Faulty mixer

[81 rangie]

My impco mixer has decided it doesn't wanna be tuned, so my engine is constantly running rich on gas. How do i make the mixture screw work again

[RangingRover]

Fit a lean idle shim.

[81 rangie]

there is a bolt to adjust it, but what the hell is a lean idle shim and where do i get one from

[Loanrangie]

Impco mixers only have a power valve and idle mixture adjustment, there is not much to go wrong with them, fit a new diaphram.

[RangingRover]

A lean idle shim is an extremely thin piece of plastic which goes between the diaphragm (i think it goes in the converter actually, not the mixer) and the metal ring that holds the centre of it. If your gas is running rich, and the mixture screw runs out of adjustment before it will go lean enough, this shim somehow fixes it - but don't ask me how the hell a paper thin shim can make that much difference, all I know is that it definitely does, proven on an exhaust gas analyser.

Question I have though, is why do you think its running rich? Have you had it on an exhaust gas analyser?

[RaginRover]

Good advice all around,

definately look at the diaphram first - cheap fix less than $20 then try and adjust her up then if it still doesn't work look at shimming the idle mixture screw - have heard this eventually runs out of adjustment.

Tom

[Loanrangie]

The weight of the spring in the converter also adjusts the sensitivity to vacumm so this may need a stiffer spring or maybe where the shim goes ?

[81 rangie]

Yeah i have had it exhoust tested and its running to rich. 20 bux for a diaphram, where abouts as i was told bout 160 for a new one

[RaginRover]

Yeah i have had it exhoust tested and its running to rich. 20 bux for a diaphram, where abouts as i was told bout 160 for a new one

I was told that sort of money too - which one is it ?

The last 4 I have bought have been 2 for omvl style converters and 2 for landi converters (primary and secondary diaphrams) were all about 20 each.

Give "Progas" in East Brisbane a call nice blokes always happy to help a hack like me fix my gas gear. Just have the model ready and give them a ring - I am sure they will post one out to you if you are an out of towner.

3 blokes told me that buying second hand converters was a waste of time as they cost as much to overhaul as they do to buy new. Biggest load of BS - I bought 2 landi's off ebay $20 for the pair - fully over hauled them
for about $45 each all diaphrams, o-rings and gaskets replaced.

Tom

[Loanrangie]

Yeah i have had it exhoust tested and its running to rich. 20 bux for a diaphram, where abouts as i was told bout 160 for a new one

I was told that sort of money too - which one is it ?

The last 4 I have bought have been 2 for omvl style converters and 2 for landi converters (primary and secondary diaphrams) were all about 20 each.

Give "Progas" in East Brisbane a call nice blokes always happy to help a hack like me fix my gas gear. Just have the model ready and give them a ring - I am sure they will post one out to you if you are an out of towner.

3 blokes told me that buying second hand converters was a waste of time as they cost as much to overhaul as they do to buy new. Biggest load of BS - I bought 2 landi's off ebay $20 for the pair - fully over hauled them
for about $45 each all diaphrams, o-rings and gaskets replaced.

Tom

Totally agree, i found a couple of impco converter's and mixers outside a wreckers on the ground and they still work fine, and every time i go to pick a part (self serve wreckers) i always scrounge for the lpg stuff that i can either use or sell on ebay

[RaginRover]

one thing that I just thought of this morning is what size is the converter ?

is it a 425 or smaller like a 225. I know of a few blokes who haven't been able to tune a 425 on a rover 3.9 V8 motor - not enough adjustment in the mixer.

One of the members of this board had that problem and it was recommended that he change to a 225 and re tune - the result was that it had better economy and power with the smaller converter

Tom

[81 rangie]

ill have to check what it is

[Loanrangie]

If its upside down on an elbow its a 300a, if its horizontal on a cast intake, its a 425 (square filter) 225 is an inline mixer with round body, 200 is inline with a 90degree inlet.

[81 rangie]

dunno what it is, but this is what it looks like

[81 rangie]

pic didn't work

[81 rangie]

why aren't the pictures working ?, is it me or the site

[RaginRover]

Pretty sure it is the site - you can email one to me if you like

Tom

[81 rangie]

that would be awsome, but im gunna need your adress, or is there something i'm missing

[fnukle]

use this site matey
http://www.imageshack.us/

[RaginRover]

Here is the pic

Tom

[81 rangie]

cheers for posting

[Loanrangie]

Ok, its an impco 200a mixer, should be right size may just need a new diaphram and maybe do the converter as well.

[81 rangie]

does anyone know a good spot in eastern melbourne to get some cheap diaphrams, what would be wrong with the conerter?

[peter r]

G`day

Can`t help with the diaphram , though the last kit i bought for an Impco converter was over $90 and that was about 5yrs ago . Not long after i bought a new L or E converter ( have to look to be sure ) which was around $ 140 , so i`d suggest your ring around and get prices on both but it would be a very good idea to get someone that knows what there doing to fit a kit , i`d also suggest .

Am i right in think the LPG has not long been fitted ?

If so what did it come off ?

Also i remember one of your old posts about not idling on petrol , if the LPG is new to it , the reason will be because the mixer restricts it , like putting a piece of rag over part of the aircleaner .

The idle screw on the mixer only effects idle .

The power valve will effect the quantity of gas that passes , it`s the thing ( probably with 2 flats on it ) just behind and below the idle screw , on the engine side near where the hose from the converter connects to the mixer .

If you look at it , it could have ( some do some don`t ) an L and an R with notches between .

If there are no letters L/R put the alignment notch on the thing with the 2 flats in the middle of the graduation marks on the body , this is neutral or the starting point , for loss of a better term .

Turning it 1 way will be rich , turning the other will lean , all it does is restricts the flow in the lean direction and increases the flow in the rich direction .

The only other things that effect mixture ( running mixture ) are a spring and a pin inside the converter if every thing is fitted correctly .


All the best , Peter .

[81 rangie]

nah the mixer in the pic is my old car that the gas came off, it is now in the new rangie, which did have problems idling when cold before the gas, then about 3 days after the gas was fitted it won't really idle and runs overly rich

[Loanrangie]

Pull the coverter apart and clean it, it may have a buildup of gas solids also check the diaphrams and gaskets.I cant see why you would have probs with gas setup as impco systems are about as simple as you can get, i have done 2 rangie impco conversions and both ran great as soon as they were bolted on.

[81 rangie]

if i take it apart will i need new gaskets

[Loanrangie]

if i take it apart will i need new gaskets

If you are careful you wont.

[RaginRover]

gaskets are pretty cheap - I would replace them unless you are going to make a habit of taking it apart

Tom

[81 rangie]

will try it and let use know after i do the waterpump. can i use ordinary gasket goo