Engine Slow To Start When Hot

[speedtripledan]

Ok update..

I have done as instructed by CANEMS and disconnected CAM sensor ( basically disabling ECU) engine spun over faster. So looking like aapping issue for hot running. Hopefully a simple fix...

wish mine were that simple !

[femster87]

The sheer mass of the starter would mean a huge heat capacity so you would need a fair number of these to cool it down whereas a bucket of cold water is cheaper and more effective in this case.

 

Electric motors are designed to run at elevated temperatures. Have you felt the heat pumped out the back of any conventional hoover? Does it run any slower when hot?

 

I still think a simple check to see if the engine is tight when hot with a long wrench turning the engine over would prove useful and takes less than a minute to do.

 

Simon.

 

Cause temperature does affect motor performance, the heat at the back of the hover is mainly the heat gained from compressing the air

The DC Motor Curve

DC motor performance curves can be generated under various conditions. For example, the motor curve illustrated in Figure 1 was created using a rapid test on a motor dynamometer. The test was done by quickly loading the motor from no-load to locked rotor (stall) using a fixed terminal voltage from a power supply with low output impedance. A test like this is done to get a “baseline” measure of motor performance while the motor is at room temperature. Motor shaft speed and current are plotted as a function of motor torque. From this test and a few resistance readings, the torque constant, voltage constant, and terminal resistance values can be determined. This information is very useful to ballpark basic motor performance and can be sufficient for an application that requires intermittent operation with a long rest period between each duty cycle.

A typical motor performance curve created using a rapid test on a motor dynamometer. Such tests give a baseline measure of motor performance at room temperature.

In applications such as repeated point-to-point moves, applications requiring frequent starting and stopping of a high inertia load, or applications that require the motor to be moving for long periods of time (such as a fan application) the motor data illustrating performance at room temperature is not adequate and can result in misapplication of the motor or exceed the motor’s maximum temperature rating.

As the motor temperature increases, the resistance will increase and the torque constant and voltage constant will decrease. This results in an increase in no-load speed and a decrease in locked-rotor torque. Figure 2 illustrates an example of both “cold” and “hot” running conditions of the same DC motor. The “hot” motor curve demonstrates how much the performance can change when operating the motor at an elevated temperature.

The graph illustrates changes in motor performance from room temperature to an elevated temperature, showing how much performance can change with an increase in temperature.

[sj-bradley]

Interesting. Thanks for enlightening me. So then it appears that the OP has both an overheating starter combined with the ignition firing too early when hot causing excess pressure before reaching TDC.

 

I don't mind being corrected as this was interesting to find out these details.

 

Simon.

[Tazzzzman1]

Right 99.9% sure I've got it sorted now...

After working on it over the weekend and again disconnecting the CAM sensor, it still had issues of slow to crank...hmmm not the same result as before, so definitely not the ECU then...Damn.

Femi turned up with a spare battery today. So fitted that and ran the car for almost 2hrs...car starting a dream...no issues. Battery holding 12.7-13.3V. My old battery was at best only at 12.1-12.3V. Apart from taking the car on a run to give it proper testing, I'm now pretty confident issue solved...

I reckon that the old battery although holding a decent charge was not giving out sufficient cranking amps due to degradation. My old battery had been run flat a few times over the past 2 years and gel batteries don't like that too much... So fingers crossed, all ready for Scotland. Just need to find some snow chains to fit now

[sj-bradley]

Just need to find some snow chains to fit now

 

Oh, you optimist Only snow chains ? Glad you finally sorted the problem.

 

Simon.

[theduck]

Good to hear it is sorted!

[femster87]

Nice one uncle terry

[kevin the chicken]

If the weather forecast is like it is this week you would be better off with a hull rather than chains

[Guest mower man]

Used to work to the rule if the battery wont hold 12.8 / 13 volts is on its way mick

[Guest peter2b2002]

I found out why my 2b is slow to turn over been getting worse over the last year, the cable that goes the the starter has a poor crimp on the eyelet that bolts onto the starter motor, only noticed it cos I saw smoke comming from that area when I had the bonnet up

peter2b