Smog Question

[Toadhopper]

I didn't pass Calif smog yesterday due to high HC and CO and I'm in the process of going through the FSM in order to trace down the problem.
First a little background:
Here are my failing numbers
15mph at 1790rpm HC137ppm (max allowed 125) CO 1.40ppm (max allowed 0.79)
25mph at 1701rpm HC 130ppm (max allowed 96) CO 1.20ppm (max allowed 1.20)

2 years ago with the CAT brand new it passed easily.

My cat and air pump are new. The CAT has been in storage for the last 2 years and the air pump as about 3K miles on it.
The air pump has flow to it, but I dont have the SST to test the pressure. It's a NAPA one, so the quality is suspect, but there IS air flow. The VSV #1 & #2 are working and the VSV for the EGR was just replaced (my NOX are really low, 15 at 15mph and 13 at 25mph) The carb was rebuilt by Jim C about 4K ago. When I go through the FSM the ABV seems to be working OK (FSM 3-21 steps 1-6 and 3-24 steps 1&2) Its had a sulphorus smell for a long time which smells like an overheating CAT, so I kept my new one on the shelf until I figure it out.
OK here is the question, on page 3-21 step #7 it shows checking the decel feul cut system to VSV (2. When I pinch the line and accel up to 2K rpm I dont get any misfire or airflow out of the ABV. When I check the vacuum switch the continuity checks out OK and the solenoid checks out OK.


So where is the problem if the deceleration fuel cut system isn't working? I Could there be a problem in the hard line, or maybe I've got the vacuum hose hooked up to the wrong spot on the carb?
Toad

 

[Dynosoar]

ABV is a likley suspect. Look in your SMOG maunal for the Air Injection System. There is a lot more to it than just the pump. If you old pump s*** the bed and you did not clean the ABV then you will have pieces of the carbon veins stuck in the ABV and or hoses. The VSV's for the system seem to fail as well.


Dynosoar

 

[2mbb]

did your smog report show the redisual Oxygen (O2) value? With a properly working system, there should be some measurable O2 left over. If not, then something is running really rich, or there is something wrong with the Air Injection.

 

[lovetoski]

Old ABV's do go bad. Pretty sure mine is toast. A local mech told me that you could bypass the ABV (by re-routing the airpump hoses) and almost certainly pass the tailpipe test. You'd fail visual (if they do it). Not good to run this way for long, but OK for the test. I found this out after paying somebody enough so I could pass.

 

[Toadhopper]

did your smog report show the redisual Oxygen (O2) value? With a properly working system, there should be some measurable O2 left over. If not, then something is running really rich, or there is something wrong with the Air Injection.

On the test there wasn't any residual O2, so something is wrong!

I rechecked all the ABV and ASV tests in the smog manual (3-21 steps 1-6 and 3-24 steps 1-3) and everything seems fine. Air is being pumped to the air rail upstream at the exhaust manifold just like it should at idle.

Although on 3-21 step 7 the deceleration feul cut system didnt seem to work properly.

When I R&Rd the air pump I got the crap out of the valve and took the top off and everthing seemed to move smoothly.

The FSM said a clogged air filter can cause high HC and CO, would it have to be REALLY clogged?

Is there something I'm not seeing?

 

[Toadhopper]

To the Top1

 

[2mbb]

I don't think you failed smog because of the decceleration fuel cut. That system is designed to lean out the carburetor when at high rpm and high manifold vacuum (under decceleration). This condition is not part of the california smog test, as far as i know. They test the emissions with the truck operating at constant speed & load, not under decceleration.

The tests demonstrating that the ABV and ACV are working properly don't test that the air actually makes it into the exhaust stream. The pressure delivered by the air pump needs to be sufficient to push into the exhaust stream. High backpressure in the exhaust system (crushed pipe, clogged muffler) will prevent enough air from being delivered, as will a weak air pump. you should test the check valves to make sure they are not restricting flow. Finally, you say you tested the relief valve, but that you don't have the SST? If the relief valve is weak, this could also reduce the amount of air that is delivered. If you did check the relief valve and it is OK, then I would assume the pump may be putting out enough pressure and i would definitely test the check valves.

Good luck.

 

[Toadhopper]

I don't think you failed smog because of the decceleration fuel cut. That system is designed to lean out the carburetor when at high rpm and high manifold vacuum (under decceleration). This condition is not part of the california smog test, as far as i know. They test the emissions with the truck operating at constant speed & load, not under decceleration.

The tests demonstrating that the ABV and ACV are working properly don't test that the air actually makes it into the exhaust stream. The pressure delivered by the air pump needs to be sufficient to push into the exhaust stream. High backpressure in the exhaust system (crushed pipe, clogged muffler) will prevent enough air from being delivered, as will a weak air pump. you should test the check valves to make sure they are not restricting flow. Finally, you say you tested the relief valve, but that you don't have the SST? If the relief valve is weak, this could also reduce the amount of air that is delivered. If you did check the relief valve and it is OK, then I would assume the pump may be putting out enough pressure and i would definitely test the check valves.

Good luck.

Thanks! I put in a new OEM check valve for the exh. manifold side about 2K ago, but I'm gonna go back and check the relief valve. One thing I found curious is that the smell from the exhaust stopped once I put in my first napa air pump about 2 years ago. A bearing went out so I put in another one (the smell had returned in the meantime), but the smell never went away like it did the first time once I put in the new pump. (weak air pump maybe).

I'll go through the steps you outlined and post back up!

THANKS AGAIN!
Bryan

 

[JLH911]

ABV is a likley suspect. Look in your SMOG maunal for the Air Injection System. There is a lot more to it than just the pump. If you old pump **** the bed and you did not clean the ABV then you will have pieces of the carbon veins stuck in the ABV and or hoses. The VSV's for the system seem to fail as well.


Dynosoar

Took the words right out of my mouth. I'd open up that ABV vavle and look into it. Replace the screws with some hex head ones for easy removal next time. Do a search for one of my posts where you'll see what was in my ABV.

Good luck

 

[Toadhopper]

I'm going back int there today and see if there is anything in there.
I'm guessing that any foriegn material would keep the valve either open or closed and route air to the wrong place at the wrong time.

Since I recently replaced the air hoses its pretty easy to get them off. When I pulled all the output hoses and ran through the tests I was able to simulate low speed high speed and bypass without any problems, but now i'm too curious and I gotta go back in the and see every nook and cranny. Maybe something is sticking. The CA smog test simulates driving up to 25mph so I should only need to make sure the below 45mph low speed circut is working and that the high speed circut isnt partially (or fully) engaging. I'll keep you all posted.
Bryan
P.S. Anyone who has an air pump SST I can borrow to test the output pressure please let me know!

 

[Toadhopper]

Still looking but haven't found any AHHAHs! I cant test the relief valve or the pump pressure w/o the tester and I can't find anyone with one.
Bryan