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Old 21-07-2018   #1
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Difficulty starting

Hi All,
Got an odd one this time.

My 8v mjet with a 6 month old battery, fresh oil and a fuel filter that's about a year / 3000 miles old is proving very difficult to start all of a sudden.

It starts on the third or fourth try from cold and first time when warm and the engine's turning over strongly, it just won't fire.

I cleaned the boost sensor at the last service about a year ago.

I've tried unplugging the maf but it didn't make a difference.

There's no error recorded in mes but are there any settings / readings I should check?

Also, are there any other easy tests I should run.

The car's been parked up for a lot of the past 5 years but I've done a bit of driving in it recently. It's not short of power, runs smoothly, has no egr issues and is regenerating the dpf fine.

As always any help or advice is greatly appreciated.
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Old 22-07-2018   #2
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Re: Difficulty starting

High Brian - when I had my Croma I had a problem starting one winter. Found Two glow plugs were faulty but only on start up . They do stay on for a while to help cold running and once started they appeared fine.
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Old 23-07-2018   #3
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Re: Difficulty starting

Starter motor turning to slowly?
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Old 24-07-2018   #4
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Re: Difficulty starting

Mine does the exact same. I always joke that the 4th times a charm.

Sometimes it on the button. Other times it's reluctant to get going. It seems to be worse with a warm engine, or when the weather is warm. Cold weather cold starting is fine.
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Old 24-07-2018   #5
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Re: Difficulty starting

Remove battery Clamps and clean them and terminals with wire wool
Do the same for the other end of the main earth cable
Should ensure starter motor is getting maximum voltage
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Old 1 Week Ago   #6
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Re: Difficulty starting

I've tried a few different things now but the problem seems to slowly be getting worse.

Any chance that it could be the fuel pump itself? If so is there any easy way to check using mes maybe?

It seems to be worse when parked on a hill for a few hours would that be an indicator of anything?
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Old 1 Week Ago   #7
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Re: Difficulty starting

Could be the fuel pump or regulator. You can check the pressure and other parameters with MES. they are uner the Engine Parameters tab (scroll down).


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Old 1 Week Ago   #8
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Re: Difficulty starting

Quote Originally Posted by g8rpi View Post
Could be the fuel pump or regulator. You can check the pressure and other parameters with MES. they are uner the Engine Parameters tab (scroll down).


Robert G8RPI.
Hi Robert will do. You wouldn't happen to know what the pressure should be or where I would find it would you?

Thanks, Brian
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Old 1 Week Ago   #9
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Re: Difficulty starting

Fuel pressure went up to 413 bar as soon as I tried to crank the car, desired pressure about the same. They are hovering around 390 to 400 bar at idle after a couple of minutes.

Fuel pressure sensor showing between 1285 and 1435mV and changing constantly.

Pressure regulator 28.7% at idle, pressure regulator opening mprop 35% to 36% at idle
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Old 1 Week Ago   #10
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Re: Difficulty starting

Checked fault codes again and have a P0683 preheating control unit error. Reason is unit has received a very low signal from the sensor.

Does anyone know what that means and how easy is it to fix?

Battery voltage showing as 12.727v with engine off, key in start position. goes to 14.1v on start, dropped as low as 10.5v for a fraction of a second whilst cranking
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Old 1 Week Ago   #11
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Re: Difficulty starting

Inj correction cyl 1 is positive 2.1 mm3/l, other three are negative 1.08, 0.47 and 0.5 respectively.

Is any of this relevant / important?
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Old 1 Week Ago   #12
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Re: Difficulty starting

Quote Originally Posted by BrianMcL View Post
Checked fault codes again and have a P0683 preheating control unit error. Reason is unit has received a very low signal from the sensor.

Does anyone know what that means and how easy is it to fix?

Battery voltage showing as 12.727v with engine off, key in start position. goes to 14.1v on start, dropped as low as 10.5v for a fraction of a second whilst cranking

Hi,

The preheating control unit controls the glow plugs so is highly likely to be conneced to the starting issue you are having. I'm not sure what sensor that the code refers to. first thing is to clear the code and see if it comes back when you start the car. You should also check the glow plugs and all the connections.


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Old 1 Week Ago   #13
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Thanks again Robert.

I cleared the code and it came back right away.

Is there any way to check which one glow plug or plugs it might be without pulling them out?

Looking at YouTube videos and trying to peer down into the engine getting them out of the 8v mjet looks like a nightmare.
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Last edited by BrianMcL; 1 Week Ago at 16:05.
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Old 1 Week Ago   #14
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Re: Difficulty starting

You can check the glow plugs without removing them. How depends on what equipment you have available. The ideal tool is a clamp-on DC ammeter but I assume you don't have one of those. Any other test requires that you disconnect the glow plugs.

You need to disconnect each glow plug and check individually (still in engine). If you have a digital multimeter set it to ohms (lowest range if manual selection) connect the probes together and note the reading which should less than an ohm. You need to subtract this from the plug readings. Measure each plug from terminal to engine block. They should be approximatly 1 ohm (al the same)
If you don't have a meter, connect a healamp bulb from battery postive to each plug in turn and see that it lights to the same brightness for each. High resistance or dim light is a bad plug.



The eLearn descrition of the system is:

Diesel preheating relay T19 of B001 is supplied by the line protected by fuse F20 of B001.
It is energized by a control signal (earth) from pin 68 connector A of M010 and supplies power to diesel heating resistance inside K100.
Control unit M015 that manages preheating of the heater plugs A040 is supplied directly from the battery via a line protected by maxifuse F72 of the control unit on the battery B099.
This is supplied at connector A - from the line protected by fuse F11 of B001, and exchanges command and control signals with pins 52 and 93 of connector A of M010, which controls the timing; connector C is connected to the heater plugs A040.


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Old 1 Week Ago   #15
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Re: Difficulty starting

Hi Robert, Thanks again. I think I follow that and it sounds like a much better idea than taking each one out given his tricky some of them are to get at.

I'll have a bash tomorrow weather permitting.
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