system throws low gas pressure fault and wont manually switch untill high reducer temp (fixed: post #43)

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Darren
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system throws low gas pressure fault and wont manually switch untill high reducer temp (fixed: post #43)

#1 Post by Darren » Thu Feb 07, 2019 6:42 pm

Hello,

I was directed to this forum about looking for advice with an issue i have recently come across with my LPG system. A few details about the system is that it is a KME Nevo Plus unit with either a KME silver or gold reducer. I am not too sure on what injectors are installed. The vehicle is a 2002 E46 330ci (m54 straight 6 3L engine) which i purchased a few months back.

Up until this recent cold snap the LPG system worked flawlessly and would switch over to LPG at a reducer temperature around 30°c (i have a laptop that i used to code a few features onto the car which also has the KME software installed on it) About 2 weeks ago, with a full tank, i started getting a low gas pressure error code (i have checked accessible hose connections for leaks with no results) whenever the reducer was warm enough to switch over to LPG. I ignored it for a few days thinking it was just the cold but it kept happening.

I installed a new fuel filter which by the looks of it hadn't been replaced since its installation in 2015. With hope i started up the car from cold and waited for it to warm up to its 30°c switch over temp, which it again threw a low gas pressure error code at me. At this point i'm thinking the reducer needs a service but i'm not too keen on messing with that until i educate myself more on said reducer.

After the gas filter change didn't fix the issue i hooked up my computer to do some tests and i noticed that everything seemed normal, once the reducer got to 40°c all the numbers settled and stayed more or less the same so i tried to manually switch it over to gas, no luck. i waited for the reducer to raise another 10°C and tried again with the same result, low gas pressure. this continued until the reducer reached 68°c where it would finally let me manually switch the system over to LPG. In my head all i can think is that the reducer is clogged with something and wont allow the correct pressure to build up until whatever is in there is warm enough. But as i have very mild knowledge of LPG systems i have looked online for a few days and eventually was directed here for help.

Looking forward to any replies with many thanks in advance,
Darren
Last edited by Darren on Sun Feb 17, 2019 2:32 pm, edited 2 times in total.

Brian_H
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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#2 Post by Brian_H » Thu Feb 07, 2019 7:03 pm

The Nevo uses a pressure sensor which does both the map and gas pressure in one unit - it does say on the installation instrcutions that it has to be mounted the right way up, with the connector facing upwards. Really the question is what pressure does that show in the software? As if its misdetecting it for some reason that will cause the problem. I'd expect if it was, that it would be saying something daft though.

Its possible the reducer is clogged with heavy ends (the stickier/thicker bits of the residue in the gas), but its more likely that the solenoid (either at the tank or the one on the reducer) is not opening properly as its gummed up. Much easier to rule that out first and can be fixed by disassembling the solenoid post (best leave the one on the tank until you can either confirm its a 4 hole with a shut off tap, or run the tank to empty first, the reducer one can be removed as long as your happy the rear shut off works - if the post is as it should be, when switching it should click/clunk if you listen)

Its also worth keeping an eye on the reducer temperature - if this is too low (can be down to the way its plumbed in to the coolant system, which can be more of a problem on some vehicles than others, equally can be down to a low coolant level as the reducer will feed off the heater circuit, which generally has the highest bits of plumbing in the system anyway) it can cause the reducer to freeze up. The Nevo does usually switch back if the temp drops too low, though you may be able to set it not to.

Darren
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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#3 Post by Darren » Thu Feb 07, 2019 7:28 pm

(edit: images are huge sorry i had no idea they would end up that big)
The pressure switch does not seem to be installed as you described and once the system actually switches over to LPG the pressure is at around 1.2/3, i have checked the tank solenoid and it clicks when activated and the solenoid on the reducer clicks i single time when switching lpg off and clicks 4-5 times when switching on. i have just ran out to the car now and the engine was still warm so it switch directly to lpg with no problems at all at the temperatures in the screenshot. It seems that whenever i start the car with the reducer higher than 40~ it will switch straight to lpg with no problem at all. The low gas pressure error only seems to happen from cold starts.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#4 Post by Brian_H » Thu Feb 07, 2019 7:38 pm

Real question is what does it show when the system is cold for pressure?

I'd be suspecting the solenoid post is gummed as a likely cause, as not much else will be effected by temperature.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#5 Post by Brian_H » Thu Feb 07, 2019 7:39 pm

Also you haven't found the pressure sensor in those pictures, its usually an inline one in the pipework between reducer and injectors.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#6 Post by Darren » Thu Feb 07, 2019 7:46 pm

If i remember correctly on first start up from cold the pressure reads dead 0, then as the system warms up it will slowly go to about .5/.6 until i can manually switch the system over at around 70° reducer temp where it jumps to 1.3 as shown in the picture. ill let the engine cool down and have another look in a few hours but if memory serves right that is how the cold startup usually goes. i cant remember what the pressure was like on cold starts before the issue started happening unfortunately. I see, just pulled up a system diagram and saw the placement of the pressure sensor. ill head out and have another look around to see if i can find it.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#7 Post by Darren » Thu Feb 07, 2019 7:51 pm

I have now found the pressure sensor and it is indeed installed correctly with the connector facing upwards.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#8 Post by Brian_H » Thu Feb 07, 2019 7:55 pm

If you goto the faults page and press on the low pressure fault, it will tell you a bit more detail of sensors readings when the fault occurred.

If it is showing 0 pressure, you should be able to verify that by squeezing the pipe the sensor is located in. But i'd suspect that is working correctly.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#9 Post by Darren » Thu Feb 07, 2019 8:04 pm

I will grab the laptop out and have a look at that fault code when the car cools down as i have already cleared the fault code from my phone today, thank you for your help so far and i will get back with more details of the cold start pressures later on tonight. Are there any other screenshots/pictures i should grab while i have the laptop out that would be of help? also would uploading the settings profile be of any use at all?

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#10 Post by Brian_H » Thu Feb 07, 2019 9:00 pm

Doubtful - the most useful thing to do is verify the pressure sensor is working (squeeze the pipe and compare when it says 0 pressure vs working with 1.3 pressure - or undo a hose clip and see if you get any pressure out). If there is no presssure there, the next thing would be to track back to where there is pressure in the system - if the line coming in from the tank is pressurised but the output from the reducer isn't, then you have narrowed the fault down somewhat. Theres no point looking at settings given the sensor shows 0 pressure as that would explain what its doing. I'd suspect the solenoid post personally, as you'd expect to get at least some pressure through the reducer if it was clogged up, whereas if the front solenoid fails to open it could be blocking anything getting through. I'd say front is more likely as you seem to be able to tie it to temperature, and the tank doesn't have anything to help it get warm whereas the reducer obviously does!

The snapshot info I've got from the phone app, not tried the software on laptop to get the same info so not sure exactly how you do it without checking.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#11 Post by Darren » Thu Feb 07, 2019 9:09 pm

ok ill give that a go in a little bit, when i was looking online about what to do i came across a video saying to take off the vacuum hose while the engine was running to test the reducer, when i did this at the t piece connector the idle went a little crazy sucking air into the t piece and didnt settle nicely until i attached the hose again. not sure if that information is any help at all or not. i also did not smell any gas from the vacuum hose. again im not sure if that has anything to do with the issue but i thought id mention it.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#12 Post by Darren » Thu Feb 07, 2019 9:27 pm

Ran outside again and started the car up with the readings shown in this screenshot, again started straight to lpg even though the reducer is nowhere near where i need it to manually start up from cold start. i loosened the hose on the furthest side of the fuel filter. reducer > pressure sensor > fuel filter > loosened hose. and slowly took it off until i heard gas. when i could hear it the pressure didnt noticeably change but once i more of less pulled it off the pressure did drop. lowest i could see before quickly putting the hose back on was from 1.34 down to 1.12. so i think its safe to say that the pressure sensor is indeed working. although before taking the hose off i tried just squeezing the hose around the sensor which did nothing to the pressure level.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#13 Post by Darren » Thu Feb 07, 2019 9:31 pm

also before starting the engine it was at 1.01 pressure, i forgot to add that to the previous post.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#14 Post by Brian_H » Thu Feb 07, 2019 9:36 pm

That would suggest its a solenoid failing to open issue to me. Possible its the coil going bad and not working at cold temp. worth a clean first, if its still playing up remove the parts inside the solenoid post and see if that improves it, if so you know the problem is on the solenoid somewhere, a multimeter might give you an answer on the coil, though it may be hard to reliably test it (resistance test of it with it disconnected is what you need to look at).

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#15 Post by Darren » Thu Feb 07, 2019 9:54 pm

Thank you very much for your help! I will have a look at the solenoid over the weekend and report back with any findings.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#16 Post by LPGC » Fri Feb 08, 2019 10:32 am

Could be a dodgy solenoid, but...

Nevo features injector pre-heating - Below a certain startup reducer temperature (default 15degC) what happens is... The gas injectors are pulsed slowly before the solenoids are opened even when the engine is flat cold, during this period gas pressure falls to zero because the injectors are being pulsed with closed solenoids, as pressure gets closer to zero the gas injectors are pulsed faster (they couldn't be pulsed fast with pressure in the system as that would cause the engine to run too rich but it doesn't matter how fast they pulse if there's no pressure as no gas will flow to the engine), pulsing gas injectors heats the injector coils which heats the mechanical parts of the injectors. Then injectors stop pulsing, solenoids are turned on, there may be a pause to allow the vapour side of the system to prime with gas pressure, then the system switches to running on LPG. Pre-heating injectors allows them to work properly in cold conditions, helps make them less sticky (sticky from hc's / heavy ends / gloop that we see in inlet manifolds etc that condensed inside from both the engine itself and from the LPG), helps soften plunger seals and get internal tolerances closer to what they'll be in usual operation. It can be a great feature for some installs (particularly demanding installs), at higher pressures, is more necessary with some types of injectors than others.

Everything is settable by the installer... pre-heating on/off and (if on) reducer temperature below which it is activated, minimum number of seconds for the engine to switch to LPG (even with hot engine), number of seconds between valves opening and the beginning of switching cylinders to LPG (this is effectively priming time), number of milliseconds between switching individual engine cylinders to LPG. If pre-heating was activated (because the engine was started with reducer temp less than say the default 15degC) and priming time is set to zero, then particularly if number of milliseconds between switching individual cylinders to LPG is low (or zero) you might get exactly the symptoms you've described - because there will be zero pressure in the feed to injectors following pre-heating injectors and without any priming time the injectors will start out trying to fuel the engine with zero pressure in the system. When pre-heating has been activated it will run it's full cycle, even if reducer temperature gets above switchover temperature it won't switch to LPG until pre-heating is completed... So if preheating is set to activate when the engine is started with reducer below 15c, if changeover temp is set to 30c and the reducer quickly warms to above 30c the engine still won't switch to LPG at 32c if preheating hasn't finished (unless the engine is turned off, lights on the LPG switch go out and the engine is restarted, because now the ECU reads reducer above 15c when the engine is started so preheating is not activated).

Curious why the solenoids pulse 5 times on changeover... If you're sure that's what's happening (most injectors are silent during preheating but some sound like main solenoids pulsing)? What version of firmware are you running (at least later firmware doesn't pulse solenoids)? Some (other) systems do pulse main solenoids on cold startup (may help open cold gummy solenoids) but pulsing main solenoids can also be a symptom of low voltage / bad main power connections to the ECU (so when injectors start to pulse voltage is pulled lower and main solenoids close when injectors are pulsed). Wouldn't expect a main solenoid fed with constant voltage to pulse open/close and even if that was likely it would still be less likely for a sticky solenoid to do it.

Nevo will generate an error and switch back to petrol whenever reducer temp gets lower than 15c. You wouldn't want to be running on LPG with a reducer colder than 15c... but if you did the only way to get around switching back to petrol with reducer colder than 15c is to tell Nevo it has a different spec temp sensor (so the reducer temperature it reads is higher than actual reducer temperature). If this error is being activated the real problem(s) may be plumbing as Bri said (BMWs feature heater water flow control solenoids, reducer plumbing has to be to the correct side of the solenoids) and/or setting too low a changeover temperature. Pic of your reducer looks like it's mounted high up on a wing which may be too high a position, that might have been OK with series plumbing but you've got to do parallel plumbing (with heater matrix's) on BMWs.. with parallel plumbing if the reducer is the highest point of the cooling system it'll be prone to airlocks.

Whatever is causing the problem... high reducer position, plumbing, sticky solenoid, not enough priming time following preheating, it shouldn't be too difficult to sort out anyway. High reducer or plumbing issue probably the worst case scenarios, priming time and sequential changeover periods are easily sorted by just a change to a software settings, sticky solenoids can have internals cleaned or replaced. On another note have a look at where your petrol pressure regulator gets it's vacuum reference from on your engine (yes petrol not LPG vacuum reference).. If it gets reference from the vacuum side of the throttle body this won't have any effect but if it gets reference from between the throttle body and air filter (so not from vacuum) there are things that can be done in Nevo to make calibration a lot better than you could get with other ECU's (compensate for petrol pressure being referenced to atmosphere while LPG pressure is referenced to manifold pressure). Another thing that can cause Nevo (and most other ECUs) to switch back to petrol is if they don't receive a petrol injection pulse for one or more cylinders, your car's petrol ECU will quickly stop pulsing a petrol injector(s) if it senses a misfire, a misfire on changeover is likely on cold changeover if calibration or temperature / pressure compensation isn't correct or with long pipe runs between injectors and manifold, there are settings in Nevo that can help in all these respects but for purpose of running a test (to see if a misfire is causing it to switch back to petrol) you could sidestep switching back to petrol in the event of a missing petrol injector pulse by ticking the 'hemi' box in settings.

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Darren
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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#17 Post by Darren » Fri Feb 08, 2019 4:21 pm

That was a lot to try and digest, but i have a question. If it is indeed a problem in the settings then is there any way for settings to change without using a laptop/mobile? Only curious because the system has ran completly fine for the last 6 months I've had the car. I have done a firmware update in the last 2 months which thinking about it now could be the cause with the pulsing injectors you mentioned. I saved a screenshot of the previous firmware incase such issues arised so i could reinstall it. The current firmware is 4.0J r1 Bootloader 7? 2017-3-27 release. (The previous firmware was 4.0H r1 bootloader 7.9r1? (2014-11-07 release)

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#18 Post by LPGC » Fri Feb 08, 2019 6:34 pm

Settings don't change unless you change them with laptop/mobile.
You didn't change any settings when you updated firmware 2 months ago then?
Different versions of firmware support different settings, the list of settings usually grows with later versions of firmware but some settings settings that were supported in older firmware are not supported in newer firmware. There were no big changes between H and J firmware though (mostly just support for the multi coloured DG7 switch), and if a setting isn't supported in later firmware the software informs you when uploading the calibration file after updating firmware anyway. Nevo calibration files are unlike most system's calibration files, instead of being just a binary file they're in some kind of XML format and you can read them with a text editor. Seems there will be some bigger changes in the next versions of software and firmware though, beta copies are available for download from KME.
Could be that before the firmware update pre-heating worked a bit differently or prime time was lower / could be a hardware problem such as the reducer solenoid / quite a few other things it could be but the most likely things to have caused recent symptoms are also these simple things to check. If injector pre-heat isn't set it's easy to check if the reducer solenoid is the problem by removing it's plunger but if preheating is set (default is set to active below 15c) then you shouldn't remove the plunger solenoid else preheating will take longer because the reducer will be fed with fuel from the tank to reducer solenoid line.
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Darren
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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#19 Post by Darren » Fri Feb 08, 2019 7:00 pm

All i did was backup the settings, installed the update then reinstalled the backup. As far as i remember there was no popup. Is there any harm in rolling back the firmware to see if that fixes any issues? Ill have a chance to check the Nevo settings tomorrow around mid day.

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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#20 Post by Darren » Sat Feb 09, 2019 10:37 am

threw the laptop on this morning to grab a picture of the settings that might help explain anything
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