the dutch guy wrote:on the top one it looks like the fuel pressure (green) has pegged the needle. i would think the sensor is having that the time of the month.
Mikexx wrote:the dutch guy wrote:on the top one it looks like the fuel pressure (green) has pegged the needle. i would think the sensor is having that the time of the month.
I'm struggling to understand what you mean.
If the pressure is OTT, then wouldn't it be easy to start from a bit of over fuelling?
knobby1 wrote:
The "Green" trace is actually the "Desired" fuel rail pressure, (38,500kpa ~5,582psi), the "Red" is the actual recorded pressure, (49560kpa ~7,186psi). Looks like they're quite a ways apart. I wonder if the PCM will disable the injector pulse if the pressure isn't within a specified range of the desired pressure.??
Are you able to do an injector pulse trace whilst trying to start??...Might show something.
Looks like she may need a pump, pilot and injector learn done.
Lord Knobrot.
Mikexx wrote:Thanks, I will try tomorrow. Starting is very variable, sometimes I can try 2 or 3 times, others first go. Please bear with me.
I have the Forscan software which I believe can initiate these learns?
The engine will try and fire, but not sufficiently to pickup to idle. Doesn't that suggest it's not disabling the injector pulse?
knobby1 wrote:
If the engine is trying to fire and then stops, it "may" be the PCM dropping the pulse to the injectors after the fuel rail pressure goes too high.
This is the way I "think" it may be happening.....The rail pressure can only increase if the engine is turning over and hence the pump is also turning, once the pressure gets to the "correct range", the PCM will initiate a pulse to the injectors and she'll start to fire, once the pressure rises above a certain preset level, the PCM might be cutting the pulse to protect the system.. hence why she's cutting out...
Have you re-checked the PRV to make sure it's still in one piece?? Although I suspect it may be ok if your rail pressure is higher than desired. Won't hurt to check though..!
Lord Knobrot
Mikexx wrote:It doesn't stop, just needs the starter to assist the firing until it can turn under its own power. I haven't checked the PRV. There aren't any codes related to pressure.
If I take it off, what am I looking for? It's late and I'm flailing, I'll have a look when I have the chance at what I need to do.
Many thanks for the feedback.
knobby1 wrote:With the PRV, sometimes they still look fine but the spring inside may be broken....other times the whole thing will be in pieces.....But since your rail pressure is still high-ish, I suspect it's still ok. The genuine ones usually have a thin washer, the "non-genuine" ones often have a thicker aluminium washer.
If you can do the pump, pilot and injector learns via Forscan, that may help. Also, doing an injector leak-off check first will give a good idea of injector health, if they fail miserably you're wasting your time doing anything else.
Can you tell me what oil you're using in the engine please??
Lord Knobrot.
Mikexx wrote:The rest of the time it runs fine, no hint of a problem so thought it is unlikely to be a PRV with a high pressure, but then I'm not familiar with high pressure rail systems and more familiar with old CAV pumps. I'm using 5/40 fully synthetic, is that an issue? I am aware the spec is for 3/30.
v8dave wrote:I'd suggest the next test is a leak-off test on the injectors.
Have a look at these two threads if you don't have access to a leak-off test set.
viewtopic.php?f=5&t=161948&p=1370805&hilit=leakoff+test#p1370805
viewtopic.php?f=5&t=176075&hilit=leak+off+test#p1499078
There probably worth a read anyway.
I've not tried Forscan for the pump learns as I have ids that works OK, do you get an error code from Forscan when the learn fails?
v8dave wrote:I'd suggest the next test is a leak-off test on the injectors.
Have a look at these two threads if you don't have access to a leak-off test set.
viewtopic.php?f=5&t=161948&p=1370805&hilit=leakoff+test#p1370805
viewtopic.php?f=5&t=176075&hilit=leak+off+test#p1499078
There probably worth a read anyway.
I've not tried Forscan for the pump learns as I have ids that works OK, do you get an error code from Forscan when the learn fails?
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