New member but long time reader

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New member but long time reader

#1 Post by mick1960 » Thu Jul 11, 2019 12:38 am

Hi my name is Mick I am a mechanic and MOT tester by trade and the proud owner of a 2006 Honda CRV with a Stag 300 gas conversion.
The Honda was bought as a distress buy to aid my increasingly frail and disabled father around. It allowed him to get in and out easily without the efforts of a low slung saloon car it also had ample space for walking frame and wheel chair. The Gas conversion was a bonus. I knew nothing about lpg when I bought it other than it was cheaper per litre but access was the main priority.
When I first started to use the car I would do 1/4 mile and there would be a click and it would change to gas. on coming to a junction the revs would rise and fall almost stalling this was in no way correct for gas. I then switched it back to petrol and it did the same. No problem its the air idle valve they stick and I have stripped and rebuilt several (although I'm told you can't ??) The only problem is there isn't one It's a fly by wire throttle body... I clean it no difference... It then occurs to me that the previous owner got really good mpg did he change up at low revs? ie below VTEC range ? Had the VTEC system got seized?? First an oil change although the oil was't that grimey then all the valves were adjusted to their maximum allowed tollerance ( they were very tight 0.005 thou) ,and these engines do suffer from valve seat recession. NGK laser plugs were added and a good check over. So now to see if the VTEC system was working nice open road and I started to wind it up the revs rose gently and no perceptable shove in the back but all the way to 7000 revs and down again. After serveral bursts of this it was getting progressivly quicker but still a droop in the idle. Using a diagnostic tool reconfigured the throttle body and base idle no difference no fault codes cam crank syncronisation perfect .. It is mechanical and the only thing it can be is the VTEC dephaser being "sticky" or filled with gummy oil. At every opportunity I hit high revs up and down the car just got quicker and quicker many people do not realise what a CRV with a VTEC engine can do, including many owners they just don't rev them, let alone one on lpg.( I later found out over 6000rpm it goes back to petrol). Any way the car was fliying by now and then one day I noticed the idle drop had gone and has never returned The VTEC system had unsiezed !!!
After a few months of good running at @26mpg and paying 40p/litre life was great. Then came the first cold snap and the car took longer and longer to switch to gas. Still learning I assumed that the vapouriser took longer to switch over. the Stag system kept beeping at me, by this time i had downloaded the software and got a lead. Temps were all good but pressure was low , thinking it was all temp related I adjusted the switch over temp up so the vapouriser got hotter before changing over. No joy the car still ran perfectly on petrol and it would change to gas after 10 or so miles if I used the manual switch and went back and forth, I ordered some filters,injector cleaner and all new rubber pipes from the LPG Shop in Leicester they were helpful and quick. I have photos of what I took off ! these filters had been "changed" just before I bought the car when the previous owner had paid over £200 for an lpg service in Tamworth 5 months earlier. The gas one was gooey, I cut it open to see what was inside, I replaced it along with the pipe which had serious cracks in it. The liquid gas filter was a ball of iron filings and rather inaccessable but with some stripping down of air filter boxes doable, It had never been changed in my eyes. What had been serviced ?.
Carried on through the winter and the problem stayed the same, a pain but managable.I looked into valve saver kits and came to the conclusion its time to get one .It came from The LPG Shop no dramas worked well easy to fit and set up. In the spring I read about vapouriser problems with diaphrms etc. So I ordered a kit and waited kept getting updates from the delivery's on the van.. nothing I copied the emails to the LPG shop they were great they rang and sent one out by Royal mail 24. All they asked was that I send the original back if/when it arrived.. it never has.

I took the vapouriser off and stripped it down and cleaned all the parts the diaphram was cracking and hard. Must have sorted it by now. I re assembled it and even made an aluminium heat shield to stop icy air from the wheel well getting on it.. NO JOY still the same.

A week or so later after much thought I wondered if the solenoid valve next to the liquid filter could be faulty? I was't giving it much hope because either they work or they don't. I put a meter across it and got strange ohms readings so I took it off. I slid the coil off the stem and checked it again it was then I realised the battery in the meter was low and the coil was ok on another meter. About to give up I looked at the valve and wondered how it worked ..a slug of steel in a brass tube with a rubber seal and a spring pushing it down,so it fails safe. I decided to take it apart sure enough the slug with the seal was sticking out so I gave it a poke IT WOULD NOT MOVE so I poked harder and it went in but would not come out ! lack of servicing had let gas goo into the tube where it goes sticky. when its cold its very viscous until heat gets through and softens it then the valve will work hence the 10 mile change over period. Cleaned it all out with brake cleaner nice and loose checked it with a battery fine put it all back together checked for leaks took it down the road 3-400 yards CLICK it went onto gas and has never looked back.
It has run smoothly ever since, its due a major filter service soon and I will clean the valve again but its doing 26 mpg and on a long run 33mpg is obtainable driving sensibly which I think is great.
One quirk is is the engine management light comes when going down the M5 into Bristol, this is a long hill and is basically driven down with the throttle closed and gives a lean mixture fault code. All I can think of is that the long time on fuel shut off on the over run with high revs, the ECU thinks there is a fault..
The CRV is no longer required for the purpose for which it was bought anymore, but with the price of lpg in Birmingham being 50 - 54p/litre and 26mpg its cheaper to fill up than my Yaris and roomier, although the road tax is stupid, after all 52p vs 125p which one would you use and which is greener?
I will try and post some photos of the filters etc

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Re: New member but long time reader

#2 Post by LPGC » Thu Jul 11, 2019 4:38 pm

Welcome Mick.
Could point you towards sorting the downhill Mil issue and possibly switching back to petrol over 6000rpm.
A lot of Stag systems are setup by default to switch back to petrol after 6000rpm, you can change that in software easily but then watch pressure, gas injector pulse lengths and mixture (via OBD live data) before leaving it set like that.
Just in case you do decide to sell it - you are allowed to advertise LPG cars for sale on this forum :-)
Full time LPG installer
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2 miles A1, 8 miles M62,

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Re: New member but long time reader

#3 Post by Gilbertd » Tue Jul 16, 2019 5:46 pm

Welcome from me too, it makes a change to find someone who has the right mindset to learn how something works, how it comes to bits, take it to bits and then fix it. You are a dying breed my friend. I'm like you. I could buy something small and economical as a run around and keep my 4.0 litre V8 powered Range Rover for when I need something bigger but why would I want to? With the fuel costs working out to the equivalent of 30-35 mpg on petrol, I may as well use it as my everyday car.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.

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Re: New member but long time reader

#4 Post by mick1960 » Sat Jul 20, 2019 11:36 pm

Hi thanks for the welcome,
I have often read some of the problems encountered by members and thought that they were not always gas related, I have in the past got tunnel vision on a problem and the solution was often embarassing simple in the other direction but hey ho thats life.
The Honda is going great and there are no plans to sell it. Its far too useful carrying builders stuff and trips to the dump. The yaris would struggle ! The EML light on the Honda is not really a worry as I know what it is and only comes on half a dozen times a year and i can check it and reset it no problem. As for the 6000rpm switch back to petrol is of no real consequence as I very rarely get up that high, it does get a blast just to make sure the surge is there showing the vtec is working and sometimes to disillusion the odd X3 or Freelander (still a kid at heart). I had thought of converting my supercharged MX5 but i'm not gas qualified ,it only comes out in the summer now and boot is small enough already !! I will try and post some photos of the filters and the vapouriser rebuild.
Cheers mick

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