[CtrlAltDl]

First time poster, but I've been lurking for awhile. I just bought a 95 2500 4x4. It's not my first cummins though. I have a 49 Willys Pickup with a 4bt, but I haven't done much to it, so I guess you could say I'm still a cummins newb.

In WA state I can't transfer the title into my name until it passes emissions. I brought it in after a good run on the freeway and it failed opacity at 48 when the limit is 40.

I thought easy enough I'll just adjust the starwheel, but that didn't seem to have any effect on the smoke. It is now adjusted all the way back (towards cab) and it still smokes about the same.

If I do the snap test it blows a pretty good black smoke right off idle which is immediately follow by equal white smoke. Is this any indication of any problems?

 

[Stump Jumper]

opacity???

losen the bolts on the AFC and slide it all the way back till you get the test doneit will be a dog and take forever to build boost but should be smoke free.

 

[ykdave]

also try backing off on the 'smoke screw' at the back of the afc, that will allow the AFC arm to be pushed farther back by the spring.

How many miles on the truck? could be a crapped out injector, in which case its likely that you will not be able to get it to pass.

 

[CtrlAltDl]

also try backing off on the 'smoke screw' at the back of the afc, that will allow the AFC arm to be pushed farther back by the spring.

losen the bolts on the AFC and slide it all the way back till you get the test doneit will be a dog and take forever to build boost but should be smoke free.

After looking at the diagrams of the p7100, won't those both do the same adjustment?

opacity???

Opacity - Wikipedia, the free encyclopedia
Basically how dark it is.

How many miles on the truck?

208K on the clock. If the motor has been neglected as bad as the rest of the truck than it is probably lucky to have had a oil change.

 

[ykdave]

After looking at the diagrams of the p7100, won't those both do the same adjustment?

The spring controls how soon and at what rate vs boost the fuel comes in at. The housing position and 'smoke screw' settings are what sets the AFC arms 'starting' or no boost position.

 

[Crolando910]

iv slid my plate all the way back before and the truck wouldent start and shut off seionoid got really hot id back the smoke screw off a little

 

[JohnBer]

just move up north of mt vernon...... no testing up here!

 

[illflem]

Turn the idle up also.

 

[CtrlAltDl]

just move up north of mt vernon...... no testing up here!

lol, I'd love to, but there aren't too many software dev jobs outside of the sh!tty(city).

 

[CtrlAltDl]

The housing position and 'smoke screw' settings are what sets the AFC arms 'starting' or no boost position.

That sounds like the ticket, since the snap test is at no (or low) boost.

 

[CtrlAltDl]

Turn the idle up also.

Does that help with the off-idle smoke?

 

[Joe G.]

Don't fool around with adjusting the AFC. Just disconnect the boost hose from it. That prevents it from working at all. After you pass inspection reconnect it and you are good to go without having to change any adjustments.

It it still smokes then take the AFC off and see if it has been gutted.

 

[CtrlAltDl]

Do I need to plug up that hose or should I not bother, since it is only temporary?

 

[bart9505]

I had to test the '97 once, and at the time, I could get it to smoke if I wanted to, even though it was pretty close to stock. The motor was replaced by the dealer, and the mechanic said he turned the pump up a bit. When I was doing the test, I didn't stomp on the throttle, I just gave it enough to rev up just fast enough to get the guy to let me go. Does better if you throw some cetane booster in there too. You might get a knothead, but most of them just want to collect the fee and get you out of there.

 

[Joe G.]

The AFC works by pressure from the turbo. So if it's disconnected the AFC throttle stop won't move. No need to plug it up or anything like.

 

[ykdave]

Don't fool around with adjusting the AFC. Just disconnect the boost hose from it. That prevents it from working at all. After you pass inspection reconnect it and you are good to go without having to change any adjustments.

It it still smokes then take the AFC off and see if it has been gutted.

True, but thats not going to help if the 'smoke screw' has been screwed in before and/or the hoiusing has been slid forward. With or without the boost line, its still going to fuel harder than it should be off idle.

Also, like mentioned, bump the idle up a bit too, that will usually help a bit, especially if its really low.

 

[CtrlAltDl]

The AFC works by pressure from the turbo. So if it's disconnected the AFC throttle stop won't move. No need to plug it up or anything like.

I tried that and it ran really bad and wouldn't rev up much.

 

[ykdave]

yes, with the afc disabled the fueling is cut back to pretty much nothing. It would be one hella dog to drive like that.

 

[CtrlAltDl]

Ok, I backed out (towards firewall) the smoke screw a couple turns and turned the starwheel back about a 1/4" (also towards firewall).

It actually seems to run better and there does seem to be about half the smoke. I'll take the test again tomorrow without the air filter.

Thanks for the help guys, and wish me luck.

 

[Joe G.]

True, but thats not going to help if the 'smoke screw' has been screwed in before and/or the hoiusing has been slid forward. With or without the boost line, its still going to fuel harder than it should be off idle.

Also, like mentioned, bump the idle up a bit too, that will usually help a bit, especially if its really low.

He doesn't mention any mods in his post, so if it has not been messed with then just disabling it will work. If the AFC smoke screw has been adjusted then, of course, you have to back it out. Anyway, it's easy to test. Disconnect the AFC and see what happens. It should run fine except that a kid on a bicycle can beat you across an intersection.