forming in the filter and thus reducing the amount of diesel getting through.

I doubt this is your problem but my dad had a tad of trouble starting his 205D the other week when it was really cold. He had not filled up since June (car only runs to shops and back) and he was still running on summer diesel.... A fill-up and all well.

When cold I always prefer to run a well-known brand of diesel and not supermarket stuff. Mine seems to not start quite so well ion Tesco finest when the brass monkeys are about.

The cold start. Does your pump (I'm assuming a Lucas pump) have the cold start advance solenoid (big cylinder on the front of the pump with wires going to it)? If so, this is operated by a contact on the end of the cold start lever, the one operated by the waxstat. Giving some cold advance makes a big difference on a Lucas; try tying the cold start lever in the maximum cold-start position and see if things improve. Check the advance solenoid (if fitted) is actually operating - check the switch contacts.

That's problem No.1 (hopefully) sorted.

So, what's problem No.2 ?

[CitroXim]

Amazing When I started typing my reply, not one other post. Now there's four!!! My typing slow or what

Do check for air leaks very carefully. Some say they don't matter in a Lucas system but I know they do. Leakoffs are always a favourite and worth a change even if they look OK.

[Kitch]

Right, well it sounds like it's worth changing the leak off pipes....I think I've got a bit of the stuff under my desk at work!
I'll test the plugs if that doesn't fix it.

I did try priming the bulb before starting....no difference, although a mate commented he thought it seemed to need too many pumps to make it go hard (ooh err!)

So any other leak could be under the car then? But I guess it's much more common for it to be under the engine bay....hopefully?!

Valve clearances offer the most accurate reply to the initial problem, so worth remembering. I'll probably check those later though, after all the easy stuff.

Looks like I'm getting my hands dirty over the weekend!

[demag]

I have actually heard of the priming bulb deteriorating over time and getting porous enough to let air in but not diesel out.

Check the wiring from the glow plug relay to the heater plugs. I had a right game last year trying to start the Xm in the cold. Turned out the main connector on the bottom of the relay was hanging on by a whisker. But the heater light still used to come on when I turned the key!

You can also carry a can of cough mixture for emergencies. Don't use it too much though they become addicted.

Edit works!!!

[CitroXim]

One thing when using the primer with a Lucas pump. The ignition must be on so the stop solenoid is energised. On ly then can fuel flow through the pump.

[CitroXim]

Kitch,

I'm sorry, forgot to say last night...

A good way of tracing air leaks is to replace the fuel line from the filter to the pump and from priming bulb to filter with lengths of translucent pipe. You can then see if the fuel is draining away overnight. A bit of clear pipe in the return line can also reveal things.

Whatever pump, it is essential that the pump stays full to the brim with fuel. Any leakage means the pump has to refill and as in both, the passage to the HP pumping elements is at the top of the pump and if the level falls too low, air will be drawn into the HP pumping elements.

[jonathan_dyane]

Hi Kitch,
I don't know if this applies in the TUD but on the XUD there is a quirk whereby the valve clearances are tightest when the engine is stone-cold. If it so happens that they are a bit marginally tight when at reasonable tenmperatures, in the real cold they can be so tight as to lift the valves off the seats and thus loose compression. A bit of heat and all fine again. It might be worth checking valve clearances.

Spot on; this is very much a TUD problem! For reasons unknown to me, if the TUD lump gets a tad hot it has a tendency to lose its valve clearances (stretching valves?). If the glow plugs check out ok, first thing I'd be doing would be to pop off the rocker box... Although as with the XUD the cam must be moved for reshimming, it isn't a bad job at all.

[Kitch]

More interesting points. Think I need to repipe this thing to be sure!

Valve clearances....I have to remove the cam??!! Or did I read that wrong?

[jonathan_dyane]

Sadly (as with the XUD) you do need to remove the cam to set the valve clearances; they are set by changing the shims which sit on the top of the tappet buckets and (unlike the XUD) are directly acted on by the cam... Although it sounds a nightmare, it really isn't that bad

If when checking them with the feeler gauges they are too tight, note the actual gap (which may be zero, or indeed in a bad case less than zero as the valve is then unable to close) then pop the cam out and measure the problem shims with a micrometer (ignore the figures on them, they wear and also may have been ground down...) Work out how much smaller the shim needs to be for correct clearences and then either get a handy mate with access to a workshop to reduce their width or pop to your friendly Peugeot or Citroen dealer. They probably will have them in stock, it is a common issue

The main difficulty is the need to 'guesstimate' shim sizes where the valve has closed up entirely...

[Kitch]

That sounds a bit more involved than I'd really want to get! Cam out is cambelt off etc, and truth be told I prefer my runarounds to be the type of vehicle I never have to open the bonnet on.....I've been spoiled by a BX 1.9D in the past I reckon!

If it's the valve clearances, I'll break it and sell it as parts. Worth more in bits, as the MOT is up next month. Only thing I wonder is that if the valve clearances were too small and the valves remained open slightly, surely that would affect the running as the engine got hotter? It runs beautifully once warm, its just after starting cold that it tends to muck about with funny idling.

I think I'll try and eliminate any air leaks first as that's cheap and easy. Fuel filter is new, so I've discounted that (and it's not leaking!) I think we've even got some new primer bulbs on the shelf at work so could try that too.

I might try using this clear pipe then too, see if it gives me a clue.

Cheers!

[CitroXim]

Thing is Kitch, it only takes a tad of heat in the head to expand it just enough for the valves to close again and for fully normal performance to be restored. You'd never know.

It really is quite remarkable. I had it on a 205D. Below zero it would not start, a couple of degrees above, start reluctantly but within seconds, running like a clock and at anything over 5 degrees it started absolutely perfectly!

Had I not experienced this quirk personally, I'd never have believed it possible

Little diesels seem to suffer more. It's common on the XUD7 but comparatively rare on the XUD9

I tend to set valve clearances to the wider side of the tolerance if I do them in the summer.