Technical Multijet no start.

[DaveMcT]

P0180 Diesel temperature sensor

Are we ignoring this ?

I can’t find a diesel temperature sensor.
The pressure sensor (LH end of fuel rail) has three contacts. The pressure controller (RH end) has two contacts. Is a temperature sensor built into one of them?

 

[koalar]

I can’t find a diesel temperature sensor.
The pressure sensor (LH end of fuel rail) has three contacts. The pressure controller (RH end) has two contacts. Is a temperature sensor built into one of them?

Doesn't your car have a fuel preheater on top of the filter housing

 

[DaveMcT]

OK - scratch my previous question.

The service bulletin says the fuel temperature sensor is in the fuel filter housing.
Does it require a new filter housing or just a new filter element?
I will check the wires for damage. They are small gauge and not well protected.
Edit - the wires look good. I’ve not tested with multimeter as no idea what to look for.

Fuel in is top right.
Fuel to injection pump is top front
Third fuel pipe goes to the common rail pressure regulator.
The big electrical plug at top has a yellow and a blue wire.
Water sensor plug is at the bottom.
There’s a yellow plastic “pin” on the wires, which must have been fitted before the connector. I have no idea what that does.

 

[bugsymike]

I still think it is worth having a look at the pressure controller on fuel rail.

 

[DaveMcT]

The pressure regulator valveI on the rail has never been opened and still has the yellow seal paint.
Fuel pressure sensors cost from £50 to £200. Who knows why the big price difference
The pressure regulator is more like £50.
I’d love to know how to test them.

I’ve just found this - complete fuel filter unit
EBay number 274318449928
There are cheaper ones need to see if they are used or new.

 

[bugsymike]

The pressure regulator valveI on the rail has never been opened and still has the yellow seal paint.
Fuel pressure sensors cost from £50 to £200. Who knows why the big price difference
The pressure regulator is more like £50.
I’d love to know how to test them.

I’ve just found this - complete fuel filter unit
EBay number 274318449928
There are cheaper ones need to see if they are used or new.

I think if kept clean it could be unscrewed from the fuel rail and then confirm that the metal valve inside actuated by the solenoid is sliding freely and no dirt particles stopping it from sealing the vent that bypasses excess pressure, that might be enough although some test them by powering up the solenoid to check action.
Does this look like it ? eBay item number:386991248455

 

[PuntoHowTo]

OK - scratch my previous question.

The service bulletin says the fuel temperature sensor is in the fuel filter housing.
Does it require a new filter housing or just a new filter element?
I will check the wires for damage. They are small gauge and not well protected.
Edit - the wires look good. I’ve not tested with multimeter as no idea what to look for.

Fuel in is top right.
Fuel to injection pump is top front
Third fuel pipe goes to the common rail pressure regulator.
The big electrical plug at top has a yellow and a blue wire.
Water sensor plug is at the bottom.
There’s a yellow plastic “pin” on the wires, which must have been fitted before the connector. I have no idea what that does.

Stick a meter across it on Ohms and make sure it gives some sort of reading, in the first instance you’re probably looking to make sure it’s not open circuit or a dead short.
Maybe check the wiring leading away make sure nothing has broken when you’ve been doing the head, fiat use the same wiring under the bonnet as they did elsewhere in the car so it moved around around combined with age they could still break internally

 

[DaveMcT]

Andy -
I will check the filter contacts shortly.
Edit. It’s open circuit between the contacts.

I might just replace the unit. At least I’ll get QD pipe connections that work. An eBay offer came through at £39. Need to know if it includes the filter element.

 

[koalar]

No idea

However it works like this, according to fiat

FUEL TEMPERATURE CONTROL​

With the temperature of the fuel at 80°C measured by the sensor in the diesel filter, the control unit operates the pressure regulator to reduce the line pressure and, if this is not enough, to also reduce the amount of fuel injected.



When you get your OBD scanner working

Battery voltage
Target Diesel pressure
Measured Diesel pressure
Atmospheric pressure
Engine rpm
Engine coolant temperature



Would be helpful

 

[PuntoHowTo]

So potentially the temperature sensor cannot be read so the pressure regulator is not able to regulate the fuel pressure.

Obviously the fuel will expand with temperatures the same mass of fuel will have a higher pressure due to increased temperature, without being able to calculate for this it may default to a specific pressure which with cold fuel is not enough to start and run

 

[bugsymike]

No idea

However it works like this, according to fiat

FUEL TEMPERATURE CONTROL​

With the temperature of the fuel at 80°C measured by the sensor in the diesel filter, the control unit operates the pressure regulator to reduce the line pressure and, if this is not enough, to also reduce the amount of fuel injected.



When you get your OBD scanner working

Battery voltage
Target Diesel pressure
Measured Diesel pressure
Atmospheric pressure
Engine rpm
Engine coolant temperature



Would be helpful

What I noticed using the MaxiECU tool was that during the short period it ran, watching target fuel pressure and measured fuel pressure, the figures were comparable with other vehicles I have tested, roughly 5-10 bar difference/lag in matching revs.
One other thing was, when engine died , fuel pressure dropped instantly, which I believe according to some data on other vehicles I have read, should not be the case, more progressive fall at the common rail.
From memory on this one it fell to the figure that showed with ignition on/engine off prior to test of approx. 7 Bar.
I don't claim to have the knowledge of a diesel specialist but feel that either a signal to the fuel regulator or a blockage at the regulator valve would have that instant affect rather than a signal from a temp. sensor on the fuel filter, but I would be happy to be proved wrong as I understand Dave was intending to replace that "UFI" type filter anyway
Further to this I have just gone to my 2010 Fiat Doblo 1.6 MJ and confirmed my thoughts regarding pressure drop on ignition turning off.
In my as usual poor photos it should be possible to read the rail pressure and tapering down once engine off but ignition still on. If photos blown up it is possible to read the pressures although some are in reverse order, just to confuse further

 

[DaveMcT]

A fault in the filter temperature sensor could cause the pressure regulator to open wide & that would dump the pressure. When the engine did run at tick-over, touching the accelerator pedal killed it. That’s consistent with fuel pressure low.

The filter unit is cheap and mine has damaged (but not leaking) connectors. It makes sense to swap that and move to the pressure regulator as the next step. I really don’t want to disturb it unless no other option.

Waiting for seller to reply on whether it includes the filter element.

 

[bugsymike]

A fault in the filter temperature sensor could cause the pressure regulator to open wide & that would dump the pressure. When the engine did run at tick-over, touching the accelerator pedal killed it. That’s consistent with fuel pressure low.

The filter unit is cheap and mine has damaged (but not leaking) connectors. It makes sense to swap that and move to the pressure regulator as the next step. I really don’t want to disturb it unless no other option.

Waiting for seller to reply on whether it includes the filter element.

It also died without touching anything, but I agree with you it is well worth changing the filter first.

 

[koalar]

I would expect the fuel rail pressure, to drop very quickly at engine off by design,



There no need to change anything, Just graph it fuel temperature sensor, should be stable and valid

If it's not, then change or if it's okay move on

 

[DaveMcT]

The new filter unit at £40 has sold. Others are double the price. Does anyone know how to test that sensor? Should the contacts be closed or open circuit?

 

[bugsymike]

I would expect the fuel rail pressure, to drop very quickly at engine off by design,

@koalar I can't honestly say I agree regarding your thoughts that "I would expect the fuel rail pressure, to drop very quickly at engine off by design".
I have seen it personally on at least two different vehicles that ran fine with no errors, plus I have read online it mentioned that the fall off was gradual in a technical piece on diesels.
Perhaps others with MES could see what theirs records when engine stops but still showing live Common Rail Pressure readings in Bar. So with pressure recording in live data switch engine off then ignition only on, to continue measuring.
I appreciate my photographic skills leave a lot to be desired , but I was able to take several photos as pressure slowly fell on my 1.6 Doblo, I have also seen the same on the Peugeot engine Scudo.
Where as Dave's Panda when engine stopped whilst recording fuel Common Rail at the time, pressure instantly fell to Zero, which I suspect is an indication of a fault, whether the UFI filter as Dave has his suspicions or the Pressure Regulator on the Common Rail that I suspect.

 

[DaveMcT]

The new OBC interface has arrived with drivers. So I’ll be getting that set up on Mrs Dave’s Windows laptop.

I have ordered a fuel filter unit. The existing one needs A LOT of torque on the screw down lid to prevent any leaks and the connectors have broken release caps.

I would love to jump link the two wires on the top connector. But I have no idea what resistance if any there needs to be. Is it a simple temperature switch or is it a resistance bulb?

 

[DaveMcT]

The fuel filter top connector (aka thermal switch) has a 5V supply at the wiring loom end. I dare not mimic a simple switch by shorting it out as I’ve no idea what it’s connected to. It is tempting though.

 

[PuntoHowTo]

@koalar I can't honestly say I agree regarding your thoughts that "I would expect the fuel rail pressure, to drop very quickly at engine off by design".

On these modern diesels that run stupidly high pressures I was always under the opinion they do drop off pretty quickly. That being said everything is relative and are we talking seconds. milliseconds or even less than that. it all depends on the sample rate.

The high pressure pump on these is tiny and my understanding of the multijet is that it would keep the pressure in sync with the firing of the injectors to maximise the presure at the point the injector opens.

As it is compressing diesel which as a liquid, don't compress too good, as soon as the pump stops spinning the pressure would drop off quite rapidly. I can however appreciate that older diesels or ones that use a much lower fuel pressure may not drop off quite so quickly if they have a different pump design?

The fuel filter top connector (aka thermal switch) has a 5V supply at the wiring loom end. I dare not mimic a simple switch by shorting it out as I’ve no idea what it’s connected to. It is tempting though.

I definately wouldn't short it out. If you have one you can easily access a 47KΩ resistor, would probably made a fairly good approximation of the fuel temp on start up on a warmish day, based on the spec of most standard thermistors that get used in things like this. At least with some resistance across it you're not going to cause any damage.

 

[DaveMcT]

Excellent news. Engine is running with no faults. WTF

I set up the laptop as described in the thread linked above and connected my new interface. It’s on Com3 by the way at 37,000 baud. It all worked.

It read fault codes as shown below.

I deleted the codes and tried to start the engine. It cranked a few seconds, but fired up and started. It revs up and down normally. What the heck?

No codes came back. Which seems odd because the glow plugs are the same old ones. But whatever. I was too surprised to image the screen

The only thing I’ve done before trying a start was to test the fuel filter “heater” voltage. It’s 5 volts so can’t be doing much heating. The wires are good as far as I can see. There are no weak links indicating broken conductors.

I believe the fuel filter was causing fuel to recirculate to the tank. So have ordered a new one. I can’t handle another week of non start stress.

I have no graphs as (for now) my MES is the free version.