Air Injection System BackFeed?

[82BlazerMan]

1982 Blazer
305 CI
2WD

Hey Guys,

Is it possible for the the Air Injection system to backfeed exhaust back through the air pump?  I'm having an exhaust leak (smell) problem that seems to be coming from the engine compartment.  Recently I cleaned up all my oil leaks, made sure my exhaust turned out the side rear just behind the wheels and bought new rear window and tail gate seals just to narrow down the problem.  This helped alot.  I also had a slight exhaust leak coming from one of the AIR INJECTOR FITTINGS so I plugged the air injector and the exhaust hole.   Still, somehow, a slight amount of exhaust is getting into the cab.  What I notice when I open the hood is the same slight smell coming from the engine compartment as in my cab.  It also gets worse when I set the a/c to vent or defrost.  Any help or experience with this would be greatly appreciated becuase I've either got to fix this or sell it, it's killing me.

[dvdswan]

I would think more you have an exhaust leak in the engine compartment and its getting into the ventilation system.

do you have AC?

is your ventilation system sealed?

if you don't have AC, are both the kick panel vents closed completely?

do you have any rust holes in your floorboard? 

I've never had a vehicle that had an air pump so I can't tell you if its possible for get exhaust fed through it.  but it does have something to do with gas fumes and I think unburned fuel.

so I thought I'd look to see if I could find how the system is...



if that is how yours is, I would check the "check valve" at the back of the engine.  check valves are usually one-way so it could be letting exhaust to the diverter valve into the pump.

[82BlazerMan]

I do have a/c and I noticed it's not as bad when set on max which I think is supposed to close up all the vents.  I recently had the heater core replaced so maybe somethings amiss with that.  I'll check the kick panels tonight.

[dvdswan]

I don't remember if the kick panel vents get air from the bottom or not.  if it is the bottom I would look more for a small hole in the exhaust towards the ex. manifolds.  possibly were to pipes connect together and are not welded.  exhaust donuts get old too.  do you hear any small pop in the exhaust when running?  I'm sorry, I just throwing out guesses here on where to look.

you did say you found a leak in one of the fittings, did you get it sealed? 

[82BlazerMan]

I did have a leak at one of the injection points at the exhuast manifold but I fixed it and it no longer makes your typical exhaust leak sound.  That's what's bugging me.  I've looked up and down the exhaust, listened and hav'nt really found or anything except this one leak. 

Thanks for the graphic.

[dvdswan]

you're welcome, other than that I have no ideas right now.

[Captkaos]

use a piece of cloth around the manifolds if possible and see if there are leaks there.  The AC pulls air from the outside under the cowl.  If it has rust holes it "could" pull air in from the engine bay, but that is not the design.

[82BlazerMan]

When the a/c is on max the right vent thats at your foot opens up and I ccan see the outside fender whele. Is this right?

[82BlazerMan]

Update.

Heater a/c At the firewall has a 16th gap. Im guessing some fumes are being sucked in there

[dvdswan]

if you smoke lite a cigarette and use it to see where the smoke gets sucked in.  it should work with just the key on and engine not running and run the fan/ac/heater in all positions to see if the smoke goes some where.

[82BlazerMan]

Thanks!!  I dont smoke but I'll try that this weekend

[82BlazerMan]

I tried the cigarette test and I could easily tell it was sucking the smoke right through the cracks.  So......I sealed up all around the a/c heater case all around the firewall, the fan and even where the a/c hose went in.  Hopefully this fixes any smell coming from the engine compartment.  By the way I think I have a pin hole radiator leak.  I smell a slight hint of antifreeze.  This explains a lot, I've read where antifreeze is'nt good to breath either.  There were times when I felt like jumping out of my skin after driving this old truck.  Anyway, I hope this works.  My next task will be to find the radiator leak.  Thanks for the help guys.

[dvdswan]

sounds like you made some good progress.