high pressure during cut off

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Gilbertd
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Re: high pressure during cut off

#21 Post by Gilbertd » Tue Nov 17, 2020 9:36 pm

Looks to me like the bottom union is cross threaded so not screwing in fully. It looks to be at an angle and there's far more thread showing than on the top one. The connector you link to is for orange hose, vapour hose used to connect a Propane cylinder to your barbecue or patio heater. Intended for vapour not liquid at 10 bar.
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mgrover
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Re: high pressure during cut off

#22 Post by mgrover » Wed Nov 18, 2020 8:34 am

indeed, i will be getting this to marry them

https://www.lpgshop.co.uk/farotypeo88mm ... gxwM_aUVvM

also dunno if the lpg installers know but theres also a FB group thats pretty active if they want to ply their trade there.

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Re: high pressure during cut off

#23 Post by LPGC » Wed Nov 18, 2020 10:05 am

I would have advised using 1 of the inline Faro to Faro connectors you linked to in your last post. You could use 2 to extend the pipe without touching the existing ends of pipe, or 1 if the pipe is long enough without extending, or 1 if it's not long enough so you need to extend but you don't mind re-making connections at the reducer end.

But the fittings you have should work if not cross-threaded. Sometimes if you cross thread a pipe-nut it deforms the olive.
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Brian_H
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Re: high pressure during cut off

#24 Post by Brian_H » Wed Nov 18, 2020 6:04 pm

If you can't locate which bit is leaking, then some soapy water will narrow it down, as above, the faro to faro joiner would be much neater (I did try finding a 90 degree elblow last night in that setup but couldn't, if it doesn't need to be an elbow that would be much easier).

The faro connectors can also be reused much more easily than the copper ends for them, you can reuse the copper ends if you can get them to seal, or get the olive off and replace it if needed. As said what you have should work, but doesn't look quite right in the photos, is it possible any debris has got caught where the olive sits (you should be able to get away with undoing it to check, best to depressurise it first though)

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Re: high pressure during cut off

#25 Post by Brian_H » Wed Nov 18, 2020 6:06 pm

Other thing I meant to say above - is it Faro branded pipe your using, or someone elses brand?. They differ slightly, and that might be the source of your leak as well.

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Re: high pressure during cut off

#26 Post by mgrover » Wed Nov 18, 2020 8:47 pm

It's some other type pipe I think.

I've probably cross threaded it tbh, I'll saw the olives off both sides, fit fresh connectors and olives and be gentle this time :lol: think I rushed a bit too much in my excitement :p

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Re: high pressure during cut off

#27 Post by Gilbertd » Wed Nov 18, 2020 9:16 pm

It isn't the side with the olive, it's the male to male threaded bit that is screwed into the elbow that appears to be cross threaded. It's probably easier to see on your picture than it is when looking down on it but there's far more thread showing on the lower one than the upper one.
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Brian_H
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Re: high pressure during cut off

#28 Post by Brian_H » Wed Nov 18, 2020 9:39 pm

Before you pull it apart, test it with soapy water. Bubbles will show you where the problem is, then you can leave the bits that are ok alone. The bottom one in your photo as said above, looks skewed. This may be a sign that the joiner itself is not of the best quality rather than it being cross threaded.

The bit you posted above if it will fit into the gap, should sort the issue anyway, There is an olive on either end of the convertor, the one on the copper end is the one I'd suspect to be where your problem is (not the split one that holds the poly pipe).

Brand wise Faro is probabbly the most common pipe, but whichever one it happens to be should be marked on it. As long as you can't see any leaks using the soapy water method from the larger end of the adaptor, you should be fine with the adaptors you are using.

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Re: high pressure during cut off

#29 Post by mgrover » Thu Nov 19, 2020 11:08 am

Brian_H wrote:
Wed Nov 18, 2020 9:39 pm
Before you pull it apart, test it with soapy water. Bubbles will show you where the problem is, then you can leave the bits that are ok alone. The bottom one in your photo as said above, looks skewed. This may be a sign that the joiner itself is not of the best quality rather than it being cross threaded.

The bit you posted above if it will fit into the gap, should sort the issue anyway, There is an olive on either end of the convertor, the one on the copper end is the one I'd suspect to be where your problem is (not the split one that holds the poly pipe).

Brand wise Faro is probabbly the most common pipe, but whichever one it happens to be should be marked on it. As long as you can't see any leaks using the soapy water method from the larger end of the adaptor, you should be fine with the adaptors you are using.
i can actually see the leak :P like if i swap to lpg and open the bonnet its leaking out haha

My pipe says, "Transfer Oil - LPG Automotive Class" on it. Is that Faro?

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Re: high pressure during cut off

#30 Post by Brian_H » Thu Nov 19, 2020 9:06 pm

Doesn't sound like it, but if you can see it where does it come out? The above highlighted threaded joint, or somewhere else?

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Re: high pressure during cut off

#31 Post by LPGC » Fri Nov 20, 2020 9:30 am

Some Faro pipe does have 'transfer oil' written on it, still the correct stuff for use with LPG, has 'Lpg' written further along it's length.
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Re: high pressure during cut off

#32 Post by mgrover » Sat Nov 21, 2020 6:19 pm

its fine, the connection worked, no leaks, love it. all seems well, no overpressure situation.i doubt it was my reducer thats damaged tbh. and we're about to find out because am going to use the spare reducer to have a dual reducer setup.
cant seem to keep a consistent 1.3/1.4 bar pressure with one.

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Re: high pressure during cut off

#33 Post by mgrover » Sat Jan 16, 2021 4:00 pm

bit of an update. two reducers seem to be the cure here. i mean my car is still running lean but feels like theres something fucking with my fuel trims in terms of sensors because it gets wayy worse on lpg.

but, lpg no longer surges, idles well and overall just coping with extra power, this car also has the 10% pulley so even more gas required. now revs all the way to redline with no issues.

now i just need to deal with the cars fuel trim problems.

two magic power with outlets nozzles each.

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Re: high pressure during cut off

#34 Post by LPGC » Sat Jan 16, 2021 5:39 pm

Right at the top end of engine load it may switch to open loop and then fuel trim readings might be weird, in that case though you should check wide band lambda equivalence readings to make sure mixture is correct (suitably rich under high load open loop conditions).

Another thing that can cause a sudden switch to lean running on LPG at high engine loads on these engines is if a physical fuel return is fitted that doesn't have big enough jet. The petrol delivery system reads fuel pressure and controls fuel pump output on a closed loop basis (closed loop in this context related to fuel pressure not mixture as with lambda readings and fuel trims etc) but it still expects to drive the fuel pump a certain amount for a certain engine load... If the jet isn't big enough then at high engine loads even with the fuel pump driven for the minimum for that condition the jet may not allow enough fuel to pass to keep fuel pressure readings around where they would normally be if running on petrol. This has the effect of causing the petrol ECU to compensate for the higher petrol pressure by reducing petrol injector pulse duration which (since the LPG ECU primary input is pinj) has the effect of leaning the mixture when running on LPG. To see if this is the thing that's causing the lean running at the top end of engine load on LPG compare fuel pressure readings running on LPG to fuel pressure readings running on petrol (flat out in both cases obviously).

Other than that, any chance of a pic of your LPG map and a screen pic showing readings or just info comparing ginj versus pinj when it goes lean at the top end?
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Re: high pressure during cut off

#35 Post by mgrover » Sat Jan 16, 2021 10:35 pm

It leans out during closed loop operation. Bank 1 is definitely the problem to the point where the LTFT is way higher.

Could this be wrong shim sizes?

Also the return line is working as it should, when I check the fuel pressure its around 40psi which is normal fuel operating pressure.

Realistically I need to fix the petrol, but I've been trying for the best part of a year without any luck.

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Re: high pressure during cut off

#36 Post by LPGC » Sun Jan 17, 2021 5:39 pm

Well that seems to rule out the fuel return as the problem.

It could be wrong shim sizes. Are you implying the same kind of thing happens on petrol? Or what is wrong with running on petrol?

What happens with bank 2 trims when bank 1 trims go high (question for both fuels)?

On an engine with a single MAF the ECU can normally assume 50% of airflow goes to bank 1 and 50% to bank 2. If one of the banks flows more than the other (uses more air) it will need more fuel too. So on this type of setup highly positive trims on bank 1 and highly negative trims on bank 2 can point to bank 1 taking most of the air... and of course air intake is effected by valve timing/lift/etc.

I do a lot of work on Nissan Elgrand V6's, these are prone to catalytic convertor problems. Being a V engine with cats on both sides of the V and having a single MAF it is possible to tell which side of the exhaust a cat blockage is because that side of the engine will use less air and therefore also need less fuel - If bank 1 has a cat blockage bank 1 will not be able to pump out all it's exhaust gasses so will not be able to suck in as much fresh air as bank 2, so bank 1 trims become negative because bank 1 gets less than 50% of airflow through the Maf and bank 2 trims become positive because it is getting more than 50% of airflow through the Maf. In which case it may sometimes seem the problem is on bank 2 due to highly positive trims but the real problem would be bank 1 even if trims are not at maximum negative - It might depend on where the baseline trims would be (baseline might not be 0% ltft if the problem did not exist)... Let's say there's some underlying problem with engine breathing that means B1 gets 40% of air from the Maf and B2 gets 60% of air from the Maf, if without the problem trims on both banks might normally be around +10% then with the problem trims on B2 might be +20% and trims on B1 might be 0% but it would still be B1 with the problem because B1 wouldn't be using as much air as it should. Or if without the problem trims would both be -10% with the problem trims would be -20% on B1 and 0% on B2 and in this case reading trims would point to the correct bank being at fault. Sometimes you have to kind of work backwards to see the full story.
Last edited by LPGC on Sun Jan 17, 2021 5:57 pm, edited 1 time in total.
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Re: high pressure during cut off

#37 Post by mgrover » Sun Jan 17, 2021 5:51 pm

so

bank 1 is leaner than bank 2. on petrol bank 1 is defo leaner. check out these adaptive fuel trims.

Image

both are lean, but bank 1 is leaner.

if theres an issue with the cats then the subfeedback trims in the pic above would be higher, but they're like 0%.

ive seen some people saying issues with thermostat so worth replacing.

i also did accidentally spill a bunch of coolant on my MAP :lol

am also going to inspect the plastic intake for cracks because most my smoke tests are with it off.

finally, the wide band lambda sensors, 1 means perfect ratio, if its 0.9 is it rich or lean?

edit:

this is now an old pic above, i need to relearn the trims because ive been messing with them on lpg quite a bit and now their all at like 20% :lol:

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Re: high pressure during cut off

#38 Post by LPGC » Sun Jan 17, 2021 6:13 pm

I see nothing really telling in the screenshots of ltft's, it might be more telling to see a vid of a code reader showing live data including ltft and stft for both banks under various conditions as you drive the car. Would also be helpful if lambda equivalence ratio readings for both banks were shown in live data because when trims have been upset on an engine with wide band probes they might not be learned on timescales we're used to for vehicles with narrow band probes.

Yes I would have added you need up to date data now you've made changes to the engine (had bits off, changed LPG mapping, etc). Ltft's don't really point to much at all by themselves if stft's are not close to zero.

0.9 normally points to rich.

I've found that on L322 4.2 SC's it is possible to reset ltft's to 0% using only a normal scan tool by causing a really hard OBD error sucg as disconnected petrol injectors, then when you reconnect the injectors and clear the code pointing to disconnected injectors it resets the trims. But beware doing this because idle trims (particularly) don't work or read like you'd expect during the initial learn process after doing this.
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Re: high pressure during cut off

#39 Post by mgrover » Sun Jan 17, 2021 6:25 pm

ive got an iidtool and dealer software so I can reset the adaptive fuel trims and ltft at will. i actually did it this morning cause MOT is tomorrow so dont wanna risk an engine light coming on :lol:

hmmm that lambda comment is interesting, cause when am driving its mostly 0.9/1 while short term fuel trims are saying its lean.

so it seems something other than the sensors are signalling its lean, whether its the map sensor, the maf sensor, maybe the thermostat and it never getting up to temp.

ill have to dig into that more.

just to make sure, the wide band sensors are just the normal precat o2 sensors right?

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Re: high pressure during cut off

#40 Post by LPGC » Sun Jan 17, 2021 6:46 pm

It will generate an error pointing to trims being lean/rich if trims are at an extreme even if mixture/lambda are OK.

You could be looking at command lambda (the mixture it's aiming for) instead of looking at lambda readings but I doubt it if you're looking at equivalence ratio for both banks, there's only one command lambda.

What you should find is lambda readings stay close to command lambda, they tend to stay a lot closer when fuel trims have been correctly learned than when fuel trims are being learned. Command lambda may be slightly more than 1 under very low load conditions but may go down to say 0.8 at high loads, under most low/medium load conditions command lambda is 1. Unlike engines with narrow band probes where the aim is always to steer mixture to equivalence ratio very close to 1 under closed loop conditions, engines with wide band probes aim to steer mixture to command lambda and fuel trims reflect the same (if command lambda for say 4000rpm 1.1 bar manifold pressure is 0.8 the ECU map designers might expect fuel trims of close to 0 when lambda equivalence readings flick around 0.8 as opposed to flick around 1).

The pre-cat sensors are the wide band sensors I have referred to.
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