Technical It Dies, strange combination of fault codes and sensor readings

[westfielder]

Hi, Thanks for looking.
I have a 2001 Punto 1.9JTD


It dies while driving - got it home almost with a few restarts (only 1/2 a mile)


Pushed onto drive. Connected laptop and got


P0191 Fuel Rail Pressure (2)
P1672 Fuel pressure regulator
and the associated descriptions on FIAT ECU scan


I cleared the errors and it restarted. It would Idle If I slowly revved the engine it would run as long as I didn't come off the power - at which point it would die with the P0191 error


I noticed while idling and checking other parameters a number of odd things


Fuel Pressure does not match Desired Fuel Pressure (up to 100 bar difference or more)
Thought maybe that was something to check


I then noticed that Air intake quantity didn't match Desired Air intake quantity. up to double the amount difference.
So 2 different sensors - odd.


Then after a while and engine warm and disconnecting and reconnecting a few plugs it suddenly started behaving. The Desired and actual parameters matched and I could rev the engine fine. Went for a spin 500 yards and all fine.


This morning the wife managed 50 yards before it died.
When home from work I put on laptop and now




P0235 Boost pressure (1)
P0190 Fuel Rail Pressure (1)
P0191 Fuel Rail Pressure (2)


all of these are described as sensor and wiring errors and for different systems/parts


Now if I clear the errors it will start but just die within a couple of seconds with just the P0191 Fuel Rail Pressure (2) error- so the problem is getting worse.


I am thinking - is it a bad earth somewhere and the sensors are not reading against a true earth so the voltages and hence the interpreted values are wrong??


Anyone else had similar or could point me in the right direction - I would be very very grateful


The battery voltage is reported at 14.54 or thereabouts while idling


Many thanks in advance


Nick

 

[oldhammer]

Hi,
iwouid check the fuel preasure Regulator, sometimes the needle on the end of
them Gum up,

the regulator is bolted onto the HP pump, be careful when cleaning these they can be abit frail,

 

[oldhammer]

(I then noticed that Air intake quantity didn't match Desired Air intake quantity)

M.A.F fault? perhaps unplug and see if it runs better unplugged,
id resolve fueling issue first mind,

 

[Brendan W]

While I was scratching my head I'd be changing the fuel filter if it had been a while since it was done.
Air and fuel sensors can each blame the other if they get out of balance. I'm bigger than you no I'm smaller than you kind of stuff.

 

[westfielder]

Thanks Oldhammer and Brendan W,


I took your advice, I also spoke to Fiat who advised that as well as the pressure regulator a sticking EGR valve could also throw up fuel pressure errors. They said that the EGR was known for causing lots of different errors. As it's reasonably easy to get to they often start difficult diagnosis jobs by unplugging and removing the EGR and blanking off with a metal plate.


So I took it off and did as they said. It was very coked up inside with a sticking plunger. I also took off the pressure regulator which had just the smallest bit of gunge inside.


Put it back together minus EGR and it ran ok
Put the EGR back in and it still ran. A test drive has gone Ok.


The only thing I will say is that I may have caused it to become good again like last night by all the plugging and unplugging that I did like last night.


So I'm not 100% confident but time will tell. I will post updates in the next few days.
So thanks again.


P.S.
Other research reveals that if you haven't renewed your fuel filter for a long time and it's gunged - it's a cheap fix to try (and good to have if that's not the cause anyway - it'll pay for itself through better economy)
Low fuel supply pressure from fuel tank may give P0191. Pump may run but under load engine fails.
Old fuel pumps tend to send tiny metallic bits into fuel stream and on to injectors and regulators that often causes damage and many fuel related error codes - empty fuel filter into jar and examine for light coloured metallic debris.
when you put the filter back you should hear all the gurgling and fuel pump running which should tell you if it's working.
Also take off the top sensor that reads the boost pressure in the middle of the inlet manifold and check that there is one 5v line with a voltmeter as ECUs are known to fail and produce a lower voltage.

 

[westfielder]

Today it died again when the wife was out and about.
It was the same P0191 error as before but this time the engine would idle again after restarting if the error was cleared. However if the engine was revved the graph showed that the actual fuel pressure reported was much higher than the desired pressure and the engine would die (of the order of 750psi actual vs 400psi desired). You could see when graphing the output that as soon as the difference was too high the engine would die.

So I unplugged and replugged the fuel pressure regulator and the car was fixed again and the two pressures tracked each other fine. I drove the car 8 miles home with no problems.

As you can see in a previous post when measuring the desired air volume and actual air volume when I was having the same fuel pressure differences there was a difference there too.

So – is it a wiring issue – because unplugging and replugging seems to fix it AND I had the air volume difference too

Or

Would I have seen the air volume difference because the fuel pressure was too high? In which case should I suspect the pressure regulator – because if it were a wiring issue I would either have a fault like today or no fault like after I replugged. BUT 2 days ago when I had the fault the engine wouldn’t even idle and today it would....

I’m so confused

Any help gratefully received – thank you

Nick

 

[Brendan W]

Don't suppose you have one of those magic fuelling boxes fitted, they have been known to cause it. I would check the wiring as it's a cheap fix but I suspect the regulator itself.
PS check around - some of the old grey cells are telling me there may have bed a mod for the harness to the regulator.

 

[Ziggy122]

The regualator will be a simple mechanical valve, which should be unseating if the pressure reachs a set figure
if the valve has defunked, or is gunked up, then this could be a cause

If there anything like the Astra's,the valve, fuel rail and sensor are all one and costs too much But i have no evidence of this

Ziggy

 

[FiatLadyee31]

Did you ever solve this problem and how? I have a standard 1.9 w reg punto not a JTD and am having exactly the same issue. I changed the whole pump just under a year ago and it ran fine up until the last two weeks.

Thanks Kirsty

 

[oldhammer]

Fiat 1.9D is on old lucas pump set up,
they is one of the worst diesel pumps evermade,
but theyre a basic simple set up,

if it starts up moody in amorning..revs its self..hunts and scaven'ges before shaking to a halt, id take a gamble on cranksensor,

 

[FiatLadyee31]

Not sure if the partner did change the crankshaft sensor but both think he did a year ago, will order another one anyway and try....however my cousin plugged it in and it come up with a fault code saying the sensor inside the pump was shot or on its way out....it's weird as partner has moved all wiring about and seem to run fine, then next minute it wouldn't run the next morning.
It seems to not idle 1st thing in the morning and hunts a lot on idle til it does cut out, but keeping revs up its a lil lumpy but will continue to run, will mess about like this for a while until I turn off ignition after a while and then it's fine for rest of the day.

However crusing at 30ish mph in forth gear it does jump about abit as if I'm in too low of a gear, it's defo fuel related somehow and it's confusing everyone.
Put another pump on last year as the original pump was naffed and wouldn't run long enough to drive at all and I'm worried this is going to happen again, there's fuel there and sometimes runs lovely but it's always hunting 1st thing in the morning throwing engine management light on and then cutting out.its getting to the stage of taking it to my nearest scrap yard!!!!!

 

[oldhammer]

What was the fault code do you know?

 

[FiatLadyee31]

Top of my head no but was told it was the sensor inside the fuel pump.....

Kirsty

 

[oldhammer]

Have you had this punto a while or is it a recent buy?
Has it been run on veg?
it couid be gummed up have you tried some sort of fuel treatment/cleaner?


FWIW my old 1.9d ihad to turn ignition off and on again after first start as ignition barrel was iffy..it wouid run like a dog until idid this,

its not a blue one is it reg ending in MCB

 

[FiatLadyee31]

I've had it since August last year. It came with the problem which was said to be the fuel pump so changed it.
It ran fine for a while and started to mess about again so looked into it again and found out it was glow plugs,so changed them and that's where it started to play up worse. All wiring checked ect ect just baffled with it now.
And yes it is blue but numberplate ends in era, if it carries on it will be the end of a era lol.

 

[FiatLadyee31]

Owe and tried that with the ignition barrel.......still the same lol

 

[oldhammer]

Try unplugging connector on Air flow box,
simalar to M.A.f

see if it starts up any better with it unplugged,

these 1.9d are a p.i.t.a but once they is running good they return excellent mpg

iwas getting 60 mpg ish out of mine..i miss it for this, car iwished inever sold.

price of road tax put me off keeping it long term.

 

[FiatLadyee31]

Cool will try this morning and let u know thank you!!