Cavesurfer wrote:Good morning all
Looking online at various forums there seemed to be a theme with fuel rail problems, specifically the PRV and SCV, so I replaced these, blead the fuel system and tried again. No change.Thank you
teeone wrote:Are you using forscan on your laptop?
If you are you can check the crank sensor is syncing while cranking.
Itll also tell you if you have fuel pressure etc
As for pulling it appart, its a 7mm socket, and down below the vac pump area top of the gearbox, pretty much all by feel. Get a light and a mirror and youll see what your dealing with.
When you know you can do it one handed
knobby1 wrote:Cavesurfer wrote:Good morning all
Looking online at various forums there seemed to be a theme with fuel rail problems, specifically the PRV and SCV, so I replaced these, blead the fuel system and tried again. No change.Thank you
Was it running ok before this issue? Did it happen suddenly or has it been getting progressively worse..?? Is you fuel filter full or empty..??
When you replaced the SCV & PRV, were the pump, pilot and injector learns carried out sucessfully..?? If not it will never run properly. No need to bleed a TDCi fuel system, they are self bleeding.
Forscan will give real time date on fuel rail pressures, cam & crank sync etc. Forscan & IDS have a "Starting issues" tab in the service functions menu. You need proper diagnostics rather than just throwing parts at it and hoping for the best.
As you've no doubt found out, guessing and throwing parts at it is costly and time consuming....for no result.
Lord Knobrot
knobby1 wrote:If it's hard to start after standing for a while, you may have an "air leak" in the low pressure side of the fuel system. This allows air in and the fuel then siphons back to tank...making it difficult to start later on...or the next day. The Euro-4 machine low pressure lines actually run at a small vacuum and have to basically "suck" the fuel up from the tank to the pump. The Pre-Euro-5 machines don't have an in-tank pump. Common places to look are the filter seal, filter head itself, they can crack letting air in, the 4 lines connected to the filter head have O-rings in them which can perish and crack, again, letting air in. Lastly is the leakback lines and/or their tiny green O-rings on the injectors...same result. Also worth checking the fuel "pick-up" line in the tank...we've had them break off or split causing similar issues.
If the filter is empty after sitting for several hours or overnight, you more than likely have air ingress.
Lord Knobrot
knobby1 wrote:I think you're looking too much at many things which don't really matter, if there were faults with any of the sensors, they would normally throw fault codes.
Were the SCV and PRV genuine Denso or Ford items..?? If not you may be doing them again. Have you done an injector leak-off test..?? If the injectors are marginal, it will cause the pilot/injector learn to fail.
PRV needs to be sealed properly, it's tightening torque is silly high and in two stages, #1 is 30nm (22lb-ft), then mark the housing and valve with a marker and another line on the rail 3mm away, then #2 is 172nm (126lb-ft) and the line on the valve must pass the second line on the rail.. Internal sealing washer must be new or it will probably leak internally.
Lord Knobrot
Cavesurfer wrote:Yes, I think it's absolutely the case that I'm looking into too much...just thought I'd go through the whole lot to see what I can see. This is all completely new to me so I have a great deal to learn. Back in the day when I had a defender, there was basically one simple rule...if diesel was getting into the engine then it would work. It's certainly not that simple any more.
So yes, the PRV and SCV are both genuine Denso items as this seemed like a good plan.
If the injectors are marginal (meaning internal components worn??) will that mean I get excessive leak-off? Is there a means of running this test this that is quantifiable in some way? I'm thinking fuel hose running from the leak-off line of the injectors into a measuring container of some kind?
Or is there a test I can do with forscan? The leak-off line just seems to go to the fuel filter housing with no sensors of any sort on the way.
I'll check the torque settings for the PRV and follow your guidance there. I don't actually recall the washer, but I will check that as well. Is it a copper item?
I read another similar item on this forum earlier today that seemed to suggest injectors could be the problem, i.e. excessive leak-off in that they are old. The van is 115bhp with about 130,000 miles on it. I've had it about three years and I'm no Michael Schumacher for sure, but I can't speak for the previous owners and how they treated it.
On the issue of air in the fuel line, I realised today that the main fuel line running to the pump from the fuel filter is semi-transparent. While the van was running today I shone a light through the line and there were no bubbles at all so I'm hoping that's fine. On another posting on this forum I saw quite a few comments about always fitting a genuine ford filter (which I didn't) as this not only fits better but will also likely include a finer grain of filter than pattern parts such as the one I have. This, in turn, isn't great for the injectors. Makes sense. Could this go part way to explain why this problem started just a few hundred miles after I fitted the current fuel filter?
Thanks for your invaluable input. Much appreciated.
Cavesurfer wrote:So the PRV valve I purchased (genuine Denso) included two aluminium washers. One was clearly a replacement for the copper washer shown in the photo you attached in your last post. It’s thicker than the copper original, which is a cause for concern, but i’ve put it in place and the leak has disappeared. Being thicker and made of a softer material it deformed more than the specification your gave, so in order to achieve the correct tightening torque i had to turn the PRV through nearly 180 degrees after the initial stage of tightening. I’m going to keep a close eye on this. Not sure why denso felt it necessary to replace the original item with an aluminium washer, but it’s not leaking.
Also purchased a leak off test kit and have just run the test this morning. All four injectors we’re well over the 40ml in 4 minutes...in fact I had to terminate the test at around 3m 30s as cylinder #4 had filled the 100ml bottle.
So 4 injectors on order and then I have the fun of fitting and reprogramming I guess. Do you have any words of advice for this? I’ve looked at a couple of videos on this and forscan seems to set up to run this process.
Thanks
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