Focus 2.0 Diesel cranking no start. P0087-71 error

[laserhalen]

Hi,

2010 Focus 2.0 diesel, 150k miles trouble free until last month.

Car failed to start one day in a routine drive to the shops, after trying for a while it was left for a couple of hours for someone to pick it up at which point it started and ran fine. the issue of course returned a couple of weeks later and this time it wouldn't start at all and hasn't since. On investigation the only thing they found was the pair of wires to the pressure control valve on the pump were frayed and exposed and could potentially have been in contact. These were traced a little either way, no other exposure found so they were taped back up again. This didn't solve the problem.

The car is belonging to my uncle and I looked at it for the first time on Friday evening. I downloaded Forscan and purchased a connector in advance. Forscan gave me the error code P0087-71 "Signal is above Max Threshold"

 

These are the potential causes that Forscan lists and i have added what we have checked.

Leaking Injectors - Leak off test was done on the Injectors and they are fine.

Fuel leakage - lines checked and there doesn't seem to be any leaks at all.

Insufficient fuel - the Pump seems to be getting fuel, we have disconnected pipes to check, when you crank it just seems to be returning all the fuel it is bringing up.

Low fuel pressure / High fuel pressure - i don't know how to check this.

Faulty or damaged PCM - again i dont know how to check.

 

I checked the voltage in the wires to the control valve on the pump. one is 12v the other 4v is this correct? i also checked continuity with the wire that goes to the plug over the nearside front wheel, again fine.

Rail pressure sensor has been changed prior to me seeing the car. is it possible to check the rail pressure with Forscan?

My uncle wants to try a new PCM but surely before going that route there are other checks to be made?

 

Thanks for reading and any help is appreciated.

[Tizer]

If you open up FORScan, go to Dashboard or Table or Oscilloscope then look in the PCM there should be a PID for Fuel Rail Pressure plus some other ones relating to fuel. Bring them all up and press Play, then try to start the car. 

There should be some pressure while cranking and even a small amount of residual pressure with just the ignition on, although it might be 0 if you have opened up the fuel lines. 

[laserhalen]

Thanks for the advice, I got back to the car last night and tried it. Attached are the oscilloscope screenshots. 

 

No pressure on the fuelStart feed at all.

The rail pressure built up very slowly from about 6 / 7 seconds of cranking until it got to about 110 bar. The car stops cranking after that, I presume its a timeout.

Is the Pressure control valve (PCV) related to the fuel? if it is then is it significant that the PWM is only going to <50% (maybe this is the working max opening?)

There are 2 valves on the pump, the one on the top looks like a on/off solenoid, the one on the underside i'm assuming is the PWM valve?

I have checked the wires on both of them, on each i get 12v in one and 4v in the other. (didnt get to check whilst cranking so i can do this tonight)

does anyone know what I should be getting in those wires? is there anywhere I could get wiring diagrams on these circuits? 

last thing, I checked a few times but there were no errors in the PCM last night, before or after cranking. it was always the case that if you cleared the error it would come up again after cranking.

thanks again.

[laserhalen]

hi, sorry to bump this but really looking to get some help on this issue.

thanks.