Hi Guys, OT I know on here but I have just had a 3.2 XJ jag converted on a closed loop single point system (OMVL) system runs fine apart from sometimes when decelerating , especially braking quite sharply into a corner for example the revs die to a couple of hundred and then when the loud pedal is pressed the car lurches forward as it comes back on song.
I am obviously going to take it back but just wanted to have some arrows to shoot at them, always good to look as if you know what you are on about :-)
PS my fuel computer is still working showing instantaneous MPG average MPG etc - is this valid, i.e. is it reading on LPG ?
Also the 61L tank only took around 34 L to fill today ( first fill) the guy told me it would take three or four fills to reach max capacity - is this true? and if so why?
On or around Mon, 1 Aug 2005 18:59:23 +0100, "StaffBull" enlightened us thusly:
Could be vaporiser orientation - if the vap. is mounted facing fore-and-aft. The face where the pipes attach should normally point across the vehicle, not forwards or backwards.
other possibility is incorrect tuning - the OMVL 90E has a fixed bleed which allows a small amount of gas through all the time the vlaves are open (system live) and one of the functions of this is to reduce the chance of stalling on deceleration, but I think it's more about when you lift off coming to a standstill.
depends on how it meters. Some of them work on the airflow, and thus still read but may not be accurate.
if the tank's been properly installed, that shouldn't be so. Was it empty when you filled it?
if it's a 61L water capacity tank, then it'll hold about 48-49L of LPG in normal use with an 80% fill valve.
Normally, reduced capacity is either that the tank orientation is wrong, incorrect float valve in the tank, or tank incorectly/not purged of air at fitting.
properly, you put a small amount of liquid gas in, invert the tank and open the outlet valve, to get the air and/or inert gas from the tank. Once purged thus, the vapour space in the tank will contian mostly LPG. If the tank was full of air at atmopspheric pressure when installed, and not purged, then this air (61L) will compress to about 7-8 bar (normal pressure in a part-full propane tank which will occupy about 8L of your volume - not enough to upset things. If the tank happened to be filled with air at 2 bar, then when it's compressed to 7-8 bar it'll occupy about 16L, which is borderline - the compressed air, if too much, will cause overpressure in the tank, and since most pumps have a pressure shut-off, you may not get a full fill.
Hi Austin, the vap appears to be positioned correctly - I will post up some pics tomorrow and send you a link - if you would cast your peepers on em I would appreciate it. On looking at the system now, if I put my nose to the vap I can smell LPG, the car was last run 2 hours ago - I cant seem to remember that on my Disco - I'd sometimes get a whiff but that was only even on start-up. Is this normal?
I was hoping this was going to be as reliable as my Disco, but I'm a little wary now!! just paid £1100 for it, you don't expect it to play up first 50 miles!! or are there teething troubles with new set ups?
Hi Austin, called em today and its booked in on Sat, the guy told me that the tank had not been purged, but will evacuate the air in subsequent fillings !! now I cant see how, surely the air is trapped in the top portion of the tank due to the liquid gas at the bottom, being a liquid take off at the bottom of the tank the air cant escape. Am I right? I don't want to make a T1T out of myself by arguing the toss on Saturday.
Cheers, - i have also found out they have not adjusted the timing on the car - I thought this needed to be adjusted for running LPG?
On or around Tue, 2 Aug 2005 18:35:00 +0100, "StaffBull" enlightened us thusly:
hehe. well... hard to say. depends on how much air. You can get it down to atmospheric pressure if necessary by running on gas 'til it runs out, then go to the top of a big hill, and switch back to the empty gas tank, then run downhill in gear with the ignition on. This will keep the valves open and allow the pressure to get out of the tank. Air at atmospheric pressure should not give trouble. Apart from that, you're right, the air can't get out of a bottom-outlet tank with liquid in it. But see above - when you run out of gas, your liquid level will probably drop below the outlet level now and again.
ah, well, now you're getting to the complicated bit. LPG runs better with more initial advance and less high-speed advance, in other words, with a different advance curve. To make that happen requires an ignition processor which costs extra. You can do a cheaper option which is to advance the spark timing about 3 degrees from the 4* setting or about 6 degrees from unleaded setting. This will make the gas run a bit better and shouldn't compromise the petrol running too much. Check it doesn't pink too much on petrol though.
Sorry for delay in replying, just back from holiday. I think from what I've read that Austin & co have pretty much suggested all that I would look for initially myself. Moving on, what OMVL system is it, is it the Millenium? If so, get it on the computer, clamp the "idle closing steps below default" to
5 and adjust the vapouriser idle bleed to a point where it can only just cycle rich-lean, remaining rich for longer than lean (bear in mind these rich and lean values are only just off perfect mixture, we're not talking drastic mixture changes here) and going rich almost as soon as the stepper motor starts to open towards default, checked by selecting the default lock option and selecting "idle opening steps above default" to zero and monitoring the lambda readout on the computer, then put it back to 25 steps, so that the system has the scope to cope with increased loadings on the engine. Also check if the fuel overrun cut-off option has been selected, if so it may be cutting off too much fuel, or not reinstating fuel until too low an rpm threshhold. Good luck. Badger.
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