Rochester QuadraJet 4bbl Carburetor issue
Hello
My truck (1986 GMC Sierra K2500 with 5.7L) have issues with starting, engine will crank but it’ll not start, I replaced the fuel tanks, new sending units, new fuel hoses, new fuel pump, new fuel filter, rebuild the stock carburetor (Rochester QuadraJet 4bbl), fuel comes to the carburetor. Issue: It will start if I put fuel in the carburetor for the 1st of the day, subsequent starts are ok. If I leave the truck overnight, next day it’ll not start (it’ll crank, but no start). Need help Thanks |
Re: Rochester QuadraJet 4bbl Carburetor issue
If filter in carb was replaced was it installed right?
Sorry, delete that question. Filter must be good from your description. Does your choke work? Any fuel from the accelerator pump when you pump it first time when cold? Could be leaking fuel bowl wells also. That’s not normally a problem with your carb though. How new is the fuel pump? |
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Filter is installed correctly, Choke is electrical but how do I test it? Because it starts no idle after starting, Not sure about the accelerator pump, do I look inside the primary to see if fuel comes out? Fuel pump is less than a month old (brand new) I didn’t do the rebuild myself, someone else did it. |
Re: Rochester QuadraJet 4bbl Carburetor issue
Yup!
Look in the carb. Hold the choke blade wide open. Stroke the throttle quickly. Look for fuel beside the boosters. Up near the top front. Should see two shots. One on each booster. To check choke open throttle 1/4 way and choke flap should move and close off top of primaries. |
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Off.
Sometimes easier to use a small flashlight to see inside the carb. |
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I’ve not started the truck for the past 5 days, Today before starting I checked to see if i can see fuel is squirting inside the carb if I push the paddle, and it did. So I cranked the car, fuel stopped squirting, So I waited for few minutes I repeated the process Pushing the paddle without cranking, and nothing, no fuel coming I’ll check after few hours. |
Re: Rochester QuadraJet 4bbl Carburetor issue
It only squirts when you stroke the throttle
It should squirt every time you stroke it. If not (like in your second test), then the pump well is low, float level is low. And possibly the check ball is stuck. Will the choke blade close when you stroke the throttle? |
Re: Rochester QuadraJet 4bbl Carburetor issue
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IIRC, there is a spring in with the fuel filter. Make sure you have it on the correct side of the filter. Also double check that the filter is going the right way.
I did this once when I was young and had to pay a mechanic to put it in right. If you have a paper filter make sure the end with the hole is going towards the fuel line, opposite the spring. |
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Re: Rochester QuadraJet 4bbl Carburetor issue
Well plugs in the bottom of the bowl could be draining overnight. Quite common area to fix when rebuilding the carb. Mix up some JB weld--apply and wait a few hours
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We’ll help fix that but first a question. When you do get it running and when driving down the road and you step on the pedal, do you feel a slight stumble? |
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Re: Rochester QuadraJet 4bbl Carburetor issue
The black cap on the side of the carb should have 3 screws on it. Loosen them and rotate the cap counter clockwise. Hold the throttle open and the choke blade should close. Turn it until it just closes then tighten the screws.
That should help starting. I’d do that first. If it helps the no start situation then you know the well are good. |
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The fuel pump works, The fuel filter is correct I turned the choke cap to the left, it only turned less than 1/4 turn. Truck started but with stuck full throttle, I shut down. I checked the throttle cables they’re ok, throttle moves ok, gas paddle moves ok. Started again, full throttle. I moved the choke cab back to where it was, started again, full throttle, shut it down, So I gave up, 😡😤 |
Re: Rochester QuadraJet 4bbl Carburetor issue
It’s likely still on high idle.
There’s a high idle screw under the choke pull off pot on the front passenger side. It’s a Phillips head screw. A little hard to see. Rotate it ccw a couple turns and try again. See how that works. |
Re: Rochester QuadraJet 4bbl Carburetor issue
I’ll tonight and see what happen,
Question Where can I buy stock or rebuilt Rochester QuadraJet 4bbl for 1986 GMC Sierra C/K2500 with 5.7/7.4L engines? |
Re: Rochester QuadraJet 4bbl Carburetor issue
What’s your budget like?
Any rebuilt might not run very well. Depending on your carbs original set up. Different jetting, rods, etc. Can you post a pic of yours? |
Re: Rochester QuadraJet 4bbl Carburetor issue
It took more than 4 ccw to get the idle correct, truck started for the 1st time without any help 😁 thanks to you all for the help
Pictures will be uploaded shortly |
Re: Rochester QuadraJet 4bbl Carburetor issue
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Pictures
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Re: Rochester QuadraJet 4bbl Carburetor issue
Awesome!
Where in the world do you live? |
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I live in a country that temp @6:30 pm is close to 41c? State of Qatar However the truck is imported from USA either UT or CO? Among other trucks I own👍🏻 This truck have a loud clunk when in reverse, not sure why? :gmc2: |
Re: Rochester QuadraJet 4bbl Carburetor issue
A balmy 16C here this morning. Might get to 25C by end of day.
If you have a two piece driveshaft the clunk could be the centre bearing, or a bad u-joint. |
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If you’re curious about my location!
I live in a little village by the sea! On the east coast of Vancouver Island. Province of British Columbia. About 80 km due west of Vancouver across the water. Very quiet here except for the sometimes fun of a big bird like this. Injured. Couldn’t fly. Eagle rescue caught her. They’ll fix her up and release her. The clunk you’re getting. Is your truck 4 wheel drive? |
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Could be noise from transfer case.
And sometimes bad motor or trans mounts will make a clunk. |
Re: Rochester QuadraJet 4bbl Carburetor issue
If it only clunks in 4 wheel drive, suspect the X-fer case or forward drive train.
If it clunks in both 2 & 4 wheel drive, suspect the rear drive train. Possible that since your idle is fixed, the clunk will largely go away. Even a new drive train has enough slop that switching from D to R or back at high speed can make a noise. |
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Re: Rochester QuadraJet 4bbl Carburetor issue
Is the carb working better?
Does it start right up like you want? I’ve installed a torque strap a couple times to limit the motor from moving. Whenever put in gear the motor wants to torque to the passenger side. I used a short chain with a turnbuckle. Attached to the frame and a convenient bolt down beside the power steering pump. If the clunk goes away then you know something is hitting somewhere. If you try that don’t leave the strap in place. Your steering can be effected. |
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Im waiting for free time so I can diagnose it probably. Thank you and the other who helped me to fix the issue. 👋🏻. The only thing is where to fine a NOS or remanufactered carburetor that fits my truck. 🌺🌹🌷💐 |
Re: Rochester QuadraJet 4bbl Carburetor issue
Why are you looking for a nos one or reman carb?
Does your truck start normally now? You know. Pump it a couple times to set the choke, fire it up, it runs on a high idle, tap the throttle after a couple minutes, it idles down to normal, put it in gear and off you go. |
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I’ve other :gmc2: trucks, one requires a 800cfm carb, one requires 750cfm Thanks again |
Re: Rochester QuadraJet 4bbl Carburetor issue
I’ve had two Sean Murphy quadrajets. A bit more in price but excellent parts.
And they can restore your original carb for you. Look around on here. https://www.smicarburetor.com/ |
Re: Rochester QuadraJet 4bbl Carburetor issue
Those electric choke mechanisms die after a while. That's probably all you need.
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