Starting issue

[BrendanM]

My 1996 2.0 petrol injection turbo XM has always been a good starter until recently.

I now have to press on the accelerator pedal to stop the engine from stalling when I start it from cold.

After one minute I can remove my foot and it will idle OK. It drives OK.

Starting with a warm engine is OK. However on two occasions I had great difficulty starting the engine when I left it for 20 minutes in a supermarket car park.

The battery seems OK. I have changed the spark plugs.

What could be causing this problem?

[Peter.N.]

Can't help you with that I'm afraid I have only run diesels, hopefully someone will be along who can.

Peter

[BrendanM]

It started relatively easily in the morning but when I tried to start a hot engine it was impossible.

I had to let it cool for an hour before it would catch. The petrol pump makes a steady but quiet whine when the ignition is on.

Engine temperature seems to be a factor.

[Peter.N.]

Could be a faulty sensor but the last petrol car I owned had a carburetor and distributor and probably a dynamo.

Peter

[BrendanM]

I disconnected the battery negative and unplugged every relay, sensor and ECU connector I could find. I could not find the coolant and air intake thermistor sensors.

I measured the resistance between pins 26 to 45 and 26 to 44 of the ignition ECU plug.
These should connect with the coolant and air intake thermistor sensors.
They measured 3170 and 3120 Ohms respectively.

Afterwards there was no improvement. The coolant sensor may be at the rear of the block behind the ignition coil on this XU10J2TE engine. Unfortunately there is little information on this engine in the pdf manual.

A forum post in 2008 suggested that the 'flywheel sensor' might be faulty.
There is a TDC sensor, knock sensor and engine speed sensor mentioned in the electrical section.

Is there another name for it and where can I find it?

[BrendanM]

Apparently the flywheel sensor is above the bell housing/gearbox.

I will try to measure its resistance.

[Peter.N.]

If its the same as the diesel one its just below where the cylinder head meets the bellhousing, there is a 2 pin connector on the diesel, this can sometimes give problems so if you can find it give it a clean.

Peter

[BrendanM]

I made several resistance checks from the ECU plug. No obvious problems.

The 'Engine speed sensor' measures 364 Ohms. It is the same from the connector on the end of the sensor cable.

This is a bit higher than the 330 Ohms I have seen mentioned elsewhere but it may be due to a different manufacturer.

I am reluctant to replace it as it requires a fair bit of disassembly to get to it but it may be my best option.

[BrendanM]

If the engine speed (flywheel) sensor is a simple coil then a resistance check should confirm if it working.

However, if it contains a magnet its correct function may be degraded by a weakened magnet.
I believe magnets get weaker when they warm up.

Is there a magnet in the flywheel sensor?

[xmexclusive]

These sensor can degrade its performance with age.
Usually this is noticed as occasional engine running glitches.
So much of the time the signal works and the engine runs fine.
A simple resistance check of the sensor will not spot this as a fault.
With a dead sensor the engine will not start or run.

John

[BrendanM]

I have fitted a new crankshaft sensor and then did the bare minimum to let me start the engine.

It is still reluctant to start easily and control its idling. At least I have not made it worse.

I am considering swapping/replacing the Engine Management unit. I need to find out if the unit from my scrapped 1997 unit is compatible with my '1996' model.

If I can get the 1997 ignition coil off the other car I may try that and the ignition amplifier.

[BrendanM]

To update this thread - I have installed a new crankshaft sensor, fitted the ignition amplifier and knock sensor from my scrapped 1997 car.

Cold starting is still difficult. Driving is fine. Hot starts are either OK or impossible.

It eventually starts after it has cooled down for an hour.

I will try to measure fuel pressure at the injector rail. It 'feels' like a fuel issue.

[BrendanM]

I replaced the battery clamps and tried to start the car.

Lights came up on the dashboard but when the starter motor tried to crank, all the lights went out.

For some reason the headlights were on but very dim. Battery voltage on the lead pillars was 7.5V.
I wonder if the hot starting issue was due to an intermittent battery?

When I replaced the battery the cold starting issue was still there.

I tried an engine ECU from a similar car and the cold starting is now normal.

I have posted an ECU question in the electrical section.

My family and neighbours keep telling me that life is too short to be working on cars.

Diagnosing problems when there are several faults requires a methodical approach and maybe a bit of luck. Stubbornness and persistence can be a virtue.

Many thanks for your help.

[Peter.N.]

If the lights go out altogether that would indicate either a duff battery or a very poor connection somewhere which will be getting very hot.

Peter