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Got some general LPG questions, if anyone can help?

 
 
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Elder
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Joined: 02 Apr 2007
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PostPosted: Mon Apr 02, 2007 8:33 pm    Post subject: Got some general LPG questions, if anyone can help? Reply with quote

I've just bought an '89 classic 3.5 with LPG. It appears to be a bit if a bitsa.
Two tanks in the boot, a Kar-Gas reducer, and a "BRC elegant" switch bodged with a couple of toggle switches to operate the solenoids.

It drives and idles on petrol, and drives but won't idle even when warm on LPG. When rolling it drives fine, but as soon as revs drop, it dies instantly.

The reducer is this one, second one down.


These is one spring fitted adjustment screw and one below it a brass hex head bolt.

In the LPG line is large valve with a sprung knurled knob.
I think the idle setting is messed up, but without any manual for Kargas stuff available, i'm a bit stuck were to start and which to adjust.

Any ideas? The mixer itself has no adjusters on.

Are there any generic PDF documents out there for basic LPG adjustment?
Thanks all
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webber1982
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Joined: 21 Jan 2007
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Location: St. Helens



PostPosted: Tue Apr 03, 2007 4:22 pm    Post subject: Reply with quote

there are no generic documents for setting LPG systems up as almost every manufacturers regulators are different if the valve in the LPG line has been moved set it to just over half open as this is the flow control valve and will cause all sorts of problems if too much or too little gas is going in just over half open is a good starting point and on a engine that big u will probably need to open it more if u have not moved it and when Ur driving on gas its not flat then don't move it. there could be a number of things causing this problem mostly regulator related if the reg is old then the seals inside could be shot allowing too much gas to get through at idle and flooding the engine causing it to stall. on the reg there should be 2 adjustments mixture and diaphragm pressure it sounds to me like u need to adjust the mixture before u explore the other options either weak or lean will both give u the same faults so the best thing to do is to get the car running on gas keep it going by revving the engine by the throttle linkage under the bonnet and keep the engine going as slowly as it will run without stopping then adjust the mixture screw usually the smaller of the 2 screws but not always and just adjust the screw until u can let go of the throttlr and it idels then its best to get it set on a gas analyser about 1.5 % co is ok but ur allowed 3.5% for mot i think unless its got cats then it shouldnt have the system its got on ne way.
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Elder
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PostPosted: Tue Apr 03, 2007 7:39 pm    Post subject: Reply with quote

OK, after some fiddling last night I messed it up, but tonight, I played with the inline valve so it at least drives. In the end, I think the inline valve is something like 2.5-3 turns out. I started at 3 turns, didn't work, turned it out half a turn, didn't work, tried another half, still didn't, so ona whim I turned it in 1.5 turns and now it will run above 1k revs on gas (driving but not idling), or fine on petrol (idling and driving).

I've discovered there is a semi recessed screw head that is visible in the picture and a second spring bolt with a screw driver head.

I'm thinking that the LPG mixture screw is the recessed screw head toward the top, and the diaphram tension screw is on the side. What does the tension screw do?

Also, is it likely that the mixture screw is in for lean, out for rich or the other way round? It's just shame that nobody (including google) knows much about Kar-Gas components.

I want to get this one licked. And yes, I'm lucky, nice wide CO and HC emissions levels to play with on a 1989.
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webber1982
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Joined: 21 Jan 2007
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PostPosted: Wed Apr 04, 2007 11:43 am    Post subject: Reply with quote

the diaphragme pressure scrwe does exactly what its name implies it sets the ammount of spring tension on the rubber disc inside so making it harder or easier for the vacume caused by the engine to overcome the spring tension and allow fuel to flow.

the mixture will probarbly be in for weak out for rich but not always i have never come across a kar gas system and all the advice i can give is general setting advice which applies to 99% of systems might be worth searching e bay for a diffrent reg omvl or a romano are common on the bay dont cost the earth and spares are readily available for them there also quite self explanitary how to set them up.
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Elder
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PostPosted: Wed Apr 04, 2007 12:17 pm    Post subject: Reply with quote

Thanks.
The mixture screw was fairly far out, and the tension screw in, which might explain a lot.

I was recommended to take out the idle screw an clean behind it with carb cleaner.
Do you reckon that might be worth a go?
Guess what my weekend worth of jobs is going to be.
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webber1982
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Joined: 21 Jan 2007
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Location: St. Helens



PostPosted: Wed Apr 04, 2007 5:14 pm    Post subject: Reply with quote

lol bit like my week of jobs probarbly to be honest i dont think taking the screw out will do u any good but then i cant see it doing any harm that is if it will come out somtimes there held in from the inside oif the reg. when setting up u should start with the mixture screw all the way in then just slacken it slightly and the pressure screw all the way out this should allow the car to run but it wont be good then tightern the pressure screw until the engine almost stalls then open the mixture screw as a general rule of thumb u should have the pressure screw in far enough so that u dont have to have the mixture screw out more than 1.5 turns which when u come to fine tune it ull find that the tinyest ammount of movement on the mixture screw is a big adjustment.
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Elder
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PostPosted: Wed Apr 04, 2007 9:52 pm    Post subject: Reply with quote

OK, I think I ave this right, the recessed screw is captive, and appears to be the pressure screw, mess with it and the car will run on gas, but is flat as a kipper's cock. The other one on the side with the spring is the idle mixture I think, as it removable and has a short needle protruding from the end.

OK, will look again. Will start with one turn out on the mixture and tweak it half a turn each way and see if I can get any closer.
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The Original Tom
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PostPosted: Wed Apr 04, 2007 10:21 pm    Post subject: Reply with quote

What is your induction set up? Standard carb with elbows and air box? Where are the mixers? Bolted onto the carbs or in the elbows?
If it's non-standard and too free-flowing, that's your problem. In the case of LPG, some induction restriction is 100% necessary.
I had a large cone air filter attached directly to each carb, no pipe whatsoever. This provided no pressure drop whatsoever, so there was insufficient venturi effect to draw in the gas at low revs, but it went ok at high revs.
Today I added some pipe and a t-piece, running both carbs off 1 filter with some pipe to create air swirling - it now runs like a dream.

From my experience:
Small brass screw with straight head is the idle mixture. Lean in rich out.
Black plastic adjuster is the diaphragm pressure. lean in rich out.
In-line sprung screw is high-range adjuster.
If you can't work it out another way, try this:

-Turn the 2 screws on the vap all the way in, the in-line one all the way out.
-Run up to normal operating temperature on petrol.
-Undo the brass one by 3 turns and attempt to start up. Keep loosening by 1/2 turn until an idle of 1000rpm is obtained.
-Next, still at idle, undo the plastic diaphragm screw until the engine note changes, then tighten up by 1/4 turn (i.e have it as far undone as possible without it changing the idle speed)
-Now get someone to hold the throttle so the engine is at approximately 3000rpm. Do up the in-line sprung screw until the exhaust note changes, then back off by 1/2 turn.

Et voila, a fool-proof way of tuning a gas system, never failed me yet and I've done it on 2 engines with 2 different vaporisers. They're all basically the same just the adjusters are in different places.

Good luck.
Tom.
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The Original Tom
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PostPosted: Wed Apr 04, 2007 10:24 pm    Post subject: Reply with quote

A = idle screw
B = diaphragm screw
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Elder
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Joined: 02 Apr 2007
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PostPosted: Thu Apr 05, 2007 6:31 am    Post subject: Reply with quote

The system is an EFI A
It has a small cone filter.

Tom, you sure about the screw order?

I was thinking it was the other way round, as the sprung one on the VAP is removable and has a small needle on the end? I thought that would have been a mixture valve, with the other being the tension screw.

But thanks for the adjustment guide, I'll give that a bash.
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The Original Tom
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PostPosted: Thu Apr 05, 2007 6:49 am    Post subject: Reply with quote

Ah, ok efi. Same principal I believe - if you still can't make it run I'd try using the original air filter+box (if it's still there!).

I'm not 100% but in my limited experience that is the way around they have been for me.
If you cant get it right, try it that way around, you'll not damage anything unless you run it really lean for a while and then you're into cracked liner territory...

Let us know how it goes either way.
Tom.
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webber1982
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Joined: 21 Jan 2007
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Location: St. Helens



PostPosted: Thu Apr 05, 2007 7:19 am    Post subject: Reply with quote

-Turn the 2 screws on the vap all the way in, the in-line one all the way out.
-Run up to normal operating temperature on petrol.
-Undo the brass one by 3 turns and attempt to start up. Keep loosening by 1/2 turn until an idle of 1000rpm is obtained.
-Next, still at idle, undo the plastic diaphragm screw until the engine note changes, then tighten up by 1/4 turn (i.e have it as far undone as possible without it changing the idle speed)
-Now get someone to hold the throttle so the engine is at approximately 3000rpm. Do up the in-line sprung screw until the exhaust note changes, then back off by 1/2 turn.

u gotta be kidding me. u never want the mixture screw out by more than 1.5 - 2 turns if u have to have it out by more than this then there is too much tension in the diaphragm. u also need to have some flow restriction which is y they fit a flow control valve if u screw it all the way out it might as well not be there and ure using the reg to control the flow which will shorten its life no end. the correct way to set up the reg is as i said in my previous posts there is a big difference between it running and being right.

what i dont understand is u say its an efi. so does it have lambda sensors and if so does the gas system have a control box that wires into them and the throttle position sensor.
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Elder
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PostPosted: Thu Apr 05, 2007 8:32 am    Post subject: Reply with quote

Basic old EFI, no Lambda or CAT.
Old 3.5 Lucas/Bosch EFI with flap air flow meter.



It is just a normal mixer system AFAIK, rather than a direct or sequential injection setup.
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webber1982
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Joined: 21 Jan 2007
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PostPosted: Thu Apr 05, 2007 12:10 pm    Post subject: Reply with quote

yeah i know the set up so there will be no control box for the lpg and the tuning method remains the same
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Elder
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PostPosted: Fri Apr 06, 2007 2:37 pm    Post subject: Reply with quote

Hmm, set to almost max out on the diaphram pressure screw, and checked between .5 and 1.5 turns out on the idle mixture screw.

New cap fitted this morning along with a new battery.
Need to check the plug gaps, but won't idle on gas at all not even a rough popping farting hunting type idle.

I guess it is time to see people for prices of getting it looked at and be prepared for half of it to be pulled out and replaced with known new kit.

Anyone know any trusted not over the top garage who who know LPG. Doesn't have to be an approved fitter as it doesn't have a cert anyway, just someone who is known and trusted to do a good job. I know some of the approved places can be just as bad as the backstreet guys.
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Elder
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PostPosted: Sat Apr 07, 2007 5:03 pm    Post subject: Little update. Reply with quote

Having spent a couple of hours at a friendly garage, with a mate of a mate, and said mate, we got a rangie that could rev really cleanly, or a rangie that could idle spot on, but not both.

Lambda of 1.0 at 3k revs is great, but couldn't get it to idle at all.

As soon as you messed with the mixture and diaphram to get it to idle you needed to play with the main gas setting.

But I have one basic stupid question, on the back of the vaporiser is a hole about 1cm across, should this be a hole or should this be plugged?

Does that allow the diaphram to see atmosphere behind it and vacuum in front?

I haven't tried plugging it yet, but just wondered if it should be open or should have a plug or gauge of some kind fitted.

I'm thinking that the vaporiser must be funny if an owner of several LPG rangies and a mechanic who has had lots of LPG experience can't get it to run right.

It has a stupid small mesh/foam filter on, but the foam is pretty scabby and broken up so I wonder if that isn't allowing enough pressure drop i the intake to idle?
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The Original Tom
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PostPosted: Sat Apr 07, 2007 11:53 pm    Post subject: Reply with quote

Weber1982: They are the instructions given in the vap manual I have (voltran), it works fine for me and returns very reasonable MPG and the last vap ran for 6 years like that with no parts replacement. (is that a reasonably long life?)
I'll post up a photocopy of the manual I have saying that is the way to set it up if you like.
Having said that I'm now interested in these 2 completely different ways of setting up so I'm going to try mine with the way you suggest.
I'll report back when I know how it goes...
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The Original Tom
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PostPosted: Sat Apr 07, 2007 11:59 pm    Post subject: Reply with quote

P.S my vap is rated 140-200bhp, and I estimate my engine at 160-170bhp, so surely the mixture screw will need to be quite a way out to supply the correct gas volue at idle?
Also I never suggest that the in-line screw should be left open.
I say to close it until the engine speed changes. If you screw it in any more it'll cause lean running and over-heating surely? Then you have the same problem as the original 4.6 P38A rangeys? Big expense fixing that roblem...
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PostPosted: Sun Apr 08, 2007 12:00 am    Post subject: Reply with quote

Oh yeah - Elder.
Yes it should be a hole. Both my vaps had it and it's for atmospheric pressure : vacuum pressure as you suggest.
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Elder
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PostPosted: Sun Apr 08, 2007 11:21 am    Post subject: Reply with quote

Thanks Tom.
Might be a ripped diaphragm then, because while we could adjust the main gas to get a nice clean lambda 1.0@3k revs, it wouldn't idle cleanly, no matter what we did to the vaporiser.

But a quarter turn less on the main inline gas valve would be sufficient to allow a clean MOT pass idle, but not a hope in hell of revving at all, without missing stumbling and certainly not revving through.

I think the plan is, spend money on petrol for the next week until I see what it needs for the MOT, then work out whether I should spend £50 on a new Autronicvaporiser, or work out whether I have the the necessary skills to rebuild it using This diaphragm repair kit. Both methods will entail disconnecting the gas and coolant supplies, but the replacement won't require any rebuilding skill, while the repair won't require any replumbing of supplies, I will need to know what I doing.
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webber1982
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PostPosted: Tue Apr 10, 2007 7:22 am    Post subject: Reply with quote

yeah 6 yrs is a long life for a reg for certain. if thats what the instructions say for urs m8 then thats what they say. ive never come across a reg that needs to have the mixture screw so far out without it being fooked but hey there u go. the way i described is the way described in the tartarini installers hand book. and i was also told to set up emme gas and romano regs in the same way.
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Elder
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PostPosted: Tue Apr 10, 2007 8:53 am    Post subject: Reply with quote

If it helps anyone, the Kar-gas reg is a Kar-Gas Airod, sold as Airod in some markets, and included with Longas kits.

I've heard of Airod and Longas kits being fitted in the UK, but can't find much about them.
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Elder
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PostPosted: Mon Apr 16, 2007 8:15 pm    Post subject: Reply with quote

OK, replying to my own posts isn't great, but, I've been advised that a couple of things might help my idle problems.

Because it has a cone filter, I might need to raise the flow restriction outside the flap to create a bigger pressure differential, it was suggested I add wire pan scrubs (I assume inside the cone filter).

Another suggestion is to add a flap opener as the flap might be restricting the idle by not letting enough air through so making the mixture too rich to idle. It would of course also provide backfire protection, but a good setup system won't backfire anyway Wink

Also it was suggested is, what I need is a mixed before the flapper, rather than on the one on the plenum like I have now.

Any opinions on those suggestions, which would you try first, and which is a complete load of cock.
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The Original Tom
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PostPosted: Tue Apr 17, 2007 4:10 am    Post subject: Reply with quote

I'd try getting a mixer in before the flapper. This way the fuel/air mixture will be more constant, and it will be better mixed by passing over a longer distance with restrictions.
Mixers aren't very expensive, and are really easy to home install without playing with settings.
http://cgi.ebay.co.uk/LPG-Range-Rover-V8-Mixer-...dZ1QQcmdZViewItem
Okay this one is quite pricey, but if you visit any local LPG fitter they can supply one that's fine for about £20, at least mine could.
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Elder
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PostPosted: Tue Apr 17, 2007 6:12 am    Post subject: Reply with quote

Looking at that one, it looks like a plenum install, I have seen a plate one for the AFM though.

I also found This flap opener Although he says it is for OMVL vaporisers only, I can't think why and can only assume that is because he sells them. I've asked hiim why and I am awaiting an answer.

If I can get it cheap it enough it will be even lower than a mixer, and wouldn't a mixer infront of the AFM with the flap shut cause no gas and air to get in, where as a mixer behind causes no air to get in? Don't both equal a "no run" situation anyway?
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Elder
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PostPosted: Tue Apr 17, 2007 9:12 pm    Post subject: Reply with quote

I found out why that opener is for OMVL only. Because only the R90E has an outlet that will allow the LPG itself, not the manifold vacuum to open the flap.
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