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Old 08-16-2010, 11:38 PM   #26
motornut
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

yup it's my 85
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Old 08-17-2010, 12:32 AM   #27
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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now i'm curious........not up there?
The shiny aluminum box with the rusty strap holding it up is your ECM.
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Old 08-17-2010, 07:29 AM   #28
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

my fuel pump relay is there on my firewall,whats all the wires on the right?looks like fun there
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Old 08-17-2010, 05:05 PM   #29
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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My 85 3/4 ton Suburban had the same emissions equipment, Dual smog pumps, No catalytic converters, No EST, No feedbak Quadrajet, Dual exhaust, Leaded gasoline compatible.

There is a "smog pump control module" on the firewall. Heres a pic of mine, The circle is where it used to be. It grounds the "check engine light" bulb when a fault is detected in the "Air Diverter solenoid" curcuit. Unplug the module, the light should go out.
WOW.....great info...I had just gotten back from some more picture taking and research and took a picture of that little box on the firewall to find out what it was and if that could be the culprit....I plan to give it a shot next time I drive it. As far as mine goes here is some more info......

Stock true dual exhaust with no Y pipe, no cats and no O2 sensor. It is very obvious this is the original exhaust by the shields all over the pipes.

Absolutley no computer behind the glove box.
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Old 08-17-2010, 07:25 PM   #30
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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yup it's my 85
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Originally Posted by motornut View Post
my fuel pump relay is there on my firewall,whats all the wires on the right?looks like fun there
That doesnt look like a 85, Looks like a 87-91? But to answer your question that is the main harness to your ECM.
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Old 08-19-2010, 05:49 PM   #31
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

mine or his dosn't look 85
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Old 08-19-2010, 09:07 PM   #32
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

I think he means yours....with that fuel pump relay I believe it should be a throttle body that started in 87....Thats probably what he is talking about.
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Old 08-19-2010, 10:42 PM   #33
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

Well i was told it was a diesel when bought new.but vin says 454 2 wheeler and it's C20-4X4
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Old 08-19-2010, 10:48 PM   #34
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

http://67-72chevytrucks.com/vboard/s...d.php?t=416576

FYI is another 85 not sure if he's tbi too tho,i just asked him
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Old 08-19-2010, 11:38 PM   #35
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

I have never seen a 85 chevy/gmc C/K/S/T/M platform have TBI. Even the 85 4.3s had feedback Quadrajets on them.

Last edited by clinebarger; 08-19-2010 at 11:42 PM.
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Old 08-20-2010, 01:22 AM   #36
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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I have never seen a 85 chevy/gmc C/K/S/T/M platform have TBI. Even the 85 4.3s had feedback Quadrajets on them.
Can you post a photo of your 'fuel mixer' please - suspense is killing me!!!

//RF
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Old 08-20-2010, 07:20 AM   #37
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

I'll get prettier pics this weekend if you want,but the 85 tbi etc was all matching my 87 that i had.I've only since finding this site i've explored rpo's and vin #s,and yes as you say it shouldn't be(just read to do it u have to shave bolts and other stuff?)........So when i turn the key i shouldn't hear the fuel pump humpin,before startin, should be manual pump?And no wires in there either.hmmmm
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Old 08-20-2010, 07:40 AM   #38
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

would i have the computer above the glovebox with out tbi,as it would seem it was born with a 454 but sadly it was removed.replaced with a 350........i am asumming the puters don't interchange....i figured the 2x to 4x4 frames/driveline were changed.........but to change the rest?Got any ideas how i would check/know........i posted/started some pics in a build thread...........16 inch tires if i read right?
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Old 08-20-2010, 11:00 AM   #39
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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would i have the computer above the glovebox with out tbi,as it would seem it was born with a 454 but sadly it was removed.replaced with a 350........i am asumming the puters don't interchange....i figured the 2x to 4x4 frames/driveline were changed.........but to change the rest?Got any ideas how i would check/know........i posted/started some pics in a build thread...........16 inch tires if i read right?
The CCC (computer controlled carb) used ECM - which is located above globe box. It possible to take later 87+ TBI 350 with ECM and harness and swap it in place of CCC without great deal of effort.

//RF
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Old 08-20-2010, 01:45 PM   #40
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

Have you run your VIN to confirm its year?
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Rottenwood Garage and Speed Shop.....where everything must be racy!

It's not just a hobby..It's a LIFESTYLE!!!

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Last edited by 72freak; 08-20-2010 at 01:45 PM.
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Old 08-20-2010, 02:16 PM   #41
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

yup checked the vin year is right.ownership says C20
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Old 08-21-2010, 03:30 AM   #42
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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now i'm curious........not up there?
That box above the heater/ac box is the computer (ECM). You will need to change out distributors to an older pre-81 HEI and if carb has wires for mixture it will need to be changed.

Also in pic looks like your heater/ac diverter valve is broken.

http://67-72chevytrucks.com/vboard/s...diverter+valve

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Old 08-21-2010, 11:31 AM   #43
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

Quote:
Originally Posted by motornut View Post
I'll get prettier pics this weekend if you want,but the 85 tbi etc was all matching my 87 that i had.I've only since finding this site i've explored rpo's and vin #s,and yes as you say it shouldn't be(just read to do it u have to shave bolts and other stuff?)........So when i turn the key i shouldn't hear the fuel pump humpin,before startin, should be manual pump?And no wires in there either.hmmmm
Actually there is a harness, but with air filter on you can not see it. ECM harness is placed on the right (passenger) side of intake - injectors, TPS, IAC, CTS, EGR and AIR form a rather thick bundle. Can not miss it. Going to carb is a wrong approach.

//RF
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Old 08-22-2010, 07:33 AM   #44
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

OK.........There were two plugs in the bottom of this "smog pump control module". One plug has about 5 wires and the other has 2 wires. I unplugged both sets and the check engine light as mentioned above has NOT come back on. I have watched the truck closely and everything seems to work correctly.

Anyone know what these 2 plugs route to? The 5 wire and the 2 wire?With the info given above Im sure its all smog related but thats a lot of wires for just the smog system. I want to make sure I dont unplug something needed.
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2004 Chevrolet Suburban C1500
2001 Chevrolet 2500HD Crew 6.0
1999 Harley Davidson Electra Glide
1972 Chevrolet C-20 Custom Camper "Dump Truck"
1972 Chevrolet C-20 Suburban "Big Green"
1969 Chevrolet C-50 Wedge Hauler "Leonidis"
1966 C-10 2x4 short fleet 327 4 speed "Race Truck"
1952 Plymouth Cranbrook "Rican" (my grandfathers)
1931 Ford Model A Coupe "Black Beauty"
1930 Ford Model A truck "Club Cab" 4x4


Rottenwood Garage and Speed Shop.....where everything must be racy!

It's not just a hobby..It's a LIFESTYLE!!!

Thanks for nothing Barrett-Jackson

You cant fix stupid or teach accountability!


Time wasters, looky Lous and tire kickers are everywhere!

Last edited by 72freak; 08-22-2010 at 07:38 AM.
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Old 08-22-2010, 08:38 AM   #45
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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OK.........There were two plugs in the bottom of this "smog pump control module". One plug has about 5 wires and the other has 2 wires. I unplugged both sets and the check engine light as mentioned above has NOT come back on. I have watched the truck closely and everything seems to work correctly.

Anyone know what these 2 plugs route to? The 5 wire and the 2 wire?With the info given above Im sure its all smog related but thats a lot of wires for just the smog system. I want to make sure I dont unplug something needed.
I am very curious as to the answer to this question as well! I have an 86 de-smogged K20 and have had the same struggles with check engine and choke light as you. I am tearing it apart for restoration now and was wondering what that box was for. This thread has helped me a ton! Thanks for posting it!
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Old 08-22-2010, 05:20 PM   #46
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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I am very curious as to the answer to this question as well! I have an 86 de-smogged K20 and have had the same struggles with check engine and choke light as you. I am tearing it apart for restoration now and was wondering what that box was for. This thread has helped me a ton! Thanks for posting it!
Someone with a good service manual and a complete wiring schematic should be able to answer all the questions. I was glad we finally got some great info......I knew there was a real answer to the symptoms!!! "There is nothing to figure out, its just an electrical problem, a gremlin, take out the bulb and smog pump wont throw a check engine light" was not really the answer or solution I was looking for.
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1966 C-10 2x4 short fleet 327 4 speed "Race Truck"
1952 Plymouth Cranbrook "Rican" (my grandfathers)
1931 Ford Model A Coupe "Black Beauty"
1930 Ford Model A truck "Club Cab" 4x4


Rottenwood Garage and Speed Shop.....where everything must be racy!

It's not just a hobby..It's a LIFESTYLE!!!

Thanks for nothing Barrett-Jackson

You cant fix stupid or teach accountability!


Time wasters, looky Lous and tire kickers are everywhere!

Last edited by 72freak; 08-22-2010 at 05:21 PM.
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Old 08-23-2010, 10:11 AM   #47
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

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Originally Posted by 72freak View Post
OK.........There were two plugs in the bottom of this "smog pump control module". One plug has about 5 wires and the other has 2 wires. I unplugged both sets and the check engine light as mentioned above has NOT come back on. I have watched the truck closely and everything seems to work correctly.

Anyone know what these 2 plugs route to? The 5 wire and the 2 wire?With the info given above Im sure its all smog related but thats a lot of wires for just the smog system. I want to make sure I dont unplug something needed.
This is the only diagram I chould find, It only shows the 5 wire connector? Im not sure on the 2 wire connector.....Its been 6 year since i ripped all this stuff off mine. What colors are the 2 wires?
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Old 08-23-2010, 11:39 AM   #48
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

WOW....great info.....I guess you just confirmed the smog stuff DOES run through the check engine light!!!!!

I am going to plug the 2 wire back in and see if I notice anything.
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1972 Chevrolet C-20 Custom Camper "Dump Truck"
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1966 C-10 2x4 short fleet 327 4 speed "Race Truck"
1952 Plymouth Cranbrook "Rican" (my grandfathers)
1931 Ford Model A Coupe "Black Beauty"
1930 Ford Model A truck "Club Cab" 4x4


Rottenwood Garage and Speed Shop.....where everything must be racy!

It's not just a hobby..It's a LIFESTYLE!!!

Thanks for nothing Barrett-Jackson

You cant fix stupid or teach accountability!


Time wasters, looky Lous and tire kickers are everywhere!
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Old 08-24-2010, 11:41 AM   #49
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

The pic i took while i was repairing the heater core and that valve,i use it to show why the air box don't work right,and where it would/how it would be broken,and where the ECM is .........and i too hope to be smog free
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Old 08-24-2010, 07:25 PM   #50
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Re: HELP...1986 C20 5.7....smog removed,,,Check engine light???

my 1985 sub intake
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