Hi Jamie, welcome to the forum 00000732

Here are a couple of suggestions that might be worth checking :

Could your non start be caused by an immobilizer fault? Have you tried using another ignition key to see if that has any effect.

Has the EGR valve been checked? Stalling at traffic lights/junctions and starting problems can sometimes be caused by the EGR valve not fully closing allowing exhaust gasses to enter the inlet when they shouldn't be. Carbon deposits on the valve seat can prevent the valve from fully closing or the control solenoid could be leaking allowing vacuum to lift the valve off the seat when the solenoid is switched off.

Regards.

Scottie.

 

Thanks scottie,

I am meeting with the mechanic this afternoon (I work away from home and hysterically this fault mostly occurs when my wife is alone with the kids leaving her stranded and me getting earache on the phone).

The car only stalled once at the lights, apart form this the car seemed to run perfectly, I toured scotland for a month in it and then drove to Italy with out one issue. The non-starting began a couple of months ago, about the time we started doing more <5 km journeys. The failure to start happens hot (for example failing to start after a trip to the supermarket, however after 15 mins it started) and cold, I think it has got worse in the recent colder weather.

The mechanic has both keys and it is failing to start with both.

I will pass your suggestion on to the mechanic after passing it through google translate.

The other theory which I found online seems to be that the grounding connections corrode and this messes up the voltage to the ECU which intern cuts off the fuel pump. The fact that when the car is going it seems fine seems to make this a possibility, any thoughts?

This seem to be a reasonably common problem and I have seen a few forums with bewildered owners changing part to no avail. I will up date with progress on this saga.

Many thanks

Jamie

 

The other theory which I found online seems to be that the grounding connections corrode and this messes up the voltage to the ECU which intern cuts off the fuel pump. The fact that when the car is going it seems fine seems to make this a possibility, any thoughts?

I think bad grounds are the default answer for a lot of people when they run out of other ideas. In my experience working as an auto electrician for the past 25+ years, bad grounds are pretty rare.

The engine PCM supplies the ground to several of the engine sensors so a bad ground to the PCM would mean a bad ground to the sensors too. The sensors are normally easier to get at than the PCM itself so if I suspected a PCM grounding issue I'd try to confirm that by measuring voltage drop on the sensors grounds. The fuel rail pressure sensor, coolant temp and fuel temp sensors are 3 that I know off the top of my head that will get grounded via the PCM. Since poor PCM grounds would effect the signal voltages from the engine sensors, I'd expect to see some range/performance DTCs logged from the effected sensors too, but you didn't mention any codes in your original post. Having said all that, since the fault is so intermittent it probably wouldn't hurt to remove and clean the PCM grounds. The voltage tests would only be meaningful if you managed to do them when the fault was happening and that could be difficult.

Another thing that could be worth checking is the throttle valve. Diesel engines and petrol engines differ in the way the throttle valve works. On a diesel the throttle valve should be fully open pretty much all the time. It only really closes when the EGR is active and at engine shut down (and during DPF regeneration, but I think yours is a bit too early for that). If the valve isn't opening at engine start, the engine can't draw in air which will cause a non start.

On later engines the throttle valve is controlled by an electric motor with a feedback sensor. If the valve isn't in the position commanded by the PCM it logs a trouble code. On earlier engines the valve was vacuum controlled and didn't have any feedback sensor so the PCM has no way to know if the valve was in the commanded position. That means the valve could be closed and no code would be logged. I'm not sure when they changed to the motor driven valve.

One of the signs of a closed throttle on a diesel is the boost pressure sensor indicating low pressure in the boost system. At engine start, boost pressure shouldn't be lower than the ambient air pressure. You can monitor both values on the scan tool data list during start. If the boost pressure drops during crank that indicates a restriction in the engine's air intake probably caused by a closed throttle valve. Again, you'd need to do the check when the fault is present which is the problem with diagnosing these intermittent faults.

Regards.

Scottie.

 

Just an up date, The signal arriving at the injector is lower than it should be, intermittently, the mechanic has tested all the other signals coming from the ECU and now does not think the ECU is faulty. He has changed the ground contacts which were corroded and now we are going to change out the starter motor which was apparently in a bad state. He showed me lots of black powder which came from the starter, I am no expert but this did not look to healthy to me when he showed me. So we will change the starter motor and see where that takes us. It would be hard enough to work out what is going on in english but in Italian I am clueless, but he seems to be getting to the bottom of it. The saga continues.

 

I had similar issues with my 2007 Santa Fe.. Stalling at traffic lights, having to restart engine.. would be fine for a while then stalling again.

Anyways, ended up being the fuel pump. One day it completely went and nothing.. must have been on the way out for a while and causing dramas.
How many Kms on the car?

 

I did ask the mechanic about the fuel pump and filter as another forum suggested this. Apparently there is a tendency for paint in the tank to loosen and for the paint to clog the filter. However the mechanic was insistent that the fuel delivery is fine. 99% of the problems have been starting the car the stall at the lights was a one off, possibly connected.

The car is at 90 K miles, 144 KM. I have seen reports of these cars doing double this, and I bought this in the hope of getting at least one trouble free year out of it. So much for luck.

Thanks anyway.

J

 

Yeah... know how that feels. Just sounds very similar to my issues.
Next time it happens, and it wont kick over.. pay extra attention and try and hear the fuel pump kick in.. its an internal pump and sits inside the fuel tank. You get to it via inside the car and behind/below the rear seats..
You could also disconnect the fuel line and see if the pump pushes fuel when you try to kick it over next time it wont start.
Mine did the same thing around 200k kms stall at lights, then wont start in the morning and be difficult to start.. till one day nothing..absolutly nothing. Best of luck!

 

Well after 2 weeks the mechanic finally got around to changing out the starter which cost about 500 euros. Result: car still will not start consistently. I am starting to lose faith that this car will ever get fixed. The mechanic seems to take forever to get parts organised and then a an extra delay while he does the work and tests the result.

So far:
starter changed
Crank sensor changed
Cam sensor changed
Ground contacts replaced.

Any further suggestions?

thanks

Jamie

 

Any further suggestions?

Sorry to hear your still having troubles. Has the mechanic checked the output voltage from the rail pressure sensor when the engine fails to start? A low output from the sensor will prevent the PCM from operating the injectors, so the engine just cranks over but wont fire. I've already posted some details on checking the sensor output here : 2002 Santa Fe CRD wont start

Scottie.