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Intermittent Starting Failure


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#1 Gewitty

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Posted 30 November 2010 - 11:12 PM

Since the cold weather arrived I have experienced a sharp increase in the occurence of starting problems which I have had for several months with my 06 plate 2.0 TDCi Titanium.

Previously, I would occasionally find that the car refused to start, but if left for a while, it would usually respond. However, since the cold weather set in, the problem has become much worse. Last week, I could not get it started for two days. Although the engine turned over and sounded as if it was firing, it would not actually start. Eventually, I called out my local garage. I looked pretty stupid when they arrived and the thing started first time. They took it in and ran diagnostics, but could find no faults and no indication in the logs of anything amiss. I took it back home and sure enough, the very next day it failed to start again.

The one thing I noticed was that when the sun came around and shone on the bonnet for a while, the starting problem disappeared, so I tried an experiment. The next couple of times it refused to start, I stuck a hair dryer in the engine compartment with the nozzle under the plastic engine cover. After five minutes of blowing hot air, the car started with no trouble.

This makes me wonder if there is a problem with the intake air temperature sensor. The fault can't be anything actually inside the engine, because five minutes of hair dryer heat could only be affecting something on the surface.

Of course, this may be a complete red herring and the fact that it seems to respond to a bit of heat might be coincidence, but it's the only lead I've got and it does seem to work.

The questions that remain are: What is it that a few minutes of hot air seems to affect; and why does the fault appear intermittently, rather than all the time?

Any thoughts or suggestions would be welcome.

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#2 mintalkin

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Posted 01 December 2010 - 10:52 AM

you could have a problem with the glow plugs or there relay.

#3 Gewitty

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Posted 01 December 2010 - 02:23 PM

you could have a problem with the glow plugs or there relay.


That's certainly a possibility, but the glow plug indicator light comes on, and then goes out on the display after a couple of seconds, which I assume means that all is well?

It also doesn't explain why a bit of heat seems to sort it out.

#4 tommy.h

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Posted 01 December 2010 - 10:34 PM

Hi Gewitty

find attached lists. it is just a matter of elimination.
if this helps.
you need any more info just ask i will do my best

tom

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#5 Gewitty

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Posted 01 December 2010 - 10:55 PM

Hi Gewitty

find attached lists. it is just a matter of elimination.
if this helps.
you need any more info just ask i will do my best

tom


Thanks for the useful list. I'm guessing that not all of these possible faults would be intermittent, or would respond to the hot air treatment I mentioned in my original post, so which might be worth checking first?

#6 Gewitty

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Posted 02 December 2010 - 01:36 PM

Had to dig the car out of several feet of snow this morning. As I expected, it absolutely refused to start, so I tried the hairdryer trick again. Three or four minutes after I started blowing warm air under the engine cover, it started first go. This is the fourth time I've tried this and it works every time, so it would seem fairly conclusive that the problem is a sensor mounted somewhere around the top of the engine.

I suspected the intake air sensor, but have been told that it is unlikely that this would stop the car starting. A more likely suggestion is the camshaft sensor. Apparently, this, along with the crankshaft sensor, is critical to engine starting.

Has anyone any idea of what I should be looking for around the top of the engine?

#7 mintalkin

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Posted 02 December 2010 - 03:33 PM

i do not see how heat can effect sensors which take there readings internally,i would still check the glowplugs first as the hairdryer trick could be warming the fuel in the injectors/pipes enough to ignite when required

#8 taffg

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Posted 02 December 2010 - 07:55 PM

Had to dig the car out of several feet of snow this morning. As I expected, it absolutely refused to start, so I tried the hairdryer trick again. Three or four minutes after I started blowing warm air under the engine cover, it started first go. This is the fourth time I've tried this and it works every time, so it would seem fairly conclusive that the problem is a sensor mounted somewhere around the top of the engine.

I suspected the intake air sensor, but have been told that it is unlikely that this would stop the car starting. A more likely suggestion is the camshaft sensor. Apparently, this, along with the crankshaft sensor, is critical to engine starting.

Has anyone any idea of what I should be looking for around the top of the engine?


hi gewitty, ive not got a diesel engine but a petrol focus, however ive had a read of my manual to try and assist. yes the extra heat from blowing hot air under the emgine cover could well assist with the ignition of the diesel. However you say that no fault codes are shown when you run diagnostics, but i presume your car was driven to the garage and fully warmed up prior to the diagnostic test,so if a five minute hairdrying cures the fault,then a good run to the garage would be more than ample and no fault codes showing would suggest all is well with the engine management system.

from what i read on the focus you need four major requirements to start your car, a battery delivering a sustained high ampage to the glow plugs. fuel, then the engine management system above all requires an accurate tenperature reading and the crankshaft position (please forgive me ignoring the plethora of other sensors). Now a diesel from the year 2000 on a focus would have a replacement to the traditional temperature sensor, in that the sensor locates in a blind hole and measures the temperature of the metal by direct contact.
could yours be the same.

i quote from the haynes bible "information on the engine temperature is critical for acurate fuelling calculations, and is also used to control the pre-heating system for cold starts". I'm thinking if the sensor is innacurate then your glow plugs may not be on long enough for the extreme cold weather.
"the cold starting performance is automatically controlled by the ecu and pump control unit. under cold start conditions the injection pump timing is advanced by the pump control unit, the pump control unit is supplied with information from the main engine management module(ecu)and from this, is able to calculate the most appropriate values for injection timing and quantity(injection duration). while the ecu operates the glow plug circuit"

you state you occasionally had snags starting the car (i presume the weater was normal ie,rain blowing,warmer etc)so i am also thinking fuel starvation, vacuum on the tank side of the pump, blocked fuel filter,etc because if you had problems with fuel supply when the weather was warmer, then the cold weather would certainly thicken the the fuel in the pump etc and maybe your not getting enough into the cylinder, then you warm up what you have got and it fires up.(under cold start conditions the injection pump timing is advanced by the pump control unit, while the ecu operates the glow plug circuit").


anyway for me i would definately carry out a glow plug test even if it was to eliminate them. i would definately disconnect every electrical connection to do with the engine management system "especially the temp sensor," use contact cleaner to drive out moisture ( moisture makes for crappy contacts in normal weather and ice when its freezing another crappy contact, hair dryer dries out moisture and and ice particles?) then i would seal each connector with some b.p jelly (vaseline) and reconnect each connection ensuring a good fit.

remember the heat could be drying out moisture, and also thinning up the available diesel so do not rule out fuel starvation. It also states in the haynes that the glow plug circuit will remain on after starting in extreme cold conditions, to aid warm-up.

anyway excuse the ramblings had half an hour to kill, hopefully more experienced "oilers" can shoot down some of my theories and help you narrow down rhe snag. hope you get it sorted
tg.

#9 Gewitty

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Posted 02 December 2010 - 11:12 PM

Thanks for the thoughts taffg. Much of what you say is in line with some other advice I've had from an engine management systems specialist.

The whole issue of glow plugs has come up several times in this discussion, but I'm told that with modern high pressure injection systems, faulty glow-plugs are unlikely to prevent a car starting. Even if they do go faulty, this should show up with a fault light on the dash.

When the car went into the garage last week, they actually parked outside for the night, just to see what would happen before they ran the diagnostics. Sod's Law came into play then, because it started first time!

As you say, probably the most critical sensor is on the crankshaft, but that's pretty much ruled out given the fact that it's way down below the top of the engine and so would not be affected by the blown hot air.

One other suggestion is that there might be a bad connection in a cable loom, which is creating a high resistance and !Removed! up a sensor reading.

If the weather improves a bit tomorrow, I'm going to pull the plastic engine cover off and take a look to see exactly what's lurking under there that might be affected by the cold/heat. While I'm doing that, I'll follow your suggestion of checking connectors and using a bit of silicone grease to prevent moisture ingress. I might also try using a narrow nozzle on the hair dryer so I can point the air-stream at individual components, which just might isolate the fault.

#10 noddy

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Posted 05 December 2010 - 08:08 AM

Although I have an S-Max my reply comes from my experience of previously owning a petrol engine Subaru which sounds like exactly the same problem as you describe on your car. Very embarassing as it always started when the AA man turned up but never for me!

In the end it was what he called the "crank angle sensor". Not sure if he meant the crankshaft sensor.

Anyway, after spending 100 on the sensor it cured the problem.


Obviously different car, different engine....but it does sound like the same problem. I could not diagnose my problem and attribute it to the cold weather though as for me it just seemed completely random.

Not sure if this helps.

#11 Gewitty

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Posted 05 December 2010 - 11:02 AM

In the end it was what he called the "crank angle sensor". Not sure if he meant the crankshaft sensor.


This has come up before in discussions I've had about the fault. It may well turn out to be the culprit if the hair-dryer solution proves to be a red herring.

Talking to an expert on these things, I was told that the most critical sensor for starting is the crank angle sensor. It's the one thing that is guaranteed to ensure a starting failure. A modern diesel engine can cope pretty well with most other faults, but that one will always screw things up.

I think I'll make one last attempt to prove or disprove the heating theory, by doing what I suggested the other day - pull off the engine cover and heat any components I can find individually. If that fixes the problem, I'll replace whichever bit responded to heating. If it doesn't work, then it will have to go into the garage to get the crank angle sensor checked.

#12 MrrNoName

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Posted 05 December 2010 - 03:09 PM

from what you describe it probably is the crank sensor, however to rule out the glowplugs not heating enough, try turning the ignition on and waiting for the glowplug light to go out, then turn ignition off. then on again and wait for the light to go out 3 or 4 times. this is to give the plugs more time to heat up. if the car starts first time after this you know its something to do with them. if its exactly the same you can rule them out.

my 1.8tdci will not start in this cold weather enless i let the plugs heat up and wait for the light to go out. so i guess they are integral to the starting :P

i would check it as its easy to do. like said before though, does sound like the crank sensor playing up in the cold :)

#13 Gewitty

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Posted 05 December 2010 - 08:33 PM

from what you describe it probably is the crank sensor, however to rule out the glowplugs not heating enough, try turning the ignition on and waiting for the glowplug light to go out, then turn ignition off. then on again and wait for the light to go out 3 or 4 times. this is to give the plugs more time to heat up. if the car starts first time after this you know its something to do with them. if its exactly the same you can rule them out.

my 1.8tdci will not start in this cold weather enless i let the plugs heat up and wait for the light to go out. so i guess they are integral to the starting :P

i would check it as its easy to do. like said before though, does sound like the crank sensor playing up in the cold :)


OK. I'll give that a try next time it refuses to start. I don't think the glow-plugs are the culprits, since I always wait until the light goes out and I've been told that even if they do go faulty, modern high pressure injection systems are not particularly affected and should still start.

#14 stevemc75

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Posted 12 November 2013 - 01:10 PM

Did you ever find out what the issue/fix was? - I'm having this exact issue on my 2.0 TDCI.

 

Thanks



#15 MartinToton

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Posted 10 December 2013 - 10:12 PM

Hi, Me too - have a similar problem to the above, 1.8 tdci, usually starts fine first time, but occasionally doesn't and then pretty much refuses to start. When it fails to start, it catches fine but only spins for a second or so before dying. I Usually heat the glow plugs for two turns of the key, and just replaced the battery to give me more goes at starting, but if it's one of those non-starting scenarios, it's like the other post, it generally isn't going to start. Very dieselly smell outside the car after several attempts to start. Think it had a couple of glow plugs changed a year ago, it's a 56 plate, 75k. Could it be the glow plugs, injectors, crankshaft sensor, any help appreciated! If so what's the likely cure and likely cost? Thanks!

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