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General Car Related Discussion.To discuss anything that is related to cars and automotive technology that doesnt naturally fit into another forum catagory.
i have a strange fault with out 59 plate 2.0 diesel mondeo that i need some opinions on.
every now and again we get a hesitation that feels like a misfire and engine malfunction appears on the screen - an intermittent problem
the first thing i did was change the fuel filter which has not sorted the problem
i took the car to a diesel specialist and discovered that the car is throwing up a P120f fault which relates to fuel pressure being outside specified range. As this was a suspected pressure regulation valve the whole pump was replaced and the car felt ok for a short while but the problem is still there.
i have since discovered that the issue is worse if the ac compressor is running? when looking at live readings on ford IDS the fuel pressure at idle is nice an consistent without the AC on but starts to fluctuate when the compressor clutch engages? again this is intermittent.
the problem has also there without the ac running but is far less noticeable
does anyone have any thoughts on how the ac compressor could effect the fuel pressure? sounds like madness but it's happening and we are out of ideas.
we have checked the voltage to the pressure regulation valve with the ac on and off and it seems fine.
the only part of the fuel system that we haven't checked is the injectors. however i cant see there being an issue there as it just doesn't feel like an injector fault. All four are reading ok on IDS
The pump is run off one of the cams so i suppose that's possible?
Interestingly when we were cycling the ac on/off yesterday whilst it was plugged into ids we noticed that the clutch was engaging with a bit of a 'clonk' and every time it did this the fuel pressure would jump all over the place.
Then it started to engage normally and was running fine?
However it's played up without the ac being on too, this just seems to make the problem alot worse
Could the ac clutch still be partially engaged even when switched off.could you possibly pick up a non ac auxiliary belt and fit it to check if there is any difference.its a long shot I know but strange how the problem is worse when the ac is on so maybe the ac clutch isn't disengaging properly.
Maybe sometimes the ac clutch doesn't release properly?
I'll have the car back monday so the first thing I'll check is if the compressor is rotating freely. Im not totally sure how they work, if it has gone stiff would it only show up when spinning at engine speed?
The belt idea is good, i might measure up to miss the compressor.
It still all sounds like a bit of a long shot to me?
Does the auxiliary belt on your car only drive the alternator, pas and the ac if so just remove the belt and see what your pressures are with no extra load on the engine. It is all a long shot but at least this way it rules out all 3 parts and it's free.
Maybe someone with more knowledge on these engines can shed some light on your problem also.
I can't remember exactly what the belt drives, i think its just as you have suggested.
Its been at a diesel specialist for 3 weeks and they are stumped.
We know the pressue regulator on the hp pump is going out of range but cant find out why it is doing this? Their last suggestion is to have the injectors out and test them but i can't see there being a problem found?
the water pump is driven of the timing belt on these,
so as long as theres plenty juice in the battery then you can run it short term with no fan belt
I do a fair bit of work on these engines in the peugeot experts and fiat scudo
Its the same engine but the fuel system is a little differant on the ford 1's
Theres a common prob with the pressure sensor on the rail, but tbh it doesnt sound like that with yours
I've changed plenty injectors on them for all manor of reasons so its possibly worth getting them checked out
the water pump is driven of the timing belt on these,
so as long as theres plenty juice in the battery then you can run it short term with no fan belt
I do a fair bit of work on these engines in the peugeot experts and fiat scudo
Its the same engine but the fuel system is a little differant on the ford 1's
Theres a common prob with the pressure sensor on the rail, but tbh it doesnt sound like that with yours
I've changed plenty injectors on them for all manor of reasons so its possibly worth getting them checked out
I initially thought rail pressure sensor but it seems that is working ok.
Interesting that you suspect injectors as i thought the Siemens system was fairly unproblematic?
As its intermittent its sods law that if i pull the injectors out for testing they will check out fine.
One other thing worth mentioning is that at the start of all this the car cut out sitting in traffic and wouldn't restart. But after a relay home of course it did.
There were 5 fault codes on it at this point which were as follows (i have no idea how historic these codes are, however its only the p120f that's come back)
Ive checked the continuity of the wiring between the rail sensor and ecu plug and it all seems ok.
After having the battery disconnected, ecu out and rail sensor disconnected, when all connected back up it ran fine for a few days. I thought maybe it was a poor connection on the sensor but the problem has has come back. P120f is the only dtc im getting.
Its generally ok without the ac switched on but runs poorly with it switched on (most of the time, sometimes its ok)
We've noticed something else that now makes me think its an earth problem. You can sometimes feel it start to run rough when the auto lights come on and my wife said it did it when she turned the heated seat on. It would be a similar scenario with the power to the ac clutch when it engages although i dont know how they would be related unless it's all powered from the same fuse box etc?
Does anyone know if there are any suspect eaeth points on a mk4 or which ones i should check first?
My mazda 3 mps started doing some strange things. It would switch on the cruise control when I started it. It would start every time no probs though. Read a few threads and changed the battery and all was fine.
Although not related to you issue it sounds almost like a lack of power to run various items on your car.
If the battery has a bad cell it can give all sorts of weird faults, especially on a car with lots of electronics. You could replace it to rule it out, make sure you use the proper calcium type.
Ok, i found out about the fact they require a calcium type battery yesterday. I had a look at the one on the car as much you can see without taking it out and its just a plain black battery, i assume its the original on a 59 plate car?
However, i was checking the main engine loom and found a section that has been rubbing on an ac pipe near the oil filter. There were two wires that you could see the copper where it had worn through. I've taped them up for now and cable tied the loom away from the pipe. Went out for a drive and it was all good.
Not claiming a win just yet but at least ive found something wrong
Suppose I'll know in the next few days if its sorted it
Ok, i found out about the fact they require a calcium type battery yesterday. I had a look at the one on the car as much you can see without taking it out and its just a plain black battery, i assume its the original on a 59 plate car?
However, i was checking the main engine loom and found a section that has been rubbing on an ac pipe near the oil filter. There were two wires that you could see the copper where it had worn through. I've taped them up for now and cable tied the loom away from the pipe. Went out for a drive and it was all good.
Not claiming a win just yet but at least ive found something wrong
Suppose I'll know in the next few days if its sorted it
Nice one mate. So satisfying when u find something like that
It was a spot of luck finding it but I'll take that!
I just hope thats what all the problem is.
It was the metal part of the pipe crimped on the rubber so would have been shorting the two cables out.
Happy days mate. I bought a mk3 mondeo few months back and engine management light was on and failed mot on emissions. Turned out the guy had previously changed the coil-pack to solve a misfire and had undone sensors for whatever reason I couldn't fathom. I plugged all the sensors back in and fixed a split vacuum pipe and eml light went out and runs spot on. Sold it to my mate and now he's burned the bloody clutch out :-(
16-07-2016, 10:06 PM
mk4 mondeo tdci fault
