Rochester DualJet Electric Choke how-to [Archive] - El Camino Central Forum : Chevrolet El Camino Forums

: Rochester DualJet Electric Choke how-to


Arttu
02-20-2004, 12:34 PM
Hello everyone! I'm wondering if anyone bother to explain to me HOW the HELL is this Dual Jet electric choke supposed to work??? I have '80 ElCamino as daily driver, here in Finland and it is VERY desirabe to have choke function
properly.
My Elky have all original 229 V-6 with M2ME carb (2-barrel) and electric choke (ofcourse). When I bought it, it had (and still have) choke wire disconnected, BUT when I connected it, nothing happened except that "CHOKE" -light turned on, but air baffle didn't move! How, in the name of GM is this choke mechanism supposed to work? :?
I know, the wire supposed to heat coil inside choke housing, but Is this
air baffle supposed to be in CLOSED or OPEN -position when engine is OFF? How about when engine is ON? And when and how the warning light is supposed to go OFF? And why baffle is not moving or why the engine (cold) is dying when I manually closed baffle?
Please,Please,Please,Please tell me all! I must know everything, but I can't find clear information on this topic. Even not in repair manual (chilton). I just hate that there is so many Rochesters out there and no one knows the TRUTH about choke mechanism!" Everyone seems to talk about HORSEPOWER, but it's HORSE**** when basic functions of a car don't work!!!

Big Tex
02-20-2004, 07:10 PM
I have an 87 elky, When i first got it the choke did not work either. It stayed closed all the time. I finally got a new electric choke. With engine off and cooled down the baffel should be closed. When you turn on the key to start engine it should give 12 volts to choke coil to heat it up, but will not open up until coil is hot enough and you have to hit the gas pedal one time to release mechanism for baffel to open. Also on mine when i installed the new choke it still would not work, come to find out the spade ternminal was not making good connection to choke . Repaired spade and everything works good. When choke coil is good and hot the baffel should be wide open.

spoonplugger
02-21-2004, 12:00 AM
Howdy from Chattanooga, Tennessee. Take the air cleaner mechanism off the carburetor when the engine is overnight cold so you can observe the operation of the choke plate (I call it the butterfly but I think you call it the baffle). The choke plate should be straight up and down in the position it was in when the hot engine was last shut down. When you depress the accelerator once or operate the throttle linkage by hand, the choke plate should snap SHARPLY to the fully closed position (fully choked). Start the engine. Immediately upon starting, a vacuum operated "choke pull off" diaphragm will pull (just barely crack open) the choke plate allowing a small amount of air to pass into the carburetor. As the engine warms up, the electric choke allows the choke plate to slowly return to the straight up and down position, the normal position for a hot engine. This is a greatly simplified description of how the choke works.

If the choke plate does not sharply snap to the closed position, you must determine if some of the linkage or the plate itself is in a bind that prevents it from closing. If not in a bind, the choke spring may not be tight enough, in which case you will need to tighten the spring (adjust the choke spring).

If the choke plate closes, but does not open slightly as soon as the engine starts, the choke pull off diaphragm has failed or is out of adjustment.

The electric choke gets its power (12 volts) from an oil pressure switch located on the intake manifold. On my V-8, this oil pressure switch is beside the distributor, tight up against the firewall and difficult to reach. I do not know where it is located on your V-6. If this oil pressure switch has failed, there will be no voltage at the electric choke itself and the "Choke" light on your dash will be on all the time. With the ignition switch in the "on" position but the engine off, test for 12 volts at the spade located on the electric choke housing. If no voltage is present, find and replace the pressure switch.

As you can see, there are many possibilities that will keep a choke from working properly. Causes are sticking/binding linkages, sticking choke plate, vacuum pull off diaphragm failure or misadjustment, etc. Usually, one or more of these will be the culprit, but it is essential that the engine be overnight cold when you begin the trouble shooting process. Good luck and keep us posted with your results.

spoonplugger
02-21-2004, 12:02 AM
As a second thought, be sure to use the search feature for other helpful tips.

Arttu
02-21-2004, 03:08 AM
I'm very grateful for your replies, and I will try those tips as soon as possible, the only concern is that my carb doesn't have this vacuum pod (diaphragm or something), I looked at Chiltons' repair manual photos and found that it must be there (or must it?), so my first job will be to find thad vacuum device. Luckily I have a "pile" of Rochester Q-Jets in a box, I guess I can find it there.
In Finland it's no problem to find parts for American Cars, but I live in small town, and here we have, say 5-8 older American automibiles,so we have no part store which specializes in these roadrockets...And ordering these small carb parts is frustrating. But I will find out the way and report about my progress later. Thank you.

Tommy
02-21-2004, 06:04 AM
You are helping keep the Elky pressence alive all over the world! I salute you. :-)

Arttu
02-24-2004, 01:04 PM
Thanks for a compliment! Yeah, if only ALL americans were as proud as I am of their automobiles, then there would be less tasteless cars (read Toyotas & others alikes) on the road! I wonder why american people would want those cars?! Well, anyways, this isn't right place to talk about it, I guess... So I want to ask couple more questions about carb.
I mentioned, that I don't have choke pullback diaphragm, so I wonder, is there a way to bypass it? :? (I didn't find any compatible units in my stash of Q-Jets). If not, I must consider couple options. Either I buy new one OR
my friend have Dual Jet WITH intake manifold from 4.3L V6, which is from his
BOAT and best of all, it's like new, because he switched to Q-Jet very soon after bought that boat! The problem is that it's clearly not calibrated for a car, but it does have choke, so IS IT possible to switch main jets and needles
from my carb and "drive away"?? And is a 4.3 L V-6 intake any better flowing than mine stock 3.8L (229cu.in.)piece? I assume it's compatible to my motor(?)