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Discussion Starter #1
ok first howdy. new guy here. I am tryingot help my boss with his truck. He is having a hard time passing emmissions. We live in boise idaho. the problem is that we went to get emmission tested today and they told him he is over fueling. the last time he was tesetd in 07 he passed with 15 ppm of the allowable 40. The truck is a 96 cummins 12 valve with a manual tranny. 4x4 2500. this past fall he put on a afe cold air intake and a bully dog 4inch cat back stainless steel exhaust. any suggestions for starting places to look.

He hadnt noticed a over fueling problem because when he put on the exhaust and cold air intake his fuel mileage went up to 21 to 24 miles per gallon on the high way.
 

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It's probably failing what they call the snap test, flooring it from idle.
You can turn up the idle a little bit. Instructions> Ram Diesel Problems

Also turn the starwheel so the top rotates away from the engine. Ten clicks will be good.
You'll find the starwheel here but you want to turn it the opposite of the instructions.
CumminsDatabase.com :: Turning Up A P7100 Pump
 

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^
x2

Its about a 5min job to tighten up the starweel which is going to reduce preboost/transient fueling and should hopefully make it pass with flying colors. Then once it passes just spin it back to where it was!

Kind of funny how it wont pass the test now with a couple of modifications that do everything except hinder airflow in and out of the engine...

Do you know the exact result of the test (how EXACTLY it failed). If it was @ WOT maybe their is a boost leak somewhere (the lower passenger side boot is common for cutting itself on the sheetmetal when it expands)
 

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Discussion Starter #4
ok turned the star wheel all the way out from the motor and it still failed the snap test. Also adjusted the idle speed up and it still failed. any other suggestions. When driving the truck, when you stab the gas to accelerate the black cloud is less now. But when you let off the gas to decelerate there is a black cloud now.
 

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You shouldn't have smoke on deceleration. How many miles on the truck?? Has the injectors ever been cleaned and pop tested???
 

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How does it idle? any haze, roughness that may indicate a pootched injector?

Smoke on decel, i would start looking at injectors.
 

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Discussion Starter #7
is there any way to test the injectors my self. or do i have to take it to a shop. The truck idles great, no haze or roughness. there are 176,000 miles on the truck. the injectors have never been out of the truck but have run the lucas fuel additive to clean the injection system. the injectors have never been tested.
 

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Discussion Starter #8
what is a optimal setting range for the star wheel with a stock truck with cold air intake and 4 inch cat back exhaust.
 

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You could build a poptester, but for the sake of simplicity and accuracy your almost best off having a shop do it. that way if they are screwed they can repair/shim them for you and you know everything is done 100%

The 'optimal' setting for the starwheel is not as simple as '10 turns' or anything. its more or a trial and error procedure. Anything more than a haze off the line is considdered a waste of fuel. but since your also dealing with smog machines you may want to be conservative enough as to not fail the test. In the perfect world you would tune it on a dyno and have the smog sniffer present to get it dialed in for best performance and still pass the sniffer
 

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A piece of wood under the carpet works great...

Best tune up for a snap test that I've seen was a 2x4 under the carpet to keep the motor from revving over 2,500RPM.

You could also just disconnect the air line that goes to the AFC housing....

I'm a total newbie when it comes to that, as I have always run AFC'less, but I'm sure some of these guys could help you out. I just thought I'd throw my $.02 in..


Merrick
 

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If its a leaky injector thats not going to help because it will still be pissing out fuel when it shouldnt be!
 

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A piece of wood under the carpet works great...

Best tune up for a snap test that I've seen was a 2x4 under the carpet to keep the motor from revving over 2,500RPM.

You could also just disconnect the air line that goes to the AFC housing....

I'm a total newbie when it comes to that, as I have always run AFC'less, but I'm sure some of these guys could help you out. I just thought I'd throw my $.02 in..


Merrick
I dont why I never thought of that, Im gonna have to tell the rest of the CA boys about that. its so stupid simple it might just work!:lol4:
 
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