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

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

#41 Post by LPGC » Tue Feb 12, 2019 1:40 pm

It's a very quick and relatively uninvolved job to take apart the reducer solenoid, it is external of the reducer and quite separate from it, you don't even have to remove it from the reducer to work on it.

Putting a repair kit in a reducer isn't too difficult but takes more time and is relatively involved. A repair kit won't solve all types of reducer problem, you only really get soft parts such as seals and diaphragms in a repair kit. If a (the) diaphragm is broke gas will come out of the reducer's vacuum pipe, if a water seal is broke gas may get into engine coolant or leak externally out of the reducer, if certain gas seals are broke gas may leak externally of the reducer. Such problems amount to just about the only types of reducer problems a repair kit would fix but as yet nothing you've said points to such a problem (though I don't think you've yet checked for gas coming out of the vacuum pipe?).

Someone already explained that there are 2 solenoids one on the tank one on the reducer. Since the problem only seems to occur when the engine is cold and goes away when the engine is warm it would seem that the part causing the problems (if any) will be one that sees different conditions when the engine is cold/warm and the only solenoid out of the 2 to see different conditions (cold/warm) when the engine is cold/warm is the reducer solenoid. There's also more potential for the reducer solenoid to see a wider difference in inlet/outlet pressures than the tank solenoid (assuming both solenoids close)... because as engine bay temperatures cool gas vapour in rubber engine bay pipes will cool, pressure will fall with lowering temperature, when pressure falls below a certain level the reducer will convert liquid gas (from the small bit of liquid gas between the reducer solenoid and the reducer itself) into vapour, if/when all that liquid gas is used the pressure on the outlet side of the reducer solenoid will fall sharply. Due to solenoid design it takes more mechanical/magnetic effort to open a solenoid as the pressure difference across it (inlet pressure greater than outlet pressure) increases. Could still be the tank solenoid but (if it's a solenoid problem at all) the symptoms point more to the reducer solenoid.
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Darren
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Re: system throws low gas pressure fault and wont manually switch untill high reducer temp

#42 Post by Darren » Tue Feb 12, 2019 2:41 pm

Ok i will avoid taking the reducer apart as i can not smell or see and gas leaks around the reducer, i have tried unplugging the vacuum hose and again there was no smell of gas and no noticable draft coming from the reducer vacuum hose while the engine was running. Yes i believe brian pointed that out to me and we were focus solely on it being a mechanical problem but ive learned quite a bit more than i did before about the software from your help so this has been very educational. Are there any settings that i should change back or are they good where they are? (I still have Hemi ticked which im unsure if that was only meant for the one test or not)

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

#43 Post by Darren » Sat Feb 16, 2019 5:43 pm

Ok so i just got back from the shed which is in the middle on nowhere with 0 reception. Did some few maintenance bits on the car while i let the reducer/valve cool down enough to work with. And oh boy was it dirty!! Pulled the solenoid off and then unscrewed the valve. Had strange inner workings and i couldn't figure out how to remove the spring inside the valve so i left it as shown in the picture. First i cleaned the cylinder which had quite a decent amount of gunk in it. Then i proceeded to push the spring in and out and cleaning the metal that was visible from the inner workings each time it got gunked up until i could no longer get gunk out, had a little help with some brake cleaner. Cleaned it up as much as i could and put the whole assembly back together and waited for the engine to cool down, waited until it was at 20c and fired it up letting it idle. Temp got to 27c and long and behold a smooth switch over to lpg. Now i must wait until i can try a proper cold start but from all the build up it does indeed look like the problem was a gunky solenoid valve! Thank you both so much for your help!!

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(image folder https://imgur.com/a/U8afUZE )

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

#44 Post by Brian_H » Sat Feb 16, 2019 9:04 pm

Good stuff - it doesn't take a lot to block it as its quite small as you now know. No need to remove the spring either.

Thanks for posting back when you have, least it lets people know what the fix was so might be useful for others with the same sort of problems.

If you do still find the odd problem theres another one on the tank of the same sort of design, but make sure you either shut the valve off if it has one, or empty the tank as far as possible first.

You should be able to post images directly to the board btw - shouldn't be a need to use imgur anymore (not a problem if you do unless they go the way photobucket did, but also should be easier to do that and link it as well as it will all be on the same site).

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

#45 Post by LPGC » Sat Feb 16, 2019 11:06 pm

I had a customer the other day, a Stag system I didn't fit on a Merc E class V6 but was asked to sort. When switched to gas it would constantly misfire on one cylinder, turned out that one of the injectors was really gunged with thick black sticky stuff that severely raised the closing speed of that injector and led to the cylinder that injector fed with gas running very rich, though the injector would seal when not worked. I identified stripped and cleaned the suspect injector but even then it still flowed too much gas due to lateral play in the injector shaft and disintegrated rubber pad (at the top of the plunger that prevents plunger from metal to metal contact at the top of it's stroke) and still flowed much more gas than other injectors. I managed to sort it all so it runs great on LPG but only by cleaning out the injector and then setting a -25% fuelling adjustment for the affected cylinder, +10% adjustment for all other cylinders and a large adjustment to the map. Still a workaround because with lateral movement of the plunger(s) at that extent and a fuel trim of that extent the real (and soon to be only possible) fix will be to fit new injectors. It is very unlikely that any sort of injector cleaner would have cleared the gunj I did, the gunj causing most of the problem that created the misfire was at injector spring level (high in the injector) where cleaner would not get to. To me an injector or bank trim more than just a few% indicates an underlying problem, but on this install I had to set an effective single injector trim of 35%... it will definitely need new injectors soon and I would recommend a different brand of injectors.
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

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