2007 XC70 does not start in cold temperature - SOLVED

GabrieS · Post by **GabrieS** » 01 Apr 2021, 17:29

I have posted on this subject in January 2020. Thanks to all who replied. Below the link to the original thread is the short story of what fixed the issue in just a few words...

viewtopic.php?f=9&t=92553

A BAD STARTER WAS CAUSING THE ENGINE NOT TO START.
The problem was very confusing because the original starter was cranking with no problems every time I tried it. The engine would crank but would not start or it would start after many attempts (and it was a lottery draw whether I would go to work that day or not). It was impossible to suspect a bad starter. So I kept looking elsewhere for the problem.
However, through the perseverance of all the minds on the thread, we pulled it off and we did not get fooled by the seemingly good starter that was actually the cancer of the engine start.
I want to thank all who helped me troubleshoot and fix this problem. I spend $40 (if I remember correctly) at the local U-pull yard to pull a used Bosch starter out of a Volvo XC70. I was going to replace the original starter and test to see if that was indeed causing my issue. And the issue disappeared immediately after replacing the original starter with the one from the junkyard. I was going to buy a brand new $400 starter later but I am still driving with the Bosch starter from the junkyard. It works like a champ and I trust it better than anything new.
The dealer wanted to replace many parts for upwards of $4000 CAD and also said "I'm not sure if it will fix the issue". So this thread was not only a great and satisfying challenge for the mind...but also a great money save rand stress saver.

Best regards to all!

Gabriel

Post by **jonesg** » 02 Apr 2021, 07:26

WHat diagnostic indication would I look for in a similar no start, flickering tach ?

GabrieS · Post by **GabrieS** » 02 Apr 2021, 10:03

I had a flickering tach among other symptoms. You can see a few videos of the no start condition that I posted in the original thread. But the kicker is that none of the symptoms are indicative of a bad starter.
So... if you are looking for specific symptoms that would convince you that you have the same issue as me...I don't think there are any.
Some people suggested to me that there was evidence coming from some discussion forum in Russia that a fault in the starter would cause an increased interference with other signals traveling to and from the ECM. This would prevent the computer from getting its data correctly and it would not allow for the computer to command a synchronised start.
This made some sense to me as I looked at all 3 components that mix in any combustion engine (gas, air, spark)... and I could not find anything wrong with any of the 3 systems. So... in my mind... if I have gas, spark and air... the engine is cranking just fine... why would it not start? The only addition to the modern combustion engines is the ECM to fine tune things electronically. So if anything interferes with the signals to and from the ECM... it will not allow the engine to start.
I figured that an old starter from the junk yard would not be a high price to pay to rule this possible condition out. And it turns out that is exactly what was happening.

GabrieS · Post by **GabrieS** » 02 Apr 2021, 15:31

I do not know exactly what goes wrong with these starters. All I know is that you want a good quality starter (ideally Bosch brand) which Volvo used to install on these cases initially.
But when Ford bought Volvo... many parts were replaced with cheaper less quality made parts.
In a few words this is how I imagine it:
Any wire where you have current traveling creates an electromagnetic field. If the starter somehow creates an electromagnetic field greater than it is supposed to (due to a combination of cold weather and internal components failing) it will interfere with the surrounding wires and electronics... much like your radio in the car has interference when you drive under power lines. We are talking about very delicate signals that travel to and from the ECM to coordinate the start and smooth operation of the engine. Once these signals get disrupted the ECM will simply not know what's what and will not command a spark or an injector to spray...etc.
Bottom line is... both the original starter and the used Bosch starter crank the engine strongly and without hesitation for as long as you want. But the car only starts with the Bosch used starter all the time. The engine does not start with the original starter in colder weather and it hesitates even in less cold conditions.
As soon as I removed the original starter and put the used Bosch starter in... all the issues disappeared. No more hesitation starting the car, no more flickering, no more codes whatsoever. It's been over one year and I did not have one single hesitation.

Gabriel

GabrieS · Post by **GabrieS** » 02 Apr 2021, 15:35

If anybody reading this thread is so inclined... you can elaborate on what is happening inside a starter that creates such a condition. I am not a mechanic or an electrical engineer. The above theory is just how I picture things with my limited knowledge.
That said...I am always interested in learning and understanding the inner works of all things.

Gabriel

Post by **jonesg** » 02 Apr 2021, 16:16

maybe a draw meter on the starter cable?

Post by **abscate** » 03 Apr 2021, 16:39

Any current in a wire induces a magnetic field. The sensitive circuitry is designed to work with the presence of such fields, but in an older car, wires are often replaced and not routed the same way as factory, so then the design criteria is not met.

A bad starter might not have the same shielding, or, my guess is, intermittent brush contact , generating AC type fields which aren’t in the design plan.

You would need an oscilloscope to measure these artifacts