Does anyone have experience with the air injection system on 1st gen carby engines? I just took my TP sedan for a roadworthy check (it passed :happy:) but at first the inspector thought it had an exhaust leak. It has become increasingly noisy lately with induction noise, much like when you take the air cleaner off. The cause is the air injection system. He showed me that if you pull the vacuum line from the thermo valve and delay valve off the air cut valve, it immediately runs as quiet as a mouse.

So, it seems there's a problem somewhere. I've read up on it and started to investigate.

Firstly, the secondary air filter is filthy which is not surprising as it has never been replaced. I didn't even know it existed until yesterday when I found a diagram in a 2nd gen. workshop manual. It is on the side of the main air filter housing where the air supply hose goes from the air cleaner to the air cut valve. It is inside a small metal housing that is held onto the main air filter housing with 4 small bolts. It is not even mentioned in the owners' manual.

My questions are: (1) Has anyone bought one of these secondary air filters and if so, where did you get it? I can't find any mention of them online. (2) Is the noisyness an indication of what is wrong? I've read up on how to test the reed valve, delay valve, thermo valve etc. but I don't have a vacuum test kit. I'm miles from anywhere but can get one next time I go to Tamworth. In the meantime, if anyone has some clues they can share, they would be appreciated.

I've used some air filter material from an air conditioner folded over a couple of times to fill that space in the secondary air filter chamber.
Never had any noise from that part of my TP though.

Thanks for the reply. I will try Repco, Autopro and Bursons at Tamworth. If none of them have or can get the filter, I'll try washing the old one in petrol or metho.

You get noise when the reed valve fails as it stops exhaust gases and noise coming back up into the air filter. Take the air filter lid off and you will hear the noise increase while it is running.Sometimes it gets so hot it will burn that little filter.
Common problem on lots of older cars with air injection.
Between you me and the gate post i have blocked a few off in the past. But you should be able to pickup a serviceable unit at a wreckers.

Thanks for the reply and please accept my apologies for not getting back sooner. I've been busy with other things. Today I attempted to wash the filter in metho. I'm not sure how effectiive that was but a lot of dust and oil residue came out of it. I also took the air injection system off and tried to test it. The reed valve itself seems ok as I cant blow through it in either direction but can suck air through it in only one direction. I couldn't test the air cut valve without a vacuum tester, so I just put it all back on but left the vacuum hose disconnected.

I am going to Tamworth tomorrow and will call in at the wreckers. It is a gamble whether a used one will be any better than mine but if I can get one for $20 or so, it is worth a try. Otherwise I will see how it goes with it disabled. My fuel consumption is already horrible so I hope it doesn't get worse.

Thanks for the reply and please accept my apologies for not getting back sooner. I've been busy with other things. Today I attempted to wash the filter in metho. I'm not sure how effectiive that was but a lot of dust and oil residue came out of it. I also took the air injection system off and tried to test it. The reed valve itself seems ok as I cant blow through it in either direction but can suck air through it in only one direction. I couldn't test the air cut valve without a vacuum tester, so I just put it all back on but left the vacuum hose disconnected.

I am going to Tamworth tomorrow and will call in at the wreckers. It is a gamble whether a used one will be any better than mine but if I can get one for $20 or so, it is worth a try. Otherwise I will see how it goes with it disabled. My fuel consumption is already horrible so I hope it doesn't get worse.

I had a TP wagon with 2.6L and carburettor. Yes, the fuel consumption is horrible. (Worst I have seen though was a 3 speed sigma with 2.6L carburettor engine, like 20 MPG, whatever that is in in Km/L - yes, I put a new engine in. The TP was manual and better on fuel.)
The younger a Magna is, the better the fuel economy is, despite the engines getting bigger and more powerful. True story.

Doubt it will do much to the economy of the car. Had an old Ford Laser once we had to disconnect the air injection due to it rusting out and got better perfomance with it out of action and slightly better economy.
Yup TP are not that good on fuel but last week i did 1800km in mine and average around 10litres to the 100km 28-30mpg with aircon flatout and on the otherside of 100 most of the time so not that bad for a very large 4 banger auto i guess. Better than some old Holdens and early 80's commodores. Expect it might be a shade better with a manual box but will have to wait a while longer to find that out for myself.
You should be able to block the system off without it being obvious.

The younger a Magna is, the better the fuel economy is, despite the engines getting bigger and more powerful
Thats the benefit of technology and reduction in friction of the moving parts as well as better transmissions!!

Hi coly,
The air injection valve is a non return valve combined with a shut-off diaphragm.
With the vacuum control line disconnected, the valve must be closed. ie you cant suck or blow from either of the big air ports. When the engine cooling water warms slightly (>20 degree C), the vacuum line has vacuum (due to the Thermal valve shutting off the port to atmosphere), and this will make vacuum available to the air control line to the AIJ. When this line has vacuum, the diaphragm in the AIJ will open and allow air to be sucked from the air cleaner side to the exhaust side.
If you disconnect the large hose from the aircleaner to the AIJ, when the engine is cold, there will be no noise from the hose. When the engine warms slightly and the vacuum control line gets vacuum, you will hear the pulsating sucking of air into the disconnected hose from the air cleaner. As the pressure of air on the exhaust side increases, (by revving the engine), there must be no air flowing back the air cleaner. The reed valve will stop exhaust gas flowing back to the air cleaner.
As a piece of information, if you suck hard on a closed tube, the maximum vacuum you can generate with your mouth is about up to 40 kPa. Any old vacuum gauge is useful because you can detect slow leaks or other problems. There are plenty of old vacuum gauges at wreckers or outboard motors etc, so you can pick one up with a bit of digging.
I have a centre zero gauge; vacuum on one side; pressure on the other; the scale is about 0 to 80 kPa for pressure and vacuum. I also have an old mercruiser? vacuum gauge calibrated in inches of mercury. 30 inches of mercury is 1 atmosphere which is 14.7 psi or 100 kPa or 1 bar. Take your pick of units, but Mitsubishi, being metric, will use kPa mostly.
Hope this helps.
rumpfy.

I recently went to SuperCheap and got a K & N air filter. Absolutely magic. It cost $125. But the economy went up 10%. No worries. Next I'm doing the HiClone thing and those Mickey Mouse plugs they've got.