Hot start issue, starter won´t crank when hot
 

Since I bought my 2006 D5 XC90 1 year ago, I'm having issues with a hot start problem.
Previously the symptoms were a long cranking time when engine was hot. No issues when cold, so I thought it couldn´t be the battery.
I've already replaced the starter and the battery in separated steps, and in each step it seemed it was solved, but after a while, the problem is back again.

Now, it's even worst. After driving a while if I stop the engine, I have to wait a litlle (10-15m) to cool it down before I can attempt to start it again. The starter won´t even turn, and it seems it makes a short-circuit to the battery because it drops to 9V.
I don´t know if it's possiblle, but I think I can have a heat soak problem with the starter. I haven´t tried yet using a booster cable directly from the battery to the starter suspecting it could be a corroded cable but I thing that would also cause problems when cold. Is it possible that a heat shield around the starter could prevent this from happening?:thinking2:

Thanks

I would not take for granted that the replacement starter is all good - the voltage drop is a sign that either it is siezing or you have a bad connection (depending on where you are measuring that voltage).

The longer cranking may be injectors - suggest you do a leak back test - lots of videos on Youtube on this. If they are leaking excessively it then takes longer for the fuel system to pressurise.

The minimum voltage value was taken from torque app using OBD connector. I guess this is the value present in the front fuse box and reported through ECM. The voltage level at the starter can be lower because you have an aditional cable from the fuse box to the starter. Anyway if it's already bad at the fuse box when trying to start the engine, maybe the end lead to the starter shouldn´t be the problem. I will try to put back the original starter to see if the behavior is the same. The new starter I've fitted it's equivalent, it also has bosch reference printed, but it is not from bosch. It was a lot cheaper than the original, so maybe the quality is not the same.

A faulty crank position sensor will cause it to not start when hot although that wouldn't stop the starter from turning

According to Volvo´s new features release information in 2006, regarding engine D5244T4 the cooling fan was supposed to work afterrun in order "to protect various engine components from overheating".
Mine doesn´t work when I stop the car, unless I've been driving with air conditioning on. Is this normal, does it have to be always working for a certain time after switching off engine?

VOLVO NEW CAR FEATURES 0520
Theroretical sessions
Engine D5244T4/T5/T6/T7
Afterrun
The cooling fan is activated for a certain time after the engine has been switched off in order to protect
various engine components from overheating.
Fan activation time and fan speed are dependent on coolant temperature and driving style (engine load) when
the engine is switched off. Afterrun takes place as follows:
• Initially a high speed is used, following which the speed is lowered in stages. There are three
"variants".
• When stage 4 (top fan speed) is used the afterrun initially continues for 360 seconds.
When stage 3 (intermediate speed) is used the afterrun initially continues for 255 seconds.
When stage 2 (next lowest speed) is used the afterrun initially continues for 150 seconds.

I would suggest that if the engine is cranking over at the normal rate, the problem isn't the starter motor at all.

This video shows how to do some simple multimeter tests on the starter motor and this video shows how to interpret live data to narrow down the issue.

I'm following your channel on youtube since I bought this car. You rock, I'm not a mechanic and it's been very helpfull for me following your videos. I've almost downloaded all of those related to volvo D5. I have to say thank You for sharing all that great stuff and for the clarity of speech.:cool:

The problem is that when the engine is hot, it doesn´t crank at all, it behaves like a dead battery. The starter tries to turn over, but it seems it doesn´t have enough power and the voltage drops to 9.3v.
The attached image from torque, shows the data after switching off engine and trying to start it again.


Thanks

Thank you for your kind words and I'm glad you find them useful.

Some further testing for you.....

If you have a multimeter, definitely follow the starter testing video but in addition, get a voltage reading by probing the small spade connector on the starter solenoid.
It should be zero when not attempting a start then battery voltage with the ignition key in the starting position.
No voltage at the spade during a starting attempt is an issue with the starter relay or spade wiring.

If there's voltage at the spade but no click from the starter solenoid, tap the solenoid with a piece of wood or heavy plastic during an attempted start.

Additionally clamp the red multimeter lead (set to DC Volts) to the starter body where it meets the engine and the black lead to the earth lead bolt on the chassis side during cranking.
Anything above 0.2 Volts DC suggests a knackered earth cable.

Better still, if you have a jump lead, connect it to the starter body at the engine and to the chassis.
This bypasses the main earth lead.
If the starter then turns, the earth lead is definitely toast.

I'll add that if the voltages check out and the earth bypass gives the same lame starting, you'll need to remove the starter and open it up.

There are detailed starter tear down and reassembly videos on my channel.

Key test for your symptoms' of a no crank but heavy voltage drop is to use an inductive current clamp of the starter cable and measure amps, typical diesel starter will draw an initial 300 amp and once the starter turns about 250 amp steady. If you have high current draw and a heavy battery voltage drop then that would indicate the starter winding's are internally shorting causing high current draw and low magnetic field in the winding not enough to turn the motor.

Low current draw and battery voltage drop is a failing battery who's capacity has weakened.

Low current draw and little battery voltage drop is a high resistance in the starter circuit creating unwanted voltage drop.