Wow this machine has been a nightmare right from day dot. 3 days in, the engine starts idling very rough, no power, blowing white smoke until hot etc etc. Diagnosis of course was a faulty injector, a spring inside the assembly had broken. Anyway, I was in a tight financial situation at the time so my uncle replaced all 4 injectors with re-conditioned ones and all seemed to be good.
Interestingly though, the engine intermittently had an issue whereby the idle was fluctuating like their was an air leak somewhere. It would just take some patience to wait for it to clear its throat and then it was all good, until a few months down the track it wouldn't start and had a tendency to conk out on me when I eventually did get it going. So I took it to a mechanic who was well known for working on the 4JX1's. His diagnosis was a faulty glow plug. Of course they were seized in the head so they needed to remove it and get them out that way (I told him to replace all 4 while he was in there). Anyway, a week or so later I pick the car up and as soon as I leave I'm getting a 'check engine' light, exhaust is noisy and the engine lacks power. So I take it back several times to allow them to troubleshoot the MIL light, they ascertain it is EGR related. They stop the light but the EGR was making a weird humming sound. I really didn't care at the time I just wanted a car to get around in!
So, it turns out that I am still having problems starting the engine and it still has a tendency to conk out on me and rock and roll around like there is an air problem somewhere. Back to the mechanic and it stays up there for a couple of weeks. They sort the EGR noise by checking and changing hose configurations and adjusting some sensor near the air intake. They find the fuel filter is sucking air so they replace that and the filter head and they are still having issues. They then check the orifice at the back of the head and it is blocked. So they clear the blockage, place non-return valves in every possible spot to eliminate any possible drain back issues, adjust the TPS as it is out of synch, replace the coolant sensor, check the little butterfly thingy in the exhaust (something to do with rapid warm up) and all seems to be good. it starts fine so I go and pick it up. The mechanic mentioned the ORPS needs to be replaced at some point as it is badly leaking.
Couple of days later, same issues across the board so back to the mechanic. They check the oil pickups in the sump (someone had already been in there from the days of the previous owner) seals were all good and the pickups hadn't broken off. My uncle had mentioned in his paperwork that he was unable to remove one end of the oil rail to replace the seal. So I had a spare oil rail here, they replaced all the seals and the ORPS. Much to my mechanics frustration, after the all the work he had put in, the car still has a problem with starting and he was quite frustrated by the fact that the pressure in the rail was dropping to 0 when the key was turned to the off position. He then installed a small electronic fuel priming pump mounted near the firewall and finally.... the car has been good. The cold start is still ordinary and it blows a little bit of white smoke when it starts due to what I would believe to be a fuel problem STILL! The cold start is noticeably worse when the vehicle is nose up.
I spoke to Chilby about the outcome and I think his comments would be great for those troubleshooting issues with these engines:
"I'll have to read a bit on this. It seems that whatever mechanism holds pressure in the rail - isn't. I expect there's a combination of operations for that. You have two fluids remember - oil at high pressure being fed into the rail, and diesel fuel gurgling through the head at a much lower pressure. By what you mechanic says, it's the oil pressure that drops suddenly - so the problem would be in that circuit.
There is a by-pass system in the fuel circuit that allows excess fuel to return to the tank but your mechanics says it's OIL pressure that drops suddenly when she's turned off, not fuel. So that would be way down on the list of things to check.
But you say there was "a very badly leaking ORPS" which is exactly the kind of fault i'd be looking for.
If the ECM is reading that oil rail pressure is ok "No worries guys! plenty of pressure here to drive fuel.." , but in fact the real pressure is leaking out the other end of the sensor, that would explain why she stops when the engine slows down. The injector solenoids would be opening but the fuel delivery would be slow.
In other words the main problem may already be fixed.
Perhaps to elaborate and carry that forward a bit. .. A common rail injector system has the advantage of holding fuel pressure high "even at idle" they say... but the reality is that at idle the main rail pressure does drop a bit since the oil pump isn't going as fast. The quick fix to that is to raise the idle so the pressure never drops that low.
What your mechanic has done is rather clever - he's holding fuel pressure high at idle with an electric pump instead. This would have the effect of picking up fuel delivery a tad at idle. Top marks!
Barring more pressure leaks in the oil circuit etc.. ( which I doubt since you've had guys scratching their head over it and leaks/seals are obvious to the eye ) to my mind all this points to a lazy Rail Pressure Control Valve. It's located on the back of the high pressure pump. It's a powerful solenoid and is the main ECM control system over oil rail pressure. Like any device bathed in oil, it tends to get gummed up with varnish over time. The cheap fix is to carefully take it apart and clean it. Preference is given to buying a cheap ultrasoninc cleaner off eBay so that it's gently cleaned and all the tiny orifices inside get well flushed out. This is a common maintenance item with the 4JX1. I very much doubt that the solenoid in it is faulty - since I would suggest that someone has been reading the ECM while all this work has been going on - and a solenoid reading high resistance etc would be picked up straight away and likely be leaving a dashboard MIL code as well. But it would only be "lazy" ( slow to react because of a bit of sludge ) not totally footed since the engine seems to be running ok off idle.
There were a number of interesting phenomena noted when people started buying Tech2's on this forum. They noted the oil rail pressure jumping around at idle. It was only noticeable with the Tech2 reading and the engine idle was smooth with no other problems. This was likely a combination of 2 things - the ECM is a digital device so sends PULSES to the RPCV instead of a smooth analogue signal. If the valve is a bit gummed up at the same time you can imagine the effect.. the pressure jumping around a bit. So perhaps what's happening to your engine is the next step up from that phenomena - the valve is starting to jam open or closed when at idle.
Of course i'm only guessing. But if the story is a bit like the above your vehicle is already repaired. I have experienced personally what a bugger it can be to clear the fuel line of air bubbles so wouldn't doubt that could be a problem. In that case it's just a matter of running her for a bit. The electric priming pump would be a bonus.
I suggest you think about getting a Tech2 if keeping the vehicle. It tends to be a lot of indecipherable gobbledegoop, but with regular use you start to notice when things change. Also when you get time to go through the huge chapter on fault finding with a Tech2 in the *.pdf manual it seems like a good thing. Then you can follow the regular GMH maintence schedule in the maunual as well. YOu become GMH. They're down to $420 delivered now at this site:
http://www.aliexpres.../573637766.html
cheers,
Cliff"
Anyhow, I have since found out that the mechanic replaced the RPCV with a second hand one. So it would seem that isn't the problem unless the second hand one is dodgy of course. However, my next thought when I get it serviced again is to try GENUINE filters as there have been a number of occasions where I have read about similar issues with these vehicles when using RYCO filters. So I'll give that a go next time and post the outcome. As for the ongoing fuel problem...... any ideas? My mechanic said he was astonishingly sure the filter head was new but he may be wrong and he'll check it next time. He also asked me to check for fuel leaks but I haven't been able to spot anything. I do sometimes here the sound of liquid touching a hot metal surface after stopping the engine but buggared if I know where it's coming from....
So I think it comes down to this. This engine HAS NOT been looked after based on all the stuff that was wrong with it. She goes like a steam train now though, I love driving it. Just needs new shocks, fresh power steering and brake fluid and I finally have it up to date with maintenance.