hot start probs

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cliftyhanger
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hot start probs

Post by cliftyhanger »

My poor old xantia TD starts a dream when cold, but hates starting when hot. Also seems to have got quite chuggy??? when hot and idling. Any ideas, is there a cold start sensor or other gizmo that might be making it rich??
Any help/pointers appreciated, as it gets boring sitting turning it over, and my my missus is talking about getting rid of it if it doesn't get better!
Cheers
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AndersDK
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Post by AndersDK »

There is an engine (coolant) temp sensor for the ECU to decide the richness of fuel mix. This also works as the cold start choke device.
If this sensor (or cable) is disrupted, the ECU thinks the engine is (very) cold and richens the fuel mix, no matter how hot the engine is.
This makes for flooding at hot starts and lumpy idle.
But surely then you have an engine fault lamp on ?
More hints here : http://www.andyspares.com/discussionfor ... IC_ID=9166
cliftyhanger
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Post by cliftyhanger »

No warning lamps at all. I will investigate the sensor, hope it is straightforward as I get lost with "modern" technology.
Any other ideas please??
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mbunting
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Post by mbunting »

What year is the car ?
May not be any electronics at all....
I think it was about 96-97 ( ie. M/N reg ) that Xantia's went ECU.
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Kowalski
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Post by Kowalski »

The cold idle on a TD doesn't "richen the fuel mix" its not a choke device there is no throttle butterfly, no carburetor and definately no choke. All that it does is alters the injection advance and increases the idle speed.
Poor hot idling could be many things. The most likely are the injectors being worn or mucky, the injector pump being worn or the timing out. Have you tried a bottle or two of injector cleaner? Worn / dirty injectors or a worn injector would tend to make your exhaust smoky all of the time, and very smoky under hard accelaration.
Another possibility is the head gasket, get a compression leakdown test done....
cliftyhanger
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Post by cliftyhanger »

The car is a 98R plate, just pre facelift. It does smoke under hard acceleration when cold, but soon loses the smokyness. I think the injectors should be ok as I did use some of that evil injector cleaner recently. Really more concerned about the poor hot starting.
How do you do a leakdown test too???
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Post by nick »

I've heard that incorrect valve clearances can be a reason for poor hot starting on the 1.9 diesel too.
Nick
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AndersDK
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Post by AndersDK »

I did not read your 1.st posting properly [:I][:o)][:(]
- a TD can NOT have a choke [8)] - I was thinking petrol [B)]
On a diesel you have a coldstart device, which does NOT richen the fuel, but instead adjusts the injection timing a bit.
This is a cylindric device with a bowden cable protruding and connected to a regulator arm on the diesel roto pump.
Read all about it here : Diesel coldstart device
martyhopkirk

Post by martyhopkirk »

Could be simple.... My ZX TD had exactly the same problem - it was an air leak in the fuel line. Even mechanic was puzzled, said he would expect it when cold but not hot...got so bad it used to cut out whilst driving too when hot.[:(!]
Can you pump the primer bulb on your TD (assuming it has one) and does it get hard (oooh err missus!) - if it pumps withough going hard you have a leak somewhere. The best cure is just to replace all the rubber pipes, as it saves buggering about trying to find tyhe leaky bit.[;)]
My leak was comming from a plastic box t connector under the pump, Citroen couldnt supply a similar bit so i bodged using a Y connecta sourced from Intensive care used in Hemofiltration and some silicone. I am sure similar bits could be sourced elsewhere (its surprising what bits you can use from an operating theatre! O2 bubble tube for bleeding brakes and so on..... (all stuff heading for the bin in case you were wondering!)
Its been right as ninepence ever since.
cliftyhanger
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Post by cliftyhanger »

OK, had another look in daylight. Seems very lumpy when cold too (don't usually see this as the wife drives it mostly) and smokey too. Had a look for the cold start devive, but the cable from the back of the pump seems to end at a short cylinder thing connected to a bit of small (5mm o/d)rubber pipe which pulls off and may be vacuum pipe?? but no water at all, which in turn connects to a T piece and 2 more cylinders, these both have electrical connectors attached. Am I looking at the wrong bit? Is my car really odd? Help please!!!
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