ZX diesel smokes on start-up

[RussellF97]

Hi All,

I've had my 1995 ZX Elation 1.9 non-turbo diesel for about 18 months now and it has this curious habit of smoking on start-up during spring and autumn.

Essentially, it seems that when it's been cool at night (like now, when we are starting to get into autumn), on starting, there's a big cloud of blue smoke and some rough running for a few seconds, then everythings fine. During the summer or winter (less night/day temperature variation), no (or very little) smoke and starts fine.
Once the engine has started, it's fine for the rest of the day.

It was on 98,000 when I bought it, and it's now done just over 121,000 miles and goes like a good-'un. Returns mid-to-high 50's mpg and uses very little oil, less than 1 litre between oil changes at 4,500 miles.

Has anyone come across this strange phenomenon?

[dnsey]

Sounds as though you have one or more failed glowplugs.
Checking the current drawn will pinpoint an open-circuit plug, but they can fail to heat properly while still taking current.
Does the relay operate correctly? On some models, a faulty plug can alter the 'on' time.
At 122k, it's probably worth replacing all the plugs if in doubt.

Edit: just noticed that it's OK in the winter. Could be that the temp sensor is misinforming the glowplug timer. How does the 'on' time vary with temp?

[RussellF97]

Hi dnsey, thanks for your reply:

I'm not too sure about a failed glowplug though: Last winter here, we had sub-zero temperatures and it started fine. In my experience (mechanic, then AA Patrol for nearly 20 years), a failed glowplug will cause poorer starting irrespective of outside temperature. Having said that, this is the first diesel car I've owned, so I'm willing to be proved wrong on all counts!

I've just been out and started the car; the glowplug time was 8 seconds. It wasn't particularly cold here last night, so only a small amount of smoke; do you know what the glowplug on time should be?

I have to go out soon, but I will check the glowplugs asap to see if any of them are open circuit or have wildly varying resistances.

Cheers...

[spider]

Eight seconds sounds about right.

Be aware the earlier models are completely time controlled not temperature though, not 100% sure when it changed over, and its different for N/A vs Turbo units in this regard too.

The other possibility is the cold start advance is not working (although I threw mine away completely as it liked to stick on) but not all N/A XUD's have this anyway, it does not seem to have much effect really without it (the annoying part is fitting the early NA plate so the timing is right without it) apart from a slightly smelly exhaust when stone cold, at least from my experience anyway.

I don't think you have post heating at this year, and again its not really 'essential' either.

Also note that glowplugs can read correct regarding resistance, when you bench test them you see they can have odd faults such as glowing in the middle ( ! ) instead of the tip, that would cause a loss of heat in that cylinder during the initial start and the first few seconds of running.

[JohnD]

Daughter's Pug 306 is the same engine as yours. The gloplugs take 8 secs on the light followed by a further 10 secs after the light has gone out.

[Peter.N.]

Have you tried the effect of not starting the engine until the glow plug relay drops out, this gives it a lot more heat and will usually start much quicker, if it cures the smoke its still not conclusive, may be because the glow plugs are weak or that the compression is a little low - personally if it goes off quickly I wouldn't worry about it.

Peter

[the_weaver]

Russell

If it's not a glow plug then it could be an air leak into the fuel system. I would check around the connections to the rubber priming bulb for any fuel leaking out. Check the rubber priming bulb itself for splits. Then move along the fuel pipe in both directions. Even if you can't find fuel leaking out you might still have an air leak inwards. You might be able to reduce the smoke in the morning by pressing the priming bulb a few times before starting the engine.

Paul

[RussellF97]

Thanks for your replies folks. I finally got round to checking the glowplugs: I pulled three of them out to have a look and there were no weird marks that might show they weren't heating properly.

It's definitely excess oil on starting that is causing the smoke and poor running initially, but I'm still at a loss as to where it's coming from. The only place I can think of is the breather; but why would it only do it when the car's been standing overnight? Strange...

[jgra1]

Russel are the plugs back in? I often bridge them across a battery, it's then proof they work or not?

John

[RussellF97]

Hi,

Yep, they're back in and I've been running around in it.

I've just been reading another thread on here where someone had starting probs after having some new glowplugs fitted and the rail wasn't making contact with the plugs. I think I may just clean all the connections tomorrow and do a meter check to see if power is getting down to them all.

[uhn113x]

Make sure the connectors on the GP leads are clean and tight; there's a lot of current flowing through there!

[RussellF97]

Removed the GP wiring and cleaned up the connectors, still the same.

I come back to my original query: why should it only seem to start badly and smoke when it's colder at night than during the day?

Last winter, in temps of -4 degrees C or so, it started no probs. In the summer, no probs. Spring or autumn, cough, cough, splutter, smoke...

It's got me beat...!

[spider]

It cannot be light sensitive

The only thought I have about that is perhaps there is more moisture around in the atmosphere at night...