lumpy startup zx td (starting technique?)

deian · Post by **deian** » 09 Oct 2007, 19:13

Hi,

Whenever I start my car from cold it seems lumpy for the first few seconds. When I put some throttle on it will chockingly clear up in about 10 seconds.

Other times it's ok. Another question I wanna know is... the glow plug... it will light up, and then i hear a solenoid, it starts better after this. So is all this related?

Finally, how exactly are you supposed to start a diesel engine?

1. Let the glow plug light go off, start with no throttle.
2. Let the glow plug light go off, start with throttle
... this is where I think it goes wrong, I start after the light, but obviously it's not warm enough, and I've been using throttle, so it may be too cold, and flood, hence the smoke WHEN it starts.

It's still lumpy, when it starts anyway.

Any advice?

Thanks

XantiaMan · Post by **XantiaMan** » 09 Oct 2007, 19:22

Not using veg are you?

I start up straight after the glowplug light goes out,literally half a second and it cant wait to fire, and isnt lumpy, if i leave it a few seconds after then it takes longer to fire and can be lumpy.

Post by **RichardW** » 09 Oct 2007, 19:31

This weather the glowplug light should be on for about 7 - 10s. It should start straight away when the light goes out, with no throttle, and then run nicely. If it doesn't then chances are it needs a new set of glow plugs. Have fun

If it's really high mileage then it might need the valve clearances resetting, but a set of plugs is only £25 and an hour (

) to change so it's worth doing.

deian · Post by **deian** » 09 Oct 2007, 19:31

Not veg, not yet, when I'm happy it's a happy engine then it can have some of the good stuff

Sl4yer · Post by **Sl4yer** » 10 Oct 2007, 10:20

Mine does the same. There was another thread on here recently about similar problems, and one solution may be to replace the leak-off pipes on the Bosch pumped cars. Breaking-down of the original fuel hoses is a problem on these cars, due to their age. It's also worth checking if the hose from the fuel filter to the pump is the original braided one, and change it if it is.

Mine usually misfires after a second or two running, with white smoke (it starts instantly though). It's often better after waiting a few seconds after the light goes out, which is hard to explain if the problem IS the leak-off pipes!

James

Post by **RichardW** » 10 Oct 2007, 10:46

Leaky leak off hoses will normally cause a delayed (or not at all) start. Lumpy starting that is cured by a longer or second application of the plugs is normally down to the plugs starting to fade - even if they are not completely kaput they can still heat up, but tend to do so towards the tip, whereas when in good condition they should heat from the tip. You can eliminate air leaks as a cause of poor starting easily anyway - just pump the primer a few times before cold start - starting improved: air leak problem. Not improved - glow plugs (or compression....).

It's not unkown for the 1.9TD once it gets beyond 100k to need the valve clearances (particularly exhaust) resetting - and this can influence the starting. New glowplugs are easier though....

Brian UK · Post by **Brian UK** » 10 Oct 2007, 11:59

Check the glow plugs first.
BTW on all the XUD turbo engines, the plugs are not switched off when the light goes out, they stay on for up to 2 minutes after as a means of reducing smoke.
If you look at the cable lever on the top of the pump, you will see a small microswitch. When the lever hits this for more than a certain time, the plugs are turned off. (This will be different on the fly-by-wire pumps).
Engine temperature will also turn them off.

Post by **Peter.N.** » 10 Oct 2007, 17:44

As Brian says, the glowplugs stay for a while after the light goes out. For immediate starting (assuming all your glow plugs are working) wait until you hear the relay drop out. If you watch the panel lights, you will see them increase slightly in brightness when the relay opens.

deian · Post by **deian** » 10 Oct 2007, 18:38

I have recently discovered the relay switching off AFTER the light goes off, does this mean the glow plugs go off too?

I have seen the micro switch (the one with the roller yea), so if this switches off the glow plugs then what does the relay do?

I do have a SLIGHT leak near this little black cylinder thing on the drivers side of the fuel filter housing, there seems to be a few pipes coming off it, the top drivers side pipe isn't seated properly, and if i pump using the priming bulb you can see fuel drip from it.

I will take your advice about the glow plugs too, and assume for the time being it is a combination of both the leak off pipes (which i think is the little black thing mentioned about) and the g.plugs.

So thanks for that guys. It was kind of what I was expecting, it's nice to hear more than one expert agree of my thoughts, and also many ways of looking at the same problem.

Brian UK · Post by **Brian UK** » 10 Oct 2007, 19:57

deian wrote:I have seen the micro switch (the one with the roller yea), so if this switches off the glow plugs then what does the relay do?

The microswitch controlls the relay.

Bren · Post by **Bren** » 11 Oct 2007, 21:01

My xantia does the same - but not when I use BP ultimate diesel - it does start and run better.

deian · Post by **deian** » 12 Oct 2007, 20:20

So if I put my foot on the throttle when I start her up the glow plugs will go off. But If I leave it and let it catch first, then it don't work so well.

Brian UK · Post by **Brian UK** » 13 Oct 2007, 11:49

It's not that simple, there is a time delay too, so opening the throttle wide as you start it will not turn the glow plugs off. I think the switch has to remain activated for a certain period, so blipping the pedal will not make any difference.