Hi Guys. Im new to the forum so any help or info would greatly be appreciated.


I have a 2005 Fiat Punto Mk2 1.3 JTD Multijet. I have been driving this car for the last 6 months without any problems. Car has 200000km on the clock. For the last month the vehicle has been giving me issues when trying to start. It will crank over fine but not start. After 5 - 10 minutes of consistent cranking she will eventually light up and run really well. It will start up fine a few times thereafter, then after being parked for sometimes 10 minutes or longer back to the cranking trying to get her started again. It almost as if there seems no spark (I KNOW ITS A DIESEL)


Things I've done thus far :
Diagnostic gave 2 faults
1 : RPM Sensor Fault (Crankshaft)
2 : Intermittent Key


After clearing the faults only the RPM sensor fault came up


Dealership in SA takes 3 weeks to get a sensor so referred me to
a reputable company who deals in aftermarket sensors. Took the
sensor to them, the guy there was nice enough to test the sensor
and told me it measured 780ohm which is correct for the sensor.
I then went home traced the wires form crank sensor to the ECU
and measure it to ensure that I was getting 780ohm to the ECU and
this checked out fine.


Glow Plugs Changed
Glow plug Relay Tested
New Battery
New Diesel Filter ( Air Was Bled form system)


Now i'm lost and not sure what to check next. have I overlooked
something ? Like I say the car cranks and some times you can feel
she wants to light up but does not.

Does the temperature of the engine make a difference? My Mercedes wouldn't warm start. Fine when cold. Was Cam sensor after garage replaced crank sensor twice!! Mines a diesel too

Jon

No temperature does not make a difference. Happens when the vehicle is cold or hot. What exactly was the Crank sensor supposed to measure as some sites say between 300-500ohm yet the Tech I went to see says it should be in 600-800 region ? last thing I want to do I waist money on a sensor and it does not make any difference.

Ifarrath said:

No temperature does not make a difference. Happens when the vehicle is cold or hot. What exactly was the Crank sensor supposed to measure as some sites say between 300-500ohm yet the Tech I went to see says it should be in 600-800 region ? last thing I want to do I waist money on a sensor and it does not make any difference.

Click to expand...

https://www.fiatforum.com/punto-mk2-2b-guides/147923-fiat-jtd-crank-rpm-sensor-removal-replacement.html

Ziggy

Update. So I've changed the crankshaft sensor and guess what ........... The car is still the same. Not sure what's left to do

I'm not too familiar with fiats but on my merc the cam sensor is used to start and crank for running. Had huge issues getting it sorted 2 garages. Only when I got my own software did I source fault to cam sensor. Got Merc specialist to confirm and recheck. Perhaps look into getting that sensor checked.

Had the original sensor checked and tested by a reputable company and even though they informed me that my original was fine I still went on to buy a new sensor thinking MAYBE these guys made a mistake.

Might be worth further investigation of the fuel system although it's not showing faults any drop in the fuel rail pressure even slightly means that you don't get a good spray pattern at the injector and then the fuel and air doesn't mix properly these cars need stupidly high fuel pressure and the high pressure fuel pumps are very small, start by checking for any leaks around the pump

Andy has good suggestion. Modern cars have less margin for error.

You've not made in clear as to whether both camshaft and crankshaft sensors were checked. That or my excessive night shifts made me miss something.
I don't know what the correct resistance values are for crank and cam sensors but should be easy to find out. I quite like a mystery. My 8v petrol is giving me hassle also so know the frustrations. Especially when you believe you've checked everything. I'm having another bash at Mine tomorrow going back to square one and starting from scratch. Luckily its my project/learn from car so have the luxury of not needing it

As Andy said - fuel pressure is the first thing to check by looking at the amount of fuel leaking back from the injectors. There is supposed to be some but as injectors get on a leak is enough to drop the rail pressure to where no cylinder will fire. One leak affects the lot. People are still changing glo plugs when these don't start but in reality fuel pressure is the decider of clean starts. Glo plugs on many modern common rail motors are only needed on cold days - typically 7 deg C or less. If I had a penny for every faulty glo plug replaced that made absolutely no difference to starting................
Get some clear bottles and tubing and connect four to the leak off points on the injectors, let it idle and see how much flows into each after a minute or two. I don't know what the limits are for this car but typically limits are 40cc/minute and no more than a 3:1 difference between the best and worst , something along those lines. Loads of vids on youtube.

It is 'hdi derv engines 'PSA/BMW..
That arnt 'glow plug dependant..

I think 'most fiat are..

Iwouid be checking the fuel 'pressure regulator on the 'high pressure pump.
They can gum up.. and stop it from starting..

Update .... Even before reading all the posts, this past weekend I decided to play mechanic and do some searching in the engine bay for any sign of damaged wires or anything that may seem out of order. My eyes fell on the high pressure pump where I seen some Diesel residue on one of the pipes leading into the pressure pump. Started the car and realised diesel leaking form this pipe. Unscrewed the torx bolt holding the pipe down, put some RTV silicone around it where there are 2 small little o-rings, bled the system cranked her up and BOOOOOOM she starts straight away. Been cranking her up and starting her for the last 2 days without any problems at all.


Seems like I had air going into the system where the pipe was leaking


Fingers crossed it stays this way, will keep you all informed if I have any changes from here.


Thanks Andy for your correct diagnosis, you are a Legend.

Good result and thanks for coming back to close the loop. Keep an eye on it. Long term might be better replacing the seals altogether.