73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: m3talc0re on December 12, 2016, 03:38:27 pm
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On my 83 GMC Sierra classic, where does the positive on the electric choke connect to?
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To the terminal on the choke coil.
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Smartass -_-
And the other end?
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It is part of the engine loom passenger side, same loom that goes to the alternator
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You can view the wiring diagrams here:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=25639.0
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It goes to an oil pressure switch on the back of the engine, such that it is only energized when the engine is running. Windshield wiper motor hot lead, I believe, is also connected there.
You can also connect it directly to the ignition wire, as long as you understand that sitting there with the key on and the engine not running will heat up the choke spring eventually turning off the choke.
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Thanks. I'd like to have it connected to where it's supposed to be connected, lol. I'll try to find that switch this afternoon, hopefully..
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What does the ground go to? Is it supposed to be connected to a switch in the thermostat housing?
I'm very confused atm. Right now, nothing is connected to the choke. So is the choke stuck open? The engine runs fine once warmed up, but when cold, I have to keep my foot in the throttle a little to keep the engine running.
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It's a single wire and the choke heater is grounded through the engine ground. If nothing is hooked up it will not function.
On most vehicles, an electric assist choke is incorporated onto the carburetor to aid in reducing the emissions of hydrocarbons (HC) and carbon monoxide (CO) during starting and warm-up (choke-on) period. The electric assist choke is designed to give a more rapid choke opening at temperatures of approximately 60-65°F., or greater and a slower choke opening at temperatures of approximately 60-65°F., or below. The electric assist choke system does not change any carburetor service procedures and cannot be adjusted. If the system is out of calibration, the heater control switch and/or choke unit must be replaced.
The main components of the electric assist choke system, Fig. 39, consist of a thermostatic coil, ceramic resistor, cover, bi-metal snap disc and contact spring. The electric actuated ceramic resistor heats the thermostatic coil, gradually relaxing coil tension and allowing the choke valve to open.
At air temperatures below 50°F., electric current applied to the small section of the ceramic resistor, allows slow opening of the choke valve for good engine warm-up. As the small section of the ceramic resistor continues to heat, a bi-metal disc causes the spring loaded contact to close and apply electric current to the large section of the ceramic resistor which increases the heat flow to the thermostatic coil for more rapid opening of the choke valve.
At air temperatures between 50-70°F., electric current applied to the small section, or both the small and large sections of the ceramic resistor, will produce the amount of heat required to control the choke valve position for good engine operation in these temperature ranges.
At air temperatures above 70°F., electric current applied to the small section of the ceramic resistor and through the spring contact to the large section of the ceramic resistor, provides rapid heating of the thermostatic coil for quicker choke valve opening when leaner air-fuel mixtures are required at warmer temperatures.
Diagnosis & Testing
Possible conditions for the electric choke not operating properly are listed as follows (use a voltmeter to check oil pressure and choke coil circuits):
Low or no engine oil pressure.
Faulty oil pressure switch.
No current to oil pressure switch due to:
Burned out fuse.
Broken wire to oil pressure switch.
No current between choke and oil pressure switch due to:
Broken lead wire.
Wire terminal not properly secured on coil terminal.
Faulty ground circuit between choke assembly and housing grounding plate.
Faulty choke coil assembly.
If it is determined that the choke coil assembly is inoperative, the following test must be made:
Remove choke coil from carburetor. After removal of choke coil, allow coil to cool to room temperature.
Connect a ``jumper'' wire between positive battery terminal and choke coil terminal assembly. Connect a second ``jumper'' wire between negative battery terminal and choke coil assembly grounding plate.
The tang on the choke coil should rotate 45°in 54-90 seconds.
If choke coil does not rotate or exceeds the 54-90 second time limit, replace choke coil.
If coil is within specification, check steps 1 thru 5 for possible cause.
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I went out and looked while on lunch and it looks like the choke is just staying open. Moving the linkage on either direction gives me no resistance or spring back. Does that mean the choke assist module (name?) is broken?
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It means someone probably set it so it's always open.
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How did they do that exactly? Dismantle the choke module?
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On the side of the electric choke there are 3 fasteners. Loosen them and the center piece in the housing will rotate.
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For the life of me, I cannot find the oil pressure switch where this thing should be connected...
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above the oil filter or drivers side of distributor. im not sure where they connect to the choke never seen it like that. i know thats how its supposed to be be but ive never seen a stock setup and paid attention to that
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I'm not seeing anything. The only thing I see back there is a tube coming from the engine to an aftermarket oil pressure gauge in the cab.
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what about on top of the oil filter?
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I didn't see any sort of wires coming out around it..
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The AC Delco D1811 / GM 10002798 two terminal choke heater oil pressure switch for the 1982-1986 carbureted trucks is screwed into the block just above the oil filter. It's wired as follows.
PINK/WHITE IGN power from the bulkhead plug at 350. The wiper power wires are GRAY and have nothing to do with the choke.
Two BLUE wires on the second terminal.
--LT BLUE to CHOKE heater.
--DK BLUE to the bulkhead plug at 931 and then the instrument panel CHOKE lamp.
Snippet from the 1983 GM wiring diagrams.
(http://johnnynightstick.s3.amazonaws.com/IMAGES/1983_Choke.jpg)
#13 is the oil pressure sender for the gauge.
#17 is the Choke Heater Oil Pressure Switch.
(http://gmpartswiki.com/getbigpage?pageid=57756)
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Look at the simplified diagram posted earlier by Vile...
(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=34146.0;attach=34349;image)
Unless someone removed it or tucked it up into a convoluted loom, there should be a black two-terminal, three-wire pigtail with pink/white stripe, dark blue and light blue wires that connects to a two-prong oil pressure switch (OPS)....
(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=28784.0;attach=26341;image)
Look closely in the vicinity of and just above the oil filter at the left rear of the engine. If neither appears near or above the oil filter, look around the back of the intake manifold, just behind the China Wall and left (driver side) of the ignition distributor. Keep in mind that when the aftermarket manual oil gauge was installed the choke OPS and harness may have been removed from the vehicle. Studying the firewall bulkhead connector, using the diagram above for reference, you should be able to determine whether the pink/white and dark blue wires exit the connector and enter the engine compartment harness.
The light blue wire from the OPS connects to the choke heater on the carburetor through a connector that looks like the image below.
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I think it's all been removed. I found a short small bundle of wires coming out of the firewall to the right of the brake booster. I have no reference for the shade of blue, whether it's dark or light, but the is a blue wire and a pink with white stripe wire
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Can I connect to the Pink and white one? It's hard to read those diagrams, can't tell what's what XD
Edit: actually, I think it's the blue one I want. It has 12v with the key on. Oddly, the pink/white wire had like 0.26v... Wondering if I just had a bad contact with it with you multimeter.
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12v with key on isnt bad. but if you turn your key on to listen to the radio or something then it will turn the choke on without the engine running and thats why the OPS is a good idea when it comes to the choke
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There may be a switch in there, I'm not sure, but it's definitely not connected to anything. I don't normally sit there with the key on, either. So it'll do at least until I can get the switch and all working correctly
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(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=34146.0;attach=34349;image)
Referring to ^^^^ diagram, the pnk/wht wire is powered directly from the CHOKE fuse. The dk blu wire is the "ground side" of the choke telltale light in the dash. Your voltmeter maybe tossing you a curve ball. Use an incandescent test light rather than a voltmeter when probing for power. Grounding the dk blu wire with the ignition on should illuminate the dash telltale - you cannot use the dk blu wire for power. Check the CHOKE fuse then retest the pnk/wht wire for power.
The block of rectangular cells containing numbers at the right center of the diagram is just a simplified drawing of the bulkhead connector that feeds power through the firewall, both into and out of the cab. Each cell in the block corresponds to a wire cavity in the bulkhead connector. If you compare the diagram to the bulkhead connector in your truck you'll discover which two cavities in the connector should contain the pnk/wht and dk blu wires you seek.
The numerals in the individual cells are circuit numbers. Circuit 350 is the power feed from the 20-amp CHOKE fuse (pnk/wht wire). Circuit 931 is the 'ground lead' coming from the Choke telltale in the dash (dk blu wire).
Understanding the wiring diagram symbols for the "pink wire with white stripe":
.8 PNK/WHT-350(SXL)
- .8 is the metric cross sectional area of the wire conductor in (mm)2. 0.8 corresponds to American Wire Gauge (AWG) size 18. Factory GM wiring manuals offer tables that cross reference metric wire sizes to the AWG equivalents.
- PNK/WHT is the wire color, pink with white stripe
- 350 is the circuit number, and
- SXL is the type of insulation jacketing the wire, in this case a version of cross-linked polyethylene which has exceptional ozone, heat and automotive solvents tolerance. Generally, wire insulation type is noted only when the specific application deviates from the standard PVC/GPT.
Similarly, you can decode the symbols for the remaining circuits on most GM wiring diagrams. The few eight-digit numbers adjacent to connectors in the drawing are the original GM part numbers for the connectors - unfortunately, many of the part numbers are obsolete and/or superseded by the time the manuals are published and circulated for use.
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So I should be getting 12v from the PINK/WHITE wire? So I should have the choke connected to that one, which I'll have to check the fuse and strip the wire to get better contact on it. Like I said, that probe was probably barely touching it, I think. I've got the choke connected to the blue wire atm, and yeah, the "Choke" dash light just stays on -_-
Is there any way to wire that to make it functional? So the choke like goes on and off when it's supposed to?
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Your answer is in the wiring diagram that's been posted repeatedly and the two prong OPS that's been discussed. All you really need to do is buy the OPS, maybe a connector, and some 18-gauge wire to string everything together. If you need additional help interpreting the wiring diagram, just ask. Plan on installing the OPS in its original location down near the oil filter - the OPS location is illustrated in the parts diagram already posted. Essentially, all of the information you need is in this thread - read through it again. Don't be shy. ;)
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None of these diagrams list positive or negative..
Okay, so the dark blue, is hot, but gets grounded in the ops and turns on the choke light. The pink/white is hot and goes to the ops, then a light blue positive goes from the ops to the choke heater.
I think some of my confusion is my lack of understanding of how and what the ops actually does.. Like, how does the oil pressure switch determine the choke is on or off. Looking at the diagram, why is the dark blue turning on the choke light and not an oil pressure light?
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This is where I guess the oil pressure switch is, but I don't think there are any prongs coming out of this connector or whatever this is supposed to be... I'll go out in a little while and see if I can pull that off to see what I'm working with exactly..
(http://i.imgur.com/8HYFN0V.jpg)
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i can see the prongs in the picture
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This is where I guess the oil pressure switch is, but I don't think there are any prongs coming out of this connector or whatever this is supposed to be... I'll go out in a little while and see if I can pull that off to see what I'm working with exactly..
(http://i.imgur.com/8HYFN0V.jpg)
The switch you have looks quite different from the one called for in the parts books. The plug for that switch is obsolete.
Get the correct AC Delco D1811 oil pressure switch and install it in place of that switch. The D1811 switch has 1/4" disconnects.
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lol yeah sorry thats the one for the tbi motors, right hatzie?. theres another guy on here that has OPS issues and i think hes a tbi
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hatzie whats the difference in that ac del one and PS134 from duralast?
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None of these diagrams list positive or negative..
Okay, so the dark blue, is hot, but gets grounded in the ops and turns on the choke light. The pink/white is hot and goes to the ops, then a light blue positive goes from the ops to the choke heater.
I think some of my confusion is my lack of understanding of how and what the ops actually does.. Like, how does the oil pressure switch determine the choke is on or off. Looking at the diagram, why is the dark blue turning on the choke light and not an oil pressure light?
The choke OPS is a simple normally open ON-OFF switch that responds to engine oil pressure. Its contacts are either "open" when there is zero oil pressure, or "closed" when oil pressure rises above 3 - 7 PSI.
Ignition power sourced directly from the CHOKE fuse (pnk/wht wire) connects to one terminal (or contact) of the OPS. Both the dash telltale (dk blu wire) and choke heater (lt blu wire) connect to the opposite terminal (or contact) of the OPS. The choke OPS contacts never connect to ground; the contacts are permanently isolated from ground.
The dash telltale has 12 volts of switched ignition power applied to one terminal of the bulb. The opposite terminal of the bulb connects to the choke heater at the OPS.
When there is zero oil pressure the OPS contacts are 'open' and the dash telltale grounds through the choke heater, illuminating the telltale. There isn't sufficient current flow through the telltale to "heat" the choke heater, so the choke is unaffected. Once the engine is running and oil pressure builds above ~5 PSI, the OPS contacts close, connecting 12 volts to both the choke heater AND the "ground side" of the choke telltale in the dash. With 12 volts connected to the choke heater, the choke bi-metal spring (thermostat) begins to relax and the choke plate begins to open. At the same time, 12 volts applied to the 'ground side' of the dash telltale, balances 12 volts to both terminals of the bulb, and the telltale extinguishes.
So the choke telltale routinely illuminates only when the ignition is switched ON and the engine isn't running. It will also illuminate with the engine running if the CHOKE fuse blows or the OPS fails open. It will never illuminate if the telltale is burned out, the choke heater is burned out, the choke heater is not properly grounded or is otherwise disconnected.
Does this help sort out the confusion on circuit operation?
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This was the crap 10a fuse that was in the choke slot. I replaced it with a new 20a fuse.
(https://i.imgur.com/4oelSYT.jpg)
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why? the wires for the choke prob cant handle 20 amps so they will burn up before that fuse
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I think I understand you bd. So with my choke being connected directly to the pink/white + right now, with the key on, the coil is going to relax faster since it's not waiting to get power from the oil pressure building up and closing that circuit.
I wish I could get all the correct color coded wires to fix all this with XD I'll need to get a new switch and connector. And is that AC Delco D1811 the correct replacement switch?
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Digging on Google trying to find the fuse diagram shows 20a on the choke heaters... I can't seem to find one specific to my truck, though.
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lol yeah sorry thats the one for the tbi motors, right hatzie?. theres another guy on here that has OPS issues and i think hes a tbi
hatzie whats the difference in that ac del one and PS134 from duralast?
That's what it looks like. The Metripack mating plug for that switch is obsolete so if it's gone it's better to just go with the 1/4" disconnect part.
Standard Motor Products S-939 (https://www.summitracing.com/parts/smp-s939) or BWD PT5590 (http://www.oreillyauto.com/site/c/detail/BWD0/PT5590.oap?year=1983&make=GMC&model=C1500%2BPickup%2BRWD&vi=1143245&evaritm=BWD%2B--%2BS383&rpl=1) are replacement moulded plugs with pigtail wires for the Delco D1811 and equivalent switches. Cut the butt splices off and install with uninsulated butt splices or solder with adhesive lined heatshrink tube to cover each join.
The Duralast PS134has 1/4"NPT threads.
The AC Delco D1811 (http://www.oreillyauto.com/site/c/detail/ACD0/D1811.oap?year=1983&make=GMC&model=C1500%2BPickup%2BRWD&vi=1143245&ck=Search_d1811_1143245_4989&keyword=d1811) has 1/8"NPT threads.
The Standard Motor Products PS135 (https://www.summitracing.com/parts/smp-ps135) or BWD S383 (http://www.oreillyauto.com/site/c/detail/BWD0/S383.oap?pt=01996&ppt=C0025) or Autozone Duralast PS115 are drop in replacements for the Delco D1811 threaded in 1/8"-27 NPT... They are all right around $10. O'Rileys sells Delco & BWD parts. I'd stick with the Delco or BWD or Standard Motor Products parts.
Digging on Google trying to find the fuse diagram shows 20a on the choke heaters... I can't seem to find one specific to my truck, though.
It'll be in the owners manual. I believe that 20A is correct for some odd reason.
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Going to Autozone, it tells me the Duralast PS115 will not fit my truck, but the PS134 is an exact fit.. Are they just wrong?
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Going to Autozone, it tells me the Duralast PS115 will not fit my truck, but the PS134 is an exact fit.. Are they just wrong?
O'Rileys stocks the BWD plug and the Delco and BWD switches.
The Delco switch # I quoted is equivalent to the GM part number from the 1979-1984 GM Light Truck Parts Books.
I stated specifically why the Duralast PS134 should not work on your truck. You're welcome to go buy whatever you like. I'd pull the existing switch and measure it with a caliper if you're worried.
1/4-18 NPT is 0.540" effective outside diameter. This is the thread on the PS134
1/8-27 NPT is 0.405" effective outside diameter. This is the thread on the PS115
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My bad, I read it wrong and thought you said the 134 was the drop in replacement XD
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i believe 20A fuse is correct for the choke. It does seem a little high, but based on diagrams and the fact that i had to change one out recently, i believe it is 20amps.
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what does the fuse box say for the choke fuse?
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I think mine just says "choke", lol
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Choke is 20 amp.
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Ok, i just looked at the fuse panel and it does say 20A for the choke slot.
It does seem rather high, and i would think 5A should be enough, you know just to power the choke coil, but there you have it.
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Lol. Learn something new every day, huh?
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Does this help sort out the confusion on circuit operation?
I just realized I didn't thank you for the post. Yes it did clear up my confusion. I just came back to this thread because I'm about to go wire it up, lol.
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You're welcome. Good luck with it.
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I got it all connected right I think. But it's not working properly. When I start it, the choke light is only on for a second or two. The choke never relaxes.
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The choke light is operating normally. It is supposed to extinguish when engine oil pressure builds above 3 - 7 PSI.
Use a test light grounded directly to battery negative to probe for power at the choke thermostat while the engine is running. If there is no power, the choke is incorrectly wired. Recheck your work.
Once you have verified power to the t-stat, shut off the engine and disconnect the choke lead. Jump B+ directly to the choke t-stat terminal. The choke plate should gradually open all the way over the ensuing 2 - 3 minutes, max.
If the choke doesn't open, either the t-stat is faulty or it is not grounded. Make sure there isn't a gasket installed between the choke t-stat and its housing, insulating the t-stat from ground. With B+ still connected to the t-stat, probe the t-stat housing to make sure the test light doesn't glow. If the test light glows even slightly, the choke housing is not properly grounded through the carburetor to the intake manifold. Replace the t-stat and/or correct the ground connections as testing indicates.
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How long should it take to get 3 to 7 psi?
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How long should it take to get 3 to 7 psi?
After it starts, just a second or so.
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I checked it with a multimeter earlier and it's getting power. But it doesn't seem to want to open right. I'm wondering if the coil or something is just worn out
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Did you jump power directly to the choke t-stat and verify there is no gasket between the t-stat cover and its housing?
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I verified power and ground on the choke terminals
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Replace the choke thermostat.