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View Full Version : I think I know why I keep failing the low idle HC emission test...what do you think?


243
06-07-2002, 03:54 PM
I called Edelbrock back and asked the tech if gas could spill over into the intake causing the low idle rich condition. He said yes, it could spill over from three different areas of the carb if the floats are set to high, if the fuel boils or the fuel pressure is to high. He suggested a regulated fuel pressure of 5 1/2 psi, setting the floats at 1/2" vs. 7/16" and adding a phenolic spacer.

I had my doubts that the fuel pump would increase the fuel pressure on it's own and then I remembered the fuel return line. I checked the 1975 FSM which I received yesterday and it stated that the return line should be on top of the supply line going to the carb.

I checked the fuel filter on Blue and sure enough, I have it backwards. Before I change it tomorrow, I am going to check the fuel pressure and again, once I have it installed correctly.

I think this may be it...the fuel filter is the only thing I can remember changing after passing the test a few months ago with HC's at 500 ppm vs the state limit of 600 ppm. Right now, HC's are 1820 ppm which is believable if fuel is spilling over at idle.

[ June 07, 2002: Message edited by: 243 ]</p>

River Beast
06-07-2002, 10:48 PM
Sounds like a good troublshooting job!!! Way to go and I hope that fixes it...

I would have never thought about that return line being a problem...floats on the Edelbrock... I may have, but not the filter.... ;)

steven79
06-08-2002, 12:40 AM
Well lets hope that is it. Know that make's me think, how did i get my hc below 175 ?at idle and 125 at high speed. don't get me wrong i am not complaning, just trying to figure out how i did it. :confused:

243
06-08-2002, 02:44 AM
Steven~

Do you have all the smog equipment?

When and where did you have it inspected?

Mine was run on the dyno machine but with the sniffer only. I wonder if I should remove the front driveshaft and run it on the dyno?

steven79
06-08-2002, 12:10 PM
i got mine done last week, on the dyno but only the sniffer used. and no i don't have any smog stuff on it. not even a cat or egr.

PhilSine
06-08-2002, 01:31 PM
Steven79....What? Are you running it lean? Good way to pre-mature piston failure if you are. How is your temp when warmed up?