About my carb problems.

this isnt gonna help your truck pass now..but always put clean oil in a truck right before a etest and take the air filter out.. also you want that cat pretty much glowing red when its pulled in the shop ( this is crucial) i at a used car lot for a while so i had to get shitty cars passed on a daily basis.. also if wore comes to worse retard the ignition so that the truck just barly idles.. and tell the dude runnin the test to please be easy on the gas...but yea your truck sounds like its runnin rich

I thought of a couple more things. . .

When you put your truck back together, how did you set your ignition timing?

Where is it set to now?

Do you have a timing light?

Does it have an adjustment setting on it?

You can do some testing with it while the engine is running.

1. Verify base timing. At idle, it is 5-6 degrees before TDC. There should be a scale on the front of the timing cover that is really hard to see if you have an AC belt on the pulley. You are probably close to it, due to your idle emission readings.

2. Disconnect the vacuum advance hose, and rev the engine to 2000 rpm. You should see that the light flashes make the pulley mark seem to move to the left. If you have an adjustable timing light, you can compensate the movement to acquire the number of degrees that the centrifical advance is introducing with the increase in engine speed. It is working if it adds degrees. We just are attempting to verify operation at this point.

3. Reconnect the vacuum line. Rev the engine to 2000 rpm. You should see the pulley mark jump left even further. Again, an adjustable timing light will let you compensate the light pulses to reacquire your matchmarks. When they line up, you can look at the scale and see total advance. It should be a LOT more than 5-6 degrees.

The timing light will let you know that the advance mechanisms are working.

If you have a vacuum pump, you can verify vacuum advance at idle by hooking it up and applying a signal to the advance mechanism. At engine idle, with signal applied, engine speed should pick up.

Also, with vacuum applied, there should be no loss in signal pressure. If there is, the vacuum advance is bad.

You can also use the pump gauge to verify vacuum signal from the carburetor, by hooking it up to the vacuum line and reving the engine, watching to see if the indicator needle jumps, showing a vacuum signal.

Standard manufactures a replacement advance unit for the distributor if it is needed.

Well I will comment on a few things in your post, I still have to look over it some more but as an answer to a few:


Tests 1-3 were done at one location and the forth at a different location. The 3rd test that did much better was when I just installed the new cat and drove for about 20 minutes before.

The one I just took I drove for a good 20 but it did sit and idle at a low idle for about 10 minutes while waiting to go into the etest. I tried to get it nice and hot for all the tests. I haven't heard of taking the air cleaner out but it makes sense.

As for all of the talk about hydrocarbons and what not I completely understand I am taking a lot of chemistry courses and studying to be a nuclear engineer so it was quite interesting to read.

I will take a look at all of the vacuum stuff that you mentioned.

Yes my carb does have the pin in it still.

I did check the carb plate by pressing the gas down with the key in the on position but with the truck off and it did close completely so I think its fine.

"If you have a vacuum pump" How do I know if I do?

I did check the float before when trying to diagnose issues and it did look fine but I will check that again for sure.

Thank you both for your help and by the way Mazda Tweaker, You are unreal I would have guessed you were a Mazda engineer from your knowledge!

Zac

Just to add to everyones knowledge base here I did send Zach a Kand N filter for his truck which does let more air in and obviates the need to pull the air cleaner element.Also Zach the sight glass for my carb and maybe urs as well is on the drivers side of the carb and not the front.With the truck on level ground and wrmed up the fuel level should be at the line etched on the glass inspection plate.As someone here has already posted,the float in these old carbs may leak,fill with gas,sink a bit and let more fuel in than necassry,thus causing the truck to run rich,and fail inspections.The carb I am sending operates with the fuel level smack at the line so no worries there.will send the carb on Saturday.BJ

Also remember the trick about setting time to 5 degees BTDC and regap ur plugs to .035.Ur so close to passing that even a small increment of hotter spark and leaner mixture may be just enough to get ur unburned hydocarbon level down and that is about all u will need.Bj

Thanks BJ, I did not check the float with the engine warmed up so I will have to do that for sure tomorrow.

And thanks for sending it!

Zac

G.go here and look to see if you have one of these. If you don't, you will need one.

Zac: Carb left here today priority mail.Depending on what Canadian customs does,should be there in 3-4 days.Air cleaner bolt is packec in with it,end with fewest threads goes in the carb.It is plug and play except for choke wire which you will have to connect.It is equipped with the cruise pulley so if u dont have cruise just take the outer pulley off or leave it on.Wont bother anything.This is the carb off my 2200,and it passed inspection every time.If it doent get thru inspection up there ,then u need to look elsewhere on the truck for issues.When I took it off,I cleaned it and pcked it in plastic and stored it so it is just like it was reoved from my truck.35 plus the 25 for shipping if it passes inspection and u keep it.Send it back if it doesnt .we will both be out 25 bucks,but that seems fair to me.LUCK.BJ

Hi Zac,

By now you will have had a chance I hope to investigate some of what I had offered by way of basic detective work regarding your high HC and CO issues.

Just so you know, the truck carburetors in stock form will run rich if closed loop is not operational.

The reason being the vehicles will run, even if rich. The compurter operates to lean out the mixture "fuel trim" by varying the "on time" of a control solenoid in response to the electrical signal received by the oxygen sensor. A high votage signal from the O2 sensor causes the computer to attempt to lean out the mixture via the control solenoid. If it cannot, dwell time defaults to 27 degrees.

What does this mean for you?

If you haven't verified that your distributor advance and timing are correct, and they are not, and you replace one carburetor for another. you will flunk your emission test. You will still have to fix those problems, plus you will have made unneccesary work for yourself doing a carburetor swap. The swap may need to be done, I just don't think you need to do that until you have verified non-invasive essential subsystems are operational

When you rebuilt your motor, i.e. "took it apart" and put it back together, how did you set your ignition timing? Or did you remove the head with he distributor still clamped into it.

Do you have an ignition timing light, and does it have any adjustments available on it?

The fact that your NOX readings are very low indicates that your EGR valve is working, most likely. A vacuum pump can help you verify that it is.
The low numbers at idle and the fact that the rollpin is still installed on your carburetor means that likely your carburetor has not been tampered with.

And may not be the source of your emission problems.

Hi everyone.

I have been working through all the advice you guys have given me. And I still need some more time. (Its bloody cold here!)

Anyways, I set the timing with a timing light that I borrowed but I think I will get the shop to check the timing and set it back 5 degrees.

I am going to go through the distributor advance tomorrow night after school.

I don't have a vacuum pump but I will see what I can do.

Once again guys thanks so much. I will get back to you tomorrow.

Zac