View Full Version : Need Emissions help

December 30th, 2010, 04:00 PM
I just bought a '73 Dodge b200 van with a mopar 318 5.2L with only 72k original miles. It does not smoke and runs super smooth. I have tried our fantastic new emissions testing twice now and failed twice. The 2 mechanics I have taken it too have had no idea what it could be. The first time I passed both Hydrocarbons and Carbon at 2500rpm but failed both at idle. The former owner then helped me lean out the carb and failed hydrocarbons at both 2500rpm and idle (put gas in the tank the same day which didn't help) and failed carbon at idle. At this point I don't have the experience to diagnose and don't want to spend the new law of $750 fixing it. Anyone have any ideas on what I can do or similar experiences with this engine?

December 30th, 2010, 07:56 PM
Check ignition timing. From there it could just need a "tune-up" Plugs, wires, etc. I guess it depends, how much did it fail by?

December 30th, 2010, 08:16 PM
when I was a kid my Mom had a Chrysler 5th Avenue with a 318, one of the last carburated ones (great engine, very smooth power) and we had a similar problem. Her car ran well but couldn't pass emmisions, and it was only a few years old and nothing was obviously wrong... we got to the point of just "throwing darts" at it and a rebuilt carb fixed it. Carbon means unburned fuel, so it's a good possibility. Rebuilding those old carbs isn't so hard, either, and the kits are cheap from Napa. All you need is some carb cleaner, compressed air and basic tools, takes about 3 hours r/r.

having said that, is it tuned up? compression / leakdown test? timing set? maybe have the carb adjusted on a snifffer at a shop? sorry if that's too rudimentary, but often I overlook the basics in my panic. :) good luck!

January 27th, 2011, 12:19 PM
I had this problem with my 66 pontiac. Finally had to find a tester who will let you tune out side the shop (adjust timing and lean out carb) till you fit in the window and then pull in the shop for the test. The law states that you can not adjust any of the engine setting while in the bay but you can outside. It just takes the right 81 and older test station to help you out.

btw it took 6 tries to get the pontiac to pass

January 27th, 2011, 12:43 PM
Is that a lean burn engine????

I had a 77 360 and you had to use a formulated bottle of propane (lean burn motor) to set the the Idle correctly. And when it passed it ran terrible (sp). And that was with new plugs, wires cap and rotor... And when it passed it would get lousy fuel milage (8 mpg in town).. I finally changed the heads (milled or samller chambers I can't rember which) which upped the compression slightly and changed to a 4 barrel carb and uses really small primaries and it would pass all the time but it was close.. I would go to one of the mopar sites and they may be able to help you...

Good luck