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PostPosted: Mon Oct 01, 2018 5:06 pm 
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Hello again, seems im moving up in the world lpg wise, still havent fully fitted my omvl system to the cherokee however I have acquired the above wj which has the prins vsi fitted, generally its fine but has a couple problems, 1st once switched to lpg it throws a code p0204 and today after receiving a lead and software it shows two codes within the lpg system which i stupidly didnt take pics of so from memory one was idle pressure too low and something like running too lean which indeed it is. Much more complex than single point innit, where the hell do I start ?? Wont allow me to upload pics, too large and photobucket is no good either, it does lag on lpg when booted


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PostPosted: Wed Oct 03, 2018 7:10 pm 
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So been reading the help info supplied with the vsi software, seems reasonably straight forward however setting the lpg system using the obd2 live data way is not working, when switched to gas the fuel trims and o2 sensor graphs flatline, can see the o2 sensor on the lpg software but I need to see the short term fuel trim on my obd device to check the basics, could this possibly be the emulator at fault or something more sinister ??


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PostPosted: Wed Oct 03, 2018 9:06 pm 
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The VSI software wouldn't usually show any errors for too lean.

The low pressure at idle error is a common one, most likely the spring in the reducer has just gone a bit soft and you'll need to increase the pressure by turning the allen key adjuster on the reducer. One of the settings in VSI software will show the expected/working idle pressure, just aim to increase pressure until that pressure is reached.

OBD might show errors for lean, such errors could be due to LPG calibration / injectors / a problem with the lambda sensor / TPS / a vacuum leak. The petrol ECU's on these motors don't feature great OBD facilities - a lean code could even be caused by a misfire but you'd notice a misfire regardless of whether it was on petrol or LPG. If a misfire only occurred on petrol an emulator issue (along with lean code) would be more expected than if the misfire only occurred on LPG. If a misfire only occurred on LPG an emulator issue might be more likely if there were a rich error code.

The dreaded VSI1 emulators can be replaced with a different (and cheaper) brand such as Pitagora(s).. and it seems a lot of Prins installers do just that. But there's only maybe £25 difference in price and wiring in a Pitagora would be a bit of work

Betting is on either you have a duff lambda or the system was never calibrated well in the first place.

Assuming you have Keihin injectors, what colour banding are they? What is your software expected (working) pressure? What is your multiplier? The offset setting shouldn't make much difference on this engine unless someone entered a really silly figure.

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PostPosted: Thu Oct 04, 2018 7:00 pm 
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Thanks for the info, tbh im struggling a bit understanding the workings of it and trying to decipher the vsi help but ill keep going, im sure something will suddenly drop into place, the obd2 live readings puzzle me as to why the short term fuel trims go to 0 (flatline) switching to gas, they just switch off, answering your questions the idle pressure is set to 2.20 bar and the actual is between 2.19 to 2.21, the injectors have an orange dot on them, both lambdas have recently been replace and are working, no misfire, I dont understand multiplier what it is, ill try and link a picture of the settings from somewhere, oh the on gas check engine error is P0204 injector #4 ctrl circ


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PostPosted: Thu Oct 04, 2018 10:44 pm 
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Given that the short term trims go to zero when you switch to gas but still seems to run OKish tells me that it switches to open loop running due to detecting some electrical problem when it switches to gas, and on that basis I would have had an educated guess that such problem would be open petrol injector circuit... The P0204 injector circuit error confirms that this is the problem that your petrol ECU is seeing which is why your stfs' go to zero. You need a new Prins injection emulator / injector switching unit (only 1 if your install has 2 fitted... some 6 cyl Prins installs have a single 6cyl unit, others have 2 x 4 cyl units), unless you fancy replacing the broken Prins unit with something like a Pitagora and doing a bit of re-wiring.

Multiplier is just that, it is how much the petrol injector pulse is multiplied by to arrive at pulse time for gas injectors (before any compensation for gas pressure / temperature are factored in). in (proper Prins) VSI1 software the multiplier value is shown as RC_inj, a value of 100 would be 100%, the value should be a bit higher than 100 if well matched injectors and pressure are used.

You can also set an offset, the offset is an absolute amount of time that is added to / subtracted from the petrol injector pulse duration length before the multiplication is done, so offset affects low load and idle fuelling by a lot more than it effects medium to high load fuelling (3ms + say 0.3ms is an increase of 10% but 12ms + the same 0.3ms is an increase of only 2.5%).

Simon

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PostPosted: Fri Oct 05, 2018 9:11 am 
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Simon, thankyou, this now makes for more understanding to me, I suspected the emulator but wasnt totally convinced, there is one x 6 box which is hard wired in, think I have a pitagora here somewhere other than that I will order a new prins one, absolutely no point in going any further until this is rectified, my obd diagnostic shows OL/CL on petrol but even that information dissapears when switched over so the OL issue never occured to me, its probably the main reason why its not getting good gas mileage and is under-fuelled when floored, it is running lean but still firing on all 6


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PostPosted: Fri Oct 05, 2018 3:28 pm 
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You're welcome.

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PostPosted: Fri Oct 12, 2018 6:17 pm 
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I had posted again but removed them because I needed to check my wiring, treble checked and it is all correct however im troubled by pinout no26 on the main vsi ecu which is injector module command, according to the diagram that goes to the injector module only, however the loom from no26 runs to the petrol injectors and supplies the + power to them, it switches over but dies, almost like the tank is empty, shows 2.3 bar when on petrol then goes to 0 when switching over, no issues like this on the old im, I can hear the solenoids clicking on and I cant see half a tank of gas leaking away somehow, will check that I guess but other than that im now stumped

Tim


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PostPosted: Fri Oct 12, 2018 10:02 pm 
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Would have been simple if you'd got the same spec IM / injector switching / emulator module...

The Prins VSI1 ECU doesn't directly switch petrol injectors off, the IM does. Without checking pinout numbers (it's late!) I expect the wire you'll be referring to is just supposed to supply the 12v to the IM to 'turn it on' (i.e. disconnect petrol injectors and apply emulation).

I read your post before your edit, expected to be replying to your post the way it was.. You mentioned all the wiring colours etc before?

The Prins emulators just do the same job as a Pitagora... But they have an extra set of wires that run to the Prins ECU to allow the Prins ECU to see pinj.

Simon

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PostPosted: Sat Oct 13, 2018 8:04 am 
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Yes hmmm, I knew I had done it wrong :roll: the new IM loom is quite misleading I think, writing printed on the wires basically states that all the bicoloured injector wires go to the same pins on the vsi ecu, not so according to the wiring diagrams so I swapped them to the diagram.

The main lpg loom on the jeep is slightly different to the diagrams pin #26 is supposed to go to inj command (whatever that is) presumably though a switched supply that activates the IM when on lpg however on my jeeps system #26 supplies the petrol injector power and turns off when switching to lpg so my thinking is that I need to chop that and return the petrol injector power supply to the petrol ecu, but I dont know what to do with the red/white IM command wire, not sure if its fed with +5v or +12v or where to tap it into, possibly the gas injector supply maybe ??, shame there isnt a prins specialist near me cos I would have simply dropped it of with a just fix it please and give me the bill instruction lol, but there isnt and I didnt have a pitagora IM here so thinking I had to buy one I just bought the vsi one to keep it all the same.


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PostPosted: Sat Oct 13, 2018 7:26 pm 
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So had another look today but still no joy, it dies on switch over, the lpg injectors are triggering though so I dont know, there is half a tank of gas so It hasnt mysteriously leaked out, the lpg solenoid valves are working, im now wondering if the injectors are firing out of sequence for some reason.


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PostPosted: Sun Oct 14, 2018 1:39 pm 
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This just weird, everything is as it should be, gas is getting to the injectors, i fired one injector and i can hear gas going through to the inlet, half tank of gas, both valves turn on, injectors are switching/pulsing, 2.2 bar on the gauge wobbles slightly when switched over but maintains pressure, only thing left is injector sequence, cant see how it can be anything else, wiring loom from IM, is numbered into the vsi loom correctly, even revved the nuts off it then switched over, not even a pop


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PostPosted: Sun Oct 14, 2018 2:00 pm 
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If it's just injection sequence you should be able to keep it running by holding revs high enough whilst switching fuels.

If you are sure LPG injectors are operating and you have correct gas pressure, besides injection sequence this still leaves correct mixture to be confirmed. The Prins ECU controls the pulse duration of injectors (and hence mixture) but it can only do that if it sees pulse length of petrol injectors correctly and it gets petrol injector pulse length from the emulator - it would be possible to wire the emulator incorrectly and prevent the ECU from seeing petrol injector pulse length. E.g. If you wire the ECU's pinj signal input to the petrol injector side of the emulator (as opposed to the petrol ECU side of the emulator) you may see one or two pulses on gas injectors before gas injectors are turned off... and they would be turned off at the same time as petrol injectors... in which case you might get the gas injector pulses only for the short time before each cylinder respectively is switched from petrol to LPG (especially if the emulator features a delay between switching individual cylinders between petrol and LPG / 'sequential fuel changeover').

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PostPosted: Sun Oct 14, 2018 4:07 pm 
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I have been back out to recheck the connections, totally following the new emulator wiring instructions, I checked the pin numbers on the IM socket with the wire colours and numbers and they all correspond, bold colours to the petrol injectors, bicoloured to the petrol ecu, the other bicoloured wires to the vsi ecu, im baffled, when the engine dies down the injectors keep going, slowing down with the engine until the engine completely stops rotating, once stopped it switches back to petrol but of course the engine has stopped turning by then, looking at the laptop screen the gas injectors are copying the petrol injectors including during switchover, on petrol revving it to 3500 + then switching to gas i would expect some run-on or some sort of popping but totally nothing, + power stays at the gas injectors on switchover, i havent altered any of the settings, one other thought is spark disappearing, cant see why though, thx for your thoughts again Simon

Tim


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PostPosted: Sun Oct 14, 2018 8:11 pm 
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You mention earlier in the posts the gas pressure drops to 0 once it switches - It would be an idea to check if thats either a spurious reading or a dodgy sensor. 2.2 bar of gas will make a flexible hose reasonably solid compared to 0, does the hose leading to the pressure sensor feel solid in both the state where it shows 2.2 and the state of it showing 0 (or if you loosen the hose and check does it feel like very little pressure is there?)

If its fluctuating it would point to some sort of supply issue - partly closed tank valve, gummed solenoid, crushed feed pipe or similar, if you have a restriction it may be able to trickle past it to get the initial running, but then run out. This would explain the lack of popping etc as theres nothing to ignite (you'd expect popping from a hot exhaust if you had ignition issues and were sending gas down it).


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PostPosted: Sun Oct 14, 2018 9:20 pm 
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Hi, yes initially the gauge in the software was going to 0 however i tried an extended crank on lpg and it showed plus minus 2.2 bar, gas is there, i have fired an injector independently several times after opening the valves and it flows to the nozzle, the jeep is fitted with coil packs fitted directly to the plugs so not easy to check for spark when switched so im going to have to introduce some ether on switch over to see if it runs on a bit, other than that then its either injector sequence is wrong but i doubt that or the new IM is possibly faulty, noid lamps would be usefull here but I dont have any


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PostPosted: Sun Oct 14, 2018 9:45 pm 
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Could be getting both petrol and gas causing mixture to be too rich to run. Although, would expect very poor running but for it to still try to run if that rich. That said, if the Jeep petrol ECU has stored high positive fuel trims (e.g. +30%) due to some earlier issue (misfire on a cylinder could do it), then the combination of high trims, petrol and LPG fuelling at the same time could cause such extremely rich mixture that the engine wouldn't even seem to try to run. This ,while baring in mind that the Prins ECU outputs to gas injectors directly, the emulator switches petrol injectors off.

What year 4L Jeep is this, pre 2000 with dizzy or post 2000 with coil pack? Different engine management systems respond differently, clearing certain OBD errors on pre2000 models will also reset fuel trims to zero. Have you read fuel trims on petrol? If you don't have an OBD scanner (and/or regardless of model year) you could just try going for a drive which should then relearn fuel trims. As implied, when fuel trims are correct (and if LPG system calibration isn't too rich) I'd expect it to try to run albeit very roughly if getting both fuels at the same time but if it gets that extra 30% on top of double fuelling I wouldn't expect it to even attempt to run.

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PostPosted: Sun Oct 14, 2018 10:23 pm 
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2001 4.0L gc wj distributorless coil pack it is, my scan tool will go deep into the jeeps electrickery, petrol fuel trims are as one would expect, restarting after the failed switch-over is easy and it drives just fine, goes quite well actually lol, with the old IM it had six pairs of red and black wires plus one red the red wires went to the petrol injectors the black wires went to the vsi ecu and the petrol injector ecu, the red went to simulator, cant find a wiring diagram for this anywhere.

The newbie has 21 wires six to the petrol injectors (bold colour) six to the vsi ecu (bi coloured) and six to the petrol ecu (bi coloured) plus an ignition+, ground and Im command (whatever that means or does) checked the wiring over and over, traced the wires to each petrol injector and lpg injectors, its all correct to the prins drawings, there are two drawings, one with two fuses one with three fuses my system has three fuses so ive used that one.


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PostPosted: Sun Oct 14, 2018 10:35 pm 
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In old IM, what are you calling simulator?

IM command will be the connection from the Prins ECU which tells it when to switch off the petrol injectors. If this connection isn't made the engine will continue to get petrol injection when running on LPG...

I find it easier to follow your description of wiring connections for the new IM than your description of wiring connections for the old IM. Please clarify what wiring connections the old IM had. How many wires total?

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PostPosted: Sun Oct 14, 2018 10:55 pm 
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The old emulator has the numbers 091/0155 v2 i cant link pics anymore from photobucket but here is a link to a pic i found

https://www.google.co.uk/search?q=prins ... v57ooxCEoM

13 wires, six red, six black which went to petrol inj and vsi ecu and one red which went to a wire marked simulator.

On the prins drawing inj command from the new IM goes to pinout #26 on the vsi ecu but this is already occupied by a wire which feeds the power to the petrol injectors 12v which turns off the injectors when switched to lpg, as i mentioned earlier I was wondering if I should cut this wire and return the supply back to the petrol ecu, but if done how do the petrol injectors get turned off ?? Presumably by not receiving a signal from the IM ??


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