Technical Bad earth & poor starting

[IanWard]

This might sound odd, disconnect the Lambda sensor and try starting, yes the engine light will be on but the car will follow the fall back map? The ecu will generally run a richer mixture?

Went to try this John, the connecter for the lambda sensor on the manifold isn't in the best shape, looks like someone has damaged the locking mechanism in getting it off previously and now appears stuck - didnt want to create another problem by forcing it - this ones doing my head in enough...

 

[John202020]

Went to try this John, the connecter for the lambda sensor on the manifold isn't in the best shape, looks like someone has damaged the locking mechanism in getting it off previously and now appears stuck - didnt want to create another problem by forcing it - this ones doing my head in enough...

That's interesting wonder why it's been touched has the engine been out? Or sensor replaced ?

 

[mj2k]

Any joy yet?

I'm guessing disconnecting the lambda sensor will put it into 'open loop' (or maybe 'limp home') mode and force it to ignore a lot of other sensors; if the lambda connector's already damaged it suggests maybe somebody's tried this before as a method of diagnosis, which would suggest this isn't a 'sudden' fault and has maybe occurred before.

So it could be replacing the crank sensor will be all it needs...

 

[IanWard]

Hi Mj2k,

I have sent it into the auto-electrical place on Friday, I didn’t have the kit to relearn the phonic wheel, and couldn’t borrow it for another week, I’ll give them a call later this afternoon to see if any progress… I hope it is just the crank sensor

 

[mj2k]

Hi Mj2k,

I have sent it into the auto-electrical place on Friday, I didn’t have the kit to relearn the phonic wheel, and couldn’t borrow it for another week, I’ll give them a call later this afternoon to see if any progress… I hope it is just the crank sensor

Ooh, just remembered a totally mad similar issue I had on my Lancia Delta - on startup sometimes the crank sensor wouldn't pulse correctly and then it would run fine, but sometimes misfire or suddenly die if you rapidly accelerated. After much poking of wires and puzzling I noticed the crank pulley (where the crank sensor sender was located) was loose and the crank bolt had dropped out

Reseating the pulley and fitting the missing bolt (correctly torqued up) was enough to fix the issue. I hope yours isn't caused by anything as bonkers, but it was just as well the car gave me those 'subtle hints' - I was able to fix it before it either chewed the crank keyway to pieces or attempted to fling the pulley out through the bonnet...

 

[IanWard]

Update: Well its been an interesting day with the 500's issues, I called the auto electrical garage - they were baffled, had replaced the crank sensor but didnt fix the issue, so they refitted the previous one, and advised they were at a loss - seemed to be a timing issue between crank and cam sensor? and gave me the number of an fiat specialist in Bury and said to try them.

Got the car back in the workshop and managed to test out the crank sensor, so resistance around 1180, and with a little (lot) of help from my brother managed to test the AC voltage of the sensor - so a constant reading of around 5.5v at idle, and rose to about 20v at ~2,000 rpm. so that seems ok.

got it back on the snap on reader and traced the rpm graph - interesting at cranking doesn't show any rpm, then get a spike when it attempts to to start before flat lining again, then when it does start tracks perfectly. but could not find anything on live data for camshaft sensor?

Went on then to test the cable between crank sensor plug and ECU - eventually managed to pin out to 8th one down on row 1 and 7th one down on row 2, ran resistance test again - and consistent with previous reading 1180.

Tried to start with the crank sensor unplugged - strangely started which we weren't expecting, and much quicker 2 seconds of cranking - of course the engine light came on and no rev counter. Tried this a couple of times before plugging the crank sensor back on - back to starting after 5-10 seconds.

now have read on other posts which have suggested a software update has fixed this on other 500s, so likely to give the dealer a call explain the problem and find out how much to reflash to the latest engine software,

the saga continues....

 

[mj2k]

Wow, that is an interesting one, fingers crossed with the dealers.

Might be worth having a quick look at the DVLA's page to see if a recall has been missed for your car:

https://www.check-mot.service.gov.uk/

 

[jrkitching]

now have read on other posts which have suggested a software update has fixed this on other 500s, so likely to give the dealer a call explain the problem and find out how much to reflash to the latest engine software

IIRC yours is a 2009 car; I doubt the software for that ECU has been updated in a long time.

My understanding is that the software update you're referring to is intended to fix the problem of the engine overrevving and./or bogging down when the clutch is released; this problem is confined to the early Euro6 engines (circa 2013). IIRC these engines have a completely different ECU from a different manufacturer.

My view is that updating the engine software is a red herring which isn't going to help with your problem.

If it's been running fine for 10+ years and suddenly isn't running fine anymore, it's likely a hardware problem.

 

[jrkitching]

Might be worth having a quick look at the DVLA's page to see if a recall has been missed for your car

DVLA recalls are generally reserved for safety critical issues. I doubt a simple reflash of the engine ECU to improve running would warrant Fiat going this route; these sort of updates are normally dealt with through the franchised dealer network at service time.

The only DVLA recall I remember for the early cars was to reflash the airbag ECU software to fix a problem with the wrong side airbag activating in a collision (RHD cars only).

 

[mj2k]

DVLA recalls are generally reserved for safety critical issues. I doubt a simple reflash of the engine ECU to improve running would warrant Fiat going this route; these sort of updates are normally dealt with through the franchised dealer network at service time.

The only DVLA recall I remember for the early cars was to reflash the airbag ECU software to fix a problem with the wrong side airbag activating in a collision (RHD cars only).

True, though they do sometimes class engine running issues as safety-related. E.g. the bogging down issue you described might be classed as safety-critical since if a car bogged down when leaving a junction it could cause a crash.

Hardware related issue sounds expensive, I guess the last thing to try before considering an ecu swap would be to look at the pinout to find where the rpm sensor connects to the ecu, and try wobbling the wires whilst checking the continuity.

Has it ever been known for the stator disc to detach from the crank pulley, which would create an issue like my bonkers Lancia problem above?

 

[IanWard]

Thanks Mj2k and jrkitching, the stator disc seemed solid and not loose last night, once the car starts it runs really well with no issue.

Glad you mentioned the software being related later models, I think I may need to call the other specialist - though having a quick Google seems they are more a breakers - still worth a call though as nothing lost…

We did the pinout from crank sensor to ECU last night nothing obvious - seemed a consistent reading

 

[mj2k]

Thanks Mj2k and jrkitching, the stator disc seemed solid and not loose last night, once the car starts it runs really well with no issue.

Glad you mentioned the software being related later models, I think I may need to call the other specialist - though having a quick Google seems they are more a breakers - still worth a call though as nothing lost…

We did the pinout from crank sensor to ECU last night nothing obvious - seemed a consistent reading

Just had a quick check on the eper (I really should get on with work in a min ) and I noticed there was something called a phase sensor for the 1.2:
71749543 CONNECTION PHASE SENSOR

I'm guessing this would be the camshaft sensor. If this is the case, and you'd def need to check with someone else if disconnecting it would be safe, you could try disconnecting that and see if it makes any difference to starting.

I know on Subarus at least if there's a difference in timing between the cam sensor and crank sensor the car won't start; it's a form of failsafe to prevent the engine from starting and doing more damage if the cam timing is out. So if it will start OK with the cam sensor disconnected, looking into the sensor and cambelt might be another route of investigation.

 

[IanWard]

Just had a really good chat with a helpful guy at Club 500 in Bury, gave me a couple of things to check and common problems, (check airflow sensor, injectors, coil pack etc.) but said most of these would also show in issues whilst running, asked if it had overheated as can melt the flange on the inlet manifold.

But he too was really baffled at how the car actually started with the crank sensor unplugged as it shouldn't run at all...

MJ2K - haven't located the cam sensor yet and hasn't thrown any codes for cam, only rpm sensor, initially thought it was the solenoid at the LHS of the engine, but advised that's for VVT.

 

[jrkitching]

Hardware related issue sounds expensive

Not necessarily; it could be something as simple as a poor connection, resolvable with a squirt of contact cleaner and reseating a connector.

The hard part is diagnosis; if you knew what was causing the issue, rectification could be simple and straightforward.

I'll keep my fingers crossed that it's something trivial.

 

[IanWard]

The hard part is diagnosis; if you knew what was causing the issue, rectification could be simple and straightforward.

I'll keep my fingers crossed that it's something trivial.

You're not kidding there jrkitching, i feel like literally banging my head against the wall at the minute :bang:

A bit of a long shot - if anyone else has an early 1.2 (and the diagnostic kit to reset the light) would you mind seeing if the car will start with the crank sensor unplugged? just trying to rule out if it is normal for these cars to start - everything I have read and what people have told me is that is shouldn't - but trying to find out if this is a nuance with the car, or if this actually helps point me in the direction of the problem ?ECU?

So my daughter has used the car today to go to college, and no heater, yet the engine temperature is hot (normal on gauge - extremely hot under the lid), so need to look into if it is an airlock or the thermostat has gone - and if in someway this is related to, or the partial root cause of the problems I'm getting...

EDIT: now tells me that the fans have been on every time she's been driving the last few weeks... looks like im going to have to do some further testing on other cables just to make sure nothing has melted and shorted...

I cant believe how all this started literally overnight from no problems at all - to seemingly a multitude of issues all at once (pity party over - I'll start looking again tomorrow )

 

[jackwhoo]

Radiator fans running when ever ignition on can be caused by faulty engine coolant temperature sensor. The sensor body may contain two sensors- one for engine ecu and one for temp gauge, so possible for gauge to work but engine ecu not to "know" coolant temperature.

 

[jrkitching]

So my daughter has used the car today to go to college, and no heater

The 1.2 FIRE is normally a robust and reliable engine but it does have an achilles heel; it is absolutely intolerant of overheating. Often the head gasket fails before the temperature gauge registers any overheat.

The coolant circulates continuously through the heater matrix by design; there's no water control valve and cabin temperature is controlled by flaps which modulate the airflow over the heater core.

So loss of heater functionality is often the first sign that all is not well with the cooling system and as I've already said, if coolant level drops too low and the engine is not shut down promptly (as in stop at the roadside as soon as possible), it'll likely ruin the engine.

I'd advise in the strongest terms possible that the car should not be driven at all unless you are absolutely certain the cooling system is functioning correctly. You cannot rely on the temperature gauge offering any protection from wrecking the engine in the event of coolant loss.

 

[IanWard]

Thanks JRKitching - I’ll tell her not to use it until it can be looked at ?

 

[chris3234]

Thanks JRKitching - I’ll tell her not to use it until it can be looked at ?

Does it have the digital climate control on the more old fashioned manuals Twisty dial type?

 

[IanWard]

Manual - old school controls Chris