Q-Jet Basics.........Need some help

[NWmonte71]

My Monte Carlo is equipped with a stock 350cid with original 4 barrel Quadra-Jet. The Q-Jet has a solenoid on the side with wiring harness. I am not exactly sure what all this is...... cold choke mechanism? automatic idle adjustment for A/C? Anyway, the most important thing to discuss is my most recent event. I just picked up this clean car about 3 months ago. Before starting, I pump the gas pedal once all the way to the floor (choke/high idle). Then I start the car and it revs at high idle until it warms up.......just like it should. Last week I did the same starting procedure and the car died after it ran for a few seconds. The more I tried to crank it over, the harder it was for the starter to turn the engine over, (similiar to being vapor locked or hydro-locked). Finally, the starter would "click" and no longer turn the engine over. Note: during this attempted starting time, I would only crank for about 5-6 seconds with about 15 seconds of rest time. Frustrated, I stopped trying to crank and could smell strong gas fumes under the hood. I ended up walking away from the car to let it settle, thinking I flooded it. The next day, I decided to pull the spark plugs and check the overall condition of them. When I pulled cylinder #8 plug, to my surprise about 1 cup of fuel came pouring out!  How the heck did so much fuel get into the cylinder? and only #8? I figured that perhaps the Q-jet put excessive fuel into the engine from the attempted start the day before?  

 

I am not very savvy on carburetors and the Q-jet seems very complex on adjustments and the fact they made a million different models. I am a "set it and forget it" kinda person who really doesn't like chasing after tedious tuning to make the car run correctly. The previous owner had the carburetor professionally rebuilt just before I bought the car a few months ago. I see talk online about well plugs being sealed by epoxy, air horns that are commonly warped, etc, etc. The car ran awesome prior to this hick-up....... any suggestions. Hoping its just a little bit of crud that got into the needle/seat. 

[Rob Peters]

Regarding the solenoid.... That is an idle dropout solenoid.  One of the purposes of that solenoid is this.  When the key is turned on that solenoid will energize (extend slightly).

 

When adjusting the throttle idle this solenoid is energized and at the end of the solenoid is a bolt head that screws into that solenoid that is used to adjust the idle speed.  When the key is turned off the solenoid deenergizes which moves the throttle below idle speed to help prevent engine runon (dieseling) after the key is turned off.

 

I am not sure what caused the gas in cylinder 8 issue.  Maybe a valve issue.  I am sure some of the more knowledgeable engine guru's may help on that one

rob

[Sam (Bones)]

lots of possibilities 

 

float got stuck

chock also could have stuck

choke vacuum pull-off (vacuum pulls the choke off as it warms up)

 

but with that much fuel going into the engine I would look at the float

pull the air cleaner off and try to start it, you'll know if its the float, you'll see gas coming out of the top of the carb

sometimes you can tap on the carb with a hammer "LIGHTLY!" and it will free the float

[NWmonte71]

lots of possibilities 

 

float got stuck

chock also could have stuck

choke vacuum pull-off (vacuum pulls the choke off as it warms up)

 

but with that much fuel going into the engine I would look at the float

pull the air cleaner off and try to start it, you'll know if its the float, you'll see gas coming out of the top of the carb

sometimes you can tap on the carb with a hammer "LIGHTLY!" and it will free the float

Sam,

Thanks for replying back with a few suggestions on causes. More and more the float seems likely. The car ran outstanding prior to this issue (idle, acceleration, power, etc). Once I get some of my tune-up items put on, I will check for flooding. 

[Sam (Bones)]

you should really address the flooding issue before changing plugs, it'd be a shame to foul out a set of new plugs

[GatorDog72]

Don't change the plugs or the oil until you find the cause of the flooding, you could wind up with brand new oil with a bunch of gas mixed in. Be careful!  With as much gas as you found in #8, you could easily hydro-lock the engine and break stuff. Pull all the spark plugs out if you have to crank the engine over for diagnosis. Just cranking it won't hurt anything, but if it starts with that much fluid in the chamber it could be a disaster.

 

Like Sam said, I would check for a stuck float first. If you have a mechanical fuel pump, you will need to crank the engine and watch the vent tube on the top of the carburetor for gas spilling out. If you have an electric fuel pump, the pump should come on as soon as you turn the key to the on position.

 

In my car, the engine sits in the car tilted slightly back. That's my guess as to why only #8 filled with gas. On a dual plane intake manifold, #8 also has a pretty straight shot to the port. Could be that the intake valve just happened to be open when you stopped cranking. Good luck with the fix.

 

[NWmonte71]

Ok folks, here is an update:  Things are still just as bad as before. I got the battery hooked up and started to crank the engine. As soon as I started cranking, fuel came gushing out of the vent tube on the air horn (highlighted with green circle). I decided to lightly tap the float area on the air horn and try it again. The engine cranked very slow and seemed like it had a lot of resistance. I stopped and noticed fuel was weeping out of the base plate and getting the intake wet with fuel. To be perfectly clear, I had cranked the engine twice for only 5 seconds of crank duration. All that fuel got my attention and I stopped at that point. I decided to pull the #8 spark plug again.........once again fuel poured out of the cylinder!  I really need help with this issue, I am worried about washing down my cylinders, hydro-locking the rotating assembly, and worst of all creating a potential fire!  What do you suppose is the root cause? Stuck float I am assuming? I have owned this beautiful 71 Monte for 2 months and have only driven it twice........ both times it ran super smooth with no issues. Now I have a flooding pig that I cannot drive, let alone start. I attached photos of the carburetor and circled the areas where fuel is leaking out. How does the air horn come apart and how do I check for a stuck float? Is there an opening I can poke to dislodge the stuck float before taking things apart? 

[Mo's70MCs]

Take the carb off rebuild it I'd say. You obviously have a float issue, a sinking float, an improperly float level, a resilent needle that's burred, how about a piece of that rubber hose stuck in the needle and seat area? Seen it before, where the stock fuel filter is deleted in place of an online one. Double check that float specially​ on a rochester carb.

[NWmonte71]

Take the carb off rebuild it I'd say. You obviously have a float issue, a sinking float, an improperly float level, a resilent needle that's burred, how about a piece of that rubber hose stuck in the needle and seat area? Seen it before, where the stock fuel filter is deleted in place of an online one. Double check that float specially​ on a rochester carb.

Thanks for the feedback. I do have a Haynes manual specifically for Rochester carburetors and how to rebuild/adjust them. I read the Q-Jet section of the book thoroughly and noticed when ever a specific adjustment is required, the books says: "Refer to your specific rebuild kit for adjustment values". I have no numbers to check the float level, wondering if anyone has them handy? The carburetor was rebuilt just before I bought the car. The previous owner explained that the car had been sitting in his heated warehouse for several years and decided to have the carb rebuilt professionally before selling it. The car started, idled, and drove fantastic for me the 2 times I drove it. It would seem likely some little piece of crud is hanging up the float.

[Sam (Bones)]

I totally agree

 

The carb needs to come apart, you have a float/needle and seat issue

 

I would also pull ALL the plugs out and let the engine dry out

[Rob Peters]

I don't understand why a float issue would only fill #8 with fuel, who can answer.

 

Just a thought. Once you find the cause I would recommend draining the oil and replacing the oil and filter because with that much fuel sitting in #8 I suspect some of it would have to seeped into the oil pan, etc

rob

[stangeba]

I didn't see an answer if it is a mechanical or electric fuel pump.

I also think there is debris stuck in the needle and seat of the float that needs to be removed. Rubber hose material is a good possibility.

[John S]

I would bet the float is saturated and will feel heavy I have experienced that a couple of times.. Look for carb# it will begin with 7 and be a 7 digit #. You may very well be able to find the specs on that carb at a web site such as carbs unlimited and using that number on their site. Lots of stuff online just start searching under carbs or Rochester.

[Mo's70MCs]

As far as filling #8? I think just a coincidence. You know the motor is raked a few degrees back and it also tends to lean at times a bit more on the passenger side. Slightly.. perhaps the fuel is just finding itself to the lowest point. Also I couldn't agree more with Sam's suggestion on removing all the plugs.

[NWmonte71]

Just to answer a few questions............ the fuel pump is the normal AC Delco mechanical unit bolted on the lower corner of the engine block. I also have the car up on jack stands (front only) to troubleshoot and the engine is slanted back a ways (fuel drain back to cylinder #8 reasoning). I did locate the carburetor number on the side of the body. I just need to write it down for reference. Once I pull the top air horn off to inspect inside, what measurements should I be looking for as far as float settings?

[GatorDog72]

Usually when you purchase a float/ rebuild kit, it will come with a table to show the different float level adjustments for whichever engine you are working on.

[wallaby]

For the most part, the float should be sitting level. There are different specs, but they are like 1/32" different from each other... with your eyeball the float should be level and no  more when the needle closes.

I would bet that it's just stuck. If the "friendly" tapping on the carb doesn't loosen it, it's time to take the top off the carb.

The good news is that no fuel is going to dump out when you lift the top off. The bad news is that the top is kinda tricky to remove because of the accelerator pump linkage; you have to drive out the pivot pin just enough to release the arm... and then when you lift up the top, there are a bunch of metering rods dangling underneath. Pay attention which holes in the gasket those rods are lifting out of.

There are a couple of hidden screws that hold down the top under the choke flapper if I remember correct. A magnetic screwdriver is great for this job, but the screws cant go far as they are pretty large and won't fall past the carb venturi and into the engine or anything.

.

[NWmonte71]

UPDATE:   I got the numbers off the carburetor. They read: 17054929  I decided to pull off the air horn and see what the float/needle/seat/bowl looks like. The air horn was a little tricky with the external linkages and such, but I carefully and patiently pulled it off. Right off the bat I noticed the center part of the air horn gasket was saturated with fuel and was almost ripped apart. This part of the gasket is near the float arms, (possibly hanging the float up from going back to being fully seated?) There was just a little bit of fuel in the bottom of bowl. I manually raised the float gently by hand, seemed to move very freely. I removed the float and dried it out, no wet fuel spots were seen after drying (How do I tell the float is heavy and saturated?). I looked at the needle and seat, no debris or obvious obstructions were seen. I checked the bottom of the fuel bowl, the fuel was very cloudy and I could clearly see some kind of small sediment and algae- looking stuff floating on the bottom. I imagine this is considered very dirty and would be potential for carb needle/seat malfunctions? One item I did find that was considered unaccounted for was a small metal clip sitting on top of one of the secondary butterflies. Oh man! I was lucky it did not migrate further into the intake. I have no idea was the little clip is or where it came from. It must have fallen out when I removed the top air horn? I enclosed some pictures of what I mean. 

[71MonteCarloMD]

That small clip looks like throttle linkage clip?

[stangeba]

That small clip looks like the one that holds my choke linkage on at the top I believe.

[NWmonte71]

That small clip looks like the one that holds my choke linkage on at the top I believe.

I ended up buying a quadrajet rebuild kit for $23.00 and a new float. Not exactly sure how to test a saturated float, just figured I'd buy a new one and start fresh.The rebuild kit came with an exploded view diagram. Thinking the diagram should show the placement of the little clip.

[overdrive]

I think you're definitely on the right track. You can shake the float and listen for fuel moving inside it. If any noise at all, it's trash. Also, if you're curious, you can drop it into a cup of gas to see how well it floats. You could compare it to how well the new one floats.

 

If you can't find a linkage clip missing somewhere, it could be that the last guy rebuilding the carb lost it.

 

The gasket issue could very well be your problem, or debris in the fuel from a rubber hose, or debris from the gas tank. Hopefully, there's a filter in the line, just before the carb.

 

You have the choice of doing a complete carburetor removal and rebuild, or just using a few new parts, adjusting the float, and putting it back together. Since it was recently rebuilt, the latter may be a reasonable choice, but then if debris is in the fuel bowl, it makes me wonder where else in the carburetor it could be. It also makes me wonder how and why it got in the carburetor. The hose just before the inlet may be deteriorating, or a different hose could be, or the gas tank or the steel lines could have dirt/rust issues. If it has a fuel filter, anything downstream of it would be suspect. There should be a factory installed fuel filter inside the inlet of the fuel bowl, but many times they've been removed and replaced with a filter somewhere else in the system. The factory filter position is the best for eliminating debris in the carb, but they're sometimes too small to feed a hungry big block at wide open throttle for more than a couple of seconds. I had to remove mine and replace it with a larger filter for that reason.

 

The angle of the motor sounds like the reason you're getting fuel in #8. I'd at least check for fuel in the 4 cylinders in the back half of the motor. Better yet, after you put the carb back together, pull all 8 spark plugs and the coil wire and crank the engine to blow out excess fuel. This would best be done with the car sitting level outdoors and the proper type fire extinguisher close by. Be sure to remove the coil wire to the distributor to eliminate the possibility of a spark plug wire arcing to ground and causing a fire.

 

Check the oil level to see if it's high, due to fuel getting past the pistons. If you've cranked the motor over very little since the flooding problem began, a high oil level is unlikely. You may or may not need an oil change. A small shot of oil in the cylinders that were wet with gas would be good, before starting the motor again.

 

Good luck with your project. I respect you for taking on the job yourself. You'll be much more knowledgable, in the end. That's always good.

 

 

Dan

[Mo's70MCs]

All great advice! For the life of me I can't recall the location of the pesky clip, if my mind serves me right, I thought they were more common on a two barrel carbs? Another thing that came to mind the float seat..(needle & seat) a loose seat which is uncommon can give you the same outcome,, just something I remember seeing before. Definitely keep us posted on your finding. Another thing I noticed hardly anyone carries carburetor dip anymore.

[NWmonte71]

Overdrive,

 

Thanks so much for the detailed insight on troubleshooting! I am planning to simply clean the fuel bowl, use some carb cleaner and really clean the carburetor thoroughly with the air horn and float removed. I am thinking the rubber fuel line elbow installed on the steel fuel line (from fuel pump to carb is not stock). I assume the fuel line from the pump to the carb was continuous steel all the way up to the carb inlet. If so, who makes a factory replacement steel line for a 1971 350cid with 4brl?  I plan to change the oil after I figure out this flooding problem. The oil has not been changed for at least a decade. The car sat in a heated warehouse untouched for 10 years. I will definitely pull the plugs and crank it over with coil power disconnected to verify my flooding is gone. Burning up a "survivor" Monte is the last thing I want to do. Thanks again to everyone who has been chiming in and helping! I'll keep you all updated.

[overdrive]

You're welcome, and you're right about the rubber hose, definitely not original. There are 1 or 2 more hoses at the fuel pump to replace and at least 1 at the sending unit at the tank. Some say that ethanol in today's fuel will deteriorate the older rubber tubing from the inside and you'll get particles in your filter or the float bowl. I'd recommend changing all of them.

 

Inline Tube and Classic Tube are just 2 of the suppliers for your new tubing.

 

Dan