1994 XJSV12 Air Cleaner Cover
#21
12-10-2018, 08:04 AM
The air pump has 2 attachment nipples. One goes in, and the other goes out. If they were reversed, air might pump onto that filter and discolor it. Yes, I understand the air pump draws air from the filtered air side (inner side of air filter housing). But in order to actually draw air, the pump must overcome the very powerful suction force created by the combustion which draws air through the throttle air valve.
You could test yourself. While the engine is running, put your hand on the air intake tube. You should feel strong suction. I feel strong suction on mine. Then open the outer sir filter cover, pull out the air filter. The suction should continue. Then put your finger on the opening to the air pump supply tube inside the air filter back plate. Do you feel suction there? You should, because the air pump should be sucking air from that tube.
I agree with you - it's not likely. However, there must be a cause for the soot. Right? Where did it come from? One possible cause - even though it's unlikely - is the air pump.
How unlikely is it? You've got 2 nipples on the pump, and 2 hoses to connect. I'd say the unlikelihood may be around 50-50.
it just occurred to me, another possible cause - if the supply hose was not connected to the air pump.
You could test yourself. While the engine is running, put your hand on the air intake tube. You should feel strong suction. I feel strong suction on mine. Then open the outer sir filter cover, pull out the air filter. The suction should continue. Then put your finger on the opening to the air pump supply tube inside the air filter back plate. Do you feel suction there? You should, because the air pump should be sucking air from that tube.
I agree with you - it's not likely. However, there must be a cause for the soot. Right? Where did it come from? One possible cause - even though it's unlikely - is the air pump.
How unlikely is it? You've got 2 nipples on the pump, and 2 hoses to connect. I'd say the unlikelihood may be around 50-50.
it just occurred to me, another possible cause - if the supply hose was not connected to the air pump.
#22
12-10-2018, 04:57 PM
Veteran Member
Thanks for your suggestions, TangoFox5.
Hmmm. I don't like the idea of running the engine without an air filter in place. And the reason I think it's not likely to be reversed hoses is because the car's been inspected and gone through by a classic Jaguar professional, who should have spotted that, and because of the likelihood that it would fail emissions testing if the setup wasn't working. I'm not saying it's not impossible, just not 50-50. The chance that (a) someone replaced the hoses, and (b) had no idea what he was doing is, in my estimation, fairly low.
However, leaking supply hoses could be a culprit. As could a stuck valve. A mechanical failure due to age is, I think, the most likely. Though I will of course check the hose connections just in case, as it should be a simple matter to do so.
Another possible culprit which some reading has suggested *might* be an issue is a failing grommet around where the valve sticks into the filter box, allowing general dirt/soot to be sucked in. That's another thing that will be easy to check (though it was replaced a couple of years ago...).
Hmmm. I don't like the idea of running the engine without an air filter in place. And the reason I think it's not likely to be reversed hoses is because the car's been inspected and gone through by a classic Jaguar professional, who should have spotted that, and because of the likelihood that it would fail emissions testing if the setup wasn't working. I'm not saying it's not impossible, just not 50-50. The chance that (a) someone replaced the hoses, and (b) had no idea what he was doing is, in my estimation, fairly low.
However, leaking supply hoses could be a culprit. As could a stuck valve. A mechanical failure due to age is, I think, the most likely. Though I will of course check the hose connections just in case, as it should be a simple matter to do so.
Another possible culprit which some reading has suggested *might* be an issue is a failing grommet around where the valve sticks into the filter box, allowing general dirt/soot to be sucked in. That's another thing that will be easy to check (though it was replaced a couple of years ago...).
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