Hi People,
Need some help with this van.
The van has been brought into me from a van dealer with a non starting fault from hot. The van was bought as a non runner with the head removed and all the bits were in the back of the van.The customer (an experienced mechanic)could not see any obvious reason why the cylinder head had been removed, so replaced the head. The van started without any problems and ran up to full temperature- all fine.
The van was then switched off, left for half an hour, but on return failed to start. The next morning the customer tried the van again and it started straight away without any issues. Once warm, the van failed to start again. Having a number of similar vehicles at his disposal, he started the parts darts approach to diagnostics- without any success.
He has changed: fuel pump, injectors, air flow sensor, MAP sensor, coolant temperature sensor, glow plug control relay, ECU/key,in tank fuel pump, fuel filter housing, fuel rail (I think that is everything)
Nothing has either improved it or cured it. This is where I have got involved.
What I have worked out is that though this is a temperature related fault it is not actually a physical temperature fault- and it only happens at a very precise temperature- 39C or over. If the vehicle is physically hot and with the aid of a potentiometer if you convince the ECU the engine is less than 39C the van will start perfectly. Which leads me to think that it is a fuel strategy issue. On live data in a non starting state I can see actual fuel pressure and desired fuel pressure are matched and if you scope the injectors you can see the injectors being fired, but it will not start- it does not even attempt to start. If you give it a tiny sniff of easy start she fires straight up and runs.
When it won't start, occasionally the only fault code is P068A.
I was starting to think it's a ECU fault but as it has been replaced for a known good one, it rules that out. I have checked all powers and grounds into the ECU starting and not starting state.I have searched all over the internet for some information on the fuel strategy for this system because I believe it is allowing too much fuel to return to the tank when it thinks it is hot. However, I am not sure how to prove this. I know it is wrong to assume but, I believe it is not a mechanical issue because it runs well when it is physically hot or cold, but to contradict this I have also discovered that the air flow desired and actual have a slight difference between them. To solve this I have checked the timing, blanked the EGR valve off and disconnected the exhaust which has made no difference.This discrepancy is still there whether it starts or not.

There are probably things that I have forgotten to say, but hopefully I have covered the main bits.
I have got live data in a running and non running state on shop stream, if I need to refer to any data.
Sorry this is a bit of a higgledy piggledy post, I have had this van for so long and checked so much I am starting to loose track of what I have done and what he has changed.
I am not after a silver bullet just a guiding hand to get this van out of my workshop!
Cheers,
Andrew