The inconsistent idle with cooler engine might not be related, that could just be due to spark plugs/ignition, how the system is calibrated/setup (including changeover temperature), where injector outlets are in the manifold, failing lambda probes (which don't work properly until thoroughly heated). Though under bonnet / component temperature can effect already temperamental components (like dodgy valves/injectors) or electrical connections. If the reducer doesn't get enough hot water flow through it at idle then it could switch back due to detecting the cool reducer temperature - in which case it might get colder quicker now the weather is getting colder.
it took me a while to get all the proper answers to the questions. Here we go.
How the engine is now wired up:
Some wiring insulation has degraded at this point. I have replaced the fuses for a propper set with connectors. i could revisit this fix for connections
Components and connections are not temperamental when in good condition, can become temperamental if damaged/broken or due to wear and tear etc. Going over speed bumps could also effect temperamental components / connections, including the main power feed from the battery, fuses and earth connections. On speed bump point worth mentioning fuel slosh with low tank level could cause vapour pickup instead of liquid pickup from tank, thus causing switch back to petrol, but shouldn't be the case with enough gas in the tank. Solenoids (and the coils on them) can be effected by knocks / road bumps, you've already been into one of those, there's the one on the tank and one on the reducer. Have known Prins injector modules (small black box connected to VSI ECU) to have intermittent fault that can be brought on/cured when knocked but such fault usually brings on misfires rather than causing change back to petrol.
I have suspected the injector modules before. the local LPG guy pointed out to me too that these can fail at times, but i would heve suspected a error code on it
How did you recreate the low pressure problem on driveway? The answer stands a good chance of pointing to a problem.
Driving a small point and steering fast to the right, not the best idea but it did "work" getting the system to respond like it does on fast rights.. by switching over
Unlikely any parts from the Stag system could serve as replacement for equivalent Prins components.
Clogged filter is unlikely to be the cause - filter issues are very uncommon anyway and would expect filter issues to be most evident when most gas is flowing (foot down) rather than when going over speed bumps or on your driveway. But have known Prins solenoid filters to become clogged - If this were the case then due to the nature of your problems would expect the clog to be moving around in the solenoid filter housing, obscuring flow over bumps, something you could check for though unlikely to be the cause.
I can open this thing up and check the filter? i saw in the PRINS manual that it needs replacing around 25K. I must have driven around this or more at this point so by the book it would be needed to replace.. but it does not point this way for my problems?
You have the tuning lead and software, in parameters you should be able to see the pressure which the installer set as working pressure and compare this to the actual pressure reading. Actual read pressure should equal the working pressure setting, you can adjust the reducer (allen key middle front reducer) to achieve that. This could be the cure-all or might not have any effect but this is a good place to start. Don't try achieving equal pressure readings the other way around by adjusting the working (nominal) pressure setting in software to equal actual pressure reading, as that would definitely mess up the system calibration (presuming calibration is correct). Would expect the Prins system to log 'pressure too low/high at idle' errors if actual pressure was far from setting pressure but pressure control spring in Prins reducers does go soft over time leading to lower pressure than the original installer set (allen key re-adjustment can usually fully account for this, no need to change the spring).
So i should hook up the software and start turning the reducer, keep away from chaning parameters
If the check engine light is on then essentially the engine could be running in open loop mode, which could cause low peak power and drive-ability/smoothness problems particularly when running on LPG.
Check enginelight? does the PRINS system have this our your reffering to the check enginelight of the car. thats not on
I noticed your raceteam signature only now so apologies for anything that reads like a lesson on sucking eggs. Assuming a race driver is likely to notice a difference in power - point you back to the points on clogged filters possibly effecting top end power but not affecting idle, engine ignition and sensor points, could have a dodgy LPG injector... Dodgy Keihin injectors often caused when lube systems that inject fluid in the gas feed to injectors are fitted but this wouldn't cause switch back to petrol in itself. The Prins system may detect a fault (that causes it to switch back to petrol) in the event the petrol system cuts off fuelling to a cylinder (like it might do if it detects a misfire on that cylinder), but if this occurs would expect a fault to be logged by the Prins ECU.
I love the way you took the time to describe it to me. I do race and build and maintain my racers but there is tons of stuff i know or will ever know. so no hard feelings at all!
Regarding the rest, again with the injectors i would expect a code to be trown.
Above assumes this is an old type 1990's S90, or the Prins VSI system wouldn't be suitable and you wouldn't have had the car 2 years, new type not been made that long!
Into your Volvo's so probably know Classicswede?
Yep its a S90 classic from 98
And yes i know Classicswede. I have a bunch of stuff from him on my race car