Technical Koalar random thoughts

[koalar]

Got the car here for a few day

1.2 petrol 2011

Going to post a few pictures and video of some simple and basic tests

My well be a bit random as they pop into my head and might sort them into the proper order later

 

[koalar]

Let's start with Turing the ignition on

You should here a buzz from under the rear seat

Depending on your hearing it can be very faint


A reliable way is to put your ear to the petrol fill while a friend turns the key

Please note everytime you turn the key on and of the ECU sends a signal to start the motor regardless of what the line pressure is or what you read elswhere

This is me turning the ignition on and off several times

 

[koalar]

No noise

Check the inertial switch

Press the button under the passenger seat

 

[koalar]

Still no noise

There still two checks before we need to take the rear seats out

On my car euro 5 it's fuse F21 15A and relay T10 20A the owners manual will identify yours

sods law you have broken down in the middle of nowhere, it's worth swap them for identical one in the fuse box before calling for rescue you can live without some things like aircon, heater but not without fuel to the engine

 

[DaveMcT]

My 100HP did this after the lockdown layoff. It turned out to be a relay. The Body compute had no power. All relay and all fuses got (one-by-one) pulled and tested. All were ok but it started after that was done. Suggest start by swapping BCM relay with headlights relay (all are same spec) and see what happens.

 

[koalar]

Right you still no noise
Fuses and relay are fine
It's not the inertial switch

There one more quick thing you can try

Really needs two of you one to turn the key while one taps under the tank

Sometimes the pump sticks as they get old or have been left standing

You can just reach it without jacking the car

 

[koalar]

Lifit the seat out

There's two cables we are interested with

These can be backed probed with a T pin and a good ground, I used the seat belt bolt as a ground

Yellow and purple, the supply, should be battery voltage as the ignition is switched on for few seconds

Red and purple, the ground, should be less than 1 ohm


This are the colours in my car, they all appear to be the same but I haven't checked every combination

LHD
RHD
4x4
All models
All years

 

[koalar]

One bit I missed, said it would be all over the place as things pop into my head, This should have been first.

It does not affect many people and very rare and also depends on body computer version fitted

If you have a high end model and it's fitted with an alarm, extra security,

Locking with the remote, then the battery goes flat and you open the door with the key, can lock out some features such as the diagnostic port, you need to charge the battery and lock and open with the remote before carrying out any diagnostics

 

[koalar]

One last thing on fuel unless someone chimes in with a suggestion

The easy way to drain the tank or check fuel is reaching the injectors is to disconnect the fuel rail quick connector near the throttle body and capture the fuel as you switch the ignition on

Please do it safer than me, I have only done it like this so it's Visable in a video

 

[koalar]

Moving on to the dash

A lot of information can be learnt from just carefully watching the display

But first here a myth

You need to wait for all the cycles to finish before starting the car

Does it happen, yes, often you can limp by for years without addressing the problem, I know as I have done same


This is the first start after the car been left for a few day, This is a flyby wire model notice how quickly it drops from 1200 to 750 rpm, from memory cars with an idle control valve were a little slower

Also notice how quick from the clock coming on to the sound of the cranking less than a second

 

[koalar]

Here's the same car with a fairly flat
Battery

Listen carefully you can hear a slightly slower crank speed

Watch the behaviour of the rev counter, yes I know the lights are on just me trying different thing and forgot to retake the video, compair it to the video above, see the delay before they jump up

 

[koalar]

The body computer (BSI) needs 6-18V

If the voltage falls below 6V it looses its ability to keep it's RTC (real time clock) running and you will get this,

A high percentage will be the battery, but not always

It's important to set the time as this is often the first warning along with possibly a longer crank time that the battery is getting old

 

[koalar]

You don't need expensive diagnostic and test equipment, most of the time

This is a £5 Bluetooth obdii reader and a android smartphone and free software, giving better results than an expensive volt meter/multi meter, For around £15 you can do the same with a stand alone hand held unit if you don't have a smart phone or laptop

Be careful if you use an iPhone, it does not use standard Bluetooth and need a special obd2 dongle

Look at this graph, this is a marginal battery. Probably will not last the winter. Less than a second and the voltage while cranking has dropped to below 9V (the car will not start below 6V and it's still warm outside) most multi meters would still be still showing 12V

Not perfect as there is roughly 0.2V error but vastly better than being 3V out

This test is directly equivalent to a battery load test but for the fraction of the cost as you are using the starter as the shunt (load)

 

[koalar]

Here the warning lights start sequence

It actually tells you quite a lot

This tells us
Antenna isn't broken
Key transponder isn't broken
BSI (Body computer) is up and comunicating
ECU (Engine computer) is up and comunicating
Dash to BSI is communicating

This tells we have fuel, always a good start

 

[koalar]

These two lights (charging and oil) should be lit with the ignition on, and should only go out when the engine is turning over

Here they are not lit at all as I have I disconnected the earth, If there is high resitance, they go out as you turn the key to crank but the engine fails to turn over

These two lights are the wrong way round
The engine check light should be on and the immobiluser should be off

Engine computer has lost its ability to talk to the body computer

The engine block should be ground there should be very little voltage between the engine and the battery negative terminal even when cranking, the battery negative and block are either end of a thick cable connecting the two

Here you can see the bock go slightly positive (test light dim) when the ignition is switched on and battery voltage (test light bright) as you try and crank

If I put a smaller battery in I twist the strap to shorten it, no need to mess with bits of wood

 

[koalar]

Inlet manifold pressure should follow revs

Here near sea-level

Starts engine Off @ 100 kPa and under 40 kPa at idle

Green RPM
Red inlet pressure

First start

Idle plus blip

Contant blips

Kind of counterintuitive but if the car is running on 3 cylinders it does not effect the inlet manifold pressure (unless there is a backfire), the piston is still going up and down, the valves are still opening and closing, it's still working as a pump

Here the car with cylinder one injector disconnected
Compare to above the revs are different but not the inlet pressure

 

[koalar]

Check for inlet manifold leaks

Block the tube going to just under the throttle body, put your hand over the throttle body

The engine should stop immediately
Vacuum should be held for a few seconds, if not you probably have a leak between the head and inlet manfold

If the engine isn't pulling much vacuum and passes the above test, you either have a serious mechanical error or the sensor isn't reporting it correctly

Odds would be a timing issue

 

[koalar]

Evap

Remove the blue pipe, no suction should be felt, with the small pipe that goes under the throttle body blocked

Remove the electrical connection, block the small pipe again, wet you finger, a slight vacuum should be felt, it's easily missed

There is no difference seen by the map sensor

Pipe removed

Pipe and electrical connector removed

Manifold pressure red line, finger on and off the evap solinoid, is flat lined

 

[koalar]

Crank sensor

If you have a rev counter

Normally they either fail from cold start

Or when hot

Just carefully looking at the rev counter (if your car has one) during a cranking no start would help to diagnose this

Worth observing as a crankshaft sensor will not set a code in most cases

 

[vexorg]

Contant blips
View attachment 429266

I hate the lag in modern cars, about half a second there.