Failed emissions test

[Gary Lewis]

I am trying to test the thermactor system and after reading lots and lots of material I still can’t make heads or tails of when air is supposed to be injected into my exhaust manifold. At idle, is air supposed to be going into the EM? Or not?

It appears that I have an early CT style system with no vacuum at idle going to the “do hicky” on top of the belt driven pump.

We don't have the shop manual section on the thermactor systems on the website, but I can probably fix that tomorrow. I have the '81 and '85 factory shop manuals and will cut the sections out, assuming they differ, and put them on the site.

However we do have the 1982 Engine Emission Diagnosis manual on the site and there is a section on thermactor systems here: https://www.garysgaragemahal.com/thermactor-systems1.html

[delco1946]

We don't have the shop manual section on the thermactor systems on the website, but I can probably fix that tomorrow. I have the '81 and '85 factory shop manuals and will cut the sections out, assuming they differ, and put them on the site.

However we do have the 1982 Engine Emission Diagnosis manual on the site and there is a section on thermactor systems here: https://www.garysgaragemahal.com/thermactor-systems1.html

Thanks Gary! It looks like my version is an older style which only helps with confusion. In my reading in sounds like that also means when vacuum is/isn’t applied also flips compared to later systems .

Anywho, my current setup is resulting in a vacuum line going to the bypass valve, which is also part of the egr circuit per my hoods diagram ( with a couple delay valves in line). It’s not explicitly labeled ported vacuum, but since it’s part of the egr circuit, that makes sense in my mind (?) as vacuum to the egr would cause exhaust to circulate - not desirable during idle.

Assuming this is correct thinking, with no vacuum/ low vacuum, my thermactor system should be pushing air into my EM, and dumping air during high vacuum ( like decelerating) to prevent combustion to far down the exhaust headers. Tomorrow I will disconnect my hose to verify that air is indeed being pumped. If functioning correctly that would indeed seem to suggest the power valve as I feel like most everything else has been addressed.

[85lebaront2]

Thanks all! Rusty - we never even went past the idle test . This was at idle, and it was early in the morning and my truck sat in line for a bit so there’s always a chance it wasn’t super warmed up, but that seems like a stretch .

When you say a problem with the idle circuit, are you just saying the idle screws? Sorry it’s been so long - there’s a screw that controls air/ fuel mixture too right? It’s idling at good rpms so I don’t think I’d want to change that Willy nilly….

This is indeed Oregon and my truck was built in Ca but was sold from Seattle so it was never a CA truck. I’ve never once seen anything computerized on this truck so that would makes sense that I don’t have O2.

I should add it’s a motorcraft 2150. The oil, filter, and PCV shouldn’t be old/ bad but I should change all that I guess since it was sitting for so long. It was certainly dusty/ filthy after that time.

Christopher, just because the truck was sold in Oregon, does not guarantee it is not a CA spec or 50 state truck. Many years ago, I believe in 1980 or 81, my late mother-in-law and her brother were visiting us here in VA, on the way back to Washington state, they went back through Texas (her brother's home state) and bought her a new Chevy Citation, specifically to avoid a CA spec car. I had called a good friend at the local Chevy dealership and found that except for high altitude areas, all West coast cars were CA spec, definitely Oregon so they couldn't be bought and carried into CA to avoid the CA emission packages. Check your emission label.

[Gary Lewis]

Thanks Gary! It looks like my version is an older style which only helps with confusion. In my reading in sounds like that also means when vacuum is/isn’t applied also flips compared to later systems .

Anywho, my current setup is resulting in a vacuum line going to the bypass valve, which is also part of the egr circuit per my hoods diagram ( with a couple delay valves in line). It’s not explicitly labeled ported vacuum, but since it’s part of the egr circuit, that makes sense in my mind (?) as vacuum to the egr would cause exhaust to circulate - not desirable during idle.

Assuming this is correct thinking, with no vacuum/ low vacuum, my thermactor system should be pushing air into my EM, and dumping air during high vacuum ( like decelerating) to prevent combustion to far down the exhaust headers. Tomorrow I will disconnect my hose to verify that air is indeed being pumped. If functioning correctly that would indeed seem to suggest the power valve as I feel like most everything else has been addressed.

Christopher - We now have the 1980 factory shop manual section on thermactor systems on the site. And I've also included the sections from the 1982 and 1986 Engine Emission Diagnosis manuals on the page. They are at Documentation/Emissions/Thermactor Systems. (Yes, the '82 and '86 info is still on the pages in the respective Engine Emissions Diagnosis books, but it seemed appropriate to include it on the Thermactor page as well.)

Sorry that I don't have the 1981 info. In '80 the thermactor chapter was in the Engine book of the FSM. But in '81 it says to refer to the Engine Emissions Diagnosis book, and I don't have the '81 version of that. So 80, 82, and 86 were the best I can do. Hope that helps.

 

[Gary Lewis]

Christopher - We now have the 1980 factory shop manual section on thermactor systems on the site. And I've also included the sections from the 1982 and 1986 Engine Emission Diagnosis manuals on the page. They are at Documentation/Emissions/Thermactor Systems. (Yes, the '82 and '86 info is still on the pages in the respective Engine Emissions Diagnosis books, but it seemed appropriate to include it on the Thermactor page as well.)

Sorry that I don't have the 1981 info. In '80 the thermactor chapter was in the Engine book of the FSM. But in '81 it says to refer to the Engine Emissions Diagnosis book, and I don't have the '81 version of that. So 80, 82, and 86 were the best I can do. Hope that helps.

Also, I discovered in the 1980 document that there's the statement below on Page 5. So I did a bit of research and found SSD-4 & 5 in a 97-page chapter called "Light Duty and Heavy Duty Truck Engine Diagnosis and Service". I scanned it in and then extracted SSD-4 & 5 and inserted them at the end of the 1980 Thermactor FSM document.

So if you click on the blue box around SSD-4 or SSD-5 (in the document, not here as that's a picture) you'll be taken to the respective page. For reference SSD-4 is "Thermactor System - Non-Catalytic" and SSD-5 is "Thermactor System - Catalytic". And they have testing and repair procedures.

[delco1946]

Also, I discovered in the 1980 document that there's the statement below on Page 5. So I did a bit of research and found SSD-4 & 5 in a 97-page chapter called "Light Duty and Heavy Duty Truck Engine Diagnosis and Service". I scanned it in and then extracted SSD-4 & 5 and inserted them at the end of the 1980 Thermactor FSM document.

So if you click on the blue box around SSD-4 or SSD-5 (in the document, not here as that's a picture) you'll be taken to the respective page. For reference SSD-4 is "Thermactor System - Non-Catalytic" and SSD-5 is "Thermactor System - Catalytic". And they have testing and repair procedures.

Thank you Gary! I’ll look through all of it!

[Gary Lewis]

Thank you Gary! I’ll look through all of it!

Welcome. Hope it helps.

[delco1946]

Welcome. Hope it helps.

Took the carb off. the power valve looks new, clean and dry. So I left it in place as it looks to function. Even pulled on the plunger slightly to make sure it could move freely.

The accelerator pump also appears to move freely, no gasket tears etc. however I don’t think it’s adjusted properly- shouldn’t the pump shaft be allowed to “push” thru it’s full range Toward the radiator when off the gas? Currently the button is always resting against the lever that’s attached to the gas pedal, so the pump is only pumping for half its range or so. I thought I read somewhere that the lever should just barely be touching the button/ shaft?

Everything else in the carb looks good too. The float and needle move freely and don’t appear to be stuck.

[delco1946]

Took the carb off. the power valve looks new, clean and dry. So I left it in place as it looks to function. Even pulled on the plunger slightly to make sure it could move freely.

The accelerator pump also appears to move freely, no gasket tears etc. however I don’t think it’s adjusted properly- shouldn’t the pump shaft be allowed to “push” thru it’s full range Toward the radiator when off the gas? Currently the button is always resting against the lever that’s attached to the gas pedal, so the pump is only pumping for half its range or so. I thought I read somewhere that the lever should just barely be touching the button/ shaft?

Everything else in the carb looks good too. The float and needle move freely and don’t appear to be stuck.

I’ll check my thermactor system once I assemble the carb, but I’m wondering if all that’s needed is to turn the mixture screws clockwise slightly to lean it out.

[Gary Lewis]

I’ll check my thermactor system once I assemble the carb, but I’m wondering if all that’s needed is to turn the mixture screws clockwise slightly to lean it out.

We have the factory shop manual section for the 2150 on the page at Documentation/Fuel Systems/Carburetors, Chokes, & EFI/Motorcraft 2150. However, in looking at that document for information on adjusting the accelerator pump I found this: "Adjustment procedures and service instructions for this carburetor are contained in the Engine/Emissions Diagnosis Manual." But looking there I don't see anything about the accelerator pump.

So I don't know what to tell you about that. Perhaps Bill will?

As for the idle mix, yes you can screw the adjustment screws in and that will lean the mix. Perhaps that will be enough?