1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

air pump

Discussion in 'Chevy Trucks' started by 84'GMC4x4, Dec 26, 2000.

  1. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    my truck recently failed the MA state inspection for emissions. the mechanic told me i need to put an air pump on it. (and of course manifolds w/the air tubes too.) my truck has a HD 350 (vin M) that came stock non-cat, but according to the mechanic it should have the air pump on it. the motor does have the bracket for the A/P but i'm not sure that it's the original motor.
    truck is 1984 GMC 3/4 4x4 w/350

    my question is, does anyone know for sure that these trucks came w/A/P?
    on a side note, how does pumping air into exhaust make it any cleaner?

    if i havent given enough info to tell if my truck should have A/P let me know.
    thanks for any help

  2. thelawnguy

    thelawnguy PlowSite.com Addict
    Messages: 1,011

    The air pump will do nothing for emissions without a cat. The airpump injectsair to "fan the fire" and make the cat run hotter.

    Post some numbers along with state threshholds and see if we can help ya get that pig thru emissions.
  3. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    Bill, that is just what i figured. air, in & of itself will do nothing to make the emisions cleaner. so the mystery remains, if the truck is non-cat from the factory, why would there be an air pump? the only thing i can think of is that the extra air might dilute the nox & co2 & whatever else is there enough to make me pass the test, which would be fine for me although i cant see the factory putting it on there just for that reason.

    i have the printout w/the limits & my test #'s somewhere, i'll post them as soon as i find them

  4. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    The air pump will help,even without the Cat,it keeps the exhaust very hot,especially before the muffler,as you know,more heat=cleaner exhaust.Then ther's the dilution factor-remeber they arent measuring the quantity of exhaust,just the quality,so an air pump can be used at idle only in most cases,until the engine is totally up to temp to dilute the exhaust with Oxygen.That little bit of oxygen is enough to get some trucks that are borderline to pass an emission test.If the air pump valve sticks on or rusts up and check valve leak,which is common when they get old,air will be allowed to flow ,even at high engine speeds and after warmup,I have seen the entire exhaust manifolds glowing red,the Y-pipe and front pipe totally red from the heat that adding oxygen for to long or at high speeds.You failed the visual inspection,before you even got to the sniffer right?.Do your exhaust maniflods have the bosses for AIR tubes in them,with brass plugs in them?If so thats a give away someone removing the AIR equipment-the tubes rot out or a backkyard mechanic breaks them doing valve cover gasket job,and plugs them instaed of replacing them.If i do a VC gasket job on one of them trucks-the customer drops to the ground when i give em a price-i always put new air tubes on,figure it into the price,because they always break off when you bend them down or try to remove them.As for the Air pump brackets,some engines have them even thoiugh they dont use a pump-its just cheaper to puit the same bracket on all trucks.The emissions sticker under the hood or on the radiator shroud should read like this. Non Catalyst,AIR. if you need an air pump,if it says just NonCatalyst and nothing about an AIR puimp,them you dont need it and never did-never will.Why these idiot environmentalists bother these old trucks is beyond me-there aret many on the road,and they account for hardly any of the miles run every day.I thinlk in NY if your car/truck needs more than 200 worth of work and it is more than 12 yrs old,they will give you a waiver so you can get inspected if you cant afford the fix-Im not sure if there's truth to that or not.

    [Edited by John DiMartino on 12-26-2000 at 03:48 PM]
  5. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    John, the exhaust manifolds that were on the truck when i bought it do not appear to have the holes for air tubes. (they are pretty rusty though & i havent cleaned them to get a good look)
    unfortunately the truck is very frankenstein-like, the VIN says its an 84 w/350 yet the sticker under the hood says its a 6 cylinder & the entire front end is 82 style.
    i'll have to check the A/P bracket for any signs of having been used,i assumed it had, but never checked since i didnt think it would be there otherwise. come to think of it, i think the mechanic decided that it should have AIR just because he saw the bracket there.
    perhaps the dealer can tell me what exactly it should have if i give them the VIN?

    a friend does have a set of man's w/the tubes & the air pump that i can slap on there for the test if it comes down to it. i would hate to do that though since i would need to screw around w/my exhaust pipes to make them match up.
  6. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Is there any waiver or program for older trucks that need a lot of work to bring into compliance?If you took that truck to a repair shop to have the work done,It would cost over 750 easy-figure a new air pump,all new plumbing,new manifold with air tubes,new headpipes or new headpipe for the Y-pipe,labor etc....With an estimate you might be able to just get a waiver in order to register it,since the work needed is at least 1/2 the value of the truck.Here's my estimate,all Gm parts exc AIR pump.New manifolds-57 each,AIR tubes with check valves,85,air pump 105-core charge 25,AIr lines and clamps,AIR muffler and prefilter 27,belt,bolts, studs,misc,spark plugs,gaskets,70.Y-pipe mods 50.Labor- 5.5hrs -rough estimate .You end up with 480 in parts,and it would be 302.50 labor at our shop@55 per /hr.Add tax and disposal fees,you are over 800-and it could be higher if one of the bolts in the exhaust snaps in the head.I know you will do the work yourself-but i feel this is a lot to ask you to pay to clean up your cold start emissions slightly.The price could be even higher if your existing vacuum lines need to be replaced or the thermac switchesarent there or are broken off-this job,worse case could cost 1000 at some shops.
  7. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    I have an 84 K-20 and I dont believe it has the air pump and tubes, I will look on wed to confirm. I do have an 89 k-30 and it has no cats but has dual air pumps. I also had an 86-k-30 that was the same.

    OBRYANMAINT PlowSite.com Veteran
    from ohio
    Messages: 534

    85 blazer,305,rebuilt top end rebuilt quadrajet, a few years later it would not pass my mechanic(and others) recommended that it its close some rubbing alcohol will do the trick i think i put like a quart in to around 8 gallons passed then no probs was told only with carb and no cats

    first choice would be to waiver out if the price is right you may find your mechanic can help you with the figure if you treat him right
  9. mike reeh

    mike reeh Senior Member
    Messages: 114

    I had a 77 K10 with a smog pump and no cat. Also have a 77 K20, same deal (california emissions too, they started using cats in 78 AFAIK)

    Have a friend with a 79 suburban with a cat but no smog pump. theres really no rhyme or reason to it but Ive heard and read several times from different sources that the air injected into the exhaust actually helps complete combustion with unburned fuel (HC).. I admit I dont understand it fully, but thats what they say. I seriously doubt that the original purpose was to dilute the exhaust in order to pass the sniffer.

    as for the rubbing alcohol thing, Ive never heard of that one before! but im interested in how and why it works... maybe i'll look into it.. anyone know the answer to that one??

  10. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    John, thanks for all the info. i do think there is some type of waiver you can get in MA. the only caveat is that I'm pretty sure B4 you can qualify you need to have all stock smog equip on the truck, so that brings me back to where i am already. as soon as i get the time, I'll call the dealer to see if they can tell me what should be on the truck. then, assuming it is non-cat non-air i will look into that waiver. otherwise i guess i'll need to put the air pump on.

    OBRYANMAINT, i have heard about putting rubbing alcohol in the gas & also about putting white vinegar directly in the carb right b4 the test. i've never actually heard of anyone who did it though. i dont think the vinegar will work for me because the test they run now involves running the truck on a dyno up to highway speeds, and any benefit from the vinegar (assuming any) would probably be gone by then. the alcohol sounds like a better bet (if i'm brave enough to try it) did the rubbing alcohol change how it ran at all? any idea how close to the limits you were?

  11. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    just found the test printout

    my truck limit
    HC 6.00 8.25
    CO 157.64 94.36
    NOx 10.68 9.27
    CO2 999.99

    there is no limit listed for CO2. apparently my truck confused the machine on that anyway.

    #'s are all Grams Per Mile not the usual Parts Per Million

    BTW truck has Edelbrock performer 600 cfm carb & performer dual-plane intake if it matters

  12. JCurtis

    JCurtis Banned
    Messages: 862

    haven't had a problem with any of my trucks, the current 86 has a junkyard engine so we will see what happens at the next inspection.

    Used to have a 74 Nova, 350 2 barrel. I used to invert the aircleaner top just before going to the inspection station. More air flowing into the air cleaner, never had a problem or a high test number. Of course that was before the dyno tests that they do now. So if I were to try that they would probably catch on.

    As far as alchol,it burns cleaner, thats why there was a push to go to gasahol a few years ago. Gas/Oil cartels didn't like that, and neither did the car makers. Kinda makes you wonder where their priorities are....

    Cleaner air, better running, fuel efficient cars, OR low mpg, gas guzzling, inefficient cars and trucks.

    The designers and engineers can design a fuel efficient, clean running engine that produces sufficent horsepower... they just don't want to. Pretty soon we will have no choice but to plug in our cars and recharge the storgae batteries in our hamster cage runabouts.

    Just try plowing snow with one one these new prototype electric cars. See how far you get.
  13. thelawnguy

    thelawnguy PlowSite.com Addict
    Messages: 1,011

    From what I can tell by the test results, you should make sure the EGR system is operating properly. That will bring down NOx and CO readings.

    Last resort, slap on a $100 pep boys cat. The waiver requirements in CT are all original smog equip be present, and you show you spent at least $400 on repairs.
  14. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    Bill, couple of stupid questions.

    i know my truck doesnt have an egr. i think it goes on the carb, correct? if so, would a stock one work on an edelbrock performer 600 cfm electric choke? are there any other parts that go along with whatever goes on the carb?

  15. thelawnguy

    thelawnguy PlowSite.com Addict
    Messages: 1,011

    Some manifolds use built-in passages, some use a plate under the carb. Lol, now you need to find out if your motor originally was equipped with EGR. Maybe its cheaper to grab a sticker from a junkyard windshield lol. Your truck wouldnt by chance be white with red interior would it???
  16. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    yeah, this is definately getting out of hand. i just got off the phone w/the parts counter guy at the local dealer, he says that any earlier than 1990 and the VIN doesnt give any specific info about what emissions equip the truck came with. he also said that from his experience all the HD non-cat trucks he has seen did have the AIR system.

    the original carb had some type of EGR valve on it though i dont know if it worked or was even hooked up. I'm thinking maybe if its less trouble than adding the AIR system, i can hook up an EGR to my edelbrock. it's supposedly "50 state legal" so i assume it must be possible.

    Bill it's red & white on the outside and a lovely maroon/rust on the inside. sound like a truck you know?
    I'm thinking about taking donations of VIN plates with matching titles from 83 & earlier LOL what a PITA

  17. thelawnguy

    thelawnguy PlowSite.com Addict
    Messages: 1,011

    My brother had a truck similar to yours, cab and vin plate said 84, frame chassis motor(?) was a 74 or 78, vin said it was a K25 but the chassis and springs appeared to be a 1 ton SRW would not pass CT emissions or inspection without going thru hybrid inspection BS. Sold it soon after purchase last winter (maybe 2 years ago???).

    Check the VIn on the frame and/or motor, maybe you can get the truck thru on earlier model year specs if it turns out to have earlier running gear. depending on DMV laws in taxachusetts.

    There are co's which will title any vehicle for you. Maybe take it to ME and get it registered there, I hear they are pretty lax, most of the inner city junks around here have ME plates. (no disrespect intended for you Maniacs).
  18. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    that does sound alot like my truck. i have always gone by the dash VIN which says 84. i bought the truck from a guy in Quincy MA a little over a year ago. i dont think he had it very long, who knows could be the same truck, though it did have a MA title & sticker when i bought it.

    i know that the motor is 80's as it has the dipstick on passenger side. a friend of mine swears that the chassis is a 70's camper special or something, it is quite heavy duty definately 1 ton springs & BIG brakes etc..

    i guess i'll throw the AIR pump on there for the test & see what happens. i do want to get this to pass, as i like the truck very much and am waaay to cheap to buy a newer truck. or an older one for that matter. we'll see what happens.

  19. 84'GMC4x4

    84'GMC4x4 Member
    Messages: 42

    Bill, where could i find the VIN on the frame?

    i just talked to the Chevy customer service people & even they cant look up the info with just the VIN they need the spid? # off the label in the glove box.
    thats right, you guessed it, no label in my glove box. maybe if i find the VIN on the frame & it is indeed older than 84 maybe i can get it titled that way & avoid this trouble all together. (no emissions test at all for pre-84 vehicles in MA)

  20. thelawnguy

    thelawnguy PlowSite.com Addict
    Messages: 1,011

    You will have to wait for the chevy guys to sign on to help you out there. Chuck???