HELP...1986 C20 5.7....smog removed,,,Check engine light??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72freak · 08-11-2010, 03:50 PM

I dont have any experience with this crazy pre-87 emissions stuff. I dont have another one close by to compare it to.......We picked up this crew cab a few weeks ago.....running great. It looks like there may have been a smog pump at one time that was cut off??? A few tube things up top on each side and two plugs that go no where. It will throw a "check engine" light when on the highway. I am sure it has something to do with the unplugged stuff.

1) any pictures of what is should look like?
2)Will the plugs that arent hooked up effect this check engine light?
3)If so can they be jumped off?
4)Where do these pinched off tubes up top go to?
5) CHECK ENGINE LIGHT....are you kidding me...WHY? Whats it supposed to be telling me?

Im sure I will eventually change the intake, carb and exhaust, but for now Id like to make sure its right.

Thanks for your help!

CaliDude76 · 08-11-2010, 07:11 PM

Depending on your state, I don't know if you are required to take and emmisions test.. but if you don't... I would just unplug the bulb to the "check engine light",... most of these lights were hooked up to the emmisions system anyway (mine is)... seeings that yours was all hacked to peices (do you need it all back together?)... could be anything setting it off..... I have an 84 with all the smog stuff hooked up (strict smog laws here in Cali)... would show you pics.. but I'm pretty sure the plumbings different between 84's, and 86's..

72freak · 08-11-2010, 07:44 PM

Quote:

Originally Posted by CaliDude76

Depending on your state, I don't know if you are required to take and emmisions test.. but if you don't... I would just unplug the bulb to the "check engine light",... most of these lights were hooked up to the emmisions system anyway (mine is)... seeings that yours was all hacked to peices (do you need it all back together?)... could be anything setting it off..... I have an 84 with all the smog stuff hooked up (strict smog laws here in Cali)... would show you pics.. but I'm pretty sure the plumbings different between 84's, and 86's..

Yep...bulb is coming out. No...we dont need a smog test on it here because of its GVW. it came from Texas so I dont know if the under hood would be the sameor not.

CaliDude76 · 08-11-2010, 07:56 PM

Quote:

Originally Posted by 72freak

Yep...bulb is coming out. No...we dont need a smog test on it here because of its GVW. it came from Texas so I dont know if the under hood would be the sameor not.

.. yeah, you should be good!.. good luck with that

BTW.. Dude.. how big of a garage you got?? geez.. you got some rides LOL

Slonaker · 08-12-2010, 09:43 AM

The C10 in 1986 didn't have a check engine light unless it was a California emissions model. Your C20 may be a CA emissions model.

Slonaker

rfmaster · 08-12-2010, 11:02 AM

Quote:

Originally Posted by 72freak

I dont have any experience with this crazy pre-87 emissions stuff. I dont have another one close by to compare it to.......We picked up this crew cab a few weeks ago.....running great. It looks like there may have been a smog pump at one time that was cut off??? A few tube things up top on each side and two plugs that go no where. It will throw a "check engine" light when on the highway. I am sure it has something to do with the unplugged stuff.

1) any pictures of what is should look like?
2)Will the plugs that arent hooked up effect this check engine light?
3)If so can they be jumped off?
4)Where do these pinched off tubes up top go to?
5) CHECK ENGINE LIGHT....are you kidding me...WHY? Whats it supposed to be telling me?

Im sure I will eventually change the intake, carb and exhaust, but for now Id like to make sure its right.

Thanks for your help!

In the Photos it looks like some one really hated AIR system - (air injection) - the two plugs were used for AIR diverter valve which by-passed air from the AIR pump when not commanded to inject air into exhaust manifolds. As for check engine light I have to assume that you have CCC (computer controlled carb). Take a look at you carb it should have a model cast into it - probably M4MED or ???. Inside cab, look left of the steering column for ALDL connector.

If you have one this also means that you have ECM controlling carburetor. To determine what is causing SEL to be one - short pins A&B with a paper clip and turn ignition on, but do not start engine. SEL should blink code 12 3 times followed by the offending DTC.

//RF

Jonboy · 08-12-2010, 11:08 AM

Just unplugging the smog will not set a CEL. You have something else going on. Pull the codes like RF said, and report back. I bet it is something else entirely.

72freak · 08-12-2010, 06:24 PM

Thanks for the informative info!!! I will run out in a sec and look...HOWEVER last time I checked I DID NOT see a plug in under the dash. It was the first thing I looked for when that crazy check engine light came on. ill check to make sure it has not been unscrewed and tucked up in the dash.

72freak · 08-13-2010, 04:43 PM

There is NO OB port under the dash and NO electronic carb.

No port=no codes to repot.

Lots of smog stuff, Check engine light and I cant remember if i mentioned it before....it also has a stupid CHOKE light that glows now and again. What was GM thinking?

CaliDude76 · 08-13-2010, 07:16 PM

Quote:

Originally Posted by 72freak

There is NO OB port under the dash and NO electronic carb.

No port=no codes to repot.

Lots of smog stuff, Check engine light and I cant remember if i mentioned it before....it also has a stupid CHOKE light that glows now and again. What was GM thinking?

ehhh.. it was the 80's,... they were trying to be all "sophisticated" with the computer controlled stuff.. but bombed apparently.. I mean look at the early 80's Caddy's with the 4,6,8 HT electronically controlled engines that failed miserably.. Got a hand it to em for giving it a shot. They got better with time though....

72freak · 08-14-2010, 04:14 PM

Any other ideas why it would be throwing a check engine light?
If unplugged smog wont do it and it does not have a computer.....what throws the light?

cableguy0 · 08-14-2010, 04:17 PM

If it doesnt have the electronic carb and the rest of the stuff associated with that. If you cant find a diagnostic port and theres no computer just take the bulb out of the dash so it doesnt light up anymore.

72freak · 08-14-2010, 06:31 PM

Quote:

Originally Posted by cableguy0

If it doesnt have the electronic carb and the rest of the stuff associated with that. If you cant find a diagnostic port and theres no computer just take the bulb out of the dash so it doesnt light up anymore.

Thats what is going to happen but I am one of those "figure it out" types so the search goes on!

cableguy0 · 08-14-2010, 06:45 PM

Theres probably nothing to figure out. If theres no computer and no sensors to read. The light is simply lit because it has power to it from somewhere. trace some wires under the dash. If the choke light acts up too there could just be a wiring issue behind the dash or cluster.

72freak · 08-14-2010, 08:26 PM

Quote:

Originally Posted by cableguy0

Theres probably nothing to figure out. If theres no computer and no sensors to read. The light is simply lit because it has power to it from somewhere. trace some wires under the dash. If the choke light acts up too there could just be a wiring issue behind the dash or cluster.

It comes on only at higher speeds/longer drives (normally on the interstate)
It will go back out when you shut the truck off and it will stay off untill you are back on the interstate. It never comes on driving around town.

CaliDude76 · 08-15-2010, 12:03 AM

Quote:

Originally Posted by 72freak

It comes on only at higher speeds/longer drives (normally on the interstate)
It will go back out when you shut the truck off and it will stay off untill you are back on the interstate. It never comes on driving around town.

another possibilty could be the O2 Sensor... just a thought...

72freak · 08-15-2010, 07:47 AM

Quote:

Originally Posted by CaliDude76

another possibilty could be the O2 Sensor... just a thought...

I will look and see if I have them and report back. Any thoughts where they would be other than the exhaust? Thanks!

cableguy0 · 08-15-2010, 11:13 AM

Theres only going to be one and it should be near the exhaust manifold in the y pipe. You said you have no computer though. If thats true theres nothing for the o2 to send signal to.

72freak · 08-15-2010, 12:40 PM

Quote:

Originally Posted by cableguy0

Theres only going to be one and it should be near the exhaust manifold in the y pipe. You said you have no computer though. If thats true theres nothing for the o2 to send signal to.

My thoughts exactlt!

cableguy0 · 08-15-2010, 12:49 PM

The signal for the light should come directly from the computer. Like I said I think your chasing a ghost and theres a short or electrical problem in the dash itself.If theres for sure no computer then the light shouldnt be lit.

CaliDude76 · 08-15-2010, 01:14 PM

.. I could be spit-ballin here... but if it had smog stuff,.. and a check engine light.. it has to have a brain(ECM) somewhere?...no? Did you check under the dash,.. behind the glove-box? I know that's where mine is located...

motornut · 08-16-2010, 10:35 PM

now i'm curious........not up there?

72freak · 08-16-2010, 11:13 PM

I cant tell what I am looking at......is that behind the glove box?

*87 chevy silverado* · 08-16-2010, 11:22 PM

yes that is

clinebarger · 08-16-2010, 11:28 PM

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.

08-11-2010, 03:50 PM	#1
72freak Rottenwood Garage Member Join Date: May 2005 Location: Marietta, Georgia Posts: 4,321	HELP...1986 C20 5.7....smog removed,,,Check engine light??? I dont have any experience with this crazy pre-87 emissions stuff. I dont have another one close by to compare it to.......We picked up this crew cab a few weeks ago.....running great. It looks like there may have been a smog pump at one time that was cut off??? A few tube things up top on each side and two plugs that go no where. It will throw a "check engine" light when on the highway. I am sure it has something to do with the unplugged stuff. 1) any pictures of what is should look like? 2)Will the plugs that arent hooked up effect this check engine light? 3)If so can they be jumped off? 4)Where do these pinched off tubes up top go to? 5) CHECK ENGINE LIGHT....are you kidding me...WHY? Whats it supposed to be telling me? Im sure I will eventually change the intake, carb and exhaust, but for now Id like to make sure its right. Thanks for your help! Attached Images __________________ 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; 08-11-2010 at 03:53 PM.

08-11-2010, 07:11 PM	#2
CaliDude76 All About the BOWTIE Join Date: May 2010 Location: Los Banos, California Posts: 436	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? Depending on your state, I don't know if you are required to take and emmisions test.. but if you don't... I would just unplug the bulb to the "check engine light",... most of these lights were hooked up to the emmisions system anyway (mine is)... seeings that yours was all hacked to peices (do you need it all back together?)... could be anything setting it off..... I have an 84 with all the smog stuff hooked up (strict smog laws here in Cali)... would show you pics.. but I'm pretty sure the plumbings different between 84's, and 86's.. __________________ CaliDude76 "... Being "SQUARE".. is where it's at...." Proverbs 15:30 .... "A Cheerful look brings joy to the heart, and good news gives health to the bones..." Be exceedingly blessed today, my friends!... Last edited by CaliDude76; 08-11-2010 at 07:20 PM.

08-12-2010, 09:43 AM	#5
Slonaker Insert Witty Text Here Join Date: Oct 2002 Location: San Antonio, TX Posts: 3,415	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? The C10 in 1986 didn't have a check engine light unless it was a California emissions model. Your C20 may be a CA emissions model. Slonaker __________________ '86 Chevy C10 (Sold 04/19/13 ) Stock '01 Silverado

08-12-2010, 11:08 AM	#7
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? Just unplugging the smog will not set a CEL. You have something else going on. Pull the codes like RF said, and report back. I bet it is something else entirely. __________________ 1974 Jimmy- 5.3/4L80e/NP241

08-12-2010, 06:24 PM	#8
72freak Rottenwood Garage Member Join Date: May 2005 Location: Marietta, Georgia Posts: 4,321	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? Thanks for the informative info!!! I will run out in a sec and look...HOWEVER last time I checked I DID NOT see a plug in under the dash. It was the first thing I looked for when that crazy check engine light came on. ill check to make sure it has not been unscrewed and tucked up in the dash. __________________ 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!

08-13-2010, 04:43 PM	#9
72freak Rottenwood Garage Member Join Date: May 2005 Location: Marietta, Georgia Posts: 4,321	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? There is NO OB port under the dash and NO electronic carb. No port=no codes to repot. Lots of smog stuff, Check engine light and I cant remember if i mentioned it before....it also has a stupid CHOKE light that glows now and again. What was GM thinking? __________________ 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; 08-13-2010 at 04:43 PM.

08-14-2010, 04:14 PM	#11
72freak Rottenwood Garage Member Join Date: May 2005 Location: Marietta, Georgia Posts: 4,321	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? Any other ideas why it would be throwing a check engine light? If unplugged smog wont do it and it does not have a computer.....what throws the light? __________________ 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!

08-14-2010, 04:17 PM	#12
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? If it doesnt have the electronic carb and the rest of the stuff associated with that. If you cant find a diagnostic port and theres no computer just take the bulb out of the dash so it doesnt light up anymore. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

08-14-2010, 06:45 PM	#14
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? Theres probably nothing to figure out. If theres no computer and no sensors to read. The light is simply lit because it has power to it from somewhere. trace some wires under the dash. If the choke light acts up too there could just be a wiring issue behind the dash or cluster. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

08-15-2010, 11:13 AM	#18
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? Theres only going to be one and it should be near the exhaust manifold in the y pipe. You said you have no computer though. If thats true theres nothing for the o2 to send signal to. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

08-15-2010, 12:49 PM	#20
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? The signal for the light should come directly from the computer. Like I said I think your chasing a ghost and theres a short or electrical problem in the dash itself.If theres for sure no computer then the light shouldnt be lit. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

08-15-2010, 01:14 PM	#21
CaliDude76 All About the BOWTIE Join Date: May 2010 Location: Los Banos, California Posts: 436	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? .. I could be spit-ballin here... but if it had smog stuff,.. and a check engine light.. it has to have a brain(ECM) somewhere?...no? Did you check under the dash,.. behind the glove-box? I know that's where mine is located... __________________ CaliDude76 "... Being "SQUARE".. is where it's at...." Proverbs 15:30 .... "A Cheerful look brings joy to the heart, and good news gives health to the bones..." Be exceedingly blessed today, my friends!...

08-16-2010, 10:35 PM	#22
motornut 78K & 79C Jimmys Join Date: Nov 2009 Location: Ottawa Ont CANADA Posts: 7,901	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? now i'm curious........not up there? Attached Images __________________ John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350

08-16-2010, 11:13 PM	#23
72freak Rottenwood Garage Member Join Date: May 2005 Location: Marietta, Georgia Posts: 4,321	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? I cant tell what I am looking at......is that behind the glove box? __________________ 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!

08-16-2010, 11:22 PM	#24
87 chevy silverado Account Suspended Join Date: Apr 2009 Location: lexington South Carolina Posts: 2,124	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? yes that is



Register or Log In To remove these advertisements.

08-16-2010, 11:28 PM	#25
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	Re: HELP...1986 C20 5.7....smog removed,,,Check engine light??? 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. Attached Images

Register or Log In To remove these advertisements.