Rochester Quadrajet Carburetor

Quadrajet Identification

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Rochester Quadrajet Carburetor Manual

Application Carburetor Number Carburetor Kit
1974 Oldsmobile Cuslass Toronado 7044280, 7044281, 7044282 4207
1973 Oldsmobile 455″ 7043251, 7043253, 7043252, 7043259, 7043282 4207
1969 Oldsmobile 7029250, 7029251, 7029252, 7029253, 7029254, 7029255 4207

Quadrajet 4 MC, 4 MV Carburetor Trouble Shooting

E4MC, E4ME Adjustment Procedures

 I have a Rochester Quadrajet Marine Carburetor #17059286. It appeared to be flooding at idle and the fuel was leaking excessively from the throttle body linkages (on both left & right side). I assumed the carb needed to be rebuilt and the leaking was normal (from a drain in the carb) when flooded. I rebuilt it using a kit I ordered from you. I reinstalled the carb and I’m having the same issue of fuel leaking from the throttle body linkages. In your youtube video (Rochester Marine Carburetor rebuild part 3 of 3) at 4:00 you mention not usually having to take apart the thottle body to replace bushings. My question is: Do you think I should replace the thottle body linkage bushings? And if so, do you carry the kit? I think this is what I need to do. However, I read a post online that said the fuel at the thottlebody should already be atomized, and should therefore not leak out the linkage,and that would indicate that the carb is flooding due to the float not being adjusted properly. I set the float to 3/16 like the instructions stated. Any thoughts on this would be greatly appreciated.

Your problem is not bushings. The carburetor is simply puking out too much fuel. The bushings are replaced only if you have excessive free play in the throttle shaft. Flooding fuel will leak out anywhere it can and onto the throttle valves and out the shaft is the 1st place fuel likes to go.

Too much fuel boils down to getting too much in the float bowl. Did you test the (brass) float for leaks? Immerse the float in hot water and if there are any leaks, it will bubble. If you have a Nitrophyl float (black plastic kind of thing), replace it. They absorb fuel over time.

Did you put the fiber washer where the seat screws into the float bowl.

Many times after rebuilding a carburetor and after re-starting the engine, crud from the tank and the fuel lines will rush up to the carburetor and into the needle & seat causing it to stick open. Take the carburetor apart and wash out the needle & seat and try again.

Manually move the float up and down and watch for any kind of rubbing, or catching. Also watch the needle to make sure it is move straight up and down and not getting caught up.

Too much fuel pump pressure could be holding the needle open. Any chance you replaced the pump with a new one? New pumps are always suspect because they come from China and they don’t seem to care about specifications very much yet.

These are just a few ideas, but bottom line is that too much fuel is getting into the float bowl.


49 thoughts on “Rochester Quadrajet Carburetor

  1. Bought a new rochester qj for my Omc 185. but cant get it running right. I added a 4port intake, an electronic ignition and the new carb. It starts, but after warming up It bogs down and dies when i give it some throttle. If I manully close the two choke ports half way it runs ok. The two front ports are supposed to be totally open when it is warm correct??? I know the waters here in Norway are cold, but I did not have this problem with the old two barrel..

    • My guess is that it isn’t getting enough fuel. Test your fuel pump. Other than that you will have to get into the carburetor. Could be the float level, sticking needle & seat just to start.

      Also look for vacuum leaks.

  2. We didn’t take them out as they looked good. They seem to close all the way and the shafts have no wobble. (tight to the sides) Before we did the rebuild it was running at slow idle, but it was a mess when we took it apart. Is there anything that could be plugged that is causing the issue?

  3. Hi Mike; My Son and I rebuilt a quadrajet from the ground up. When we started the engine there was no slow idle and it was running around 2500-3000 rpm. We can’t get it to slow down even with the idle jets screwed in and the fast idle screw out until it isn’t even touching. thoughts?
    After a day of trying to fix it:
    We thought that it might be the primary metering rods sticking but we weren’t expecting what we found. The main pump had started acting a little sticky on the last test run and when we removed the top of the carb. the main metering jets were STUCK down. The only way to release them was with a pair of needle nose pliers.
    The pump was sticking as well.
    The boat sat unused for 1.5 years so we put in seafoam for gas treatment. The engine seemed to run fine (except for the carb issue). Is it possible the gas turned?
    Everything was free and loose when we put it back together.

    • If I read this right you added the Seafoam after the 1.5 years of sitting. It has to be put in before. After is too late. The gas surely turned and varnished the inside of the carburetor and probably the gas tank too. You will have to rebuild the carburetor, remove and clean the gas tank, clean out all fuel lines.

      • We drained the fuel cleaned all the lines and tank and cleaned the carb again. Checking to make sure all the pistons,, metering rods, air portals were clear and open. We used a small wire and blew air throughout the carb orifices.
        We started it up and it still is idling high (but not as high as it was) (18-2000 rpm) and won’t slow down any more. However, when We pressed on the secondary metering lever (lifting the metering rods up) it did slow down to the proper idle. We also tried spraying cleaner around the carb to see if there was a vacuum leak but there was not. (the stall out method). You make it look so easy–where did we go wrong?

        • Did you remove the throttle plates when you rebuilt the carburetor. It could be they were put back wrong and not closing all the way. Turn the carburetor upside down, back out the idle screw and make sure the fast idle is off. The plates should be completely closed. It could be the got switched from side to side.

          If they don’t close completely then it will act like you are pressing on the throttle.

  4. I am having trouble with a Qjet fuel filter stopping after a couple hundred miles.. When i take it out it is clean, I can not blow through it.. After the filter sets a couple days I can blow through it like it was new.. Does the ethanol cause any fuel filter issues?

  5. rebuilt my Rochester quad over last winter, first timer!! I haven’t ran the boat much this year but was a great improvement. does fine at WOT. problem is upon acceleration. if I ease into it does fine, but if I try and get on it to quick it bogs down, wants to die if I don’t back off quickly. a little backfire. any suggestions? thanks

    • Looks like lack of fuel. My guess is that it got dirty, probably from sitting. Between the ethanol and the fact that gas turns bad over time, your carburetor doesn’t stand a chance sitting around.

  6. Hi—I am a green novice. My Mechanic says he will fix the carb if I find the parts. I need help. Do you offer over the phone ordering ? Or, can I give the carb # and parts I need and you will contact me ???

  7. I have a quadrajet on my 5.7 marine power engine. When I shut down, and the engine sets for any time, it tends to dump all the fuel out of the bowl causing flooding. Any suggestions? Rebuilt carb, still doing it.

    • On the bottom of the Quadrajet there are 2 plugs just below the main jets. These tend to leak and should be treated. Rough up the plugs a bit, then apply epoxy on them. JB weld will work for about 2 years before the ethanol turns it to jelly. There are other epoxys out there that is ethanol ready but I don’t remember what it is.

  8. I have a marine Quadrajet, which I had rebuilt by a vendor supposedly experienced. Installed on boat, replaced all filters, started and ran ok on the water hose, but 30 minutes after I shut it off, it was hard cranking, took 10 seconds to start and acted rich. Choke was open. Cleared up eventually. Did not do this before rebuild, even after hard running in summer, always started quickly. I read a lot about welch? plugs that leak down but figured this would be taken care at rebuild. Took me two months to get it back and Im nervous to send it back. What should I do?

    • You need to send it back. You are probably flooding. Test your fuel pump 1st to make sure it isn’t putting out too much pressure. 5-7 lbs is plenty. It would be normal for the plugs to be fixed on the bottom of the carburetor, but who knows.

  9. Searching for rochester quardrajet carburetor service parts list for carburetors 17087130 and 17087306. Ran across this information on the web, linked or otherwise listed as a portion of a vintage gm service parts list or manual. Can’t seem to locate it now, any ideas or leads, would be appreciated, thanks!

  10. Hey Mike, I’m a neophyte when it comes to carburetors. I am renovating a 1974 GMC C1500 pickup. I’m putting a new stock 350 from Summit in it. A friend gave me a quadrajet 17083226 3202 FKC. It is for an 81-86 Chev/GMC/Truck BOP. It has the electric choke. Can I use this on my truck? Don’t laugh too hard if I’m out in left field just educate me a little please. Thanks!

  11. Got a quadrajet 17085213 that I’m rebuilding.
    What # jets do i need for high altitude. I got #75 in it now. smells too rich.
    do i need to change the jet rod to match the jets to work better.

  12. Hello, my name is Steve Customer #5018. I recently bought a Carberator Kit #530 and a #167 Float for my Marine QuadraJet. I recently installed the Kit with the
    help of Your great Video! I found it VERY helpful and probably would not have attempted the rebuild myself without it, so Thank You very much for making it available.
    I purchased the Carburetor Kit #530 because my Boats Engine was loading up and eventually would die at idle. The Engine runs perfect at all other RPM. I have rebuilt the Carburetor as per Your Videos instruction, and am unfortunately experiencing the same symptom. In the Video there is a Part which I believe is called a “Primary or Primer Piston” which has the two Small Needles attached to it’s assembly. You mention that You rarely replace the seal on that part because they are rarely bad and it is not worth the time. Mine happens to be bad. Upon inspecting this seal I can see that about 1/3 of the sealing lip is missing from around the sealing diameter, and the whole sealing lip is very hard and brittle. I can not seem to find one of these seals in the Kit I purchased. There are several different varieties that did come in the Kit, but I tried all of them and none of them will actually “press” into the Carburetor Body and stay assembled. The first question I have is: Do You sell this seal? The next is: If this seal were leaking or bad, would it cause the Engine to load up slowly (around :30 seconds) at idle and die. The Carburetor was in very good shape with only 401 hours on this all stock unmodified 1990 350 Chevy Mercruiser Inboard Engine prior to rebuild. The Float level was set as recommended in the Video. everything else was assembled as instructed in the Video. Should the Float level be set a little lower or more because this Engine actually sits at an angle in the Boat? (It is an Inboard direct drive.)
    The only other thing that I can think of that could be contributing to this symptom is, the Fuel Pump had been replaced around the time this problem started. I bought the correct, stock marine pump at the time. Is it realistic to think that the new Fuel Pump could have too much pressure?

    Thank You Very Much in Advance for any assistance,


    • A new fuel pump is always suspect. The china built fuel pumps just don’t have the pressure they should have. Any new pump should be pressure tested to make sure it is working as required. Off hand I don’t know what it should be. Please consult your boat motor manual. The specification should be there some where. If all else fails be sure it isn’t pumping more that 7 lbs.

        • That part is called the power piston. If it were stuck either up or down it could cause up problems. Does your power piston move up and down freely? I just rebuilt my marine carb and had to replace the power piston. I’m not sure if Mike has them but I found an NOS one on ebay.

  13. I have a quadrajet on my boat. This past weekend it began to flood and actually overflow the carb until the pressure from the pump died down. Can you offer any advise and which parts ie. Rebuild kit floats etc. I will need. I have viewed your YouTube videos and have the carb torn down on the bench. Thank you.

  14. Hi,i have to rebuild my 17083226 carb,on a 1983,350 chevy truck,what up grade kit can i use,i was looking at the 17058230 HD,1983 350 truck carb to order,but what can i do to the 17083226,to maybe make it as good as the there a carb kit that works to up grade it.And who has a 17058230 to sale.Thanx for your help.

  15. I recently found a Rochester Quadrajet 4MV 7026254 that had been missing from the ’66 Cutlass my son bought. It is, however, missing the choke rod 7032727 that runs from the choke plate to inside the carb. Is the choke linkage you sell this rod?

  16. Hi Mike,

    I recently purchased a Rochester Quadrajet rebuild kit plus a new float that will go onto my mercruiser 305. Once I’ve completed the rebuild and mounted, will i need to prime the carb? If so how do i do that?

    • You don’t need to prime the carburetor. Cranking the engine should fills the carburetor quickly. Just don’t crank for more than 30 seconds at a time, then let it sit a bit. You don’t want to burn out the starter.

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