After failing to get rid I decided to see what the rail pressure sensor was seeing and its 5v supply and look at the fuel pressure regulator pwm with a trigger on no 6 injector which is furthest from the flywheel on this engine, this is what I got Ignore the bit at 41 seconds as my helper hadn't quite let the engine stop before turning the ign back on and it fired back up before being shut down again lol,
Here is a snapshot from the file above at idle speed which shows the uneven humps This system has 2 pumps that feed the rail the pumps are run off the cam which has a triple lobe for each pump so there are 6 operations per 720 degrees and its clear that 1 of the pumps aren't contributing as much as the other.
At this point I needed to Id the bad pump so I disconnected pump 1 (nearest flywheel) from the rail and tried to start the engine but it failed to start, here is what I captured From this its clear the low pulse is missing indicating no.1 pump to be at fault so I next reconnected one and disconnected 2 only this time the engine started right up... this is the capture This was during the cranking stage for fair comparison, in fact I measured both at 197rpm and pump 1 had 917mv of pressure and pump 2 980mv of pressure at the same point all of this confirmed to me pump 1 was the weaker pump so why would the engine not start on the better pump? I swapped back again and this time the engine started which is odd.
There are some tsb's concerning the cam lobes wearing and the followers having damaged rollers which in theory could give the same results so I removed both pumps to check the cam and rollers which were fine and then decided to swap the pumps position just to 100 % confirm one of the pumps are at fault. This is what happened You can see that the lower contributing pump hump has moved nearer the sync confirming that 1 pump isn't as good as the other but I still didn't know if the better pump was actually good.
At this point I made a big mistake, I thought this is going to be easy lol and rather than mess around ordering pumps and getting authorization to replace them I decided to whip the pumps out of a truck I had in the yard that belonged to me that I use occasionally and had no running issues, I also thought that I could confirm if the better pump was good and make sure it had no other issues before ordering new one/s.
Here is a capture of 1 doner pump and the better pump So lets put it all back together and send it on its way right... I wish! The active fault had gone but after 8 miles of road testing the fault code returned and back into limp mode it went, I checked it again with the scope and the pulses were still even so what now...
I had checked the leak off of the injectors at some stage with the WPS and I was happy with the pulses and the quantity of the returns over time so I moved on but here is that capture in case I missed something and the ps file
So at this point feeling a little disheartened with all time I had in it and feeling a little sorry for myself I gave up, I fitted the original pump, I was sure the pump was a problem but not the only one it had and I was getting behind with everything else that needed to be done so I asked the customer to take it away to get a second opinion and I wasn't going to charge for the time spent to that point as I didn't feel comfortable replacing the pumps knowing it would still have an issue and then I'd own the problem, the customer called back and insisted I replaced the pumps anyway and if it didn't cure it then he'd take it to the dealer, so I fitted a pair of new pumps which did make the pressure even like my pump but as expected it didn't fix all the issues so the customer took it to the dealer and they have said it needs 6 injectors and he now wants to bring it back for me to do which would be bad enough but although its possible I don't see it in my leak off captures.
What am I missing?
If the engine fails the returns volume test the next test would be to cap one injector at a time to attempt to determine which injector(s) are causing the excess flow.
I theorize that the injector design allows for fuel to flow out the return easier than the nozzle due to some sort of internal wear.
Not familiar with the D7e design, would the return flow test be an option? Agree that 6 injectors is possible, not likely but possible.
It looks like you have gone through it thoroughly. Did you check for filings in the filter housing? This is the first thing I check when I get the dreaded call for one of these. I find taking a fuel sample and putting it in a black aerosol can cap can show the particles clearly. Also the hand primer unit can suck air and give low pressure codes.
I wonder if doing the leak off test with your WPS or looking closely at rail pressure while the regulator is disconnected, which would result in max rail pressure, would show anything more conclusive with regards to injector issues?