scudderfish
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| posted on 18/7/13 at 10:53 AM |
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Identifying an exhaust leak
My engine starts, runs, and idles, and picks up quite nicely. However it is apparently idling at an AFR of about 19:1. I don't believe it. I
took the sensor out of the exhaust and recalibrated it (Techedge 2J9 controller), and it didn't fix it. The only thing I can assume is that
there is a leak upstream that is pulling in extra air. It doesn't sound like I have a hole in my exhaust, but it is pretty noisy anyway. I
can't see anything obvious. I've also checked directly on the Techedge unit and it is seeing the same values that my Megasquirt is
reporting, so it isn't a misconfig of the MS.
Are there any cunning tricks to locate and identify leaks like this?
Regards,
Dave
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mcerd1
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| posted on 18/7/13 at 11:03 AM |
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with the engine running - block up the end of the pipe (with something fairly heat resistant)
doesn't need to be 100% sealed up, just enough to create a bit of pressure inside
then start hunting for the leak which should be a bit more obvious - crude but effective  
oh and do it somewhere with lots of ventalation, you don't want to gas yourself 
[Edited on 18/7/2013 by mcerd1]
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jossey
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| posted on 18/7/13 at 11:04 AM |
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when you first start it up put your foot over exhaust while someone looks for the leak.
Dont do it for very long but hopefully it should show up the hole.
in the past i put some redex in the tank to get a little smoke from exhaust to help. Not sure I would recommend for yours but hopefully you should be
able to find it....
DJ
Thanks
David Johnson
Building my tiger avon slowly but surely.
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Mr Whippy
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| posted on 18/7/13 at 11:09 AM |
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Just a bit of tissue held in pliers soon shows the leak
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britishtrident
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| posted on 18/7/13 at 11:32 AM |
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A mechanics stethoscope can be pretty handy for jobs like this I have a Laser brand one which I found for buttons on the web.
However I am wondering if the bad reading is because your exhaust has such low back bressure air is getting drawn in through the exit of the tail
pipe with the negative pressure pulse.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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scudderfish
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| posted on 19/7/13 at 09:04 AM |
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Thanks for the comments, I've found the bugger. As my car was originally on carbs I had chopped a section out of the exhaust and bolted in a
section for the lambda sensor. When I'd put it in, I'd used exhaust sealant to keep it sealed, and it worked well. It seems that in
changing my engine, I'd broken that seal even-though I hadn't undone this part of the exhaust. I'm planning on replacing this
section anyway so for now I've just used some exhaust repair tape to seal up the joints again.
Regards,
Dave
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