Hello all,
Hope everyone's doing well.
I attempted a Liqui Moly Diesel Purge recently. As the title suggests, it didn't go too well, and am looking for advice on what to do. Prior to attempting the diesel purge, my D5 163 ran just fine (albeit with ECM-6805 saying hello occasionally), always a quick starter.
I'll try to detail as much as I can, so be warned, this might be a long read.
TL;DR: Did Liqui Moly Diesel Purge, now D5 barely starts.
After plumbing the fuel lines into a jar of Liqui Moly Diesel Purge, I managed to get the engine started. But not before:
- Destroying the small-length hose on the injector return line during the removal; replaced with a portion of the hose I bought for the diesel purge process.
- Priming the inlet hose and diesel purge filter to the LP/HP pump, including pulling a vacuum via the return line.
- A few cranking attempts before the engine "happily" ran on the Liqui Moly Diesel Purge.
After about 30 minutes of idling with the diesel purge, I tried to gradually raise and hold a steady RPM. I only got to around 1100 rpm before the engine died. A buzzing could be heard from the LP/HP pump area for around 30 to 40 seconds after the engine died.
At that point, I decided to give up on the diesel purge process and plumb the fuel lines back to the original setup.
It took a few cranking attempts to get the engine running after returning everything back to stock. When it did eventually fire, I noticed that starting was not as quick as it was before, taking just that bit longer of cranking before firing. I experienced something similar during a fuel starvation issue not too long ago, so I wasn't too concerned, yet, as I was just playing around with the fuel system after all.
This is a graphical representation of the engine parameters after that start:
I let the engine idle for around 4 minutes and revved the engine a couple of times after that. At around 350 seconds into the log, I tried to gradually raise the revs, but just before reaching 1000 rpm, the engine died, just like it did whilst running on the Liqui Moly Diesel Purge.
I cranked the engine again, and it fired back up. I tried to gradually raise the revs again hoping to replicate the engine dying but it didn't happen again. I gave it a few more revs just after the 500-second mark and everything seemed to be just fine.
I ended by shutting off the engine and restarting a couple of times, and again, everything appeared to be just fine. Because of the slightly longer cranking time before firing and the engine seemingly starved of fuel at low-ish revs, I didn't take it for a test run, for fear of stalling in the middle of the road.
Fast-forward 18 hours later, it was early morning, not much traffic to hold up in case things go wrong, I thought I'd take it for a short run to the shops. The slightly longer cranking was still there, but everything else seemed to be just fine (data below):
Went into the shops and came back out 5 minutes later. Cranked the engine 1st time: no start. Cranked 2nd time: still no start. Cranked 3rd time for a longer period: started. Unfortunately, I forgot to log the engine parameters this time. Quickly drove back home and the car sat still for about 5 hours.
I came back out to the car to investigate further, this time not forgetting to log the engine parameters:
The engine fired on the first try and I let it run for around 170 seconds, gradually raising the revs at around 90 seconds in.
I then turned the engine off and tried to restart it again. But after 7 starting attempts, the engine barely fired for a second or two but died immediately afterward. As you can see, the fuel rail pressure during this didn't indicate more than 200 bar during this time.
I've had a look around (and still reading) the forums and several issues have been mentioned (loose ECU connections, FP sensors FP regulators). I'm inclined to think I might have a leak somewhere in the plumbing to the LP/HP pump and/or rail, as I've been messing about with them and especially after discovering this on the inlet hose to the LP/HP pump:
Is the hose supposed to be 'twistable' like that? I imagine that would allow air to be sucked into the LP/HP pump, no?
That said, I'm more than happy to be corrected and pointed in the right direction.
Lastly, I hope this doesn't put off others who are interested in doing a LM diesel purge. It's been done successfully by many others with good results, just not on this occasion.
Please help!